1/*
2 * libid3tag - ID3 tag manipulation library
3 * Copyright (C) 2000-2004 Underbit Technologies, Inc.
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
18 *
19 * $Id: util.c,v 1.9 2004/01/23 09:41:32 rob Exp $
20 */
21
22# ifdef HAVE_CONFIG_H
23#  include "config.h"
24# endif
25
26# include "global.h"
27
28# include <stdlib.h>
29# include <zlib.h>
30
31# include "id3tag.h"
32# include "util.h"
33
34/*
35 * NAME:	util->unsynchronise()
36 * DESCRIPTION:	perform (in-place) unsynchronisation
37 */
38id3_length_t id3_util_unsynchronise(id3_byte_t *data, id3_length_t length)
39{
40  id3_length_t bytes = 0, count;
41  id3_byte_t *end = data + length;
42  id3_byte_t const *ptr;
43
44  if (length == 0)
45    return 0;
46
47  for (ptr = data; ptr < end - 1; ++ptr) {
48    if (ptr[0] == 0xff && (ptr[1] == 0x00 || (ptr[1] & 0xe0) == 0xe0))
49      ++bytes;
50  }
51
52  if (bytes) {
53    ptr  = end;
54    end += bytes;
55
56    *--end = *--ptr;
57
58    for (count = bytes; count; *--end = *--ptr) {
59      if (ptr[-1] == 0xff && (ptr[0] == 0x00 || (ptr[0] & 0xe0) == 0xe0)) {
60	*--end = 0x00;
61	--count;
62      }
63    }
64  }
65
66  return length + bytes;
67}
68
69/*
70 * NAME:	util->deunsynchronise()
71 * DESCRIPTION:	undo unsynchronisation (in-place)
72 */
73id3_length_t id3_util_deunsynchronise(id3_byte_t *data, id3_length_t length)
74{
75  id3_byte_t const *old, *end = data + length;
76  id3_byte_t *new;
77
78  if (length == 0)
79    return 0;
80
81  for (old = new = data; old < end - 1; ++old) {
82    *new++ = *old;
83    if (old[0] == 0xff && old[1] == 0x00)
84      ++old;
85  }
86
87  *new++ = *old;
88
89  return new - data;
90}
91
92/*
93 * NAME:	util->compress()
94 * DESCRIPTION:	perform zlib deflate method compression
95 */
96id3_byte_t *id3_util_compress(id3_byte_t const *data, id3_length_t length,
97			      id3_length_t *newlength)
98{
99  id3_byte_t *compressed;
100
101  *newlength  = length + 12;
102  *newlength += *newlength / 1000;
103
104  compressed = malloc(*newlength);
105  if (compressed) {
106    if (compress2(compressed, newlength, data, length,
107		  Z_BEST_COMPRESSION) != Z_OK ||
108	*newlength >= length) {
109      free(compressed);
110      compressed = 0;
111    }
112    else {
113      id3_byte_t *resized;
114
115      resized = realloc(compressed, *newlength ? *newlength : 1);
116      if (resized)
117	compressed = resized;
118    }
119  }
120
121  return compressed;
122}
123
124/*
125 * NAME:	util->decompress()
126 * DESCRIPTION:	undo zlib deflate method compression
127 */
128id3_byte_t *id3_util_decompress(id3_byte_t const *data, id3_length_t length,
129				id3_length_t newlength)
130{
131  id3_byte_t *decompressed;
132
133  decompressed = malloc(newlength ? newlength : 1);
134  if (decompressed) {
135    id3_length_t size;
136
137    size = newlength;
138
139    if (uncompress(decompressed, &size, data, length) != Z_OK ||
140	size != newlength) {
141      free(decompressed);
142      decompressed = 0;
143    }
144  }
145
146  return decompressed;
147}
148