src/decompress.c

   1 /* Interface to zlib.
   2    Copyright (C) 2013-2015 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Emacs.
   5
   6 GNU Emacs is free software: you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation, either version 3 of the License, or
   9 (at your option) any later version.
  10
  11 GNU Emacs is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  18
  19 #include <config.h>
  20
  21 #ifdef HAVE_ZLIB
  22
  23 #include <zlib.h>
  24
  25 #include "lisp.h"
  26 #include "character.h"
  27 #include "buffer.h"
  28
  29 #include <verify.h>
  30
  31 #ifdef WINDOWSNT
  32 # include <windows.h>
  33 # include "w32.h"
  34
  35 DEF_DLL_FN (int, inflateInit2_,
  36             (z_streamp strm, int windowBits, const char *version,
  37              int stream_size));
  38 DEF_DLL_FN (int, inflate, (z_streamp strm, int flush));
  39 DEF_DLL_FN (int, inflateEnd, (z_streamp strm));
  40
  41 static bool zlib_initialized;
  42
  43 static bool
  44 init_zlib_functions (void)
  45 {
  46   HMODULE library = w32_delayed_load (Qzlib_dll);
  47
  48   if (!library)
  49     return false;
  50
  51   LOAD_DLL_FN (library, inflateInit2_);
  52   LOAD_DLL_FN (library, inflate);
  53   LOAD_DLL_FN (library, inflateEnd);
  54   return true;
  55 }
  56
  57 # undef inflate
  58 # undef inflateEnd
  59 # undef inflateInit2_
  60
  61 # define inflate fn_inflate
  62 # define inflateEnd fn_inflateEnd
  63 # define inflateInit2_ fn_inflateInit2_
  64
  65 #endif  /* WINDOWSNT */
  66
  67 \f
  68 struct decompress_unwind_data
  69 {
  70   ptrdiff_t old_point, start, nbytes;
  71   z_stream *stream;
  72 };
  73
  74 static void
  75 unwind_decompress (void *ddata)
  76 {
  77   struct decompress_unwind_data *data = ddata;
  78   inflateEnd (data->stream);
  79
  80   /* Delete any uncompressed data already inserted on error.  */
  81   if (data->start)
  82     del_range (data->start, data->start + data->nbytes);
  83
  84   /* Put point where it was, or if the buffer has shrunk because the
  85      compressed data is bigger than the uncompressed, at
  86      point-max.  */
  87   SET_PT (min (data->old_point, ZV));
  88 }
  89
  90 DEFUN ("zlib-available-p", Fzlib_available_p, Szlib_available_p, 0, 0, 0,
  91        doc: /* Return t if zlib decompression is available in this instance of Emacs.  */)
  92      (void)
  93 {
  94 #ifdef WINDOWSNT
  95   Lisp_Object found = Fassq (Qzlib_dll, Vlibrary_cache);
  96   if (CONSP (found))
  97     return XCDR (found);
  98   else
  99     {
 100       Lisp_Object status;
 101       zlib_initialized = init_zlib_functions ();
 102       status = zlib_initialized ? Qt : Qnil;
 103       Vlibrary_cache = Fcons (Fcons (Qzlib_dll, status), Vlibrary_cache);
 104       return status;
 105     }
 106 #else
 107   return Qt;
 108 #endif
 109 }
 110
 111 DEFUN ("zlib-decompress-region", Fzlib_decompress_region,
 112        Szlib_decompress_region,
 113        2, 2, 0,
 114        doc: /* Decompress a gzip- or zlib-compressed region.
 115 Replace the text in the region by the decompressed data.
 116 On failure, return nil and leave the data in place.
 117 This function can be called only in unibyte buffers.  */)
 118   (Lisp_Object start, Lisp_Object end)
 119 {
 120   ptrdiff_t istart, iend, pos_byte;
 121   z_stream stream;
 122   int inflate_status;
 123   struct decompress_unwind_data unwind_data;
 124   ptrdiff_t count = SPECPDL_INDEX ();
 125
 126   validate_region (&start, &end);
 127
 128   if (! NILP (BVAR (current_buffer, enable_multibyte_characters)))
 129     error ("This function can be called only in unibyte buffers");
 130
 131 #ifdef WINDOWSNT
 132   if (!zlib_initialized)
 133     zlib_initialized = init_zlib_functions ();
 134   if (!zlib_initialized)
 135     {
 136       message1 ("zlib library not found");
 137       return Qnil;
 138     }
 139 #endif
 140
 141   /* This is a unibyte buffer, so character positions and bytes are
 142      the same.  */
 143   istart = XINT (start);
 144   iend = XINT (end);
 145   move_gap_both (iend, iend);
 146
 147   stream.zalloc = Z_NULL;
 148   stream.zfree = Z_NULL;
 149   stream.opaque = Z_NULL;
 150   stream.avail_in = 0;
 151   stream.next_in = Z_NULL;
 152
 153   /* The magic number 32 apparently means "autodetect both the gzip and
 154      zlib formats" according to zlib.h.  */
 155   if (inflateInit2 (&stream, MAX_WBITS + 32) != Z_OK)
 156     return Qnil;
 157
 158   unwind_data.start = iend;
 159   unwind_data.stream = &stream;
 160   unwind_data.old_point = PT;
 161   unwind_data.nbytes = 0;
 162   record_unwind_protect_ptr (unwind_decompress, &unwind_data);
 163
 164   /* Insert the decompressed data at the end of the compressed data.  */
 165   SET_PT (iend);
 166
 167   pos_byte = istart;
 168
 169   /* Keep calling 'inflate' until it reports an error or end-of-input.  */
 170   do
 171     {
 172       /* Maximum number of bytes that one 'inflate' call should read and write.
 173          Do not make avail_out too large, as that might unduly delay C-g.
 174          zlib requires that avail_in and avail_out not exceed UINT_MAX.  */
 175       ptrdiff_t avail_in = min (iend - pos_byte, UINT_MAX);
 176       int avail_out = 16 * 1024;
 177       int decompressed;
 178
 179       if (GAP_SIZE < avail_out)
 180         make_gap (avail_out - GAP_SIZE);
 181       stream.next_in = BYTE_POS_ADDR (pos_byte);
 182       stream.avail_in = avail_in;
 183       stream.next_out = GPT_ADDR;
 184       stream.avail_out = avail_out;
 185       inflate_status = inflate (&stream, Z_NO_FLUSH);
 186       pos_byte += avail_in - stream.avail_in;
 187       decompressed = avail_out - stream.avail_out;
 188       insert_from_gap (decompressed, decompressed, 0);
 189       unwind_data.nbytes += decompressed;
 190       QUIT;
 191     }
 192   while (inflate_status == Z_OK);
 193
 194   if (inflate_status != Z_STREAM_END)
 195     return unbind_to (count, Qnil);
 196
 197   unwind_data.start = 0;
 198
 199   /* Delete the compressed data.  */
 200   del_range (istart, iend);
 201
 202   return unbind_to (count, Qt);
 203 }
 204
 205 \f
 206 /***********************************************************************
 207                             Initialization
 208  ***********************************************************************/
 209 void
 210 syms_of_decompress (void)
 211 {
 212   DEFSYM (Qzlib_dll, "zlib");
 213   defsubr (&Szlib_decompress_region);
 214   defsubr (&Szlib_available_p);
 215 }
 216
 217 #endif /* HAVE_ZLIB */