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//! RXML parser and compiler framework. 
//! 
//! Created 1999-07-30 by Martin Stjernholm. 
//! 
//! $Id: module.pmod,v 1.72 2000/03/03 11:02:07 nilsson Exp $ 
 
//! Kludge: Must use "RXML.refs" somewhere for the whole module to be 
//! loaded correctly. 
 
//! WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING 
//! WARNING                                                 WARNING 
//! WARNING        This API is not yet set in stone.        WARNING 
//! WARNING        Expect incompatible changes.             WARNING 
//! WARNING                                                 WARNING 
//! WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING 
 
//#pragma strict_types // Disabled for now since it doesn't work well enough. 
 
#include <config.h> 
 
#ifdef OBJ_COUNT_DEBUG 
// This debug mode gives every object a unique number in the 
// _sprintf() string. 
#  define DECLARE_CNT(count) static int count = ++all_constants()->_obj_count 
#  define PAREN_CNT(count) ("(" + (count) + ")") 
#  define COMMA_CNT(count) ("," + (count)) 
#else 
#  define DECLARE_CNT(count) 
#  define PAREN_CNT(count) "" 
#  define COMMA_CNT(count) "" 
#endif 
 
class Tag 
//! Interface class for the static information about a tag. 
{ 
  constant is_RXML_Tag = 1; 
 
  //! Interface. 
 
  //!string name; 
  //! The name of the tag. Required and considered constant. 
 
  /*extern*/ int flags; 
  //! Various bit flags that affect parsing; see the FLAG_* constants. 
  //! RXML.Frame.flags is initialized from this. 
 
  mapping(string:Type) req_arg_types = ([]); 
  mapping(string:Type) opt_arg_types = ([]); 
  //! The names and types of the required and optional arguments. If a 
  //! type specifies a parser, it'll be used on the argument value. 
  //! Note that the order in which arguments are parsed is arbitrary. 
 
  Type def_arg_type = t_text (PEnt); 
  //! The type used for arguments that isn't present in neither 
  //! req_arg_types nor opt_arg_types. This default is a parser that 
  //! only parses XML-style entities. 
 
  Type content_type = t_same (PXml); 
  //! The handled type of the content, if the tag gets any. 
  //! 
  //! This default is the special type t_same, which means the type is 
  //! taken from the effective type of the result. The PXml argument 
  //! causes the standard XML parser to be used to read it, which 
  //! means that the content is preparsed with XML syntax. Use no 
  //! parser to get the raw text. 
 
  array(Type) result_types = ({t_xml, t_html, t_text}); 
  //! The possible types of the result, in order of precedence. If a 
  //! result type has a parser, it'll be used to parse any strings 
  //! gotten from Frame.do_return (see that function for details). 
 
  //!program Frame; 
  //!object(Frame) Frame(); 
  //! This program/function is used to clone the objects used as 
  //! frames. A frame object must (in practice) inherit RXML.Frame. 
  //! (It can, of course, be any function that requires no arguments 
  //! and returns a new frame object.) This is not used for plugin 
  //! tags. 
 
  //!string plugin_name; 
  //! If this is defined, this is a so-called plugin tag. That means 
  //! it plugs in some sort of functionality in another Tag object 
  //! instead of handling the actual tags of its own. It works as 
  //! follows: 
  //! 
  //! o  Instead of installing the callbacks for this tag, the parser 
  //!    uses another registered "socket" Tag object that got the same 
  //!    name as this one. Socket tags have the FLAG_SOCKET_TAG flag 
  //!    set to signify that they accept plugins. 
  //! 
  //! o  When the socket tag is parsed or evaluated, it can get the 
  //!    Tag objects for the registered plugins with the function 
  //!    Frame.get_plugins(). It's then up to the socket tag to use 
  //!    the plugins according to some API it defines. 
  //! 
  //! o  plugin_name is the name of the plugin. It's used as index in 
  //!    the mapping that the Frame.get_plugins() returns. 
  //! 
  //! o  The plugin tag is registered in the tag set with the 
  //!    identifier 
  //! 
  //!                 name + "#" + plugin_name 
  //! 
  //!  It overrides other plugin tags with that name according to 
  //!    the normal tag set rules, but, as said above, is never 
  //!    registered for actual parsing at all. 
  //! 
  //!    It's undefined whether plugin tags override normal tags -- 
  //!    '#' should never be used in normal tag names. 
  //! 
  //! o  It's not an error to register a plugin for which there is no 
  //!    socket. Such plugins are simply ignored. 
 
  //! Services. 
 
  inline object/*(Frame)HMM*/ `() (mapping(string:mixed) args, void|mixed content) 
  //! Make an initialized frame for the tag. Typically useful when 
  //! returning generated tags from e.g. RXML.Frame.do_return(). The 
  //! argument values and the content are normally not parsed. 
  //! 
  //! Note: Never reuse the same frame object. 
  { 
    Tag this = this_object(); 
    object/*(Frame)HMM*/ frame = ([function(:object/*(Frame)HMM*/)] this->Frame)(); 
    frame->tag = this; 
    frame->flags = flags; 
    frame->args = args; 
    if (!zero_type (content)) frame->content = content; 
    return frame; 
  } 
 
  int eval_args (mapping(string:mixed) args, void|int dont_throw, void|Context ctx) 
  //! Parses and evaluates the tag arguments according to 
  //! req_arg_types and opt_arg_types. The args mapping contains the 
  //! unparsed arguments on entry, and they get replaced by the parsed 
  //! results. Arguments not mentioned in req_arg_types or 
  //! opt_arg_types are not touched. RXML errors, such as missing 
  //! argument, are thrown if dont_throw is zero or left out, 
  //! otherwise zero is returned for such errors. ctx specifies the 
  //! context to use; it defaults to the current context. 
  { 
    // Note: Code duplication in Frame._eval(). 
    mapping(string:Type) atypes = args & req_arg_types; 
    if (sizeof (atypes) < sizeof (req_arg_types)) 
      if (dont_throw) return 0; 
      else { 
        array(string) missing = sort (indices (req_arg_types - atypes)); 
        parse_error ("Required " + 
                     (sizeof (missing) > 1 ? 
                      "arguments " + String.implode_nicely (missing) + " are" : 
                      "argument " + missing[0] + " is") + " missing.\n"); 
      } 
    atypes += args & opt_arg_types; 
#ifdef MODULE_DEBUG 
    if (mixed err = catch { 
#endif 
      foreach (indices (atypes), string arg) 
        args[arg] = atypes[arg]->eval (args[arg], ctx); // Should not unwind. 
#ifdef MODULE_DEBUG 
    }) { 
      if (objectp (err) && ([object] err)->thrown_at_unwind) 
        fatal_error ("Can't save parser state when evaluating arguments.\n"); 
      throw_fatal (err); 
    } 
#endif 
    return 1; 
  } 
 
  // Internals. 
 
  array _handle_tag (TagSetParser parser, mapping(string:string) args, 
                     void|string content) 
  // Callback for tag set parsers. Returns a sequence of result values 
  // to be added to the result queue. Note that this function handles 
  // an unwind frame for the parser. 
  { 
    Context ctx = parser->context; 
    // FIXME: P-code generation. 
 
    if (string splice_args = args["::"]) { 
      // Somewhat kludgy solution for the time being. 
      splice_args = t_text (PEnt)->eval (splice_args, ctx, 0, parser, 1); 
      m_delete (args, "::"); 
      args += parser->parse_tag_args (splice_args); 
    } 
 
    object/*(Frame)HMM*/ frame; 
    if (mapping(string:mixed)|mapping(object:array) ustate = ctx->unwind_state) 
      if (ustate[parser]) { 
        frame = [object/*(Frame)HMM*/] ustate[parser][0]; 
        m_delete (ustate, parser); 
        if (!sizeof (ustate)) ctx->unwind_state = 0; 
      } 
      else frame = `() (args, Void); 
    else frame = `() (args, Void); 
 
    mixed err = catch { 
      frame->_eval (parser, args, content); 
      mixed res; 
      if ((res = frame->result) == Void) return ({}); 
      if (frame->result_type->quoting_scheme != parser->type->quoting_scheme) 
        res = parser->type->quote (res); 
      return ({res}); 
    }; 
 
    if (objectp (err) && ([object] err)->thrown_at_unwind) { 
      mapping(string:mixed)|mapping(object:array) ustate = ctx->unwind_state; 
      if (!ustate) ustate = ctx->unwind_state = ([]); 
#ifdef DEBUG 
      if (err != frame) 
        fatal_error ("Internal error: Unexpected unwind object catched.\n"); 
      if (ustate[parser]) 
        fatal_error ("Internal error: Clobbering unwind state for parser.\n"); 
#endif 
      ustate[parser] = ({err}); 
      throw (err = parser); 
    } 
    else throw_fatal (err); 
  } 
 
  DECLARE_CNT (__count); 
 
  string _sprintf() 
  { 
    return "RXML.Tag(" + [string] this_object()->name + COMMA_CNT (__count) + ")"; 
  } 
} 
 
 
class TagSet 
//! Contains a set of tags. Tag sets can import other tag sets, and 
//! later changes are propagated. Parser instances (contexts) to parse 
//! data are created from this. TagSet objects may somewhat safely be 
//! destructed explicitly; the tags in a destructed tag set will not 
//! be active in parsers that are instantiated later, but will work in 
//! current instances. 
{ 
  string name; 
  //! Used for identification only. 
 
  string prefix; 
  //! A namespace prefix that may precede the tags. If it's zero, it's 
  //! up to the importing tag set(s). A ':' is always inserted between 
  //! the prefix and the tag name. 
 
  int prefix_req; 
  //! The prefix must precede the tags. 
 
  array(TagSet) imported = ({}); 
  //! Other tag sets that will be used. The precedence is local tags 
  //! first, then imported from left to right. It's not safe to 
  //! destructively change entries in this array. 
 
  function(Context:void) prepare_context; 
  //! If set, this is a function that will be called before a new 
  //! Context object is taken into use. It'll typically prepare 
  //! predefined scopes and variables. The functions will be called in 
  //! order of precedence; highest last. 
 
  int generation = 1; 
  //! A number that is increased every time something changes in this 
  //! object or in some tag set it imports. 
 
#define LOW_TAG_TYPE                                                  \ 
  string|array|                                                         \ 
  function(:int(1..1)|string|array)|                                    \ 
  function(object,mapping(string:string):int(1..1)|string|array) 
 
#define LOW_CONTAINER_TYPE                                            \ 
  string|array|                                                         \ 
  function(:int(1..1)|string|array)|                                    \ 
  function(object,mapping(string:string),string:int(1..1)|string|array) 
 
#define LOW_ENTITY_TYPE                                                       \ 
  string|array|                                                         \ 
  function(:int(1..1)|string|array)|                                    \ 
  function(object:int(1..1)|string|array) 
 
  mapping(string:LOW_TAG_TYPE) low_tags; 
  mapping(string:LOW_CONTAINER_TYPE) low_containers; 
  mapping(string:LOW_ENTITY_TYPE) low_entities; 
  //! Passed directly to Parser.HTML when that parser is used. This is 
  //! intended for compatibility only and might eventually be removed. 
  //! Note: Changes in these aren't tracked; changed() must be called. 
 
  static void create (string _name, void|array(Tag) _tags) 
  //! 
  { 
    name = _name; 
    if (_tags) 
      foreach (_tags, Tag tag) 
        if (tag->plugin_name) tags[tag->name + "#" + tag->plugin_name] = tag; 
        else tags[tag->name] = tag; 
  } 
 
  void add_tag (Tag tag) 
  //! 
  { 
    if (tag->plugin_name) tags[tag->name + "#" + tag->plugin_name] = tag; 
    else tags[tag->name] = tag; 
    changed(); 
  } 
 
  void add_tags (array(Tag) _tags) 
  //! 
  { 
    foreach (_tags, Tag tag) 
      if (tag->plugin_name) tags[tag->name + "#" + tag->plugin_name] = tag; 
      else tags[tag->name] = tag; 
    changed(); 
  } 
 
  void remove_tag (string|Tag tag) 
  //! 
  { 
    if (stringp (tag)) 
      m_delete (tags, tag); 
    else 
      for (string n; !zero_type (n = search (tags, [object(Tag)] tag));) 
        m_delete (tags, n); 
    changed(); 
  } 
 
  local Tag|array(LOW_TAG_TYPE|LOW_CONTAINER_TYPE) get_local_tag (string name) 
  //! Returns the tag definition for the given name in this tag set. 
  //! The return value is either a Tag object or an array ({low_tag, 
  //! low_container}), where one element always is zero. 
  { 
    if (Tag tag = tags[name]) return tag; 
    else if (LOW_CONTAINER_TYPE cdef = low_containers && low_containers[name]) 
      return ({0, cdef}); 
    else if (LOW_TAG_TYPE tdef = low_tags && low_tags[name]) 
      return ({tdef, 0}); 
    else return 0; 
  } 
 
  array(Tag) get_local_tags() 
  //! Doesn't return the low tag/container definitions. 
  { 
    return values (tags); 
  } 
 
  Tag|array(LOW_TAG_TYPE|LOW_CONTAINER_TYPE) get_tag (string name) 
  //! Returns the active tag definition for the given name. The return 
  //! value is the same as for get_local_tag(). 
  { 
    if (object(Tag)|array(LOW_TAG_TYPE|LOW_CONTAINER_TYPE) def = get_local_tag (name)) 
      return def; 
    foreach (imported, TagSet tag_set) 
      if (object(Tag) tag = [object(Tag)] tag_set->get_tag (name)) return tag; 
    return 0; 
  } 
 
  Tag|array(LOW_TAG_TYPE|LOW_CONTAINER_TYPE) get_overridden_tag ( 
    Tag|LOW_TAG_TYPE|LOW_CONTAINER_TYPE tagdef, void|string name) 
  //! Returns the tag definition that the given one overrides, or zero 
  //! if none. tag is a Tag object or a low tag/container definition. 
  //! In the latter case, the tag name must be given as the second 
  //! argument. The return value is the same as for get_local_tag(). 
  { 
    if (objectp (tagdef) && ([object] tagdef)->is_RXML_Tag) 
      name = [string] ([object] tagdef)->name; 
#ifdef MODULE_DEBUG 
    if (!name) fatal_error ("Need tag name.\n"); 
#endif 
    if (tags[name] == tagdef || 
        (low_containers && low_containers[name] == tagdef) || 
        (low_tags && low_tags[name] == tagdef)) { 
      foreach (imported, TagSet tag_set) 
        if (object(Tag)|array(LOW_TAG_TYPE|LOW_CONTAINER_TYPE) tagdef = 
            tag_set->get_tag (name)) return tagdef; 
    } 
    else { 
      int found = 0; 
      foreach (imported, TagSet tag_set) 
        if (object(Tag)|array(LOW_TAG_TYPE|LOW_CONTAINER_TYPE) subtag = 
            tag_set->get_tag (name)) 
          if (found) return subtag; 
          else if (arrayp (subtag) ? 
                   subtag[0] == tagdef || subtag[1] == tagdef : 
                   subtag == tagdef) 
            if ((subtag = tag_set->get_overridden_tag (tagdef, name))) 
              return subtag; 
            else found = 1; 
    } 
    return 0; 
  } 
 
  array(Tag|array(LOW_TAG_TYPE|LOW_CONTAINER_TYPE)) get_overridden_tags (string name) 
  //! Returns all tag definitions for the given name, i.e. including 
  //! the overridden ones. A tag to the left overrides one to the 
  //! right. The elements in the returned array are the same as for 
  //! get_local_tag(). 
  { 
    if (object(Tag)|array(LOW_TAG_TYPE|LOW_CONTAINER_TYPE) def = get_local_tag (name)) 
      return ({def}) + imported->get_overridden_tags (name) * ({}); 
    else return imported->get_overridden_tags (name) * ({}); 
  } 
 
  multiset(string) get_tag_names() 
  //! 
  { 
    multiset(string) res = (multiset) indices (tags); 
    if (low_tags) res |= (multiset) indices (low_tags); 
    if (low_containers) res |= (multiset) indices (low_containers); 
    return `| (res, @imported->get_tag_names()); 
  } 
 
  mapping(string:Tag) get_plugins (string name) 
  //! Returns the registered plugins for the given tag name. Don't be 
  //! destructive on the returned mapping. 
  { 
    mapping(string:Tag) res; 
    if ((res = plugins[name])) return res; 
    low_get_plugins (name + "#", res = ([])); 
    return plugins[name] = res; 
  } 
 
  mixed `->= (string var, mixed val) 
  { 
    switch (var) { 
      case "imported": 
        if (!val) return val;   // Pike can call us with 0 as part of an optimization. 
        filter (imported, "dont_notify", changed); 
        imported = [array(TagSet)] val; 
        imported->do_notify (changed); 
        break; 
      default: 
        ::`->= (var, val); 
    } 
    changed(); 
    return val; 
  } 
 
  mixed `[]= (string var, mixed val) {return `->= (var, val);} 
 
  Parser `() (Type top_level_type, void|RequestID id) 
  //! Creates a new context for parsing content of the specified type, 
  //! and returns the parser object for it. id is put into the 
  //! context. 
  { 
    Context ctx = Context (this_object(), id); 
    if (!prepare_funs) prepare_funs = get_prepare_funs(); 
    (prepare_funs -= ({0})) (ctx); 
    return ctx->new_parser (top_level_type); 
  } 
 
  void changed() 
  //! Should be called whenever something is changed. Done 
  //! automatically most of the time, however. 
  { 
    generation++; 
    prepare_funs = 0; 
    plugins = ([]); 
    (notify_funcs -= ({0}))(); 
    set_weak_flag (notify_funcs, 1); 
  } 
 
  // Internals. 
 
  void do_notify (function(:void) func) 
  { 
    notify_funcs |= ({func}); 
    set_weak_flag (notify_funcs, 1); 
  } 
 
  void dont_notify (function(:void) func) 
  { 
    notify_funcs -= ({func}); 
    set_weak_flag (notify_funcs, 1); 
  } 
 
  void destroy() 
  { 
    catch (changed()); 
  } 
 
  static mapping(string:Tag) tags = ([]); 
  // Private since we want to track changes in this. 
 
  static array(function(:void)) notify_funcs = ({}); 
  // Weak (when nonempty). 
 
  static array(function(Context:void)) prepare_funs; 
 
  /*static*/ array(function(Context:void)) get_prepare_funs() 
  { 
    if (prepare_funs) return prepare_funs; 
    array(function(Context:void)) funs = ({}); 
    for (int i = sizeof (imported) - 1; i >= 0; i--) 
      funs += imported[i]->get_prepare_funs(); 
    if (prepare_context) funs += ({prepare_context}); 
    // We don't cache in prepare_funs; do that only at the top level. 
    return funs; 
  } 
 
  void call_prepare_funs (Context ctx) 
  // Kludge function used from rxml.pike. 
  { 
    if (!prepare_funs) prepare_funs = get_prepare_funs(); 
    (prepare_funs -= ({0})) (ctx); 
  } 
 
  static mapping(string:mapping(string:Tag)) plugins = ([]); 
 
  /*static*/ void low_get_plugins (string prefix, mapping(string:Tag) res) 
  { 
    for (int i = sizeof (imported) - 1; i >= 0; i--) 
      imported[i]->low_get_plugins (prefix, res); 
    foreach (indices (tags), string name) 
      if (name[..sizeof (prefix) - 1] == prefix) { 
        Tag tag = tags[name]; 
        if (tag->plugin_name) res[[string] tag->plugin_name] = tag; 
      } 
    // We don't cache in plugins; do that only at the top level. 
  } 
 
  DECLARE_CNT (__count); 
 
  string _sprintf() 
  { 
    return name ? "RXML.TagSet(" + name + COMMA_CNT (__count) + ")" : 
      "RXML.TagSet" + PAREN_CNT (__count); 
  } 
} 
 
TagSet empty_tag_set; 
//! The empty tag set. 
 
 
class Value 
//! Interface for objects used as variable values that are evaluated 
//! when referenced. 
{ 
  mixed rxml_var_eval (Context ctx, string var, string scope_name, void|Type type) 
  //! This is called to get the value of the variable. ctx, var and 
  //! scope_name are set to where this Value object was found. 
  //! 
  //! If the type argument is given, it's the type the returned value 
  //! should have. If the value can't be converted to that type, an 
  //! RXML error should be thrown. If you don't want to do any special 
  //! handling of this, it's enough to call type->convert(value), 
  //! since that function does just that. 
  { 
    mixed val = rxml_const_eval (ctx, var, scope_name, type); 
    ctx->set_var(var, val, scope_name); 
    return val; 
  } 
 
  mixed rxml_const_eval (Context ctx, string var, string scope_name, void|Type type); 
  //! If the variable value is the same throughout the life of the context, 
  //! this method could be used instead of rxml_var_eval. 
 
  string _sprintf() {return "RXML.Value";} 
} 
 
class Scope 
//! Interface for objects that emulates a scope mapping. 
{ 
  mixed `[] (string var, void|Context ctx, void|string scope_name) 
    {parse_error ("Cannot query variable" + _in_the_scope (scope_name) + ".\n");} 
 
  mixed `[]= (string var, mixed val, void|Context ctx, void|string scope_name) 
    {parse_error ("Cannot set variable" + _in_the_scope (scope_name) + ".\n");} 
 
  array(string) _indices (void|Context ctx, void|string scope_name) 
    {parse_error ("Cannot list variables" + _in_the_scope (scope_name) + ".\n");} 
 
  void m_delete (string var, void|Context ctx, void|string scope_name) 
    {parse_error ("Cannot delete variable" + _in_the_scope (scope_name) + ".\n");} 
 
  private string _in_the_scope (string scope_name) 
  { 
    if (scope_name) 
      if (scope_name != "_") return " in the scope " + scope_name; 
      else return " in the current scope"; 
    else return ""; 
  } 
 
  string _sprintf() {return "RXML.Scope";} 
} 
 
#define SCOPE_TYPE mapping(string:mixed)|object(Scope) 
 
class Context 
//! A parser context. This contains the current variable bindings and 
//! so on. The current context can always be retrieved with 
//! get_context(). 
//! 
//! Note: Don't store pointers to this object since that will likely 
//! introduce circular references. It can be retrieved easily through 
//! get_context() or parser->context. 
{ 
  Frame frame; 
  //! The currently evaluating frame. 
 
  int frame_depth; 
  //! Number of frames currently on the frame stack. 
 
  int max_frame_depth = 100; 
  //! Maximum number of frames allowed on the frame stack. 
 
  RequestID id; 
  //! 
 
  int type_check; 
  //! Whether to do type checking. 
 
  int error_count; 
  //! Number of RXML errors that has occurred. 
 
  TagSet tag_set; 
  //! The current tag set that will be inherited by subparsers. 
 
  int tag_set_is_local; 
  //! Nonzero if tag_set is a copy local to this context. A local tag 
  //! set that imports the old tag set is created whenever need be. 
 
#ifdef OLD_RXML_COMPAT 
  int compatible_scope = 0; 
  //! If set, the default scope is form, otherwise it is the present 
  //! scope. 
#endif 
 
  array parse_user_var (string var, void|string scope_name) 
  //! Tries to decide what variable and scope to use. Handles cases 
  //! where the variable also contains the scope, e.g. "scope.var". 
  { 
    if(!var || !sizeof(var)) return ([])[0]; 
    array(string) splitted=var/"."; 
    if(sizeof(splitted)>2) splitted[-1] = splitted[1..]*"."; 
    if(sizeof(splitted)==2) 
      scope_name=splitted[0]; 
#ifdef OLD_RXML_COMPAT 
    else if (compatible_scope) 
      scope_name = scope_name || "form"; 
#endif 
    return ({ scope_name, splitted[-1] }); 
  } 
 
  local mixed get_var (string var, void|string scope_name, void|Type want_type) 
  //! Returns the value a variable in the specified scope, or the 
  //! current scope if none is given. Returns zero with zero_type 1 if 
  //! there's no such variable. 
  //! 
  //! If the type argument is set, the value is converted to that type 
  //! with Type.convert(). If the value can't be converted, an RXML 
  //! error is thrown. 
  { 
    if (SCOPE_TYPE vars = scopes[scope_name || "_"]) { 
      mixed val; 
      if (objectp (vars)) { 
        if (zero_type (val = ([object(Scope)] vars)->`[] ( 
                         var, this_object(), scope_name || "_")) || 
            val == Void) 
          return ([])[0]; 
      } 
      else 
        if (zero_type (val = vars[var])) 
          return ([])[0]; 
      if (objectp (val) && ([object] val)->rxml_var_eval) { 
        return 
          zero_type (val = ([object(Value)] val)->rxml_var_eval ( 
                       this_object(), var, scope_name || "_", want_type)) || 
          val == Void ? ([])[0] : val; 
      } 
      else 
        if (want_type) 
          return 
            // FIXME: Some system to find out the source type? 
            zero_type (val = want_type->convert (val)) || 
            val == Void ? ([])[0] : val; 
        else 
          return val; 
    } 
    else if ((<0, "_">)[scope_name]) parse_error ("No current scope.\n"); 
    else parse_error ("Unknown scope %O.\n", scope_name); 
  } 
 
  mixed user_get_var (string var, void|string scope_name, void|Type want_type) 
  //! As get_var, but can handle cases where the variable also 
  //! contains the scope, e.g. "scope.var". 
  { 
    if(!var || !sizeof(var)) return ([])[0]; 
    array(string) splitted=var/"."; 
    if(sizeof(splitted)>2) splitted[-1] = splitted[1..]*"."; 
    if(sizeof(splitted)==2) 
      scope_name=splitted[0]; 
#ifdef OLD_RXML_COMPAT 
    else if (compatible_scope) 
      scope_name = scope_name || "form"; 
#endif 
    return get_var(splitted[-1], scope_name, want_type); 
  } 
 
  local mixed set_var (string var, mixed val, void|string scope_name) 
  //! Sets the value of a variable in the specified scope, or the 
  //! current scope if none is given. Returns val. 
  { 
    if (SCOPE_TYPE vars = scopes[scope_name || "_"]) 
      if (objectp (vars)) 
        return ([object(Scope)] vars)->`[]= (var, val, this_object(), scope_name || "_"); 
      else 
        return vars[var] = val; 
    else if ((<0, "_">)[scope_name]) parse_error ("No current scope.\n"); 
    else parse_error ("Unknown scope %O.\n", scope_name); 
  } 
 
  mixed user_set_var (string var, mixed val, void|string scope_name) 
  //! As set_var, but can handle cases where the variable also 
  //! contains the scope, e.g. "scope.var". 
  { 
    if(!var || !sizeof(var)) parse_error ("No variable specified.\n"); 
    array(string) splitted=var/"."; 
    if(sizeof(splitted)>2) splitted[-1] = splitted[1..]*"."; 
    if(sizeof(splitted)==2) 
      scope_name=splitted[0]; 
#ifdef OLD_RXML_COMPAT 
    else if (compatible_scope) 
      scope_name = scope_name || "form"; 
#endif 
    return set_var(splitted[-1], val, scope_name); 
  } 
 
  local void delete_var (string var, void|string scope_name) 
  //! Removes a variable in the specified scope, or the current scope 
  //! if none is given. 
  { 
    if (SCOPE_TYPE vars = scopes[scope_name || "_"]) 
      if (objectp (vars)) 
        ([object(Scope)] vars)->m_delete (var, this_object(), scope_name || "_"); 
      else 
        m_delete ([mapping(string:mixed)] vars, var); 
    else if ((<0, "_">)[scope_name]) parse_error ("No current scope.\n"); 
    else parse_error ("Unknown scope %O.\n", scope_name); 
  } 
 
  void user_delete_var (string var, void|string scope_name) 
  //! As delete_var, but can handle cases where the variable also 
  //! contains the scope, e.g. "scope.var". 
  { 
    if(!var || !sizeof(var)) return; 
    array(string) splitted=var/"."; 
    if(sizeof(splitted)>2) splitted[-1] = splitted[1..]*"."; 
    if(sizeof(splitted)==2) 
      scope_name=splitted[0]; 
#ifdef OLD_RXML_COMPAT 
    else if (compatible_scope) 
      scope_name = scope_name || "form"; 
#endif 
    delete_var(splitted[-1], scope_name); 
  } 
 
  array(string) list_var (void|string scope_name) 
  //! Returns the names of all variables in the specified scope, or 
  //! the current scope if none is given. 
  { 
    if (SCOPE_TYPE vars = scopes[scope_name || "_"]) 
      if (objectp (vars)) 
        return ([object(Scope)] vars)->_indices (this_object(), scope_name || "_"); 
      else 
        return indices ([mapping(string:mixed)] vars); 
    else if ((<0, "_">)[scope_name]) parse_error ("No current scope.\n"); 
    else parse_error ("Unknown scope %O.\n", scope_name); 
  } 
 
  array(string) list_scopes() 
  //! Returns the names of all defined scopes. 
  { 
    return indices (scopes) - ({"_"}); 
  } 
 
  int exist_scope (void|string scope_name) 
  //! 
  { 
    return !!scopes[scope_name || "_"]; 
  } 
 
  void add_scope (string scope_name, SCOPE_TYPE vars) 
  //! Adds or replaces the specified scope at the global level. A 
  //! scope can be a mapping or a Scope object. A global "_" scope may 
  //! also be defined this way. 
  { 
    if (scopes[scope_name]) 
      if (scope_name == "_") { 
        array(SCOPE_TYPE) hid; 
        for (Frame f = frame; f; f = f->up) 
          if (array(SCOPE_TYPE) h = hidden[f]) hid = h; 
        if (hid) hid[0] = vars; 
        else scopes["_"] = vars; 
      } 
      else { 
        Frame outermost; 
        for (Frame f = frame; f; f = f->up) 
          if (f->scope_name == scope_name) outermost = f; 
        if (outermost) hidden[outermost][1] = vars; 
        else scopes[scope_name] = vars; 
      } 
    else scopes[scope_name] = vars; 
  } 
 
  int extend_scope (string scope_name, SCOPE_TYPE vars) 
  //! Adds or extends the specified scope at the global level. 
  //! Returns 1 on success and 0 on failure. 
  { 
    if (scopes[scope_name]) { 
      SCOPE_TYPE oldvars; 
      if (scope_name == "_") { 
        array(SCOPE_TYPE) hid; 
        for (Frame f = frame; f; f = f->up) 
          if (array(SCOPE_TYPE) h = hidden[f]) hid = h; 
        if (hid) oldvars = hid[0]; 
        else oldvars = scopes["_"]; 
      } 
      else { 
        Frame outermost; 
        for (Frame f = frame; f; f = f->up) 
          if (f->scope_name == scope_name) outermost = f; 
        if (outermost) oldvars = hidden[outermost][1]; 
        else oldvars = scopes[scope_name]; 
      } 
#ifdef DEBUG 
      if (!oldvars) fatal_error ("Internal error: I before e except after c.\n"); 
#endif 
      if (!mappingp(vars)) { 
        return 0; 
      } 
      foreach (indices(vars), string var) 
        set_var(var, vars[var], scope_name); 
    } 
    else scopes[scope_name] = vars; 
    return 1; 
  } 
 
  void remove_scope (string scope_name) 
  //! Removes the named scope from the global level, if it exists. 
  { 
#ifdef MODULE_DEBUG 
    if (scope_name == "_") fatal_error ("Cannot remove current scope.\n"); 
#endif 
    Frame outermost; 
    for (Frame f = frame; f; f = f->up) 
      if (f->scope_name == scope_name) outermost = f; 
    if (outermost) m_delete (hidden, outermost); 
    else m_delete (scopes, scope_name); 
  } 
 
  string current_scope() 
  //! Returns the name of the current scope, if it has any. 
  { 
    if (SCOPE_TYPE vars = scopes["_"]) { 
      string scope_name; 
      while (scope_name = search (scopes, vars, scope_name)) 
        if (scope_name != "_") return scope_name; 
    } 
    return 0; 
  } 
 
  void add_runtime_tag (Tag tag) 
  //! Adds a tag that will exist from this point forward in the 
  //! current context only. 
  { 
    if (!new_runtime_tags) new_runtime_tags = NewRuntimeTags(); 
    new_runtime_tags->add_tags[tag] = 1; 
    // By doing the following, we can let remove_tags take precedence. 
    new_runtime_tags->remove_tags[tag] = 0; 
    new_runtime_tags->remove_tags[tag->name] = 0; 
  } 
 
  void remove_runtime_tag (string|Tag tag) 
  //! Removes a tag added by add_runtime_tag(). If a string is given, 
  //! it's assumed to be a tag name without prefix. 
  { 
    if (!new_runtime_tags) new_runtime_tags = NewRuntimeTags(); 
    new_runtime_tags->remove_tags[tag] = 1; 
  } 
 
  multiset(Tag) get_runtime_tags() 
  //! Returns all currently active runtime tags. Don't be destructive 
  //! on the returned multiset. 
  { 
    multiset(Tag) tags = runtime_tags; 
    if (new_runtime_tags) { 
      tags |= new_runtime_tags->add_tags; 
      tags -= new_runtime_tags->remove_tags; 
    } 
    return tags; 
  } 
 
  void handle_exception (mixed err, PCode|Parser evaluator) 
  //! This function gets any exception that is catched during 
  //! evaluation. evaluator is the object that catched the error. 
  { 
    error_count++; 
    if (objectp (err) && err->is_RXML_Backtrace) { 
      string msg; 
      for (object(PCode)|object(Parser) e = evaluator->_parent; e; e = e->_parent) 
        e->error_count++; 
      if (id && id->conf) 
        while (evaluator) { 
          if (evaluator->report_error && evaluator->type->free_text) { 
            string msg = (err->type == "run" ? 
                          ([function(Backtrace,Type:string)] 
                           ([object] id->conf)->handle_run_error) : 
                          ([function(Backtrace,Type:string)] 
                           ([object] id->conf)->handle_parse_error) 
                         ) ([object(Backtrace)] err, evaluator->type); 
            if (evaluator->report_error (msg)) 
              break; 
          } 
          evaluator = evaluator->_parent; 
        } 
      else { 
#ifdef MODULE_DEBUG 
      report_notice (describe_backtrace (err)); 
#else 
      report_notice (err->msg); 
#endif 
      } 
    } 
    else throw_fatal (err); 
  } 
 
  // Internals. 
 
  string current_var; 
  // Used to get the parsed variable into the RXML error backtrace. 
 
  Parser new_parser (Type top_level_type) 
  // Returns a new parser object to start parsing with this context. 
  // Normally TagSet.`() should be used instead of this. 
  { 
#ifdef MODULE_DEBUG 
    if (in_use || frame) fatal_error ("Context already in use.\n"); 
#endif 
    return top_level_type->get_parser (this_object()); 
  } 
 
  mapping(string:SCOPE_TYPE) scopes = ([]); 
  // The variable mappings for every currently visible scope. A 
  // special entry "_" points to the current local scope. 
 
  mapping(Frame:array(SCOPE_TYPE)) hidden = ([]); 
  // The currently hidden scopes. The indices are frame objects which 
  // introduce scopes. The values are tuples of the current scope and 
  // the named scope they hide. 
 
  void enter_scope (Frame frame) 
  { 
#ifdef DEBUG 
    if (!frame->vars) fatal_error ("Internal error: Frame has no variables.\n"); 
#endif 
    if (string scope_name = [string] frame->scope_name) { 
      if (!hidden[frame]) 
        hidden[frame] = ({scopes["_"], scopes[scope_name]}); 
      scopes["_"] = scopes[scope_name] = [SCOPE_TYPE] frame->vars; 
    } 
    else { 
      if (!hidden[frame]) 
        hidden[frame] = ({scopes["_"], 0}); 
      scopes["_"] = [SCOPE_TYPE] frame->vars; 
    } 
  } 
 
  void leave_scope (Frame frame) 
  { 
    if (array(SCOPE_TYPE) back = hidden[frame]) { 
      if (SCOPE_TYPE cur = back[0]) scopes["_"] = cur; 
      else m_delete (scopes, "_"); 
      if (SCOPE_TYPE named = back[1]) { 
#ifdef MODULE_DEBUG 
      if (!stringp (frame->scope_name)) 
          fatal_error ("Scope named changed to %O during parsing.\n", frame->scope_name); 
#endif 
      scopes[[string] frame->scope_name] = named; 
      } 
      else m_delete (scopes, [string] frame->scope_name); 
      m_delete (hidden, frame); 
    } 
  } 
 
#define ENTER_SCOPE(ctx, frame) (frame->vars && ctx->enter_scope (frame)) 
#define LEAVE_SCOPE(ctx, frame) (frame->vars && ctx->leave_scope (frame)) 
 
  void make_tag_set_local() 
  { 
    if (!tag_set_is_local) { 
      TagSet new_tag_set = TagSet (tag_set->name + " (local)"); // FIXME: Cache this? 
      new_tag_set->imported = ({tag_set}); 
      tag_set = new_tag_set; 
      tag_set_is_local = 1; 
    } 
  } 
 
  multiset(Tag) runtime_tags = (<>); 
 
  class NewRuntimeTags 
  { 
    multiset(Tag) add_tags = (<>); 
    multiset(Tag|string) remove_tags = (<>); 
  } 
  NewRuntimeTags new_runtime_tags; 
  // Used to record the result of any add_runtime_tag() and 
  // remove_runtime_tag() calls since the last time the parsers ran. 
 
  void create (TagSet _tag_set, void|RequestID _id) 
  // Normally TagSet.`() should be used instead of this. 
  { 
    tag_set = _tag_set; 
    id = _id; 
  } 
 
  mapping(string:mixed)|mapping(object:array) unwind_state; 
  // If this is a mapping, we have an unwound stack state. It contains 
  // strings with arbitrary exception info, and the objects being 
  // unwound with arrays containing the extra state info they need. 
  // The first entry in these arrays are always the subobject. The 
  // special entries are: 
  // 
  // "top": ({Frame|Parser|PCode (top object)}) 
  // "stream_piece": mixed (When continuing, do a streaming 
  //  do_return() with this stream piece.) 
  // "exec_left": array (Exec array left to evaluate. Only used 
  //  between Frame._exec_array() and Frame._eval().) 
 
  DECLARE_CNT (__count); 
 
  string _sprintf() {return "RXML.Context" + PAREN_CNT (__count);} 
 
#ifdef MODULE_DEBUG 
#if constant (thread_create) 
  Thread.Thread in_use; 
#else 
  int in_use; 
#endif 
#endif 
} 
 
class Backtrace 
//! The object used to throw RXML errors. 
{ 
  constant is_generic_error = 1; 
  constant is_RXML_Backtrace = 1; 
 
  string type;                      // Currently "run" or "parse". 
  string msg; 
  Context context; 
  Frame frame; 
  string current_var; 
  array backtrace; 
 
  void create (string _type, string _msg, void|Context _context) 
  { 
    type = _type; 
    msg = _msg; 
    if (context = _context || get_context()) { 
      frame = context->frame; 
      current_var = context->current_var; 
    } 
    backtrace = predef::backtrace(); 
    backtrace = backtrace[..sizeof (backtrace) - 2]; 
  } 
 
  string describe_rxml_backtrace (void|int no_msg) 
  //! Returns a formatted RXML frame backtrace. 
  { 
    string txt = no_msg ? "" : "RXML " + type + " error"; 
    if (context) { 
      if (!no_msg) txt += ": " + (msg || "(no error message)\n"); 
      txt += current_var ? " | &" + current_var + ";\n" : ""; 
      for (Frame f = frame; f; f = f->up) { 
        if (f->tag) txt += " | <" + f->tag->name; 
        else if (!f->up) break; 
        else txt += " | <(unknown tag)"; 
        if (f->args) 
          foreach (sort (indices (f->args)), string arg) { 
            mixed val = f->args[arg]; 
            txt += " " + arg + "="; 
            if (arrayp (val)) txt += map (val, error_print_val) * ","; 
            else txt += error_print_val (val); 
          } 
        else txt += " (no argmap)"; 
        txt += ">\n"; 
      } 
    } 
    else 
      if (!no_msg) txt += " (no context): " + (msg || "(no error message)\n"); 
    return txt; 
  } 
 
  private string error_print_val (mixed val) 
  { 
    if (arrayp (val)) return "array"; 
    else if (mappingp (val)) return "mapping"; 
    else if (multisetp (val)) return "multiset"; 
    else return sprintf ("%O", val); 
  } 
 
  string|array `[] (int i) 
  { 
    switch (i) { 
      case 0: return describe_rxml_backtrace(); 
      case 1: return backtrace; 
    } 
  } 
 
  string _sprintf() {return "RXML.Backtrace(" + type + ")";} 
} 
 
 
//! Current context. 
 
//! It's set before any function in RXML.Tag or RXML.Frame is called. 
 
#if constant (thread_create) 
private Thread.Local _context = thread_local(); 
inline void set_context (Context ctx) {_context->set (ctx);} 
inline Context get_context() {return [object(Context)] _context->get();} 
#else 
private Context _context; 
inline void set_context (Context ctx) {_context = ctx;} 
inline Context get_context() {return _context;} 
#endif 
 
#if defined (MODULE_DEBUG) && constant (thread_create) 
 
// Got races in this debug check, but looks like we have to live with that. :\ 
 
#define ENTER_CONTEXT(ctx)                                            \ 
  Context __old_ctx = get_context();                                    \ 
  set_context (ctx);                                                    \ 
  if (ctx) {                                                            \ 
    if (ctx->in_use && ctx->in_use != this_thread())                    \ 
      fatal_error ("Attempt to use context asynchronously.\n");         \ 
    ctx->in_use = this_thread();                                        \ 
  } 
 
#define LEAVE_CONTEXT()                                                       \ 
  if (Context ctx = get_context())                                      \ 
    if (__old_ctx != ctx) ctx->in_use = 0;                              \ 
  set_context (__old_ctx); 
 
#else 
 
#define ENTER_CONTEXT(ctx)                                            \ 
  Context __old_ctx = get_context();                                    \ 
  set_context (ctx); 
 
#define LEAVE_CONTEXT()                                                       \ 
  set_context (__old_ctx); 
 
#endif 
 
 
//! Constants for the bit field RXML.Frame.flags. 
 
constant FLAG_NONE          = 0x00000000; 
//! The no-flags flag. In case you think 0 is too ugly. ;) 
 
//! Static flags (i.e. tested in the Tag object). 
 
constant FLAG_EMPTY_ELEMENT = 0x00000001; 
//! If set, the tag does not use any content. E.g. with a HTML parser 
//! this defines whether the tag is a container or not, and in XML 
//! parsing it simply causes the content (if any) to be thrown away. 
 
constant FLAG_NO_PREFIX             = 0x00000002; 
//! Never apply any prefix to this tag. 
 
constant FLAG_SOCKET_TAG    = 0x00000004; 
//! Declare the tag to be a socket tag, which accepts plugin tags (see 
//! Tag.plugin_name for details). 
 
constant FLAG_DONT_PREPARSE = 0x00000040; 
//! Don't preparse the content with the PXml parser. This is only used 
//! in the simple tag wrapper. Defined here as placeholder. 
 
constant FLAG_POSTPARSE             = 0x00000080; 
//! Postparse the result with the PXml parser. This is only used in 
//! the simple tag wrapper. Defined here as placeholder. 
 
//! The rest of the flags are dynamic (i.e. tested in the Frame object). 
 
constant FLAG_PARENT_SCOPE  = 0x00000100; 
//! If set, the array from do_enter(), do_return() and cached_return() 
//! will be interpreted in the scope of the parent tag, rather than in 
//! the current one. 
 
constant FLAG_NO_IMPLICIT_ARGS      = 0x00000200; 
//! If set, the parser won't apply any implicit arguments. FIXME: Not 
//! yet implemented. 
 
constant FLAG_STREAM_RESULT = 0x00000400; 
//! If set, the do_return() function will be called repeatedly until 
//! it returns 0 or no more content is wanted. 
 
constant FLAG_STREAM_CONTENT        = 0x00000800; 
//! If set, the tag supports getting its content in streaming mode: 
//! do_return() will be called repeatedly with successive parts of the 
//! content then. Can't be changed from do_return(). 
 
//! Note: It might be obvious, but using streaming is significantly 
//! less effective than nonstreaming, so it should only be done when 
//! big delays are expected. 
 
constant FLAG_STREAM                = FLAG_STREAM_RESULT | FLAG_STREAM_CONTENT; 
 
constant FLAG_UNPARSED              = 0x00001000; 
//! If set, args and content in the frame contain unparsed strings. 
//! The frame will be parsed before it's evaluated. This flag should 
//! never be set in Tag.flags, but it's useful when creating frames 
//! directly. 
 
//! The following flags specifies whether certain conditions must be 
//! met for a cached frame to be considered (if RXML.Frame.is_valid() 
//! is defined). They may be read directly after do_return() returns. 
//! The tag name is always the same. FIXME: These are ideas only; not 
//! yet implemented. 
 
constant FLAG_CACHE_DIFF_ARGS       = 0x00010000; 
//! If set, the arguments to the tag need not be the same (using 
//! equal()) as the cached args. 
 
constant FLAG_CACHE_DIFF_CONTENT = 0x00020000; 
//! If set, the content need not be the same. 
 
constant FLAG_CACHE_DIFF_RESULT_TYPE = 0x00040000; 
//! If set, the result type need not be the same. (Typically 
//! not useful unless cached_return() is used.) 
 
constant FLAG_CACHE_DIFF_VARS       = 0x00080000; 
//! If set, the variables with external scope in vars (i.e. normally 
//! those that has been accessed with get_var()) need not have the 
//! same values (using equal()) as the actual variables. 
 
constant FLAG_CACHE_SAME_STACK      = 0x00100000; 
//! If set, the stack of call frames needs to be the same. 
 
constant FLAG_CACHE_EXECUTE_RESULT = 0x00200000; 
//! If set, an array to execute will be stored in the frame instead of 
//! the final result. On a cache hit it'll be executed like the return 
//! value from do_return() to produce the result. 
 
class Frame 
//! A tag instance. 
{ 
  constant is_RXML_Frame = 1; 
  constant thrown_at_unwind = 1; 
 
  //! Interface. 
 
  Frame up; 
  //! The parent frame. This frame is either created from the content 
  //! inside the up frame, or it's in the array returned from 
  //! do_return() in the up frame. 
 
  Tag tag; 
  //! The RXML.Tag object this frame was created from. 
 
  int flags; 
  //! Various bit flags that affect parsing. See the FLAG_* constants. 
 
  mapping(string:mixed) args; 
  //! The arguments passed to the tag. Set before 
  //! do_enter()/do_return() are called. 
 
  Type content_type; 
  //! The type of the content. 
 
  mixed content = Void; 
  //! The content. Set before do_return() is called, but only when the 
  //! tag is actually used with container syntax. 
 
  Type result_type; 
  //! The required result type. Set before do_enter()/do_return() are 
  //! called. do_return() should produce a result of this type. 
 
  mixed result = Void; 
  //! The result. 
 
  //!mapping(string:mixed) vars; 
  //! Set this to introduce a new variable scope that will be active 
  //! during parsing of the content and return values (but see also 
  //! FLAG_PARENT_SCOPE). 
 
  //!string scope_name; 
  //! The scope name for the variables. Must be set before the scope 
  //! is used for the first time, and can't be changed after that. 
 
  //!TagSet additional_tags; 
  //! If set, the tags in this tag set will be used in addition to the 
  //! tags inherited from the surrounding parser. The additional tags 
  //! will in turn be inherited by subparsers. 
 
  //!TagSet local_tags; 
  //! If set, the tags in this tag set will be used in the parser for 
  //! the content, instead of the one inherited from the surrounding 
  //! parser. The tags are not inherited by subparsers. 
 
  //!array do_enter (RequestID id); 
  //!array do_return (RequestID id, void|mixed piece); 
  //! do_enter() is called first thing when processing the tag. 
  //! do_return() is called after the content (if any) is processed. 
  //! 
  //! For tags that loops more than one time (see do_iterate): 
  //! do_enter() is only called initially before the first call to 
  //! do_iterate(). do_return() is called after each iteration. 
  //! 
  //! The result_type variable is set to the type of result the parser 
  //! wants. It's any type or subtype that is valid by 
  //! tag->result_type. If the result type is sequential, it's spliced 
  //! into the surrounding content, otherwise it replaces the previous 
  //! value of the content, if any. If the result is Void, it does not 
  //! affect the surrounding content at all. 
  //! 
  //! Return values: 
  //! 
  //! array - A so-called execution array to be handled by the 
  //!         parser. The elements are processed in order, and have 
  //!         the following usage: 
  //! 
  //! string - Added or put into the result. If the result type has 
  //!         a parser, the string will be parsed with it before 
  //!         it's assigned to the result variable and passed on. 
  //! RXML.Frame - Already initialized frame to process. Neither 
  //!         arguments nor content will be parsed. It's result is 
  //!         added or put into the result of this tag. 
  //! mapping(string:mixed) - Fields to merge into the headers. 
  //!         FIXME: Not yet implemented. FIXME: Somehow represent 
  //!         removal of headers? 
  //! object - Treated as a file object to read in blocking or 
  //!         nonblocking mode. FIXME: Not yet implemented, details 
  //!         not decided. 
  //! multiset(mixed) - Should only contain one element that'll be 
  //!         added or put into the result. Normally not necessary; 
  //!         assign it directly to the result variable instead. 
  //! 
  //! 0 -     Do nothing special. Exits the tag when used from 
  //!         do_return() and FLAG_STREAM_RESULT is set. 
  //! 
  //! Note that the intended use is not to postparse by setting a 
  //! parser on the result type, but instead to return an array with 
  //! literal strings and RXML.Frame objects where parsing (or, more 
  //! accurately, evaluation) needs to be done. 
  //! 
  //! If an array instead of a function is given, the array is handled 
  //! as above. If do_return is zero, the value in the result variable 
  //! is simply used. If the result variable is Void, content is used 
  //! as result if it's of a compatible type. 
  //! 
  //! Regarding do_return only: 
  //! 
  //! Normally the content variable is set to the parsed content of 
  //! the tag before do_return() is called. This may be Void if the 
  //! content parsing didn't produce any result. 
  //! 
  //! If the result from parsing the content is not Void, it's 
  //! assigned to or added to the content variable. Assignment is used 
  //! if the content type is nonsequential, addition otherwise. Thus 
  //! earlier values are simply overridden for nonsequential types. 
  //! 
  //! piece is used when the tag is operating in streaming mode (i.e. 
  //! FLAG_STREAM_CONTENT is set). It's then set to each successive 
  //! part of the content in the stream, and the content variable is 
  //! never touched. do_return() is also called "normally" with no 
  //! piece argument afterwards. Note that tags that support streaming 
  //! mode might still be used nonstreaming (it might also vary 
  //! between iterations). 
  //! 
  //! As long as FLAG_STREAM_RESULT is set, do_return() will be called 
  //! repeatedly until it returns 0. It's only the result piece from 
  //! the execution array that is propagated after each turn; the 
  //! result variable only accumulates all these pieces. 
 
  //!int do_iterate (RequestID id); 
  //! Controls the number of passes in the tag done by the parser. In 
  //! every pass, the content of the tag (if any) is processed, then 
  //! do_return() is called. 
  //! 
  //! Before doing any pass, do_iterate() is called. If the return 
  //! value is nonzero, that many passes is done, then do_iterate() is 
  //! called again and the process repeats. If the return value is 
  //! zero, the tag exits and the value in result is used in the 
  //! surrounding content as described above. 
  //! 
  //! The most common way to iterate is to do the setup before every 
  //! pass (e.g. setup the variable scope) and return 1 to do one pass 
  //! through the content. This will repeat until 0 is returned. 
  //! 
  //! If do_iterate is a positive integer, that many passes is done 
  //! and then the tag exits. If do_iterate is zero no pass is done. 
  //! If do_iterate is missing, one pass is done. 
 
  //!int|function(RequestID:int) is_valid; 
  //! When defined, the frame may be cached. First the name of the tag 
  //! must be the same. Then the conditions specified by the cache 
  //! bits in flag are checked. Then, if this is a function, it's 
  //! called. If it returns 1, the frame is reused. FIXME: Not yet 
  //! implemented. 
 
  optional array cached_return (Context ctx, void|mixed piece); 
  //! If defined, this will be called to get the value from a cached 
  //! frame (that's still valid) instead of using the cached result. 
  //! It's otherwise handled like do_return(). Note that the cached 
  //! frame may be used from several threads. FIXME: Not yet 
  //! implemented. 
 
  //! Services. 
 
  local mixed get_var (string var, void|string scope_name, void|Type want_type) 
  //! A wrapper for easy access to RXML.Context.get_var(). 
  { 
    return get_context()->get_var (var, scope_name, want_type); 
  } 
 
  local mixed set_var (string var, mixed val, void|string scope_name) 
  //! A wrapper for easy access to RXML.Context.set_var(). 
  { 
    return get_context()->set_var (var, val, scope_name); 
  } 
 
  local void delete_var (string var, void|string scope_name) 
  //! A wrapper for easy access to RXML.Context.delete_var(). 
  { 
    get_context()->delete_var (var, scope_name); 
  } 
 
  void run_error (string msg, mixed... args) 
  //! A wrapper for easy access to RXML.run_error(). 
  { 
    _run_error (msg, @args); 
  } 
 
  void parse_error (string msg, mixed... args) 
  //! A wrapper for easy access to RXML.parse_error(). 
  { 
    _parse_error (msg, @args); 
  } 
 
  void terminate() 
  //! Makes the parser abort. The data parsed so far will be returned. 
  //! Does not return; throws a special exception instead. 
  { 
    fatal_error ("FIXME\n"); 
  } 
 
  void suspend() 
  //! Used together with resume() for nonblocking mode. May be called 
  //! from do_enter() or do_return() to suspend the parser: The parser 
  //! will just stop, leaving the context intact. If it returns, the 
  //! parser is used in a place that doesn't support nonblocking, so 
  //! just go ahead and block. 
  { 
    fatal_error ("FIXME\n"); 
  } 
 
  void resume() 
  //! Makes the parser continue where it left off. The function that 
  //! called suspend() will be called again. 
  { 
    fatal_error ("FIXME\n"); 
  } 
 
  mapping(string:Tag) get_plugins() 
  //! Returns the plugins registered for this tag, which is assumed to 
  //! be a socket tag, i.e. to have FLAG_SOCKET_TAG set (see 
  //! Tag.plugin_name for details). Indices are the plugin_name values 
  //! for the plugin Tag objects, values are the plugin objects 
  //! themselves. Don't be destructive on the returned mapping. 
  { 
#ifdef MODULE_DEBUG 
    if (!(flags & FLAG_SOCKET_TAG)) 
      fatal_error ("This tag is not a socket tag.\n"); 
#endif 
    return get_context()->tag_set->get_plugins (tag->name); 
  } 
 
  // Internals. 
 
  mixed _exec_array (TagSetParser parser, array exec, int parent_scope) 
  { 
    Frame this = this_object(); 
    Context ctx = parser->context; 
    int i = 0; 
    mixed res = Void; 
    Parser subparser = 0; 
 
    mixed err = catch { 
      if (parent_scope) LEAVE_SCOPE (ctx, this); 
 
      for (; i < sizeof (exec); i++) { 
        mixed elem = exec[i], piece = Void; 
 
        switch (sprintf ("%t", elem)) { 
          case "string": 
            if (result_type->_parser_prog == PNone) 
              piece = elem; 
            else { 
              subparser = result_type->get_parser (ctx, 0, parser); 
              subparser->finish ([string] elem); // Might unwind. 
              piece = subparser->eval(); // Might unwind. 
              subparser = 0; 
            } 
            break; 
          case "mapping": 
            fatal_error ("Header mappings not yet implemented.\n"); 
            break; 
          case "multiset": 
            if (sizeof ([multiset] elem) == 1) piece = ((array) elem)[0]; 
            else if (sizeof ([multiset] elem) > 1) 
              fatal_error (sizeof ([multiset] elem) + 
                           " values in multiset in exec array.\n"); 
            else fatal_error ("No value in multiset in exec array.\n"); 
            break; 
          default: 
            if (objectp (elem)) 
              // Can't count on that sprintf ("%t", ...) on an object 
              // returns "object". 
              if (([object] elem)->is_RXML_Frame) { 
                ([object(Frame)] elem)->_eval (parser); // Might unwind. 
                piece = ([object(Frame)] elem)->result; 
              } 
              else if (([object] elem)->is_RXML_Parser) { 
                // The subparser above unwound. 
                ([object(Parser)] elem)->finish(); // Might unwind. 
                piece = ([object(Parser)] elem)->eval(); // Might unwind. 
              } 
              else 
                fatal_error ("File objects not yet implemented.\n"); 
            else 
              fatal_error ("Invalid type %t in exec array.\n", elem); 
        } 
 
        if (result_type->sequential) res += piece; 
        else if (piece != Void) result = res = piece; 
      } 
 
      if (result_type->sequential) result += res; 
      if (parent_scope) ENTER_SCOPE (ctx, this); 
      return res; 
    }; 
 
    if (parent_scope) ENTER_SCOPE (ctx, this); 
    if (result_type->sequential) result += res; 
 
    if (objectp (err) && ([object] err)->thrown_at_unwind) { 
      mapping(string:mixed)|mapping(object:array) ustate; 
      if ((ustate = ctx->unwind_state) && !zero_type (ustate->stream_piece)) 
        // Subframe wants to stream. Update stream_piece and send it on. 
        if (result_type->quoting_scheme != parser->type->quoting_scheme) 
          res = parser->type->quote (res); 
        if (result_type->sequential) 
          ustate->stream_piece = res + ustate->stream_piece; 
        else if (ustate->stream_piece == Void) 
          ustate->stream_piece = res; 
      ustate->exec_left = exec[i..]; // Left to execute. 
      if (subparser) 
        // Replace the string with the subparser object so that we'll 
        // continue in it later. It's done here to keep the original 
        // exec array untouched. 
        ([array] ustate->exec_left)[0] = subparser; 
      throw (err); 
    } 
    throw_fatal (err); 
  } 
 
  private void _handle_runtime_tags (Context ctx, TagSetParser parser) 
  { 
    // FIXME: PCode handling. 
    multiset(string|Tag) rem_tags = ctx->new_runtime_tags->remove_tags; 
    multiset(Tag) add_tags = ctx->new_runtime_tags->add_tags - rem_tags; 
    if (sizeof (rem_tags)) 
      foreach (indices (add_tags), Tag tag) 
        if (rem_tags[tag->name]) add_tags[tag] = 0; 
    array(string|Tag) arr_rem_tags = (array) rem_tags; 
    array(Tag) arr_add_tags = (array) add_tags; 
    for (Parser p = parser; p; p = p->_parent) 
      if (p->tag_set_eval && !p->_local_tag_set && p->add_runtime_tag) { 
        foreach (arr_add_tags, Tag tag) 
          ([object(TagSetParser)] p)->add_runtime_tag (tag); 
        foreach (arr_rem_tags, string|object(Tag) tag) 
          ([object(TagSetParser)] p)->remove_runtime_tag (tag); 
      } 
    ctx->runtime_tags |= add_tags; 
    ctx->runtime_tags -= rem_tags; 
    ctx->new_runtime_tags = 0; 
  } 
 
  void _eval (TagSetParser parser, 
              void|mapping(string:string) raw_args, 
              void|string raw_content) 
  // Note: It might be somewhat tricky to override this function. 
  { 
    Frame this = this_object(); 
    Context ctx = parser->context; 
 
    // Unwind state data: 
    //raw_content 
#define EVSTAT_BEGIN 0 
#define EVSTAT_ENTERED 1 
#define EVSTAT_LAST_ITER 2 
#define EVSTAT_ITER_DONE 3 
    int eval_state = EVSTAT_BEGIN; 
    int iter; 
    Parser subparser; 
    mixed piece; 
    array exec; 
    int tags_added;         // Flag that we added additional_tags to ctx->tag_set. 
    //ctx->new_runtime_tags 
 
#define PRE_INIT_ERROR(X) (ctx->frame = this, fatal_error (X)) 
#ifdef DEBUG 
    // Internal sanity checks. 
    if (ctx != get_context()) 
      PRE_INIT_ERROR ("Internal error: Context not current.\n"); 
    if (!parser->tag_set_eval) 
      PRE_INIT_ERROR ("Internal error: Calling _eval() with non-tag set parser.\n"); 
#endif 
#ifdef MODULE_DEBUG 
    if (ctx->new_runtime_tags) 
      PRE_INIT_ERROR ("Looks like Context.add_runtime_tag() or " 
                      "Context.remove_runtime_tag() was used outside any parser.\n"); 
#endif 
 
    if (flags & FLAG_UNPARSED) { 
#ifdef DEBUG 
      if (raw_args || raw_content) 
        PRE_INIT_ERROR ("Internal error: raw_args or raw_content given for " 
                        "unparsed frame.\n"); 
#endif 
      raw_args = args, args = 0; 
      raw_content = content, content = Void; 
#ifdef MODULE_DEBUG 
      if (!stringp (raw_content)) 
        PRE_INIT_ERROR ("Content is not a string in unparsed tag frame.\n"); 
#endif 
    } 
 
    if (array state = ctx->unwind_state && ctx->unwind_state[this]) { 
#ifdef DEBUG 
      if (!up) 
        PRE_INIT_ERROR ("Internal error: Resuming frame without up pointer.\n"); 
      if (raw_args || raw_content) 
        PRE_INIT_ERROR ("Internal error: Can't feed new arguments or content " 
                        "when resuming parse.\n"); 
#endif 
      object ignored; 
      [ignored, eval_state, iter, raw_content, subparser, piece, exec, tags_added, 
       ctx->new_runtime_tags] = state; 
      m_delete (ctx->unwind_state, this); 
      if (!sizeof (ctx->unwind_state)) ctx->unwind_state = 0; 
    } 
    else { 
#ifdef MODULE_DEBUG 
      if (up && up != ctx->frame) 
        PRE_INIT_ERROR ("Reuse of frame in different context.\n"); 
#endif 
      up = ctx->frame; 
      piece = Void; 
      if (++ctx->frame_depth >= ctx->max_frame_depth) { 
        ctx->frame = this; 
        ctx->frame_depth--; 
        _run_error ("Too deep recursion -- exceeding %d nested tags.\n", 
                    ctx->max_frame_depth); 
      } 
    } 
 
#undef PRE_INIT_ERROR 
    ctx->frame = this; 
 
    if (raw_args) { 
      args = raw_args; 
      if (sizeof (raw_args)) { 
        // Note: Code duplication in Tag.eval_args(). 
        mapping(string:Type) atypes = raw_args & tag->req_arg_types; 
        if (sizeof (atypes) < sizeof (tag->req_arg_types)) { 
          array(string) missing = sort (indices (tag->req_arg_types - atypes)); 
          parse_error ("Required " + 
                       (sizeof (missing) > 1 ? 
                        "arguments " + String.implode_nicely (missing) + " are" : 
                        "argument " + missing[0] + " is") + " missing.\n"); 
        } 
        atypes += raw_args & tag->opt_arg_types; 
#ifdef MODULE_DEBUG 
      if (mixed err = catch { 
#endif 
        foreach (indices (args), string arg) 
            args[arg] = (atypes[arg] || tag->def_arg_type)-> 
              eval (raw_args[arg], ctx, 0, parser, 1); // Should not unwind. 
#ifdef MODULE_DEBUG 
      }) { 
          if (objectp (err) && ([object] err)->thrown_at_unwind) 
            fatal_error ("Can't save parser state when evaluating arguments.\n"); 
          throw_fatal (err); 
        } 
#endif 
      } 
    } 
 
#ifdef MODULE_DEBUG 
    if (!args) fatal_error ("args not set.\n"); 
#endif 
 
    if (TagSet add_tags = raw_content && [object(TagSet)] this->additional_tags) { 
      if (!ctx->tag_set_is_local) ctx->make_tag_set_local(); 
      if (search (ctx->tag_set->imported, add_tags) < 0) { 
        ctx->tag_set->imported = ({add_tags}) + ctx->tag_set->imported; 
        tags_added = 1; 
      } 
    } 
 
    if (!result_type) { 
#ifdef MODULE_DEBUG 
      if (!tag) fatal_error ("result_type not set in Frame object %O, " 
                             "and it has no Tag object to use for inferring it.\n", 
                             this_object()); 
#endif 
      Type ptype = parser->type; 
      foreach (tag->result_types, Type rtype) 
        if (ptype == rtype) { 
          result_type = rtype; 
          break; 
        } 
        else if (ptype->subtype_of (rtype)) { 
          result_type = ptype (rtype->_parser_prog); 
          break; 
        } 
      if (!result_type)             // Sigh.. 
        parse_error ( 
          "Tag returns " + 
          String.implode_nicely ([array(string)] tag->result_types->name, "or") + 
          " but " + [string] parser->type->name + " is expected.\n"); 
    } 
    if (!content_type) { 
#ifdef MODULE_DEBUG 
      if (!tag) fatal_error ("content_type not set in Frame object %O, " 
                             "and it has no Tag object to use for inferring it.\n", 
                             this_object()); 
#endif 
      content_type = tag->content_type; 
      if (content_type == t_same) 
        content_type = result_type (content_type->_parser_prog); 
    } 
    if (raw_content) content = content_type->empty_value; 
 
    mixed err = catch { 
      switch (eval_state) { 
        case EVSTAT_BEGIN: 
          if (array|function(RequestID,void|mixed:array) do_enter = 
              [array|function(RequestID,void|mixed:array)] this->do_enter) { 
            if (!exec) { 
              exec = do_enter (ctx->id); // Might unwind. 
              if (ctx->new_runtime_tags) 
                _handle_runtime_tags (ctx, parser); 
            } 
            if (exec) { 
              if (!(flags & FLAG_PARENT_SCOPE)) ENTER_SCOPE (ctx, this); 
              mixed res = _exec_array (parser, exec, 0); // Might unwind. 
              if (flags & FLAG_STREAM_RESULT) { 
#ifdef DEBUG 
              if (ctx->unwind_state) 
                  fatal_error ("Internal error: Clobbering unwind_state " 
                               "to do streaming.\n"); 
                if (piece != Void) 
                  fatal_error ("Internal error: Thanks, we think about how nice it must " 
                               "be to play the harmonica...\n"); 
#endif 
              if (result_type->quoting_scheme != parser->type->quoting_scheme) 
                  res = parser->type->quote (res); 
                ctx->unwind_state = (["stream_piece": res]); 
                throw (this); 
              } 
              exec = 0; 
            } 
          } 
          eval_state = EVSTAT_ENTERED; 
 
          /* Fall through. */ 
        case EVSTAT_ENTERED: 
        case EVSTAT_LAST_ITER: 
          do { 
            if (eval_state != EVSTAT_LAST_ITER) { 
              int|function(RequestID:int) do_iterate = 
                [int|function(RequestID:int)] this->do_iterate; 
              if (intp (do_iterate)) { 
                iter = [int] do_iterate || 1; 
                eval_state = EVSTAT_LAST_ITER; 
              } 
              else { 
                iter = (/*[function(RequestID:int)]HMM*/ do_iterate) ( 
                  ctx->id); // Might unwind. 
                if (ctx->new_runtime_tags) 
                  _handle_runtime_tags (ctx, parser); 
                if (!iter) eval_state = EVSTAT_LAST_ITER; 
              } 
            } 
            ENTER_SCOPE (ctx, this); 
 
            for (; iter > 0; iter--) { 
              if (raw_content && raw_content != "") { // Got nested parsing to do. 
                int finished = 0; 
                if (!subparser) { // The nested content is not yet parsed. 
                  if (this->local_tags) { 
                    subparser = content_type->get_parser ( 
                      ctx, [object(TagSet)] this->local_tags, parser); 
                    subparser->_local_tag_set = 1; 
                  } 
                  else 
                    subparser = content_type->get_parser (ctx, 0, parser); 
                  subparser->finish (raw_content); // Might unwind. 
                  finished = 1; 
                } 
 
                do { 
                  if (flags & FLAG_STREAM_CONTENT && subparser->read) { 
                    // Handle a stream piece. 
                    // Squeeze out any free text from the subparser first. 
                    mixed res = subparser->read(); 
                    if (content_type->sequential) piece = res + piece; 
                    else if (piece == Void) piece = res; 
                    if (piece != Void) { 
                      array|function(RequestID,void|mixed:array) do_return; 
                      if ((do_return = 
                           [array|function(RequestID,void|mixed:array)] 
                           this->do_return) && 
                          !arrayp (do_return)) { 
                        if (!exec) { 
                          exec = do_return (ctx->id, piece); // Might unwind. 
                          if (ctx->new_runtime_tags) 
                            _handle_runtime_tags (ctx, parser); 
                        } 
                        if (exec) { 
                          ENTER_SCOPE (ctx, this); 
                          mixed res = _exec_array ( 
                            parser, exec, flags & FLAG_PARENT_SCOPE); // Might unwind. 
                          if (flags & FLAG_STREAM_RESULT) { 
#ifdef DEBUG 
                          if (!zero_type (ctx->unwind_state->stream_piece)) 
                              fatal_error ("Internal error: " 
                                           "Clobbering unwind_state->stream_piece.\n"); 
#endif 
                          if (result_type->quoting_scheme != 
                                parser->type->quoting_scheme) 
                              res = parser->type->quote (res); 
                            ctx->unwind_state->stream_piece = res; 
                            throw (this); 
                          } 
                          exec = 0; 
                        } 
                        else if (flags & FLAG_STREAM_RESULT) { 
                          // do_return() finished the stream. Ignore remaining content. 
                          ctx->unwind_state = 0; 
                          piece = Void; 
                          break; 
                        } 
                      } 
                      piece = Void; 
                    } 
                    if (finished) break; 
                  } 
                  else {        // The frame doesn't handle streamed content. 
                    piece = Void; 
                    if (finished) { 
                      mixed res = subparser->eval(); // Might unwind. 
                      if (content_type->sequential) content += res; 
                      else if (res != Void) content = res; 
                      break; 
                    } 
                  } 
 
                  subparser->finish(); // Might unwind. 
                  finished = 1; 
                } while (1); // Only loops when an unwound subparser has been recovered. 
                subparser = 0; 
              } 
 
              if (array|function(RequestID,void|mixed:array) do_return = 
                  [array|function(RequestID,void|mixed:array)] this->do_return) { 
                if (!exec) { 
                  exec = arrayp (do_return) ? [array] do_return : 
                    ([function(RequestID,void|mixed:array)] do_return) ( 
                      ctx->id); // Might unwind. 
                  if (ctx->new_runtime_tags) 
                    _handle_runtime_tags (ctx, parser); 
                } 
                if (exec) { 
                  ENTER_SCOPE (ctx, this); 
                  mixed res = _exec_array ( 
                    parser, exec, flags & FLAG_PARENT_SCOPE); // Might unwind. 
                  if (flags & FLAG_STREAM_RESULT) { 
#ifdef DEBUG 
                  if (ctx->unwind_state) 
                      fatal_error ("Internal error: Clobbering unwind_state " 
                                   "to do streaming.\n"); 
                    if (piece != Void) 
                      fatal_error ("Internal error: Thanks, we think about how nice " 
                                   "it must be to play the harmonica...\n"); 
#endif 
                  if (result_type->quoting_scheme != parser->type->quoting_scheme) 
                      res = parser->type->quote (res); 
                    ctx->unwind_state = (["stream_piece": res]); 
                    throw (this); 
                  } 
                  exec = 0; 
                } 
              } 
 
            } 
          } while (eval_state != EVSTAT_LAST_ITER); 
 
          /* Fall through. */ 
        case EVSTAT_ITER_DONE: 
          if (!this->do_return && result == Void && !(flags & FLAG_EMPTY_ELEMENT)) 
            if (result_type->_parser_prog == PNone) { 
              if (content_type->subtype_of (result_type)) 
                result = content; 
            } 
            else 
              if (stringp (content_type)) { 
                eval_state = EVSTAT_ITER_DONE; // Only need to record this state here. 
                if (!exec) exec = ({content}); 
                _exec_array (parser, exec, flags & FLAG_PARENT_SCOPE); // Might unwind. 
                exec = 0; 
              } 
          LEAVE_SCOPE (ctx, this); 
      } 
 
      if (ctx->new_runtime_tags) 
        _handle_runtime_tags (ctx, parser); 
    }; 
 
    ctx->frame_depth--; 
 
    if (err) { 
      LEAVE_SCOPE (ctx, this); 
      string action; 
      if (objectp (err) && ([object] err)->thrown_at_unwind) { 
        mapping(string:mixed)|mapping(object:array) ustate = ctx->unwind_state; 
        if (!ustate) ustate = ctx->unwind_state = ([]); 
#ifdef DEBUG 
      if (ustate[this]) 
          fatal_error ("Internal error: Frame already has an unwind state.\n"); 
#endif 
 
        if (ustate->exec_left) { 
          exec = [array] ustate->exec_left; 
          m_delete (ustate, "exec_left"); 
        } 
 
        if (err == this || exec && sizeof (exec) && err == exec[0]) 
          // This frame or a frame in the exec array wants to stream. 
          if (parser->unwind_safe) { 
            // Rethrow to continue in parent since we've already done 
            // the appropriate do_return stuff in this frame in either 
            // case. 
            if (err == this) err = 0; 
            if (tags_added) { 
              ctx->tag_set->imported -= ({/*[object(TagSet)]HMM*/ this->additional_tags}); 
              tags_added = 0; 
            } 
            action = "break"; 
          } 
          else { 
            // Can't stream since the parser isn't unwind safe. Just 
            // continue. 
            m_delete (ustate, "stream_piece"); 
            action = "continue"; 
          } 
        else if (!zero_type (ustate->stream_piece)) { 
          // Got a stream piece from a subframe. We handle it above; 
          // store the state and tail recurse. 
          piece = ustate->stream_piece; 
          m_delete (ustate, "stream_piece"); 
          action = "continue"; 
        } 
        else action = "break";  // Some other reason - back up to the top. 
 
        ustate[this] = ({err, eval_state, iter, raw_content, subparser, piece, 
                         exec, tags_added, ctx->new_runtime_tags}); 
      } 
      else { 
        ctx->handle_exception (err, parser); // Will rethrow unknown errors. 
        action = "return"; 
      } 
 
      switch (action) { 
        case "break":           // Throw and handle in parent frame. 
#ifdef MODULE_DEBUG 
        if (!parser->unwind_state) 
            fatal_error ("Trying to unwind inside a parser that isn't unwind safe.\n"); 
#endif 
        throw (this); 
        case "continue":        // Continue in this frame through tail recursion. 
          _eval (parser); 
          return; 
        case "return":          // A normal return. 
          break; 
        default: 
          fatal_error ("Internal error: Don't you come here and %O on me!\n", action); 
      } 
    } 
 
    if (tags_added) 
      ctx->tag_set->imported -= ({/*[object(TagSet)]HMM*/ this->additional_tags}); 
    ctx->frame = up; 
  } 
 
  DECLARE_CNT (__count); 
 
  string _sprintf() 
  { 
    return "RXML.Frame(" + (tag && [string] tag->name) + COMMA_CNT (__count) + ")"; 
  } 
} 
 
 
// Global services. 
 
void run_error (string msg, mixed... args) 
//! Throws an RXML run error with a dump of the parser stack in the 
//! current context. This is intended to be used by tags for errors 
//! that can occur during normal operation, such as when the 
//! connection to an SQL server fails. 
{ 
  if (sizeof (args)) msg = sprintf (msg, @args); 
  throw (Backtrace ("run", msg, get_context())); 
} 
 
void parse_error (string msg, mixed... args) 
//! Throws an RXML parse error with a dump of the parser stack in the 
//! current context. This is intended to be used for programming 
//! errors in the RXML code, such as lookups in nonexisting scopes and 
//! invalid arguments to a tag. 
{ 
  if (sizeof (args)) msg = sprintf (msg, @args); 
  throw (Backtrace ("parse", msg, get_context())); 
} 
 
void fatal_error (string msg, mixed... args) 
//! Throws a Pike error that isn't catched and handled anywhere. It's 
//! just like the common error() function, but includes the RXML frame 
//! backtrace. 
{ 
  if (sizeof (args)) msg = sprintf (msg, @args); 
  array bt = backtrace(); 
  throw_fatal (({msg, bt[..sizeof (bt) - 2]})); 
} 
 
void throw_fatal (mixed err) 
//! Mainly used internally to throw an error that includes the RXML 
//! frame backtrace. 
{ 
  if (arrayp (err) && sizeof (err) == 2 || 
      objectp (err) && !err->is_RXML_Backtrace && err->is_generic_error) { 
    string msg; 
    if (catch (msg = err[0])) throw (err); 
    if (stringp (msg) && !has_value (msg, "\nRXML frame backtrace:\n")) { 
      string descr = Backtrace (0, 0)->describe_rxml_backtrace (1); 
      if (sizeof (descr)) { 
        if (sizeof (msg) && msg[-1] != '\n') msg += "\n"; 
        msg += "RXML frame backtrace:\n" + descr; 
        catch (err[0] = msg); 
      } 
    } 
  } 
  throw (err); 
} 
 
Frame make_tag (string name, mapping(string:mixed) args, void|mixed content) 
//! Returns a frame for the specified tag. The tag definition is 
//! looked up in the current context and tag set. args and content are 
//! not parsed or evaluated. 
{ 
  TagSet tag_set = get_context()->tag_set; 
  object(Tag)|array(LOW_TAG_TYPE|LOW_CONTAINER_TYPE) tag = tag_set->get_tag (name); 
  if (arrayp (tag)) 
    fatal_error ("Getting frames for low level tags are currently not implemented.\n"); 
  return tag (args, content); 
} 
 
Frame make_unparsed_tag (string name, mapping(string:string) args, void|string content) 
//! Returns a frame for the specified tag. The tag definition is 
//! looked up in the current context and tag set. args and content are 
//! given unparsed in this variant; they're parsed when the frame is 
//! about to be evaluated. 
{ 
  TagSet tag_set = get_context()->tag_set; 
  object(Tag)|array(LOW_TAG_TYPE|LOW_CONTAINER_TYPE) tag = tag_set->get_tag (name); 
  if (arrayp (tag)) 
    fatal_error ("Getting frames for low level tags are currently not implemented.\n"); 
  Frame frame = tag (args, content); 
  frame->flags |= FLAG_UNPARSED; 
  return frame; 
} 
 
class parse_frame /* (Type type, string to_parse) */ 
//! Returns a frame that, when evaluated, parses the given string 
//! according to the type (which typically has a parser set). 
{ 
  inherit Frame; 
  constant flags = FLAG_UNPARSED; 
  mapping(string:mixed) args = ([]); 
 
  void create (Type type, string to_parse) 
  { 
    content_type = type, result_type = type (PNone); 
    content = to_parse; 
  } 
 
  string _sprintf() {return sprintf ("parse_frame(%O)", content_type);} 
} 
 
 
//! Parsers. 
 
 
class Parser 
//! Interface class for a syntax parser that scans, parses and 
//! evaluates an input stream. Access to a parser object is assumed to 
//! be done in a thread safe way except where noted. 
{ 
  constant is_RXML_Parser = 1; 
  constant thrown_at_unwind = 1; 
 
  //! Services. 
 
  int error_count; 
  //! Number of RXML errors that occurred during evaluation. If this 
  //! is nonzero, the value from eval() shouldn't be trusted. 
 
  function(Parser:void) data_callback; 
  //! A function to be called when data is likely to be available from 
  //! eval(). It's always called when the source stream closes. 
 
  //! write() and write_end() are the functions to use from outside 
  //! the parser system, not feed() or finish(). 
 
  int write (string in) 
  //! Writes some source data to the parser. Returns nonzero if there 
  //! might be data available in eval(). 
  { 
    int res; 
    ENTER_CONTEXT (context); 
    if (mixed err = catch { 
      if (context && context->unwind_state && context->unwind_state->top) { 
#ifdef MODULE_DEBUG 
      if (context->unwind_state->top != this_object()) 
          fatal_error ("The context got an unwound state from another parser. " 
                       "Can't rewind.\n"); 
#endif 
      m_delete (context->unwind_state, "top"); 
        if (!sizeof (context->unwind_state)) context->unwind_state = 0; 
      } 
      if (feed (in)) res = 1; // Might unwind. 
      if (res && data_callback) data_callback (this_object()); 
    }) 
      if (objectp (err) && ([object] err)->thrown_at_unwind) { 
#ifdef DEBUG 
      if (err != this_object()) { 
          LEAVE_CONTEXT(); 
          fatal_error ("Internal error: Unexpected unwind object catched.\n"); 
        } 
#endif 
      if (!context->unwind_state) context->unwind_state = ([]); 
        context->unwind_state->top = err; 
      } 
      else if (context) 
        context->handle_exception (err, this_object()); // Will rethrow unknown errors. 
      else { 
        LEAVE_CONTEXT(); 
        throw_fatal (err); 
      } 
    LEAVE_CONTEXT(); 
    return res; 
  } 
 
  void write_end (void|string in) 
  //! Closes the source data stream, optionally with a last bit of 
  //! data. 
  { 
    int res; 
    ENTER_CONTEXT (context); 
    if (mixed err = catch { 
      if (context && context->unwind_state && context->unwind_state->top) { 
#ifdef MODULE_DEBUG 
      if (context->unwind_state->top != this_object()) 
          fatal_error ("The context got an unwound state from another parser. " 
                       "Can't rewind.\n"); 
#endif 
      m_delete (context->unwind_state, "top"); 
        if (!sizeof (context->unwind_state)) context->unwind_state = 0; 
      } 
      finish (in); // Might unwind. 
      if (data_callback) data_callback (this_object()); 
    }) 
      if (objectp (err) && ([object] err)->thrown_at_unwind) { 
#ifdef DEBUG 
      if (err != this_object()) { 
          LEAVE_CONTEXT(); 
          fatal_error ("Internal error: Unexpected unwind object catched.\n"); 
        } 
#endif 
      if (!context->unwind_state) context->unwind_state = ([]); 
        context->unwind_state->top = err; 
      } 
      else if (context) 
        context->handle_exception (err, this_object()); // Will rethrow unknown errors. 
      else { 
        LEAVE_CONTEXT(); 
        throw_fatal (err); 
      } 
    LEAVE_CONTEXT(); 
  } 
 
  array handle_var (string varref) 
  // Parses and evaluates a possible variable reference, with the 
  // appropriate error handling. 
  { 
    // We're always evaluating here, so context is always set. 
    array(string) split = varref / "."; 
    if (sizeof (split) == 2) 
      if (mixed err = catch { 
        sscanf (split[1], "%[^:]:%s", split[1], string encoding); 
        context->current_var = varref; 
        mixed val; 
        if (zero_type (val = context->get_var ( // May throw. 
                         split[1], split[0], encoding ? t_text : type))) { 
          context->current_var = 0; 
          return ({}); 
        } 
        context->current_var = 0; 
        return encoding ? ({roxen->roxen_encode (val, encoding)}) : ({val}); 
      }) { 
        context->current_var = 0; 
        context->handle_exception (err, this_object()); // May throw. 
        return ({}); 
      } 
    return type->free_text ? 0 : ({}); 
  } 
 
  //! Interface. 
 
  Context context; 
  //! The context to do evaluation in. It's assumed to never be 
  //! modified asynchronously during the time the parser is working on 
  //! an input stream. 
 
  Type type; 
  //! The expected result type of the current stream. (The parser 
  //! should not do any type checking on this.) 
 
  int compile; 
  //! Must be set to nonzero before a stream is fed which should be 
  //! compiled to p-code. 
 
  //!mixed unwind_safe; 
  //! If nonzero, the parser supports unwinding with throw()/catch(). 
  //! Whenever an exception is thrown from some evaluation function, 
  //! it should be able to call that function again with identical 
  //! arguments the next time it continues. 
 
  mixed feed (string in); 
  //! Feeds some source data to the parse stream. The parser may do 
  //! scanning and parsing before returning. If context is set, it may 
  //! also do evaluation in that context. Returns nonzero if there 
  //! could be new data to get from eval(). 
 
  void finish (void|string in); 
  //! Like feed(), but also finishes the parse stream. A last bit of 
  //! data may be given. It should work to call this on an already 
  //! finished stream if no argument is given to it. 
 
  optional int report_error (string msg); 
  //! Used to report errors to the end user through the output. This 
  //! is only called when type->free_text is nonzero. msg should be 
  //! stored in the output queue to be returned by eval(). If the 
  //! context is bad for an error message, do nothing and return zero, 
  //! and return nonzero if a message was written. 
 
  optional mixed read(); 
  //! Define to allow streaming operation. Returns the evaluated 
  //! result so far, but does not do any evaluation. Returns Void if 
  //! there's no data (for sequential types the empty value is also 
  //! ok). 
 
  mixed eval(); 
  //! Evaluates the data fed so far and returns the result. The result 
  //! returned by previous eval() calls should not be returned again 
  //! as (part of) this return value. Returns Void if there's no data 
  //! (for sequential types the empty value is also ok). 
 
  optional PCode p_compile(); 
  //! Define this to return a p-code representation of the current 
  //! stream, which always is finished. 
 
  optional void reset (Context ctx, Type type, mixed... args); 
  //! Define to support reuse of a parser object. It'll be called 
  //! instead of making a new object for a new stream. It keeps the 
  //! static configuration, i.e. the type (and tag set when used in 
  //! TagSetParser). Note that this function needs to deal with 
  //! leftovers from add_runtime_tag() for TagSetParser objects. 
 
  optional Parser clone (Context ctx, Type type, mixed... args); 
  //! Define to create new parser objects by cloning instead of 
  //! creating from scratch. It returns a new instance of this parser 
  //! with the same static configuration, i.e. the type (and tag set 
  //! when used in TagSetParser). 
 
  static void create (Context ctx, Type _type, mixed... args) 
  { 
    context = ctx; 
    type = _type; 
  } 
 
  // Internals. 
 
  Parser _next_free; 
  // Used to link together unused parser objects for reuse. 
 
  Parser _parent; 
  // The parent parser if this one is nested. 
 
  Stdio.File _source_file; 
  mapping _defines; 
  // These two are compatibility kludges for use with parse_rxml(). 
 
  DECLARE_CNT (__count); 
 
  string _sprintf() {return "RXML.Parser" + PAREN_CNT (__count);} 
} 
 
 
class TagSetParser 
//! Interface class for parsers that evaluates using the tag set. It 
//! provides the evaluation and compilation functionality. The parser 
//! should call Tag._handle_tag() from feed() and finish() for every 
//! encountered tag, and Parser.handle_var() for encountered variable 
//! references. It must be able to continue cleanly after throw() from 
//! Tag._handle_tag(). 
{ 
  inherit Parser; 
 
  constant is_RXML_TagSetParser = 1; 
  constant tag_set_eval = 1; 
 
  // Services. 
 
  mixed eval() {return read();} 
 
  // Interface. 
 
  TagSet tag_set; 
  //! The tag set used for parsing. 
 
  optional void reset (Context ctx, Type type, TagSet tag_set, mixed... args); 
  optional Parser clone (Context ctx, Type type, TagSet tag_set, mixed... args); 
  static void create (Context ctx, Type type, TagSet _tag_set, mixed... args) 
  { 
    ::create (ctx, type); 
    tag_set = _tag_set; 
  } 
  //! In addition to the type, the tag set is part of the static 
  //! configuration. 
 
  mixed read(); 
  //! No longer optional in this class. Since the evaluation is done 
  //! in Tag._handle_tag() or similar, this always does the same as 
  //! eval(). 
 
  optional void add_runtime_tag (Tag tag); 
  //! Adds a tag that will exist from this point forward in the 
  //! current parser instance only. This may only be left undefined if 
  //! the parser doesn't parse tags at all. 
 
  optional void remove_runtime_tag (string|Tag tag); 
  //! Removes a tag added by add_runtime_tag(). If it's a string, it's 
  //! assumed to always be without prefix. This may only be left 
  //! undefined if the parser doesn't parse tags at all. 
 
  // Internals. 
 
  int _local_tag_set; 
 
  string _sprintf() {return "RXML.TagSetParser" + PAREN_CNT (__count);} 
} 
 
class PNone 
//! The identity parser. It only returns its input. 
{ 
  inherit Parser; 
 
  string data = ""; 
  int evalpos = 0; 
 
  int feed (string in) 
  { 
    data += in; 
    return 1; 
  } 
 
  void finish (void|string in) 
  { 
    if (in) data += in; 
  } 
 
  string eval() 
  { 
    string res = data[evalpos..]; 
    evalpos = sizeof (data); 
    return res; 
  } 
 
  string byte_compile() 
  { 
    return data; 
  } 
 
  string byte_interpret (string byte_code, Context ctx) 
  { 
    return byte_code; 
  } 
 
  void reset (Context ctx) 
  { 
    context = ctx; 
    data = ""; 
    evalpos = 0; 
  } 
 
  string _sprintf() {return "RXML.PNone" + PAREN_CNT (__count);} 
} 
 
 
mixed simple_parse (string in, void|program parser) 
//! A convenience function to parse a string with no type info, no tag 
//! set, and no variable references. The parser defaults to PExpr. 
{ 
  // FIXME: Recycle contexts? 
  return t_any (parser || PExpr)->eval (in, Context (empty_tag_set)); 
} 
 
 
//! Types. 
 
 
class Type 
//! A static type definition. It does type checking and specifies some 
//! properties of the type. It may also contain a Parser program that 
//! will be used to read text and evaluate values of this type. Note 
//! that the parser is not relevant for type checking. 
{ 
  constant is_RXML_Type = 1; 
 
  //! Interface. 
 
  //!string name; 
  //! Unique type identifier. Required and considered constant. Type 
  //! hierarchies are currently implemented with glob patterns, e.g. 
  //! "image/png" is a subtype of "image/*", and "array(string)" is a 
  //! subtype of "array(*)". 
 
  //!mixed sequential; 
  //! Nonzero if data of this type is sequential, defined as: 
  //! o  One or more data items can be concatenated with `+. 
  //! o  (Sane) parsers are homomorphic on the type, i.e. 
  //!     eval ("da") + eval ("ta") == eval ("da" + "ta") 
  //!    and 
  //!     eval ("data") + eval ("") == eval ("data") 
  //!  provided the data is only split between (sensibly defined) 
  //!  atomic elements. 
 
  //!mixed empty_value; 
  //! The empty value, i.e. what eval ("") would produce. 
 
  //!mixed free_text; 
  //! Nonzero if the type keeps the free text between parsed tokens, 
  //! e.g. the plain text between tags in XML. The type must be 
  //! sequential and use strings. 
 
  void type_check (mixed val); 
  //! Checks whether the given value is a valid one of this type. Type 
  //! errors are thrown with RXML.parse_error(). 
 
  //!string quoting_scheme; 
  //! An identifier for the quoting scheme this type uses, if any. The 
  //! quoting scheme specifies how literals needs to be quoted for the 
  //! type. Values converted between types with the same quoting 
  //! scheme are not quoted. 
 
  mixed quote (mixed val) 
  //! Quotes the given value according to the quoting scheme for this 
  //! type. 
  { 
    return val; 
  } 
 
  mixed convert (mixed val, void|Type from); 
  //! Converts the given value to this type. If the from type is 
  //! given, it's the type of the value. Since it's not always known, 
  //! this function should try to do something sensible based on the 
  //! primitive pike type. If the type can't be reasonably converted, 
  //! an RXML fatal should be thrown. 
  //! 
  //! Quoting should be done if the from type is missing or has a 
  //! different quoting scheme. 
 
  Type clone() 
  //! Returns a copy of the type. 
  { 
    Type newtype = object_program (this_object())(); 
    newtype->_parser_prog = _parser_prog; 
    newtype->_parser_args = _parser_args; 
    newtype->_t_obj_cache = _t_obj_cache; 
    return newtype; 
  } 
 
  //! Services. 
 
  int `== (mixed other) 
  //! 
  { 
    return objectp (other) && ([object] other)->is_RXML_Type && 
      ([object(Type)] other)->name == this_object()->name; 
  } 
 
  int subtype_of (Type other) 
  //! 
  { 
    return glob ([string] other->name, [string] this_object()->name); 
  } 
 
  Type `() (program/*(Parser)HMM*/ newparser, mixed... parser_args) 
  //! Returns a type identical to this one, but which has the given 
  //! parser. parser_args is passed as extra arguments to the 
  //! create()/reset()/clone() functions. 
  { 
    Type newtype; 
    if (sizeof (parser_args)) { // Can't cache this. 
      newtype = clone(); 
      newtype->_parser_prog = newparser; 
      newtype->_parser_args = parser_args; 
      if (newparser->tag_set_eval) newtype->_p_cache = ([]); 
    } 
    else { 
      if (!_t_obj_cache) _t_obj_cache = ([]); 
      if (!(newtype = _t_obj_cache[newparser])) 
        if (newparser == _parser_prog) 
          _t_obj_cache[newparser] = newtype = this_object(); 
        else { 
          _t_obj_cache[newparser] = newtype = clone(); 
          newtype->_parser_prog = newparser; 
          if (newparser->tag_set_eval) newtype->_p_cache = ([]); 
        } 
    } 
    return newtype; 
  } 
 
  inline Parser get_parser (Context ctx, void|TagSet tag_set, void|Parser|PCode parent) 
  //! Returns a parser instance initialized with the given context. 
  { 
    Parser p; 
    if (_p_cache) {             // It's a tag set parser. 
      TagSet tset = tag_set || ctx->tag_set; 
 
      if (parent && parent->is_RXML_TagSetParser && 
          tset == parent->tag_set && sizeof (ctx->runtime_tags) && 
          parent->clone && parent->type == this_object()) { 
        // There are runtime tags. Try to clone the parent parser if 
        // all conditions are met. 
        p = parent->clone (ctx, this_object(), tset, @_parser_args); 
        p->_parent = parent; 
        return p; 
      } 
 
      // vvv Using interpreter lock from here. 
      PCacheObj pco = _p_cache[tset]; 
      if (pco && pco->tag_set_gen == tset->generation) { 
        if ((p = pco->free_parser)) { 
          pco->free_parser = p->_next_free; 
          // ^^^ Using interpreter lock to here. 
          p->data_callback = p->compile = 0; 
          p->reset (ctx, this_object(), tset, @_parser_args); 
        } 
 
        else 
          // ^^^ Using interpreter lock to here. 
          if (pco->clone_parser) 
            p = pco->clone_parser->clone (ctx, this_object(), tset, @_parser_args); 
          else if ((p = _parser_prog (0, this_object(), tset, @_parser_args))->clone) 
            // pco->clone_parser might already be initialized here due 
            // to race, but that doesn't matter. 
            p = (pco->clone_parser = p)->clone (ctx, this_object(), tset, @_parser_args); 
      } 
 
      else { 
        // ^^^ Using interpreter lock to here. 
        pco = PCacheObj(); 
        pco->tag_set_gen = tset->generation; 
        _p_cache[tset] = pco;   // Might replace an object due to race, but that's ok. 
        if ((p = _parser_prog (0, this_object(), tset, @_parser_args))->clone) 
          // pco->clone_parser might already be initialized here due 
          // to race, but that doesn't matter. 
          p = (pco->clone_parser = p)->clone (ctx, this_object(), tset, @_parser_args); 
      } 
 
      if (ctx->tag_set == tset && p->add_runtime_tag && sizeof (ctx->runtime_tags)) 
        foreach (indices (ctx->runtime_tags), Tag tag) 
          p->add_runtime_tag (tag); 
    } 
 
    else { 
      if ((p = free_parser)) { 
        // Relying on interpreter lock here. 
        free_parser = p->_next_free; 
        p->data_callback = p->compile = 0; 
        p->reset (ctx, this_object(), @_parser_args); 
      } 
 
      else if (clone_parser) 
        // Relying on interpreter lock here. 
        p = clone_parser->clone (ctx, this_object(), @_parser_args); 
 
      else if ((p = _parser_prog (0, this_object(), @_parser_args))->clone) 
        // clone_parser might already be initialized here due to race, 
        // but that doesn't matter. 
        p = (clone_parser = p)->clone (ctx, this_object(), @_parser_args); 
    } 
 
    p->_parent = parent; 
    return p; 
  } 
 
  mixed eval (string in, void|Context ctx, void|TagSet tag_set, 
              void|Parser|PCode parent, void|int dont_switch_ctx) 
  //! Convenience function to parse and evaluate the value in the 
  //! given string. If a context isn't given, the current one is used. 
  //! The current context and ctx are assumed to be the same if 
  //! dont_switch_ctx is nonzero. 
  { 
    mixed res; 
    if (!ctx) ctx = get_context(); 
    if (_parser_prog == PNone) res = in; 
    else { 
      Parser p = get_parser (ctx, tag_set, parent); 
      p->_parent = parent; 
      if (dont_switch_ctx) p->finish (in); // Optimize the job in p->write_end(). 
      else p->write_end (in); 
      res = p->eval(); 
      if (p->reset) 
        if (_p_cache) { 
          // Relying on interpreter lock in this block. 
          PCacheObj pco = _p_cache[tag_set || ctx->tag_set]; 
          p->_next_free = pco->free_parser; 
          pco->free_parser = p; 
        } 
        else { 
          // Relying on interpreter lock in this block. 
          p->_next_free = free_parser; 
          free_parser = p; 
        } 
    } 
    if (ctx->type_check) type_check (res); 
    return res; 
  } 
 
  // Internals. 
 
  program/*(Parser)HMM*/ _parser_prog = PNone; 
  // The parser to use. Should never be changed in a type object. 
 
  /*private*/ array(mixed) _parser_args = ({}); 
 
  /*private*/ mapping(program:Type) _t_obj_cache; 
  // To avoid creating new type objects all the time in `(). 
 
  // Cache used for parsers that doesn't depend on the tag set. 
  private Parser clone_parser;  // Used with Parser.clone(). 
  private Parser free_parser;   // The list of objects to reuse with Parser.reset(). 
 
  // Cache used for parsers that depend on the tag set. 
  private class PCacheObj 
  { 
    int tag_set_gen; 
    Parser clone_parser; 
    Parser free_parser; 
  } 
  /*private*/ mapping(TagSet:PCacheObj) _p_cache; 
 
  DECLARE_CNT (__count); 
 
  string _sprintf() {return "RXML.Type" + PAREN_CNT (__count);} 
} 
 
 
static class TAny 
//! A completely unspecified nonsequential type. 
{ 
  inherit Type; 
  constant name = "*"; 
  constant quoting_scheme = "none"; 
 
  mixed convert (mixed val) {return val;} 
 
  string _sprintf() {return "RXML.t_any" + PAREN_CNT (__count);} 
} 
TAny t_any = TAny(); 
 
static class TNone 
//! A sequential type accepting only the empty value. 
{ 
  inherit Type; 
  constant name = "none"; 
  constant sequential = 1; 
  VoidType empty_value = Void; 
  constant quoting_scheme = "none"; 
 
  void type_check (mixed val) 
  { 
    if (val != Void) parse_error ("A value is not accepted.\n"); 
  } 
 
  mixed convert (mixed val) 
  { 
    type_check (val); 
    return Void; 
  } 
 
  string _sprintf() {return "RXML.t_none" + PAREN_CNT (__count);} 
} 
TNone t_none = TNone(); 
 
static class TSame 
//! A magic type used in Tag.content_type. 
{ 
  inherit Type; 
  constant name = "same"; 
  string _sprintf() {return "RXML.t_same" + PAREN_CNT (__count);} 
} 
TSame t_same = TSame(); 
 
static class TText 
//! The standard type for generic document text. 
{ 
  inherit Type; 
  constant name = "text/*"; 
  constant sequential = 1; 
  constant empty_value = ""; 
  constant free_text = 1; 
  constant quoting_scheme = "none"; 
 
  string convert (mixed val) 
  { 
    if (mixed err = catch {return (string) val;}) 
      parse_error ("Couldn't convert value to text: " + describe_error (err)); 
  } 
 
  string _sprintf() {return "RXML.t_text" + PAREN_CNT (__count);} 
} 
TText t_text = TText(); 
 
static class TXml 
//! The type for XML and similar markup. 
{ 
  inherit TText; 
  constant name = "text/xml"; 
  constant quoting_scheme = "xml"; 
 
  string quote (string val) 
  { 
    return replace ( 
      val, 
      // FIXME: This ignores the invalid Unicode character blocks. 
      ({"&", "<", ">", "\"", "\'", 
        "\000", "\001", "\002", "\003", "\004", "\005", "\006", "\007", 
        "\010",                 "\013", "\014",         "\016", "\017", 
        "\020", "\021", "\022", "\023", "\024", "\025", "\026", "\027", 
        "\030", "\031", "\032", "\033", "\034", "\035", "\036", "\037", 
      }), 
      ({"&amp;", "&lt;", "&gt;", "&quot;", /*"&apos;"*/ "&#39;", 
        "&#0;",  "&#1;",  "&#2;",  "&#3;",  "&#4;",  "&#5;",  "&#6;",  "&#7;", 
        "&#8;",                    "&#11;", "&#12;",          "&#14;", "&#15;", 
        "&#16;", "&#17;", "&#18;", "&#19;", "&#20;", "&#21;", "&#22;", "&#23;", 
        "&#24;", "&#25;", "&#26;", "&#27;", "&#28;", "&#29;", "&#30;", "&#31;", 
      })); 
  } 
 
  string convert (mixed val, void|Type from) 
  { 
    if (mixed err = catch {val = (string) val;}) 
      parse_error ("Couldn't convert value to text: " + describe_error (err)); 
    if (!from || from->quoting_scheme != quoting_scheme) 
      val = quote ([string] val); 
    return val; 
  } 
 
  string _sprintf() {return "RXML.t_xml" + PAREN_CNT (__count);} 
} 
THtml t_xml = TXml(); 
 
static class THtml 
//! Identical to t_xml, but tags it as "text/html". 
{ 
  inherit TXml; 
  constant name = "text/html"; 
  string _sprintf() {return "RXML.t_html" + PAREN_CNT (__count);} 
} 
THtml t_html = THtml(); 
 
 
// P-code compilation and evaluation. 
 
class VarRef 
//! A helper for representing variable reference tokens. 
{ 
  constant is_RXML_VarRef = 1; 
  string scope, var; 
  static void create (string _scope, string _var) {scope = _scope, var = _var;} 
  int valid (Context ctx) {return ctx->exist_scope (scope);} 
  mixed get (Context ctx) {return ctx->get_var (var, scope);} 
  mixed set (Context ctx, mixed val) {return ctx->set_var (var, val, scope);} 
  void delete (Context ctx) {ctx->delete_var (var, scope);} 
  string name() {return scope + "." + var;} 
  DECLARE_CNT (__count); 
  string _sprintf() 
    {return "RXML.VarRef(" + scope + "." + var + COMMA_CNT (__count) + ")";} 
} 
 
class PCode 
//! Holds p-code and evaluates it. P-code is the intermediate form 
//! after parsing and before evaluation. 
{ 
  constant is_RXML_PCode = 1; 
  constant thrown_at_unwind = 1; 
 
  array p_code = ({}); 
 
  int error_count; 
  //! Number of RXML errors that occurred during evaluation. If this 
  //! is nonzero, the value from eval() shouldn't be trusted. 
 
  mixed eval (Context ctx) 
  //! Evaluates the p-code in the given context. 
  { 
    // FIXME 
  } 
 
  function(Context:mixed) compile(); 
  //! Returns a compiled function for doing the evaluation. The 
  //! function will receive a context to do the evaluation in. 
 
 
  // Internals. 
 
  void report_error (string msg) 
  { 
    // FIXME 
  } 
 
  PCode|Parser _parent; 
  // The parent evaluator if this one is nested. 
 
  DECLARE_CNT (__count); 
 
  string _sprintf() {return "RXML.PCode" + PAREN_CNT (__count);} 
} 
 
 
//! Some parser tools. 
 
static class VoidType 
{ 
  mixed `+ (mixed... vals) {return sizeof (vals) ? predef::`+ (@vals) : this_object();} 
  mixed ``+ (mixed val) {return val;} 
  int `!() {return 1;} 
  string _sprintf() {return "RXML.Void";} 
}; 
VoidType Void = VoidType(); 
//! An object representing the void value. Works as initializer for 
//! sequences, since Void + anything == anything + Void == anything. 
 
class ScanStream 
//! A helper class for the input and scanner stage in a parser. It's a 
//! stream that takes unparsed strings and splits them into tokens 
//! which are queued. Intended to be inherited in a Parser class. 
{ 
  private class Link 
  { 
    array data; 
    Link next; 
  } 
  private Link head = Link();       // Last link is an empty eof marker. 
  private Link tail = head; 
  private int next_token = 0; 
  private string end = ""; 
  private int fin = 0; 
 
  array scan (string in, int finished); 
  //! The scanner function. It gets an unparsed string and should 
  //! return an array of tokens. If the second argument is nonzero, 
  //! there won't be any more data later. If the second argument is 
  //! zero, the last item in the returned array is handled as unparsed 
  //! data that will be passed back to the scanner later. Tokens may 
  //! be of any type. Use VarRef objects for variables. 
 
  void feed (string in) 
  //! 
  { 
#ifdef MODULE_DEBUG 
    if (fin) fatal_error ("Cannot feed data to a finished stream.\n"); 
#endif 
    array tokens = scan (end + in, 0); 
    end = [string] tokens[-1]; 
    if (sizeof (tokens) > 1) { 
      tail->data = tokens[..sizeof (tokens) - 2]; 
      tail = tail->next = Link(); 
    } 
  } 
 
  void finish (void|string in) 
  //! 
  { 
    if (in || !fin && sizeof (end)) { 
#ifdef MODULE_DEBUG 
      if (in && fin) fatal_error ("Cannot feed data to a finished stream.\n"); 
#endif 
      fin = 1; 
      if (in) end += in; 
      tail->data = scan (end, 1); 
      tail = tail->next = Link(); 
    } 
  } 
 
  void reset() 
  //! 
  { 
    head = Link(); 
    tail = head; 
    next_token = 0; 
    end = ""; 
    fin = 0; 
  } 
 
  mixed read() 
  //! Returns the next token, or Void if there's no more data. 
  { 
    while (head->next) 
      if (next_token >= sizeof (head->data)) { 
        next_token = 0; 
        head = head->next; 
      } 
      else return head->data[next_token++]; 
    return Void; 
  } 
 
  void unread (mixed... put_back) 
  //! Puts back tokens and variable references at the beginning of the 
  //! stream so that the leftmost argument will be read first. 
  { 
    int i = sizeof (put_back); 
    while (i) head->data[--next_token] = put_back[--i]; 
    if (i) { 
      Link l = Link(); 
      l->next = head, head = l; 
      l->data = allocate (next_token = max (i - 32, 0)) + put_back[..--i]; 
    } 
  } 
 
  array read_all() 
  //! 
  { 
    array data; 
    if (next_token) { 
      data = head->data[next_token..]; 
      head = head->next; 
      next_token = 0; 
    } 
    else data = ({}); 
    while (head->next) { 
      data += head->data; 
      head = head->next; 
    } 
    return data; 
  } 
 
  int finished() 
  //! Returns nonzero if the write end is finished. 
  { 
    return fin; 
  } 
 
  DECLARE_CNT (__count); 
 
  string _sprintf() {return "RXML.ScanStream" + PAREN_CNT (__count);} 
} 
 
 
// Various internal kludges. 
 
static function(string,mixed...:void) _run_error = run_error; 
static function(string,mixed...:void) _parse_error = parse_error; 
 
// Argh! 
static program PXml; 
static program PEnt; 
static program PExpr; 
void _fix_module_ref (string name, mixed val) 
{ 
  mixed err = catch { 
    switch (name) { 
      case "PXml": PXml = [program] val; break; 
      case "PEnt": PEnt = [program] val; break; 
      case "PExpr": PExpr = [program] val; break; 
      case "empty_tag_set": empty_tag_set = [object(TagSet)] val; break; 
      default: error ("Herk\n"); 
    } 
  }; 
  if (err) werror (describe_backtrace (err)); 
}