Add zlib support via the `decompress-gzipped-region' function

This adds a new file, src/decompress.c, as well as tests for the
presence of -lz.

1 files changed, 139 insertions, 0 deletions

diff --git a/src/decompress.c b/src/decompress.c
new file mode 100644
index 00000000000..18f7884a4c2
--- /dev/null
+++ b/src/decompress.c
@@ -0,0 +1,139 @@
+/* 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"
+
+
+#define BUFFER_SIZE 16384
+
+struct decompress_unwind_data {
+  ptrdiff_t old_point, start;
+  z_stream *stream;
+};
+
+static void
+unwind_decompress (void *ddata) {
+  struct decompress_unwind_data *data = ddata;
+  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 ("decompress-gzipped-region", Fdecompress_gzipped_region,
+       Sdecompress_gzipped_region,
+       2, 2, 0,
+       doc: /* Decompress a gzip-compressed region.
+The text in the region will be replaced by the decompressed data.
+On failure, nil is returned and the data is left in place.
+This function can only be called in unibyte buffers.*/)
+  (Lisp_Object start, Lisp_Object end)
+{
+  ptrdiff_t istart, iend, point = PT;
+  z_stream stream;
+  int decompressed;
+  char out[16384];
+  struct decompress_unwind_data unwind_data;
+  ptrdiff_t count = SPECPDL_INDEX ();
+
+  validate_region (&start, &end);
+  move_gap_both (iend, iend);
+
+  if (! NILP (BVAR (current_buffer, enable_multibyte_characters)))
+    error ("This function can only be called in unibyte buffers");
+
+  /* This is a unibyte buffer, so character positions and bytes are
+     the same. */
+  istart = XINT (start);
+  iend = XINT (end);
+
+  stream.zalloc = Z_NULL;
+  stream.zfree = Z_NULL;
+  stream.opaque = Z_NULL;
+  stream.avail_in = 0;
+  stream.next_in = Z_NULL;
+
+  /* This magic number apparently means "this is gzip". */
+  if (inflateInit2 (&stream, 16 + MAX_WBITS) != Z_OK)
+    return Qnil;
+
+  /* We're inserting the decompressed data at the end of the
+     compressed data. */
+  SET_PT (iend);
+
+  stream.avail_in = iend - istart;
+  stream.next_in = (char *) BYTE_POS_ADDR (istart);
+
+  unwind_data.start = iend;
+  unwind_data.stream = &stream;
+  unwind_data.old_point = point;
+  record_unwind_protect_ptr (unwind_decompress, &unwind_data);
+
+  immediate_quit = 1;
+
+  /* Run inflate() on input until the output buffer isn't full. */
+  do {
+    stream.avail_out = BUFFER_SIZE;
+    stream.next_out = out;
+    switch (inflate (&stream, Z_NO_FLUSH)) {
+    case Z_STREAM_ERROR:
+    case Z_NEED_DICT:
+    case Z_DATA_ERROR:
+    case Z_MEM_ERROR:
+      unbind_to (count, Qnil);
+      return Qnil;
+    }
+
+    decompressed = BUFFER_SIZE - stream.avail_out;
+    insert_1_both (out, decompressed, decompressed, 0, 0, 0);
+    QUIT;
+  } while (stream.avail_out == 0);
+
+  immediate_quit = 0;
+
+  unwind_data.start = 0;
+  unbind_to (count, Qnil);
+
+  /* Delete the compressed data. */
+  del_range (istart, iend);
+
+  return Qt;
+}
+
+
+/***********************************************************************
+			    Initialization
+ ***********************************************************************/
+void
+syms_of_decompress (void)
+{
+  defsubr (&Sdecompress_gzipped_region);
+}
+
+#endif /* HAVE_ZLIB */