Add a test for decompressing gzipped data

[bpt/emacs.git] / src / decompress.c

/* Interface to zlib.
   Copyright (C) 2013 Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */

#include <config.h>

#ifdef HAVE_ZLIB

#include <zlib.h>

#include "lisp.h"
#include "character.h"
#include "buffer.h"

static Lisp_Object Qzlib_dll;

#ifdef WINDOWSNT
#include <windows.h>
#include "w32.h"

/* Macro for defining functions that will be loaded from the zlib DLL.  */
#define DEF_ZLIB_FN(rettype,func,args) static rettype (FAR CDECL *fn_##func)args

/* Macro for loading zlib functions from the library.  */
#define LOAD_ZLIB_FN(lib,func) {					\
    fn_##func = (void *) GetProcAddress (lib, #func);			\
    if (!fn_##func) return 0;						\
  }

DEF_ZLIB_FN (int, inflateInit2_,
	     (z_streamp strm, int  windowBits, const char *version, int stream_size));

DEF_ZLIB_FN (int, inflate,
	     (z_streamp strm, int flush));

DEF_ZLIB_FN (int, inflateEnd,
	     (z_streamp strm));

static bool
init_zlib_functions (void)
{
  HMODULE library = w32_delayed_load (Qzlib_dll);

  if (!library)
    {
      message1 ("zlib library not found");
      return 0;
    }

  LOAD_ZLIB_FN (library, inflateInit2_);
  LOAD_ZLIB_FN (library, inflate);
  LOAD_ZLIB_FN (library, inflateEnd);
  return 1;
}

#define fn_inflateInit2(strm, windowBits) \
        fn_inflateInit2_((strm), (windowBits), ZLIB_VERSION, sizeof(z_stream))

#else /* !WINDOWSNT */

#define fn_inflateInit2		inflateInit2
#define fn_inflate		inflate
#define fn_inflateEnd		inflateEnd

#endif	/* WINDOWSNT */

\f
struct decompress_unwind_data
{
  ptrdiff_t old_point, start;
  z_stream *stream;
};

static void
unwind_decompress (void *ddata)
{
  struct decompress_unwind_data *data = ddata;
  fn_inflateEnd (data->stream);

  /* Delete any uncompressed data already inserted and restore point.  */
  if (data->start)
    {
      del_range (data->start, PT);
      SET_PT (data->old_point);
    }
}

DEFUN ("zlib-available-p", Fzlib_available_p, Szlib_available_p, 0, 0, 0,
       doc: /* Return t if zlib decompression is available in this instance of Emacs.  */)
     (void)
{
#ifdef WINDOWSNT
  Lisp_Object found = Fassq (Qzlib_dll, Vlibrary_cache);
  if (CONSP (found))
    return XCDR (found);
  else
    {
      Lisp_Object status;
      status = init_zlib_functions () ? Qt : Qnil;
      Vlibrary_cache = Fcons (Fcons (Qzlib_dll, status), Vlibrary_cache);
      return status;
    }
#else
  return Qt;
#endif
}

DEFUN ("zlib-decompress-region", Fzlib_decompress_region,
       Szlib_decompress_region,
       2, 2, 0,
       doc: /* Decompress a gzip- or zlib-compressed region.
Replace the text in the region by the decompressed data.
On failure, return nil and leave the data in place.
This function can be called only in unibyte buffers.  */)
  (Lisp_Object start, Lisp_Object end)
{
  ptrdiff_t istart, iend, pos_byte;
  z_stream stream;
  int inflate_status;
  struct decompress_unwind_data unwind_data;
  ptrdiff_t count = SPECPDL_INDEX ();

  validate_region (&start, &end);

  if (! NILP (BVAR (current_buffer, enable_multibyte_characters)))
    error ("This function can be called only in unibyte buffers");

  /* This is a unibyte buffer, so character positions and bytes are
     the same.  */
  istart = XINT (start);
  iend = XINT (end);
  move_gap_both (iend, iend);

  stream.zalloc = Z_NULL;
  stream.zfree = Z_NULL;
  stream.opaque = Z_NULL;
  stream.avail_in = 0;
  stream.next_in = Z_NULL;

  /* The magic number 32 apparently means "autodect both the gzip and
     zlib formats" according to zlib.h.  */
  if (fn_inflateInit2 (&stream, MAX_WBITS + 32) != Z_OK)
    return Qnil;

  unwind_data.start = iend;
  unwind_data.stream = &stream;
  unwind_data.old_point = PT;

  record_unwind_protect_ptr (unwind_decompress, &unwind_data);

  /* Insert the decompressed data at the end of the compressed data.  */
  SET_PT (iend);

  pos_byte = istart;

  /* Keep calling 'inflate' until it reports an error or end-of-input.  */
  do
    {
      /* Maximum number of bytes that one 'inflate' call should read and write.
	 zlib requires that these values not exceed UINT_MAX.
	 Do not make avail_out too large, as that might unduly delay C-g.  */
      ptrdiff_t avail_in = min (iend - pos_byte, UINT_MAX);
      ptrdiff_t avail_out = min (1 << 14, UINT_MAX);

      ptrdiff_t decompressed;

      if (GAP_SIZE < avail_out)
	make_gap (avail_out - GAP_SIZE);
      stream.next_in = BYTE_POS_ADDR (pos_byte);
      stream.avail_in = avail_in;
      stream.next_out = GPT_ADDR;
      stream.avail_out = avail_out;
      inflate_status = fn_inflate (&stream, Z_NO_FLUSH);
      pos_byte += avail_in - stream.avail_in;
      decompressed = avail_out - stream.avail_out;
      insert_from_gap (decompressed, decompressed, 0);
      QUIT;
    }
  while (inflate_status == Z_OK);

  if (inflate_status != Z_STREAM_END)
    return unbind_to (count, Qnil);

  unwind_data.start = 0;

  /* Delete the compressed data.  */
  del_range (istart, iend);

  return unbind_to (count, Qt);
}

\f
/***********************************************************************
			    Initialization
 ***********************************************************************/
void
syms_of_decompress (void)
{
  DEFSYM (Qzlib_dll, "zlib");
  defsubr (&Szlib_decompress_region);
  defsubr (&Szlib_available_p);
}

#endif /* HAVE_ZLIB */