cannam@85: /*
cannam@85:  * libid3tag - ID3 tag manipulation library
cannam@85:  * Copyright (C) 2000-2004 Underbit Technologies, Inc.
cannam@85:  *
cannam@85:  * This program is free software; you can redistribute it and/or modify
cannam@85:  * it under the terms of the GNU General Public License as published by
cannam@85:  * the Free Software Foundation; either version 2 of the License, or
cannam@85:  * (at your option) any later version.
cannam@85:  *
cannam@85:  * This program is distributed in the hope that it will be useful,
cannam@85:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
cannam@85:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
cannam@85:  * GNU General Public License for more details.
cannam@85:  *
cannam@85:  * You should have received a copy of the GNU General Public License
cannam@85:  * along with this program; if not, write to the Free Software
cannam@85:  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
cannam@85:  *
cannam@85:  * $Id: util.c,v 1.9 2004/01/23 09:41:32 rob Exp $
cannam@85:  */
cannam@85: 
cannam@85: # ifdef HAVE_CONFIG_H
cannam@85: #  include "config.h"
cannam@85: # endif
cannam@85: 
cannam@85: # include "global.h"
cannam@85: 
cannam@85: # include <stdlib.h>
cannam@85: # include <zlib.h>
cannam@85: 
cannam@85: # include "id3tag.h"
cannam@85: # include "util.h"
cannam@85: 
cannam@85: /*
cannam@85:  * NAME:	util->unsynchronise()
cannam@85:  * DESCRIPTION:	perform (in-place) unsynchronisation
cannam@85:  */
cannam@85: id3_length_t id3_util_unsynchronise(id3_byte_t *data, id3_length_t length)
cannam@85: {
cannam@85:   id3_length_t bytes = 0, count;
cannam@85:   id3_byte_t *end = data + length;
cannam@85:   id3_byte_t const *ptr;
cannam@85: 
cannam@85:   if (length == 0)
cannam@85:     return 0;
cannam@85: 
cannam@85:   for (ptr = data; ptr < end - 1; ++ptr) {
cannam@85:     if (ptr[0] == 0xff && (ptr[1] == 0x00 || (ptr[1] & 0xe0) == 0xe0))
cannam@85:       ++bytes;
cannam@85:   }
cannam@85: 
cannam@85:   if (bytes) {
cannam@85:     ptr  = end;
cannam@85:     end += bytes;
cannam@85: 
cannam@85:     *--end = *--ptr;
cannam@85: 
cannam@85:     for (count = bytes; count; *--end = *--ptr) {
cannam@85:       if (ptr[-1] == 0xff && (ptr[0] == 0x00 || (ptr[0] & 0xe0) == 0xe0)) {
cannam@85: 	*--end = 0x00;
cannam@85: 	--count;
cannam@85:       }
cannam@85:     }
cannam@85:   }
cannam@85: 
cannam@85:   return length + bytes;
cannam@85: }
cannam@85: 
cannam@85: /*
cannam@85:  * NAME:	util->deunsynchronise()
cannam@85:  * DESCRIPTION:	undo unsynchronisation (in-place)
cannam@85:  */
cannam@85: id3_length_t id3_util_deunsynchronise(id3_byte_t *data, id3_length_t length)
cannam@85: {
cannam@85:   id3_byte_t const *old, *end = data + length;
cannam@85:   id3_byte_t *new;
cannam@85: 
cannam@85:   if (length == 0)
cannam@85:     return 0;
cannam@85: 
cannam@85:   for (old = new = data; old < end - 1; ++old) {
cannam@85:     *new++ = *old;
cannam@85:     if (old[0] == 0xff && old[1] == 0x00)
cannam@85:       ++old;
cannam@85:   }
cannam@85: 
cannam@85:   *new++ = *old;
cannam@85: 
cannam@85:   return new - data;
cannam@85: }
cannam@85: 
cannam@85: /*
cannam@85:  * NAME:	util->compress()
cannam@85:  * DESCRIPTION:	perform zlib deflate method compression
cannam@85:  */
cannam@85: id3_byte_t *id3_util_compress(id3_byte_t const *data, id3_length_t length,
cannam@85: 			      id3_length_t *newlength)
cannam@85: {
cannam@85:   id3_byte_t *compressed;
cannam@85: 
cannam@85:   *newlength  = length + 12;
cannam@85:   *newlength += *newlength / 1000;
cannam@85: 
cannam@85:   compressed = malloc(*newlength);
cannam@85:   if (compressed) {
cannam@85:     if (compress2(compressed, newlength, data, length,
cannam@85: 		  Z_BEST_COMPRESSION) != Z_OK ||
cannam@85: 	*newlength >= length) {
cannam@85:       free(compressed);
cannam@85:       compressed = 0;
cannam@85:     }
cannam@85:     else {
cannam@85:       id3_byte_t *resized;
cannam@85: 
cannam@85:       resized = realloc(compressed, *newlength ? *newlength : 1);
cannam@85:       if (resized)
cannam@85: 	compressed = resized;
cannam@85:     }
cannam@85:   }
cannam@85: 
cannam@85:   return compressed;
cannam@85: }
cannam@85: 
cannam@85: /*
cannam@85:  * NAME:	util->decompress()
cannam@85:  * DESCRIPTION:	undo zlib deflate method compression
cannam@85:  */
cannam@85: id3_byte_t *id3_util_decompress(id3_byte_t const *data, id3_length_t length,
cannam@85: 				id3_length_t newlength)
cannam@85: {
cannam@85:   id3_byte_t *decompressed;
cannam@85: 
cannam@85:   decompressed = malloc(newlength ? newlength : 1);
cannam@85:   if (decompressed) {
cannam@85:     id3_length_t size;
cannam@85: 
cannam@85:     size = newlength;
cannam@85: 
cannam@85:     if (uncompress(decompressed, &size, data, length) != Z_OK ||
cannam@85: 	size != newlength) {
cannam@85:       free(decompressed);
cannam@85:       decompressed = 0;
cannam@85:     }
cannam@85:   }
cannam@85: 
cannam@85:   return decompressed;
cannam@85: }