/*

SDL_mixer: An audio mixer library based on the SDL library

Copyright (C) 1997-2019 Sam Lantinga <slouken@libsdl.org>

This software is provided 'as-is', without any express or implied

warranty. In no event will the authors be held liable for any damages

arising from the use of this software.

Permission is granted to anyone to use this software for any purpose,

including commercial applications, and to alter it and redistribute it

freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not

claim that you wrote the original software. If you use this software

in a product, an acknowledgment in the product documentation would be

appreciated but is not required.

2. Altered source versions must be plainly marked as such, and must not be

misrepresented as being the original software.

3. This notice may not be removed or altered from any source distribution.

*/

#include "SDL_stdinc.h"

#include "SDL_rwops.h"

#include "mp3utils.h"

/*********************** SDL_RW WITH BOOKKEEPING ************************/

size_t MP3_RWread(struct mp3file_t *fil, void *ptr, size_t size, size_t maxnum) {

size_t remaining = (size_t)(fil->length - fil->pos);

size_t ret;

maxnum *= size;

if (maxnum > remaining) maxnum = remaining;

ret = SDL_RWread(fil->src, ptr, 1, maxnum);

fil->pos += (Sint64)ret;

return ret;

}

Sint64 MP3_RWseek(struct mp3file_t *fil, Sint64 offset, int whence) {

Sint64 ret;

case RW_SEEK_CUR:

offset += fil->pos;

break;

case RW_SEEK_END:

break;

}

if (offset < 0) return -1;

if (offset > fil->length)

offset = fil->length;

ret = SDL_RWseek(fil->src, fil->start + offset, RW_SEEK_SET);

if (ret < 0) return ret;

fil->pos = offset;

return (fil->pos - fil->start);

}

/*************************** TAG HANDLING: ******************************/

return SDL_FALSE;

}

return SDL_TRUE;

}

/* ID3v2 header is 10 bytes: http://id3.org/id3v2.4.0-structure */

/* bytes 0-2: "ID3" identifier */

if (length < 10 || SDL_memcmp(data,"ID3",3) != 0) {

return SDL_FALSE;

}

/* bytes 3-4: version num (major,revision), each byte always less than 0xff. */

if (data[3] == 0xff || data[4] == 0xff) {

return SDL_FALSE;

}

/* bytes 6-9 are the ID3v2 tag size: a 32 bit 'synchsafe' integer, i.e. the

* highest bit 7 in each byte zeroed. i.e.: 7 bit information in each byte ->

* effectively a 28 bit value. */

if (data[6] >= 0x80 || data[7] >= 0x80 || data[8] >= 0x80 || data[9] >= 0x80) {

return SDL_FALSE;

}

return SDL_TRUE;

}

/* size is a 'synchsafe' integer (see above) */

long size = (long)((data[6]<<21) + (data[7]<<14) + (data[8]<<7) + data[9]);

size += 10; /* header size */

/* ID3v2 header[5] is flags (bits 4-7 only, 0-3 are zero).

* bit 4 set: footer is present (a copy of the header but

* with "3DI" as ident.) */

if (data[5] & 0x10) {

size += 10; /* footer size */

}

/* optional padding (always zeroes) */

while (size < length && data[size] == 0) {

++size;

}

return size;

}

/* http://wiki.hydrogenaud.io/index.php?title=APEv2_specification

* Header/footer is 32 bytes: bytes 0-7 ident, bytes 8-11 version,

* bytes 12-17 size. bytes 24-31 are reserved: must be all zeroes. */

Uint32 v;

if (length < 32 || SDL_memcmp(data,"APETAGEX",8) != 0) {

return SDL_FALSE;

}

v = (Uint32)((data[11]<<24) | (data[10]<<16) | (data[9]<<8) | data[8]); /* version */

if (v != 2000U && v != 1000U) {

return SDL_FALSE;

}

v = 0; /* reserved bits : */

if (SDL_memcmp(&data[24],&v,4) != 0 || SDL_memcmp(&data[28],&v,4) != 0) {

return SDL_FALSE;

}

return SDL_TRUE;

}

Uint32 flags, version;

long size = (long)((data[15]<<24) | (data[14]<<16) | (data[13]<<8) | data[12]);

version = (Uint32)((data[11]<<24) | (data[10]<<16) | (data[9]<<8) | data[8]);

flags = (Uint32)((data[23]<<24) | (data[22]<<16) | (data[21]<<8) | data[20]);

if (version == 2000U && (flags & (1U<<31))) size += 32; /* header present. */

return size;

}

static SDL_INLINE int is_lyrics3tag(const unsigned char *data, long length) {

/* http://id3.org/Lyrics3

* http://id3.org/Lyrics3v2 */

if (length < 15) return 0;

if (SDL_memcmp(data+6,"LYRICS200",9) == 0) return 2; /* v2 */

if (SDL_memcmp(data+6,"LYRICSEND",9) == 0) return 1; /* v1 */

return 0;

}

const char *p; long i, len;

char buf[5104];

/* needs manual search: http://id3.org/Lyrics3 */

if (m->length < 20) return -1;

len = (m->length > 5109)? 5109 : (long)m->length;

MP3_RWseek(m, -len, RW_SEEK_END);

MP3_RWread(m, buf, 1, (len -= 9)); /* exclude footer */

/* strstr() won't work here. */

for (i = len - 11, p = buf; i >= 0; --i, ++p) {

if (SDL_memcmp(p, "LYRICSBEGIN", 11) == 0)

break;

}

if (i < 0) return -1;

return len - (long)(p - buf) + 9 /* footer */;

}

static SDL_INLINE long get_lyrics3v2_len(const unsigned char *data, long length) {

/* 6 bytes before the end marker is size in decimal format -

* does not include the 9 bytes end marker and size field. */

if (length != 6) return 0;

return SDL_strtol((const char *)data, NULL, 10) + 15;

}

if (length < 11) return SDL_FALSE;

if (SDL_memcmp(data,"LYRICSBEGIN",11) == 0) return SDL_TRUE;

return SDL_FALSE;

}

/* From docs/musicmatch.txt in id3lib: https://sourceforge.net/projects/id3lib/

Overall tag structure:

+-----------------------------+

| Header |

| (256 bytes, OPTIONAL) |

+-----------------------------+

| Image extension (4 bytes) |

+-----------------------------+

| Image binary |

| (var. length >= 4 bytes) |

+-----------------------------+

| Unused (4 bytes) |

+-----------------------------+

| Version info (256 bytes) |

+-----------------------------+

| Audio meta-data |

| (var. length >= 7868 bytes) |

+-----------------------------+

| Data offsets (20 bytes) |

+-----------------------------+

| Footer (48 bytes) |

+-----------------------------+

*/

/* sig: 19 bytes company name + 13 bytes space */

if (SDL_memcmp(data,"Brava Software Inc. ",32) != 0) {

return SDL_FALSE;

}

/* 4 bytes version: x.xx */

if (!SDL_isdigit(data[32]) || data[33] != '.' ||

!SDL_isdigit(data[34]) ||!SDL_isdigit(data[35])) {

return SDL_FALSE;

}

for (length = 36; length < 48; ++length) {

if (data[length] != ' ') return SDL_FALSE;

}

#endif

return SDL_TRUE;

}

const Sint32 metasizes[4] = { 7868, 7936, 8004, 8132 };

const unsigned char syncstr[10] = {'1','8','2','7','3','6','4','5',0,0};

unsigned char buf[256];

Sint32 i, j, imgext_ofs, version_ofs;

long len;

MP3_RWseek(m, -68, RW_SEEK_END);

MP3_RWread(m, buf, 1, 20);

imgext_ofs = (Sint32)((buf[3] <<24) | (buf[2] <<16) | (buf[1] <<8) | buf[0] );

version_ofs = (Sint32)((buf[15]<<24) | (buf[14]<<16) | (buf[13]<<8) | buf[12]);

/* Try finding the version info section:

* Because metadata section comes after it, and because metadata section

* has different sizes across versions (format ver. <= 3.00: always 7868

* bytes), we can _not_ directly calculate using deltas from the offsets

* section. */

for (i = 0; i < 4; ++i) {

/* 48: footer, 20: offsets, 256: version info */

len = metasizes[i] + 48 + 20 + 256;

if (m->length < len) return -1;

MP3_RWseek(m, -len, RW_SEEK_END);

#ifdef MMTAG_PARANOID

for (j = 30; j < 256; ++j) {

if (buf[j] != ' ') break;

}

if (j < 256) continue;

#endif

if (SDL_memcmp(buf, syncstr, 10) == 0) {

break;

}

}

if (i == 4) return -1; /* no luck. */

#ifdef MMTAG_PARANOID

/* unused section: (4 bytes of 0x00) */

MP3_RWseek(m, -(len + 4), RW_SEEK_END);

if (SDL_memcmp(buf, &j, 4) != 0) return -1;

#endif

len += (version_ofs - imgext_ofs);

if (m->length < len) return -1;

MP3_RWseek(m, -len, RW_SEEK_END);

MP3_RWread(m, buf, 1, 8);

j = (Sint32)((buf[7] <<24) | (buf[6] <<16) | (buf[5] <<8) | buf[4]);

/* [0..9]: sync string, [30..255]: 0x20 */

if (SDL_memcmp(buf, syncstr, 10) != 0) {

return len;

}

#ifdef MMTAG_PARANOID

for (j = 30; j < 256; ++j) {

if (buf[j] != ' ') return len;

}

#endif

return len + 256; /* header is present. */

}

if (fil->length >= 128) {

MP3_RWseek(fil, -128, RW_SEEK_END);

if (MP3_RWread(fil, buf, 1, 128) != 128)

return -1;

if (!atend) { /* possible false positive? */

if (is_musicmatch(buf + 128 - 48, 48) ||

is_apetag (buf + 128 - 32, 32) ||

is_lyrics3tag(buf + 128 - 15, 15)) {

return 0;

}

}

/* FIXME: handle possible double-ID3v1 tags?? */

}

return 0;

}

static int probe_mmtag(struct mp3file_t *fil, unsigned char *buf) {

long len;

if (fil->length >= 68) {

MP3_RWseek(fil, -48, RW_SEEK_END);

if (MP3_RWread(fil, buf, 1, 48) != 48)

return -1;

if (is_musicmatch(buf, 48)) {

len = get_musicmatch_len(fil);

if (len < 0) return -1;

if (len >= fil->length) return -1;

}

}

return 0;

}

static int probe_apetag(struct mp3file_t *fil, unsigned char *buf) {

long len;

if (fil->length >= 32) {

MP3_RWseek(fil, -32, RW_SEEK_END);

if (MP3_RWread(fil, buf, 1, 32) != 32)

return -1;

if (is_apetag(buf, 32)) {

len = get_ape_len(buf);

}

}

return 0;

}

static int probe_lyrics3(struct mp3file_t *fil, unsigned char *buf) {

long len;

if (fil->length >= 15) {

MP3_RWseek(fil, -15, RW_SEEK_END);

if (MP3_RWread(fil, buf, 1, 15) != 15)

return -1;

len = is_lyrics3tag(buf, 15);

if (len == 2) {

len = get_lyrics3v2_len(buf, 6);

if (len >= fil->length) return -1;

if (len < 15) return -1;

return -1;

if (!verify_lyrics3v2(buf, 11)) return -1;

}

else if (len == 1) {

len = get_lyrics3v1_len(fil);

}

}

return 0;

}

int mp3_skiptags(struct mp3file_t *fil, SDL_bool keep_id3v2)

{

unsigned char buf[128];

long len; size_t readsize;

int c_id3, c_ape, c_lyr, c_mm;

int rc = -1;

/* MP3 standard has no metadata format, so everyone invented

* their own thing, even with extensions, until ID3v2 became

* dominant: Hence the impossible mess here.

*

* Note: I don't yet care about freaky broken mp3 files with

* double tags. -- O.S.

*/

readsize = MP3_RWread(fil, buf, 1, 128);

if (!readsize) goto fail;

/* ID3v2 tag is at the start */

if (is_id3v2(buf, readsize)) {

len = get_id3v2_len(buf, (long)readsize);

if (len >= fil->length) goto fail;

fil->start += len;

fil->length -= len;

}

}

/* APE tag _might_ be at the start (discouraged

* but not forbidden, either.) read the header. */

else if (is_apetag(buf, readsize)) {

len = get_ape_len(buf);

if (len >= fil->length) goto fail;

fil->start += len;

fil->length -= len;

}

/* it's not impossible that _old_ MusicMatch tag

* placing itself after ID3v1. */

if ((c_mm = probe_mmtag(fil, buf)) < 0) {

goto fail;

}

/* ID3v1 tag is at the end */

goto fail;

}

/* we do not know the order of ape or lyrics3

* or musicmatch tags, hence the loop here.. */

c_ape = 0;

c_lyr = 0;

for (;;) {

if (!c_lyr) {

/* care about mp3s with double Lyrics3 tags? */

if ((c_lyr = probe_lyrics3(fil, buf)) < 0)

goto fail;

if (c_lyr) continue;

}

if (!c_mm) {

if ((c_mm = probe_mmtag(fil, buf)) < 0)

goto fail;

if (c_mm) continue;

}

if (!c_ape) {

if ((c_ape = probe_apetag(fil, buf)) < 0)

goto fail;

if (c_ape) continue;

}

break;

} /* for (;;) */

fail:

MP3_RWseek(fil, 0, RW_SEEK_SET);

/* vi: set ts=4 sw=4 expandtab: */