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