src/decompress.c

   1 /* Interface to zlib.
   2    Copyright (C) 2013 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 static Lisp_Object Qzlib_dll;
  30
  31 #ifdef WINDOWSNT
  32 #include <windows.h>
  33 #include "w32.h"
  34
  35 /* Macro for defining functions that will be loaded from the zlib DLL.  */
  36 #define DEF_ZLIB_FN(rettype,func,args) static rettype (FAR CDECL *fn_##func)args
  37
  38 /* Macro for loading zlib functions from the library.  */
  39 #define LOAD_ZLIB_FN(lib,func) {                                        \
  40     fn_##func = (void *) GetProcAddress (lib, #func);                   \
  41     if (!fn_##func) return 0;                                           \
  42   }
  43
  44 DEF_ZLIB_FN (int, inflateInit2_,
  45              (z_streamp strm, int  windowBits, const char *version, int stream_size));
  46
  47 DEF_ZLIB_FN (int, inflate,
  48              (z_streamp strm, int flush));
  49
  50 DEF_ZLIB_FN (int, inflateEnd,
  51              (z_streamp strm));
  52
  53 static bool
  54 init_zlib_functions (void)
  55 {
  56   HMODULE library = w32_delayed_load (Qzlib_dll);
  57
  58   if (!library)
  59     {
  60       message1 ("zlib library not found");
  61       return 0;
  62     }
  63
  64   LOAD_ZLIB_FN (library, inflateInit2_);
  65   LOAD_ZLIB_FN (library, inflate);
  66   LOAD_ZLIB_FN (library, inflateEnd);
  67   return 1;
  68 }
  69
  70 #define fn_inflateInit2(strm, windowBits) \
  71         fn_inflateInit2_((strm), (windowBits), ZLIB_VERSION, sizeof(z_stream))
  72
  73 #else /* !WINDOWSNT */
  74
  75 #define fn_inflateInit2         inflateInit2
  76 #define fn_inflate              inflate
  77 #define fn_inflateEnd           inflateEnd
  78
  79 #endif  /* WINDOWSNT */
  80
  81 \f
  82 struct decompress_unwind_data
  83 {
  84   ptrdiff_t old_point, start;
  85   z_stream *stream;
  86 };
  87
  88 static void
  89 unwind_decompress (void *ddata)
  90 {
  91   struct decompress_unwind_data *data = ddata;
  92   fn_inflateEnd (data->stream);
  93
  94   /* Delete any uncompressed data already inserted and restore point.  */
  95   if (data->start)
  96     {
  97       del_range (data->start, PT);
  98       SET_PT (data->old_point);
  99     }
 100 }
 101
 102 DEFUN ("zlib-available-p", Fzlib_available_p, Szlib_available_p, 0, 0, 0,
 103        doc: /* Return t if zlib decompression is available in this instance of Emacs.  */)
 104      (void)
 105 {
 106 #ifdef WINDOWSNT
 107   Lisp_Object found = Fassq (Qzlib_dll, Vlibrary_cache);
 108   if (CONSP (found))
 109     return XCDR (found);
 110   else
 111     {
 112       Lisp_Object status;
 113       status = init_zlib_functions () ? Qt : Qnil;
 114       Vlibrary_cache = Fcons (Fcons (Qzlib_dll, status), Vlibrary_cache);
 115       return status;
 116     }
 117 #else
 118   return Qt;
 119 #endif
 120 }
 121
 122 DEFUN ("zlib-decompress-region", Fzlib_decompress_region,
 123        Szlib_decompress_region,
 124        2, 2, 0,
 125        doc: /* Decompress a gzip- or zlib-compressed region.
 126 Replace the text in the region by the decompressed data.
 127 On failure, return nil and leave the data in place.
 128 This function can be called only in unibyte buffers.  */)
 129   (Lisp_Object start, Lisp_Object end)
 130 {
 131   ptrdiff_t istart, iend, pos_byte;
 132   z_stream stream;
 133   int inflate_status;
 134   struct decompress_unwind_data unwind_data;
 135   ptrdiff_t count = SPECPDL_INDEX ();
 136
 137   validate_region (&start, &end);
 138
 139   if (! NILP (BVAR (current_buffer, enable_multibyte_characters)))
 140     error ("This function can be called only in unibyte buffers");
 141
 142   /* This is a unibyte buffer, so character positions and bytes are
 143      the same.  */
 144   istart = XINT (start);
 145   iend = XINT (end);
 146   move_gap_both (iend, iend);
 147
 148   stream.zalloc = Z_NULL;
 149   stream.zfree = Z_NULL;
 150   stream.opaque = Z_NULL;
 151   stream.avail_in = 0;
 152   stream.next_in = Z_NULL;
 153
 154   /* The magic number 32 apparently means "autodect both the gzip and
 155      zlib formats" according to zlib.h.  */
 156   if (fn_inflateInit2 (&stream, MAX_WBITS + 32) != Z_OK)
 157     return Qnil;
 158
 159   unwind_data.start = iend;
 160   unwind_data.stream = &stream;
 161   unwind_data.old_point = PT;
 162
 163   record_unwind_protect_ptr (unwind_decompress, &unwind_data);
 164
 165   /* Insert the decompressed data at the end of the compressed data.  */
 166   SET_PT (iend);
 167
 168   pos_byte = istart;
 169
 170   /* Keep calling 'inflate' until it reports an error or end-of-input.  */
 171   do
 172     {
 173       /* Maximum number of bytes that one 'inflate' call should read and write.
 174          zlib requires that these values not exceed UINT_MAX.
 175          Do not make avail_out too large, as that might unduly delay C-g.  */
 176       ptrdiff_t avail_in = min (iend - pos_byte, UINT_MAX);
 177       ptrdiff_t avail_out = min (1 << 14, UINT_MAX);
 178
 179       ptrdiff_t decompressed;
 180
 181       if (GAP_SIZE < avail_out)
 182         make_gap (avail_out - GAP_SIZE);
 183       stream.next_in = BYTE_POS_ADDR (pos_byte);
 184       stream.avail_in = avail_in;
 185       stream.next_out = GPT_ADDR;
 186       stream.avail_out = avail_out;
 187       inflate_status = fn_inflate (&stream, Z_NO_FLUSH);
 188       pos_byte += avail_in - stream.avail_in;
 189       decompressed = avail_out - stream.avail_out;
 190       insert_from_gap (decompressed, decompressed, 0);
 191       QUIT;
 192     }
 193   while (inflate_status == Z_OK);
 194
 195   if (inflate_status != Z_STREAM_END)
 196     return unbind_to (count, Qnil);
 197
 198   unwind_data.start = 0;
 199
 200   /* Delete the compressed data.  */
 201   del_range (istart, iend);
 202
 203   return unbind_to (count, Qt);
 204 }
 205
 206 \f
 207 /***********************************************************************
 208                             Initialization
 209  ***********************************************************************/
 210 void
 211 syms_of_decompress (void)
 212 {
 213   DEFSYM (Qzlib_dll, "zlib");
 214   defsubr (&Szlib_decompress_region);
 215   defsubr (&Szlib_available_p);
 216 }
 217
 218 #endif /* HAVE_ZLIB */