comparison src/libid3tag-0.15.1b/util.c @ 85:545efbb81310

Import initial set of sources

+/*
+ * libid3tag - ID3 tag manipulation library
+ * Copyright (C) 2000-2004 Underbit Technologies, Inc.
+ *
+ * This program 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 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * $Id: util.c,v 1.9 2004/01/23 09:41:32 rob Exp $
+ */
+
+# ifdef HAVE_CONFIG_H
+#  include "config.h"
+# endif
+
+# include "global.h"
+
+# include <stdlib.h>
+# include <zlib.h>
+
+# include "id3tag.h"
+# include "util.h"
+
+/*
+ * NAME:	util->unsynchronise()
+ * DESCRIPTION:	perform (in-place) unsynchronisation
+ */
+id3_length_t id3_util_unsynchronise(id3_byte_t *data, id3_length_t length)
+{
+  id3_length_t bytes = 0, count;
+  id3_byte_t *end = data + length;
+  id3_byte_t const *ptr;
+
+  if (length == 0)
+    return 0;
+
+  for (ptr = data; ptr < end - 1; ++ptr) {
+    if (ptr[0] == 0xff && (ptr[1] == 0x00 || (ptr[1] & 0xe0) == 0xe0))
+      ++bytes;
+  }
+
+  if (bytes) {
+    ptr  = end;
+    end += bytes;
+
+    *--end = *--ptr;
+
+    for (count = bytes; count; *--end = *--ptr) {
+      if (ptr[-1] == 0xff && (ptr[0] == 0x00 || (ptr[0] & 0xe0) == 0xe0)) {
+	*--end = 0x00;
+	--count;
+      }
+    }
+  }
+
+  return length + bytes;
+}
+
+/*
+ * NAME:	util->deunsynchronise()
+ * DESCRIPTION:	undo unsynchronisation (in-place)
+ */
+id3_length_t id3_util_deunsynchronise(id3_byte_t *data, id3_length_t length)
+{
+  id3_byte_t const *old, *end = data + length;
+  id3_byte_t *new;
+
+  if (length == 0)
+    return 0;
+
+  for (old = new = data; old < end - 1; ++old) {
+    *new++ = *old;
+    if (old[0] == 0xff && old[1] == 0x00)
+      ++old;
+  }
+
+  *new++ = *old;
+
+  return new - data;
+}
+
+/*
+ * NAME:	util->compress()
+ * DESCRIPTION:	perform zlib deflate method compression
+ */
+id3_byte_t *id3_util_compress(id3_byte_t const *data, id3_length_t length,
+			      id3_length_t *newlength)
+{
+  id3_byte_t *compressed;
+
+  *newlength  = length + 12;
+  *newlength += *newlength / 1000;
+
+  compressed = malloc(*newlength);
+  if (compressed) {
+    if (compress2(compressed, newlength, data, length,
+		  Z_BEST_COMPRESSION) != Z_OK ||
+	*newlength >= length) {
+      free(compressed);
+      compressed = 0;
+    }
+    else {
+      id3_byte_t *resized;
+
+      resized = realloc(compressed, *newlength ? *newlength : 1);
+      if (resized)
+	compressed = resized;
+    }
+  }
+
+  return compressed;
+}
+
+/*
+ * NAME:	util->decompress()
+ * DESCRIPTION:	undo zlib deflate method compression
+ */
+id3_byte_t *id3_util_decompress(id3_byte_t const *data, id3_length_t length,
+				id3_length_t newlength)
+{
+  id3_byte_t *decompressed;
+
+  decompressed = malloc(newlength ? newlength : 1);
+  if (decompressed) {
+    id3_length_t size;
+
+    size = newlength;
+
+    if (uncompress(decompressed, &size, data, length) != Z_OK ||
+	size != newlength) {
+      free(decompressed);
+      decompressed = 0;
+    }
+  }
+
+  return decompressed;
+}