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#pike __REAL_VERSION__ 
 
#if constant(__builtin.thread_id) 
constant Thread=__builtin.thread_id; 
 
optional constant MutexKey=__builtin.mutex_key; 
optional constant Mutex=__builtin.mutex; 
optional constant Condition=__builtin.condition; 
optional constant _Disabled=__builtin.threads_disabled; 
optional constant Local=__builtin.thread_local; 
 
optional constant thread_create = predef::thread_create; 
optional constant this_thread = predef::this_thread; 
optional constant all_threads = predef::all_threads; 
optional constant get_thread_quanta = predef::get_thread_quanta; 
optional constant set_thread_quatna = predef::set_thread_quanta; 
 
constant THREAD_NOT_STARTED = __builtin.THREAD_NOT_STARTED; 
constant THREAD_RUNNING = __builtin.THREAD_RUNNING; 
constant THREAD_EXITED = __builtin.THREAD_EXITED; 
 
 
//! @[Fifo] implements a fixed length first-in, first-out queue. 
//! A fifo is a queue of values and is often used as a stream of data 
//! between two threads. 
//! 
//! @seealso 
//!   @[Queue] 
//! 
optional class Fifo { 
  inherit Condition : r_cond; 
  inherit Condition : w_cond; 
  inherit Mutex : lock; 
 
  array buffer; 
  int ptr, num; 
  int read_tres, write_tres; 
 
  //! This function returns the number of elements currently in the fifo. 
  //! 
  //! @seealso 
  //!   @[read()], @[write()] 
  //! 
  int size() {  return num; } 
 
  protected final mixed read_unlocked() 
  { 
    mixed tmp=buffer[ptr]; 
    buffer[ptr++] = 0;  // Throw away any references. 
    ptr%=sizeof(buffer); 
    if(read_tres < sizeof(buffer)) 
    { 
      if(num-- == read_tres) 
        w_cond::broadcast(); 
    }else{ 
      num--; 
      w_cond::broadcast(); 
    } 
    return tmp; 
  } 
 
  //! This function retrieves a value from the fifo. Values will be 
  //! returned in the order they were written. If there are no values 
  //! present in the fifo the current thread will sleep until some other 
  //! thread writes one. 
  //! 
  //! @seealso 
  //!   @[try_read()], @[read_array()], @[write()] 
  //! 
  mixed read() 
  { 
    object key=lock::lock(); 
    while(!num) r_cond::wait(key); 
    mixed res = read_unlocked(); 
    key = 0; 
    return res; 
  } 
 
  //! This function retrieves a value from the fifo if there is any 
  //! there. Values will be returned in the order they were written. 
  //! If there are no values present in the fifo then @[UNDEFINED] 
  //! will be returned. 
  //! 
  //! @seealso 
  //!   @[read()] 
  //! 
  mixed try_read() 
  { 
    if (!num) return UNDEFINED; 
    object key=lock::lock(); 
    if (!num) return UNDEFINED; 
    mixed res = read_unlocked(); 
    key = 0; 
    return res; 
  } 
 
  protected final array read_all_unlocked() 
  { 
    array ret; 
 
    switch (num) { 
      case 0: 
        ret = ({}); 
        break; 
 
      case 1: 
        ret=buffer[ptr..ptr]; 
        buffer[ptr++] = 0;      // Throw away any references. 
        ptr%=sizeof(buffer); 
        num = 0; 
        w_cond::broadcast(); 
        break; 
 
      default: 
        if (ptr+num < sizeof(buffer)) { 
          ret = buffer[ptr..ptr+num-1]; 
        } else { 
          ret = buffer[ptr..]+buffer[..num-(sizeof(buffer)-ptr)-1]; 
        } 
        ptr=num=0; 
        buffer=allocate(sizeof(buffer)); // Throw away any references. 
        w_cond::broadcast(); 
        break; 
    } 
 
    return ret; 
  } 
 
  //! This function returns all values in the fifo as an array. The 
  //! values in the array will be in the order they were written. If 
  //! there are no values present in the fifo the current thread will 
  //! sleep until some other thread writes one. 
  //! 
  //! @seealso 
  //!   @[read()], @[try_read_array()] 
  //! 
  array read_array() 
  { 
    object key=lock::lock(); 
    while(!num) r_cond::wait(key); 
    array ret = read_all_unlocked(); 
    key = 0; 
    return ret; 
  } 
 
  //! This function returns all values in the fifo as an array but 
  //! doesn't wait if there are no values there. The values in the 
  //! array will be in the order they were written. 
  //! 
  //! @seealso 
  //!   @[read_array()] 
  //! 
  array try_read_array() 
  { 
    if (!num) return ({}); 
    object key=lock::lock(); 
    array ret = read_all_unlocked(); 
    key = 0; 
    return ret; 
  } 
 
  protected final void write_unlocked (mixed value) 
  { 
    buffer[(ptr + num) % sizeof(buffer)] = value; 
    if(write_tres) 
    { 
      if(num++ == write_tres) 
        r_cond::broadcast(); 
    }else{ 
      num++; 
      r_cond::broadcast(); 
    } 
  } 
 
  //! Append a @[value] to the end of the fifo. If there is no more 
  //! room in the fifo the current thread will sleep until space is 
  //! available. The number of items in the queue after the write is 
  //! returned. 
  //! 
  //! @seealso 
  //!   @[read()] 
  //! 
  int write(mixed value) 
  { 
    object key=lock::lock(); 
    while(num == sizeof(buffer)) w_cond::wait(key); 
    write_unlocked (value); 
    int items = num; 
    key = 0; 
    return items; 
  } 
 
  //! Append a @[value] to the end of the fifo. If there is no more 
  //! room in the fifo then zero will be returned, otherwise the 
  //! number of items in the fifo after the write is returned. 
  //! 
  //! @seealso 
  //!   @[read()] 
  //! 
  int try_write(mixed value) 
  { 
    if (num == sizeof (buffer)) return 0; 
    object key=lock::lock(); 
    if (num == sizeof (buffer)) return 0; 
    write_unlocked (value); 
    int items = num; 
    key = 0; 
    return items; 
  } 
 
  //! @decl void create() 
  //! @decl void create(int size) 
  //! 
  //! Create a fifo. If the optional @[size] argument is present it 
  //! sets how many values can be written to the fifo without blocking. 
  //! The default @[size] is 128. 
  //! 
  protected void create(int|void size) 
  { 
    write_tres=0; 
    buffer=allocate(read_tres=size || 128); 
  } 
 
  protected string _sprintf( int f ) 
  { 
    return f=='O' && sprintf( "%O(%d / %d)", this_program, 
                              size(), read_tres ); 
  } 
} 
 
//! @[Queue] implements a queue, or a pipeline. The main difference 
//! between @[Queue] and @[Fifo] is that @[Queue] 
//! will never block in write(), only allocate more memory. 
//! 
//! @fixme 
//!   Ought to be made API-compatible with @[ADT.Queue]. 
//! 
//! @seealso 
//!   @[Fifo], @[ADT.Queue] 
//! 
optional class Queue { 
  inherit Condition : r_cond; 
  inherit Mutex : lock; 
 
  array buffer=allocate(16); 
  int r_ptr, w_ptr; 
 
  //! This function returns the number of elements currently in the queue. 
  //! 
  //! @seealso 
  //!   @[read()], @[write()] 
  //! 
  int size() {  return w_ptr - r_ptr;  } 
 
  //! This function retrieves a value from the queue. Values will be 
  //! returned in the order they were written. If there are no values 
  //! present in the queue the current thread will sleep until some other 
  //! thread writes one. 
  //! 
  //! @seealso 
  //!   @[try_read()], @[write()] 
  //! 
  mixed read() 
  { 
    mixed tmp; 
    object key=lock::lock(); 
    while(w_ptr == r_ptr) r_cond::wait(key); 
    tmp=buffer[r_ptr]; 
    buffer[r_ptr++] = 0;        // Throw away any references. 
    key=0; 
    return tmp; 
  } 
 
  //! This function retrieves a value from the queue if there is any 
  //! there. Values will be returned in the order they were written. 
  //! If there are no values present in the fifo then @[UNDEFINED] 
  //! will be returned. 
  //! 
  //! @seealso 
  //!   @[write()] 
  //! 
  mixed try_read() 
  { 
    if (w_ptr == r_ptr) return UNDEFINED; 
    object key=lock::lock(); 
    if (w_ptr == r_ptr) return UNDEFINED; 
    mixed tmp=buffer[r_ptr]; 
    buffer[r_ptr++] = 0;        // Throw away any references. 
    key=0; 
    return tmp; 
  } 
 
  protected final array read_all_unlocked() 
  { 
    array ret; 
 
    switch (w_ptr - r_ptr) { 
      case 0: 
        ret = ({}); 
        break; 
 
      case 1: 
        ret=buffer[r_ptr..r_ptr]; 
        buffer[r_ptr++] = 0;    // Throw away any references. 
        break; 
 
      default: 
        ret = buffer[r_ptr..w_ptr-1]; 
        r_ptr = w_ptr = 0; 
        buffer=allocate(sizeof(buffer)); // Throw away any references. 
        break; 
    } 
 
    return ret; 
  } 
 
  //! This function returns all values in the queue as an array. The 
  //! values in the array will be in the order they were written. If 
  //! there are no values present in the queue the current thread will 
  //! sleep until some other thread writes one. 
  //! 
  //! @seealso 
  //!   @[read()], @[try_read_array()] 
  //! 
  array read_array() 
  { 
    object key=lock::lock(); 
    while (w_ptr == r_ptr) r_cond::wait(key); 
    array ret = read_all_unlocked(); 
    key = 0; 
    return ret; 
  } 
 
  //! This function returns all values in the queue as an array but 
  //! doesn't wait if there are no values there. The values in the 
  //! array will be in the order they were written. 
  //! 
  //! @seealso 
  //!   @[read_array()] 
  //! 
  array try_read_array() 
  { 
    if (w_ptr == r_ptr) return ({}); 
    object key=lock::lock(); 
    array ret = read_all_unlocked(); 
    key = 0; 
    return ret; 
  } 
 
  //! Returns a snapshot of all the values in the queue, in the order 
  //! they were written. The values are still left in the queue, so if 
  //! other threads are reading from it, the returned value should be 
  //! considered stale already on return. 
  array peek_array() 
  { 
    if (w_ptr == r_ptr) return ({}); 
    MutexKey key = lock::lock(); 
    array ret = buffer[r_ptr..w_ptr - 1]; 
    key = 0; 
    return ret; 
  } 
 
  //! This function puts a @[value] last in the queue. If the queue is 
  //! too small to hold the @[value] it will be expanded to make room. 
  //! The number of items in the queue after the write is returned. 
  //! 
  //! @seealso 
  //!   @[read()] 
  //! 
  int write(mixed value) 
  { 
    object key=lock::lock(); 
    if(w_ptr >= sizeof(buffer)) 
    { 
      buffer=buffer[r_ptr..]; 
      buffer+=allocate(sizeof(buffer)+1); 
      w_ptr-=r_ptr; 
      r_ptr=0; 
    } 
    buffer[w_ptr] = value; 
    w_ptr++; 
    int items = w_ptr - r_ptr; 
    // NB: The mutex MUST be released before the broadcast to work 
    //     around bugs in glibc 2.24 and earlier. This seems to 
    //     affect eg RHEL 7 (glibc 2.17). 
    //     cf https://sourceware.org/bugzilla/show_bug.cgi?id=13165 
    key=0; 
    r_cond::broadcast(); 
    return items; 
  } 
 
  protected string _sprintf( int f ) 
  { 
    return f=='O' && sprintf( "%O(%d)", this_program, size() ); 
  } 
} 
 
 
//! A thread farm. 
optional class Farm 
{ 
  protected Mutex mutex = Mutex(); 
  protected Condition ft_cond = Condition(); 
  protected Queue job_queue = Queue(); 
  protected object dispatcher_thread; 
  protected function(object, string:void) thread_name_cb; 
  protected string thread_name_prefix; 
 
  //! An asynchronous result. 
  class Result 
  { 
    int ready; 
    mixed value; 
    function done_cb; 
 
    //! @returns 
    //!   @int 
    //!     @value 1 
    //!       Returns @expr{1@} when the result is available. 
    //!     @value 0 
    //!       Returns @expr{0@} (zero) when the result hasn't 
    //!       arrived yet. 
    //!     @value -1 
    //!       Returns negative on failure. 
    //!   @endint 
    int status() 
    { 
      return ready; 
    } 
 
    //! @returns 
    //!   Returns the result if available, a backtrace on failure, 
    //!   and @expr{0@} (zero) otherwise. 
    mixed result() 
    { 
      return value; 
    } 
 
    //! Wait for completion. 
    mixed `()() 
    { 
      object key = mutex->lock(); 
      while(!ready)     ft_cond->wait(key); 
      key = 0; 
      if( ready < 0 )   throw( value ); 
      return value; 
    } 
 
    //! Register a callback to be called when 
    //! the result is available. 
    //! 
    //! @param to 
    //!   Callback to be called. The first 
    //!   argument to the callback will be 
    //!   the result or the failure backtrace, 
    //!   and the second @expr{0@} (zero) on 
    //!   success, and @expr{1@} on failure. 
    void set_done_cb( function to ) 
    { 
      if( ready ) 
        to( value, ready<0 ); 
      else 
        done_cb = to; 
    } 
 
    //! Register a failure. 
    //! 
    //! @param what 
    //!   The corresponding backtrace. 
    void provide_error( mixed what ) 
    { 
      value = what; 
      ready = -1; 
      if( done_cb ) 
        done_cb( what, 1 ); 
    } 
 
    //! Register a completed result. 
    //! 
    //! @param what 
    //!   The result to register. 
    void provide( mixed what ) 
    { 
      ready = 1; 
      value = what; 
      if( done_cb ) 
        done_cb( what, 0 ); 
    } 
 
 
    protected string _sprintf( int f ) 
    { 
      switch( f ) 
      { 
        case 't': 
          return "Thread.Farm().Result"; 
        case 'O': 
          return sprintf( "%t(%d %O)", this, ready, value ); 
      } 
    } 
  } 
 
  //! A worker thread. 
  protected class Handler 
  { 
    Mutex job_mutex = Mutex(); 
    Condition cond = Condition(); 
    array(object|array(function|array)) job; 
    object thread; 
 
    float total_time; 
    int handled, max_time; 
 
    protected int ready; 
 
    void update_thread_name(int is_exiting) 
    { 
      if (thread_name_cb) { 
        string th_name = 
          !is_exiting && 
          sprintf("%s Handler 0x%x", thread_name_prefix, thread->id_number()); 
        thread_name_cb(thread, th_name); 
      } 
    } 
 
    void handler() 
    { 
      array(object|array(function|array)) q; 
      object key = job_mutex->lock(); 
      ready = 1; 
      while( 1 ) 
      { 
        cond->wait(key); 
        if( q = job ) 
        { 
          mixed res, err; 
          int st = gethrtime(); 
 
          err = catch(res = q[1][0]( @q[1][1] )); 
 
          if( q[0] ) 
          { 
            if( err ) 
              ([object]q[0])->provide_error( err ); 
            else 
              ([object]q[0])->provide( res ); 
          } 
          object lock = mutex->lock(); 
          free_threads += ({ this }); 
          lock = 0; 
          st = gethrtime()-st; 
          total_time += st/1000.0; 
          handled++; 
          job = 0; 
          q = 0; 
          if( st > max_time ) 
            max_time = st; 
          ft_cond->broadcast(); 
        } else { 
          object lock = mutex->lock(); 
          threads -= ({ this }); 
          free_threads -= ({ this }); 
          lock = 0; 
          update_thread_name(1); 
          destruct(); 
          return; 
        } 
      } 
    } 
 
    void run( array(function|array) what, object|void resobj ) 
    { 
      while(!ready) sleep(0.1); 
      object key = job_mutex->lock(); 
      job = ({ resobj, what }); 
      cond->signal(); 
      key = 0; 
    } 
 
    //! Get some statistics about the worker thread. 
    string debug_status() 
    { 
      return ("Thread:\n" 
              " Handled works: "+handled+"\n"+ 
              (handled? 
               " Average time:  "+((int)(total_time / handled))+"ms\n" 
               " Max time:      "+sprintf("%2.2fms\n", max_time/1000.0):"")+ 
              " Status:        "+(job?"Working":"Idle" )+"\n"+ 
              (job? 
               ("    "+ 
                replace( describe_backtrace(thread->backtrace()), 
                         "\n", 
                         "\n    ")):"") 
              +"\n\n"); 
    } 
 
    protected void create() 
    { 
      thread = thread_create( handler ); 
      update_thread_name(0); 
    } 
 
 
    protected string _sprintf( int f ) 
    { 
      switch( f ) 
      { 
        case 't': 
          return "Thread.Farm().Handler"; 
        case 'O': 
          return sprintf( "%t(%f / %d,  %d)", this, 
                          total_time, max_time, handled ); 
      } 
    } 
  } 
 
  protected array(Handler) threads = ({}); 
  protected array(Handler) free_threads = ({}); 
  protected int max_num_threads = 20; 
 
  protected Handler aquire_thread() 
  { 
    object lock = mutex->lock(); 
    while( !sizeof(free_threads) ) 
    { 
      if( sizeof(threads) < max_num_threads ) 
      { 
        threads += ({ Handler() }); 
        free_threads += ({ threads[-1] }); 
      } else { 
        ft_cond->wait(lock); 
      } 
    } 
    object(Handler) t = free_threads[0]; 
    free_threads = free_threads[1..]; 
    return t; 
  } 
 
 
  protected void dispatcher() 
  { 
    while( array q = [array]job_queue->read() ) { 
      aquire_thread()->run( q[1], q[0] ); 
      q = 0; 
    } 
    if (thread_name_cb) 
      thread_name_cb(this_thread(), 0); 
  } 
 
  protected class ValueAdjuster( object r, object r2, int i, mapping v ) 
  { 
    void go(mixed vn, int err) 
    { 
      if (!r->status()) { 
        ([array]r->value)[ i ] = vn; 
        if( err ) 
          r->provide_error( err ); 
        if( !--v->num_left ) 
          r->provide( r->value ); 
      } 
      destruct(); 
    } 
  } 
 
 
  //! Register multiple jobs. 
  //! 
  //! @param fun_args 
  //!   An array of arrays where the first element 
  //!   is a function to call, and the second is 
  //!   a corresponding array of arguments. 
  //! 
  //! @returns 
  //!   Returns a @[Result] object with an array 
  //!   with one element for the result for each 
  //!   of the functions in @[fun_args]. 
  //! 
  //! @note 
  //!   Do not modify the elements of @[fun_args] 
  //!   before the result is available. 
  //! 
  //! @note 
  //!   If any of the functions in @[fun_args] throws 
  //!   and error, all of the accumulated results 
  //!   (if any) will be dropped from the result, and 
  //!   the first backtrace be provided. 
  //! 
  //! @seealso 
  //!   @[run_multiple_async()] 
  Result run_multiple( array(array(function|array)) fun_args ) 
  { 
    Result r = Result(); // private result.. 
    r->value = allocate( sizeof( fun_args ) ); 
    mapping nl = ([ "num_left":sizeof( fun_args ) ]); 
    for( int i=0; i<sizeof( fun_args ); i++ ) 
    { 
      Result r2 = Result(); 
      r2->set_done_cb( ValueAdjuster( r, r2, i, nl )->go ); 
      job_queue->write( ({ r2, fun_args[i] }) ); 
    } 
    return r; 
  } 
 
 
  //! Register multiple jobs where the return values 
  //! are to be ignored. 
  //! 
  //! @param fun_args 
  //!   An array of arrays where the first element 
  //!   is a function to call, and the second is 
  //!   a corresponding array of arguments. 
  //! 
  //! @note 
  //!   Do not modify the elements of @[fun_args] 
  //!   before the result is available. 
  //! 
  //! @seealso 
  //!   @[run_multiple()] 
  void run_multiple_async( array fun_args ) 
  { 
    for( int i=0; i<sizeof( fun_args ); i++ ) 
      job_queue->write( ({ 0, fun_args[i] }) ); 
  } 
 
 
  //! Register a job for the thread farm. 
  //! 
  //! @param f 
  //!   Function to call with @@@[args] to 
  //!   perform the job. 
  //! 
  //! @param args 
  //!   The parameters for @[f]. 
  //! 
  //! @returns 
  //!   Returns a @[Result] object for the job. 
  //! 
  //! @note 
  //!   In Pike 7.8 and earlier this function 
  //!   was broken and returned a @[Result] 
  //!   object that wasn't connected to the job. 
  //! 
  //! @seealso 
  //!   @[run_async()] 
  Result run( function f, mixed ... args ) 
  { 
    Result ro = Result(); 
    job_queue->write( ({ ro, ({f, args }) }) ); 
    return ro; 
  } 
 
  //! Register a job for the thread farm 
  //! where the return value from @[f] is 
  //! ignored. 
  //! 
  //! @param f 
  //!   Function to call with @@@[args] to 
  //!   perform the job. 
  //! 
  //! @param args 
  //!   The parameters for @[f]. 
  //! 
  //! @seealso 
  //!   @[run()] 
  void run_async( function f, mixed ... args ) 
  { 
    job_queue->write( ({ 0, ({f, args }) }) ); 
  } 
 
  //! Set the maximum number of worker threads 
  //! that the thread farm may have. 
  //! 
  //! @param to 
  //!   The new maximum number. 
  //! 
  //! If there are more worker threads than @[to], 
  //! the function will wait until enough threads 
  //! have finished, so that the total is @[to] or less. 
  //! 
  //! The default maximum number of worker threads is @expr{20@}. 
  int set_max_num_threads( int(1..) to ) 
  { 
    int omnt = max_num_threads; 
    if( to <= 0 ) 
      error("Illegal argument 1 to set_max_num_threads," 
            "num_threads must be > 0\n"); 
 
    max_num_threads = to; 
    while( sizeof( threads ) > max_num_threads ) 
    { 
      object key = mutex->lock(); 
      while( sizeof( free_threads ) ) 
        free_threads[0]->cond->signal(); 
      if( sizeof( threads ) > max_num_threads) 
        ft_cond->wait(key); 
    } 
    ft_cond->broadcast( ); 
    return omnt; 
  } 
 
  //! Provide a callback function to track names of threads created by the 
  //! farm. 
  //! 
  //! @param cb 
  //!   The callback function. This will get invoked with the thread as the 
  //!   first parameter and the name as the second whenever a thread is 
  //!   created. When the same thread terminates the callback is invoked 
  //!   again with @[0] as the second parameter. Set @[cb] to @[0] to stop 
  //!   any previously registered callbacks from being called. 
  //! 
  //! @param prefix 
  //!   An optional name prefix to distinguish different farms. If not given 
  //!   a prefix will be generated automatically. 
  void set_thread_name_cb(function(object, string:void) cb, void|string prefix) 
  { 
    thread_name_cb = cb; 
    thread_name_prefix = 
      cb && 
      (prefix || sprintf("Thread.Farm 0x%x", dispatcher_thread->id_number())); 
 
    //  Give a name to all existing threads 
    if (thread_name_cb) { 
      thread_name_cb(dispatcher_thread, thread_name_prefix + " Dispatcher"); 
      foreach (threads, Handler t) 
        t->update_thread_name(0); 
    } 
  } 
 
  //! Get some statistics for the thread farm. 
  string debug_status() 
  { 
    string res = sprintf("Thread farm\n" 
                         "  Max threads     = %d\n" 
                         "  Current threads = %d\n" 
                         "  Working threads = %d\n" 
                         "  Jobs in queue   = %d\n\n", 
                         max_num_threads, sizeof(threads), 
                         (sizeof(threads)-sizeof(free_threads)), 
                         job_queue->size() ); 
 
    foreach( threads, Handler t ) 
      res += t->debug_status(); 
    return res; 
  } 
 
  protected string _sprintf( int f ) 
  { 
    return f=='O' && sprintf( "%O(/* %s */)", this_program, debug_status() ); 
  } 
 
  protected void create() 
  { 
    dispatcher_thread = thread_create( dispatcher ); 
  } 
} 
 
//! When this key is destroyed, the corresponding resource counter 
//! will be decremented. 
//! 
//! @seealso 
//!   @[ResourceCount], @[MutexKey] 
//! 
optional class ResourceCountKey { 
 
  private inherit __builtin.DestructImmediate; 
 
  /*semi*/private ResourceCount parent; 
 
  /*semi*/private void create(ResourceCount _parent) { 
    parent = _parent; 
  } 
 
  /*semi*/private void _destruct() { 
    MutexKey key = parent->_mutex->lock(); 
    --parent->_count; 
    parent->_cond->signal(); 
  } 
} 
 
//! Implements an inverted-semaphore-like resource 
//! counter.  A thread can poll or perform a blocking wait for the 
//! resource-count to drop below a certain @ref{level@}. 
//! 
//! @seealso 
//!   @[ResourceCountKey], @[Condition], @[Mutex] 
optional class ResourceCount { 
  /*semi*/final int _count; 
  /*semi*/final Condition _cond = Condition(); 
  /*semi*/final Mutex _mutex = Mutex(); 
 
  //! @param level 
  //!   The maximum level that is considered drained. 
  //! 
  //! @returns 
  //!   True if the resource counter drops to equal or below @ref{level@}. 
  /*semi*/final int(0..1) drained(void|int level) { 
    return level >= _count; 
  } 
 
  //! Blocks until the resource-counter dips to max @ref{level@}. 
  //! 
  //! @param level 
  //!   The maximum level that is considered drained. 
  /*semi*/final void wait_till_drained(void|int level) { 
    MutexKey key = _mutex->lock(); 
    while (_count > level)          // Recheck before allowing further 
      _cond->wait(key); 
  } 
 
  //! Increments the resource-counter. 
  //! @returns 
  //!   A @[ResourceCountKey] to decrement the resource-counter again. 
  /*semi*/final ResourceCountKey acquire() { 
    MutexKey key = _mutex->lock(); 
    _count++; 
    return ResourceCountKey(this); 
  } 
 
  /*semi*/private string _sprintf(int type) { 
    string res = UNDEFINED; 
    switch(type) { 
      case 'O': 
        res = sprintf("Count: %d", _count); 
        break; 
      case 'd': 
        res = sprintf("%d", _count); 
        break; 
    } 
    return res; 
  } 
} 
 
#else /* !constant(thread_create) */ 
 
// Simulations of some of the classes for nonthreaded use. 
 
/* Fallback implementation of Thread.Local */ 
optional class Local 
{ 
  protected mixed data; 
  mixed get() {return data;} 
  mixed set (mixed val) {return data = val;} 
} 
 
/* Fallback implementation of Thread.MutexKey */ 
optional class MutexKey (protected function(:void) dec_locks) 
{ 
  int `!() 
  { 
    // Should be destructed when the mutex is, but we can't pull that 
    // off. Try to simulate it as well as possible. 
    if (dec_locks) return 0; 
    destruct (this); 
    return 1; 
  } 
 
  protected void _destruct() 
  { 
    if (dec_locks) dec_locks(); 
  } 
} 
 
/* Fallback implementation of Thread.Mutex */ 
optional class Mutex 
{ 
  protected int locks = 0; 
  protected void dec_locks() {locks--;} 
 
  MutexKey lock (int|void type) 
  { 
    switch (type) { 
      default: 
        error ("Unknown mutex locking style: %d\n", type); 
      case 0: 
        if (locks) error ("Recursive mutex locks.\n"); 
        break; 
      case 1: 
        if (locks) 
          // To be really accurate we should hang now, but somehow 
          // that doesn't seem too useful. 
          error ("Deadlock detected.\n"); 
        break; 
      case 2: 
        if (locks) return 0; 
    } 
    locks++; 
    return MutexKey (dec_locks); 
  } 
 
  MutexKey trylock (int|void type) 
  { 
    switch (type) { 
      default: 
        error ("Unknown mutex locking style: %d\n", type); 
      case 0: 
        if (locks) error ("Recursive mutex locks.\n"); 
        break; 
      case 1: 
      case 2: 
    } 
    if (locks) return 0; 
    locks++; 
    return MutexKey (dec_locks); 
  } 
} 
 
// Fallback implementation of Thread.Fifo. 
optional class Fifo 
{ 
  array buffer; 
  int ptr, num; 
  int read_tres, write_tres; 
 
  int size() {  return num; } 
 
  mixed read() 
  { 
    if (!num) error ("Deadlock detected - fifo empty.\n"); 
    return try_read(); 
  } 
 
  mixed try_read() 
  { 
    if (!num) return UNDEFINED; 
    mixed tmp=buffer[ptr]; 
    buffer[ptr++] = 0;  // Throw away any references. 
    ptr%=sizeof(buffer); 
    return tmp; 
  } 
 
  array read_array() 
  { 
    if (!num) error ("Deadlock detected - fifo empty.\n"); 
    return try_read_array(); 
  } 
 
  array try_read_array() 
  { 
    array ret; 
    switch (num) { 
      case 0: 
        ret = ({}); 
        break; 
 
      case 1: 
        ret=buffer[ptr..ptr]; 
        buffer[ptr++] = 0;      // Throw away any references. 
        ptr%=sizeof(buffer); 
        num = 0; 
        break; 
 
      default: 
        if (ptr+num < sizeof(buffer)) { 
          ret = buffer[ptr..ptr+num-1]; 
        } else { 
          ret = buffer[ptr..]+buffer[..num-(sizeof(buffer)-ptr)-1]; 
        } 
        ptr=num=0; 
        buffer=allocate(sizeof(buffer)); // Throw away any references. 
        break; 
    } 
 
    return ret; 
  } 
 
  int try_write(mixed value) 
  { 
    if (num == sizeof (buffer)) return 0; 
    buffer[(ptr + num) % sizeof(buffer)] = value; 
    return ++num; 
  } 
 
  int write(mixed value) 
  { 
    if (!try_write(value)) error("Deadlock detected - fifo full.\n"); 
    return num; 
  } 
 
  protected void create(int|void size) 
  { 
    write_tres=0; 
    buffer=allocate(read_tres=size || 128); 
  } 
 
  protected string _sprintf( int f ) 
  { 
    return f=='O' && sprintf( "%O(%d / %d)", this_program, 
                              size(), read_tres ); 
  } 
} 
 
// Fallback implementation of Thread.Queue. 
optional class Queue 
{ 
  array buffer=allocate(16); 
  int r_ptr, w_ptr; 
 
  int size() {  return w_ptr - r_ptr;  } 
 
  mixed read() 
  { 
    if (w_ptr == r_ptr) error ("Deadlock detected - queue empty.\n"); 
    return try_read(); 
  } 
 
  mixed try_read() 
  { 
    mixed tmp=buffer[r_ptr]; 
    buffer[r_ptr++] = 0;        // Throw away any references. 
    return tmp; 
  } 
 
  array read_array() 
  { 
    if (w_ptr == r_ptr) error ("Deadlock detected - queue empty.\n"); 
    return try_read_array(); 
  } 
 
  array try_read_array() 
  { 
    array ret; 
 
    switch (w_ptr - r_ptr) { 
      case 0: 
        ret = ({}); 
        break; 
 
      case 1: 
        ret=buffer[r_ptr..r_ptr]; 
        buffer[r_ptr++] = 0;    // Throw away any references. 
        break; 
 
      default: 
        ret = buffer[r_ptr..w_ptr-1]; 
        r_ptr = w_ptr = 0; 
        buffer=allocate(sizeof(buffer)); // Throw away any references. 
        break; 
    } 
 
    return ret; 
  } 
 
  int write(mixed value) 
  { 
    if(w_ptr >= sizeof(buffer)) 
    { 
      buffer=buffer[r_ptr..]; 
      buffer+=allocate(sizeof(buffer)+1); 
      w_ptr-=r_ptr; 
      r_ptr=0; 
    } 
    buffer[w_ptr] = value; 
    w_ptr++; 
    return w_ptr - r_ptr; 
  } 
 
  protected string _sprintf( int f ) 
  { 
    return f=='O' && sprintf( "%O(%d)", this_program, size() ); 
  } 
} 
 
#endif /* !constant(thread_create) */