pike.git/ src/ modules/ Gz/ zlibmod.c

2003-03-31

2003-03-31 14:26:42 by Per Hedbor <ph@opera.com>

• 90c27b475a324f6d625b341eac9563c3dd6e9ba8 (45 lines) (+35/-10) ^{[ Show | Annotate ]}
  Branch: 7.9

Fix the negative argument feature for deflate as well, and while we're at it, document it.

Rev: src/modules/Gz/zlibmod.c:1.62

2:   || This file is part of Pike. For copyright information see COPYRIGHT.   || Pike is distributed under GPL, LGPL and MPL. See the file COPYING   || for more information. - || $Id: zlibmod.c,v 1.61 2003/03/30 20:45:35 nilsson Exp $ + || $Id: zlibmod.c,v 1.62 2003/03/31 14:26:42 per Exp $   */      #include "global.h" - RCSID("$Id: zlibmod.c,v 1.61 2003/03/30 20:45:35 nilsson Exp $"); + RCSID("$Id: zlibmod.c,v 1.62 2003/03/31 14:26:42 per Exp $");      #include "zlib_machine.h"   #include "module.h"
92:    *!    *! This function can also be used to re-initialize a Gz.deflate object    *! so it can be re-used. +  *! +  *! If the argument is negative, no headers will be emitted. This is +  *! needed to produce ZIP-files, as an example. The negative value is +  *! then negated, and handled as a positive value.    */   static void gz_deflate_create(INT32 args)   { -  int tmp; +  int tmp, wbits = 15;    THIS->level=Z_DEFAULT_COMPRESSION;       if(THIS->gz.state)
110:    if(sp[-args].type != T_INT)    Pike_error("Bad argument 1 to gz->create()\n");    THIS->level=sp[-args].u.integer; +  if( THIS->level < 0 ) +  { +  wbits = -wbits; +  THIS->level = -THIS->level; +  }    if(THIS->level < Z_NO_COMPRESSION ||    THIS->level > Z_BEST_COMPRESSION)    {
123:       pop_n_elems(args);   /* mt_lock(& THIS->lock); */ -  tmp=deflateInit(&THIS->gz, THIS->level); +  tmp=deflateInit2(&THIS->gz, THIS->level, Z_DEFLATED, wbits, 9, Z_DEFAULT_STRATEGY );   /* mt_unlock(& THIS->lock); */    switch(tmp)    {
312:    *! @[deflate]    */    - /*! @decl void create(int|void magic) + /*! @decl void create(int|void window_size)    *! @param magic -  *! The magic value is passed down to inflateInit2 in zlib. Specifically, -  *! if you want to uncompress PKZIP-compressed data, you have to specify -  *! -15 as the argument. What negative arguments does is undocumented as -  *! far as we know. Positive arguments set the maximum dictionary size -  *! though. +  *! The window_size value is passed down to inflateInit2 in zlib. +  *! +  *! If the argument is negative, no header checks are done, and no +  *! verification of the data will be done either. This is needed for +  *! uncompressing ZIP-files, as an example. The negative value is then +  *! negated, and handled as a positive value. +  *! +  *! Positive arguments set the maximum dictionary size to an exponent +  *! of 2, such that 8 (the minimum) will cause the window size to be +  *! 256, and 15 (the maximum, and default value) will cause it to be +  *! 32Kb. Setting this to anything except 15 is rather pointless in +  *! Pike. +  *! +  *! It can be used to limit the amount of memory that is used to +  *! uncompress files, but 32Kb is not all that much in the great +  *! scheme of things. +  *! +  *! To decompress files compressed with level 9 compression, a 32Kb +  *! window size is needed. level 1 compression only requires a 256 +  *! byte window.    */   static void gz_inflate_create(INT32 args)   {