src/decompress.c

   1 /* Interface to zlib.
   2    Copyright (C) 2013-2014 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 static Lisp_Object Qzlib_dll;
  32
  33 #ifdef WINDOWSNT
  34 #include <windows.h>
  35 #include "w32.h"
  36
  37 /* Macro for defining functions that will be loaded from the zlib DLL.  */
  38 #define DEF_ZLIB_FN(rettype,func,args) static rettype (FAR CDECL *fn_##func)args
  39
  40 /* Macro for loading zlib functions from the library.  */
  41 #define LOAD_ZLIB_FN(lib,func) {                                        \
  42     fn_##func = (void *) GetProcAddress (lib, #func);                   \
  43     if (!fn_##func) return false;                                       \
  44   }
  45
  46 DEF_ZLIB_FN (int, inflateInit2_,
  47              (z_streamp strm, int  windowBits, const char *version, int stream_size));
  48
  49 DEF_ZLIB_FN (int, inflate,
  50              (z_streamp strm, int flush));
  51
  52 DEF_ZLIB_FN (int, inflateEnd,
  53              (z_streamp strm));
  54
  55 static bool zlib_initialized;
  56
  57 static bool
  58 init_zlib_functions (void)
  59 {
  60   HMODULE library = w32_delayed_load (Qzlib_dll);
  61
  62   if (!library)
  63     {
  64       message1 ("zlib library not found");
  65       return false;
  66     }
  67
  68   LOAD_ZLIB_FN (library, inflateInit2_);
  69   LOAD_ZLIB_FN (library, inflate);
  70   LOAD_ZLIB_FN (library, inflateEnd);
  71   return true;
  72 }
  73
  74 #define fn_inflateInit2(strm, windowBits) \
  75         fn_inflateInit2_((strm), (windowBits), ZLIB_VERSION, sizeof(z_stream))
  76
  77 #else /* !WINDOWSNT */
  78
  79 #define fn_inflateInit2         inflateInit2
  80 #define fn_inflate              inflate
  81 #define fn_inflateEnd           inflateEnd
  82
  83 #endif  /* WINDOWSNT */
  84
  85 \f
  86 struct decompress_unwind_data
  87 {
  88   ptrdiff_t old_point, start, nbytes;
  89   z_stream *stream;
  90 };
  91
  92 static void
  93 unwind_decompress (void *ddata)
  94 {
  95   struct decompress_unwind_data *data = ddata;
  96   fn_inflateEnd (data->stream);
  97
  98   /* Delete any uncompressed data already inserted on error.  */
  99   if (data->start)
 100     del_range (data->start, data->start + data->nbytes);
 101
 102   /* Put point where it was, or if the buffer has shrunk because the
 103      compressed data is bigger than the uncompressed, at
 104      point-max.  */
 105   SET_PT (min (data->old_point, ZV));
 106 }
 107
 108 DEFUN ("zlib-available-p", Fzlib_available_p, Szlib_available_p, 0, 0, 0,
 109        doc: /* Return t if zlib decompression is available in this instance of Emacs.  */)
 110      (void)
 111 {
 112 #ifdef WINDOWSNT
 113   Lisp_Object found = Fassq (Qzlib_dll, Vlibrary_cache);
 114   if (CONSP (found))
 115     return XCDR (found);
 116   else
 117     {
 118       Lisp_Object status;
 119       zlib_initialized = init_zlib_functions ();
 120       status = zlib_initialized ? Qt : Qnil;
 121       Vlibrary_cache = Fcons (Fcons (Qzlib_dll, status), Vlibrary_cache);
 122       return status;
 123     }
 124 #else
 125   return Qt;
 126 #endif
 127 }
 128
 129 DEFUN ("zlib-decompress-region", Fzlib_decompress_region,
 130        Szlib_decompress_region,
 131        2, 2, 0,
 132        doc: /* Decompress a gzip- or zlib-compressed region.
 133 Replace the text in the region by the decompressed data.
 134 On failure, return nil and leave the data in place.
 135 This function can be called only in unibyte buffers.  */)
 136   (Lisp_Object start, Lisp_Object end)
 137 {
 138   ptrdiff_t istart, iend, pos_byte;
 139   z_stream stream;
 140   int inflate_status;
 141   struct decompress_unwind_data unwind_data;
 142   ptrdiff_t count = SPECPDL_INDEX ();
 143
 144   validate_region (&start, &end);
 145
 146   if (! NILP (BVAR (current_buffer, enable_multibyte_characters)))
 147     error ("This function can be called only in unibyte buffers");
 148
 149 #ifdef WINDOWSNT
 150   if (!zlib_initialized)
 151     zlib_initialized = init_zlib_functions ();
 152   if (!zlib_initialized)
 153     return Qnil;
 154 #endif
 155
 156   /* This is a unibyte buffer, so character positions and bytes are
 157      the same.  */
 158   istart = XINT (start);
 159   iend = XINT (end);
 160   move_gap_both (iend, iend);
 161
 162   stream.zalloc = Z_NULL;
 163   stream.zfree = Z_NULL;
 164   stream.opaque = Z_NULL;
 165   stream.avail_in = 0;
 166   stream.next_in = Z_NULL;
 167
 168   /* The magic number 32 apparently means "autodetect both the gzip and
 169      zlib formats" according to zlib.h.  */
 170   if (fn_inflateInit2 (&stream, MAX_WBITS + 32) != Z_OK)
 171     return Qnil;
 172
 173   unwind_data.start = iend;
 174   unwind_data.stream = &stream;
 175   unwind_data.old_point = PT;
 176   unwind_data.nbytes = 0;
 177   record_unwind_protect_ptr (unwind_decompress, &unwind_data);
 178
 179   /* Insert the decompressed data at the end of the compressed data.  */
 180   SET_PT (iend);
 181
 182   pos_byte = istart;
 183
 184   /* Keep calling 'inflate' until it reports an error or end-of-input.  */
 185   do
 186     {
 187       /* Maximum number of bytes that one 'inflate' call should read and write.
 188          Do not make avail_out too large, as that might unduly delay C-g.
 189          zlib requires that avail_in and avail_out not exceed UINT_MAX.  */
 190       ptrdiff_t avail_in = min (iend - pos_byte, UINT_MAX);
 191       int avail_out = 16 * 1024;
 192       int decompressed;
 193
 194       if (GAP_SIZE < avail_out)
 195         make_gap (avail_out - GAP_SIZE);
 196       stream.next_in = BYTE_POS_ADDR (pos_byte);
 197       stream.avail_in = avail_in;
 198       stream.next_out = GPT_ADDR;
 199       stream.avail_out = avail_out;
 200       inflate_status = fn_inflate (&stream, Z_NO_FLUSH);
 201       pos_byte += avail_in - stream.avail_in;
 202       decompressed = avail_out - stream.avail_out;
 203       insert_from_gap (decompressed, decompressed, 0);
 204       unwind_data.nbytes += decompressed;
 205       QUIT;
 206     }
 207   while (inflate_status == Z_OK);
 208
 209   if (inflate_status != Z_STREAM_END)
 210     return unbind_to (count, Qnil);
 211
 212   unwind_data.start = 0;
 213
 214   /* Delete the compressed data.  */
 215   del_range (istart, iend);
 216
 217   return unbind_to (count, Qt);
 218 }
 219
 220 \f
 221 /***********************************************************************
 222                             Initialization
 223  ***********************************************************************/
 224 void
 225 syms_of_decompress (void)
 226 {
 227   DEFSYM (Qzlib_dll, "zlib");
 228   defsubr (&Szlib_decompress_region);
 229   defsubr (&Szlib_available_p);
 230 }
 231
 232 #endif /* HAVE_ZLIB */