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/*
* 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;
}
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