src/decompress.c

   1 /* Interface to zlib.
   2    Copyright (C) 2013-2018 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 (at
   9 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 <https://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 "buffer.h"
  27 #include "composite.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);
  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, orig, 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, but
  81      without calling the change hooks.  */
  82   if (data->start)
  83     {
  84       del_range_2 (data->start, data->start, /* byte, char offsets the same */
  85                    data->start + data->nbytes, data->start + data->nbytes,
  86                    0);
  87       update_compositions (data->start, data->start, CHECK_HEAD);
  88       /* "Balance" the before-change-functions call, which would
  89          otherwise be left "hanging". */
  90       signal_after_change (data->orig, data->start - data->orig,
  91                            data->start - data->orig);
  92     }
  93   /* Put point where it was, or if the buffer has shrunk because the
  94      compressed data is bigger than the uncompressed, at
  95      point-max.  */
  96   SET_PT (min (data->old_point, ZV));
  97 }
  98
  99 DEFUN ("zlib-available-p", Fzlib_available_p, Szlib_available_p, 0, 0, 0,
 100        doc: /* Return t if zlib decompression is available in this instance of Emacs.  */)
 101      (void)
 102 {
 103 #ifdef WINDOWSNT
 104   Lisp_Object found = Fassq (Qzlib, Vlibrary_cache);
 105   if (CONSP (found))
 106     return XCDR (found);
 107   else
 108     {
 109       Lisp_Object status;
 110       zlib_initialized = init_zlib_functions ();
 111       status = zlib_initialized ? Qt : Qnil;
 112       Vlibrary_cache = Fcons (Fcons (Qzlib, status), Vlibrary_cache);
 113       return status;
 114     }
 115 #else
 116   return Qt;
 117 #endif
 118 }
 119
 120 DEFUN ("zlib-decompress-region", Fzlib_decompress_region,
 121        Szlib_decompress_region,
 122        2, 2, 0,
 123        doc: /* Decompress a gzip- or zlib-compressed region.
 124 Replace the text in the region by the decompressed data.
 125 On failure, return nil and leave the data in place.
 126 This function can be called only in unibyte buffers.  */)
 127   (Lisp_Object start, Lisp_Object end)
 128 {
 129   ptrdiff_t istart, iend, pos_byte;
 130   z_stream stream;
 131   int inflate_status;
 132   struct decompress_unwind_data unwind_data;
 133   ptrdiff_t count = SPECPDL_INDEX ();
 134
 135   validate_region (&start, &end);
 136
 137   if (! NILP (BVAR (current_buffer, enable_multibyte_characters)))
 138     error ("This function can be called only in unibyte buffers");
 139
 140 #ifdef WINDOWSNT
 141   if (!zlib_initialized)
 142     zlib_initialized = init_zlib_functions ();
 143   if (!zlib_initialized)
 144     {
 145       message1 ("zlib library not found");
 146       return Qnil;
 147     }
 148 #endif
 149
 150   /* This is a unibyte buffer, so character positions and bytes are
 151      the same.  */
 152   istart = XINT (start);
 153   iend = XINT (end);
 154
 155   /* Do the following before manipulating the gap. */
 156   modify_text (istart, iend);
 157
 158   move_gap_both (iend, iend);
 159
 160   stream.zalloc = Z_NULL;
 161   stream.zfree = Z_NULL;
 162   stream.opaque = Z_NULL;
 163   stream.avail_in = 0;
 164   stream.next_in = Z_NULL;
 165
 166   /* The magic number 32 apparently means "autodetect both the gzip and
 167      zlib formats" according to zlib.h.  */
 168   if (inflateInit2 (&stream, MAX_WBITS + 32) != Z_OK)
 169     return Qnil;
 170
 171   unwind_data.orig = istart;
 172   unwind_data.start = iend;
 173   unwind_data.stream = &stream;
 174   unwind_data.old_point = PT;
 175   unwind_data.nbytes = 0;
 176   record_unwind_protect_ptr (unwind_decompress, &unwind_data);
 177
 178   /* Insert the decompressed data at the end of the compressed data.  */
 179   SET_PT (iend);
 180
 181   pos_byte = istart;
 182
 183   /* Keep calling 'inflate' until it reports an error or end-of-input.  */
 184   do
 185     {
 186       /* Maximum number of bytes that one 'inflate' call should read and write.
 187          Do not make avail_out too large, as that might unduly delay C-g.
 188          zlib requires that avail_in and avail_out not exceed UINT_MAX.  */
 189       ptrdiff_t avail_in = min (iend - pos_byte, UINT_MAX);
 190       int avail_out = 16 * 1024;
 191       int decompressed;
 192
 193       if (GAP_SIZE < avail_out)
 194         make_gap (avail_out - GAP_SIZE);
 195       stream.next_in = BYTE_POS_ADDR (pos_byte);
 196       stream.avail_in = avail_in;
 197       stream.next_out = GPT_ADDR;
 198       stream.avail_out = avail_out;
 199       inflate_status = inflate (&stream, Z_NO_FLUSH);
 200       pos_byte += avail_in - stream.avail_in;
 201       decompressed = avail_out - stream.avail_out;
 202       insert_from_gap (decompressed, decompressed, 0);
 203       unwind_data.nbytes += decompressed;
 204       maybe_quit ();
 205     }
 206   while (inflate_status == Z_OK);
 207
 208   if (inflate_status != Z_STREAM_END)
 209     return unbind_to (count, Qnil);
 210
 211   unwind_data.start = 0;
 212
 213   /* Delete the compressed data.  */
 214   del_range_2 (istart, istart, /* byte and char offsets are the same. */
 215                iend, iend, 0);
 216
 217   signal_after_change (istart, iend - istart, unwind_data.nbytes);
 218   update_compositions (istart, istart, CHECK_HEAD);
 219
 220   return unbind_to (count, Qt);
 221 }
 222
 223 \f
 224 /***********************************************************************
 225                             Initialization
 226  ***********************************************************************/
 227 void
 228 syms_of_decompress (void)
 229 {
 230   defsubr (&Szlib_decompress_region);
 231   defsubr (&Szlib_available_p);
 232 }
 233
 234 #endif /* HAVE_ZLIB */