/*
  * MP3 demuxer
  * Copyright (c) 2003 Fabrice Bellard
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg 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
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 

 #include "libavutil/opt.h"

 #include "libavutil/avstring.h"
 #include "libavutil/intreadwrite.h"

 #include "libavutil/crc.h"

 #include "libavutil/dict.h"

 #include "libavutil/mathematics.h"

 #include "avformat.h"

 #include "internal.h"

 #include "avio_internal.h"

 #include "id3v2.h"
 #include "id3v1.h"

 #include "replaygain.h"
 

 #include "libavcodec/avcodec.h"

 #include "libavcodec/mpegaudiodecheader.h"
 

 #define XING_FLAG_FRAMES 0x01
 #define XING_FLAG_SIZE   0x02

 #define XING_FLAG_TOC    0x04

 #define XING_FLAC_QSCALE 0x08

 
 #define XING_TOC_COUNT 100

 #define SAME_HEADER_MASK \
    (0xffe00000 | (3 << 17) | (3 << 10) | (3 << 19))
 

 typedef struct {

     AVClass *class;

     int64_t filesize;

     int xing_toc;

     int start_pad;
     int end_pad;

     int usetoc;

     unsigned frames; /* Total number of frames in file */

     unsigned header_filesize;   /* Total number of bytes in the stream */

     int is_cbr;

 } MP3DecContext;

 enum CheckRet {
     CHECK_WRONG_HEADER = -1,
     CHECK_SEEK_FAILED  = -2,
 };
 

 static int check(AVIOContext *pb, int64_t pos, uint32_t *header);

 /* mp3 read */
 
 static int mp3_read_probe(AVProbeData *p)
 {
     int max_frames, first_frames = 0;

     int whole_used = 0;

     int frames, ret;

     uint32_t header;

     const uint8_t *buf, *buf0, *buf2, *end;

     buf0 = p->buf;
     end = p->buf + p->buf_size - sizeof(uint32_t);
     while(buf0 < end && !*buf0)
         buf0++;
 
     max_frames = 0;
     buf = buf0;
 
     for(; buf < end; buf= buf2+1) {
         buf2 = buf;
         for(frames = 0; buf2 < end; frames++) {

             MPADecodeHeader h;
 

             header = AV_RB32(buf2);

             ret = avpriv_mpegaudio_decode_header(&h, header);
             if (ret != 0)

                 break;

             buf2 += h.frame_size;

         }
         max_frames = FFMAX(max_frames, frames);

         if(buf == buf0) {

             first_frames= frames;

             if (buf2 == end + sizeof(uint32_t))
                 whole_used = 1;
         }

     }
     // keep this in sync with ac3 probe, both need to avoid
     // issues with MPEG-files!

     if   (first_frames>=7) return AVPROBE_SCORE_EXTENSION + 1;

     else if(max_frames>200)return AVPROBE_SCORE_EXTENSION;

     else if(max_frames>=4 && max_frames >= p->buf_size/10000) return AVPROBE_SCORE_EXTENSION / 2;

     else if(ff_id3v2_match(buf0, ID3v2_DEFAULT_MAGIC) && 2*ff_id3v2_tag_len(buf0) >= p->buf_size)

                            return p->buf_size < PROBE_BUF_MAX ? AVPROBE_SCORE_EXTENSION / 4 : AVPROBE_SCORE_EXTENSION - 2;

     else if(first_frames > 1 && whole_used) return 5;

     else if(max_frames>=1 && max_frames >= p->buf_size/10000) return 1;

     else                   return 0;
 //mpegps_mp3_unrecognized_format.mpg has max_frames=3
 }
 

 static void read_xing_toc(AVFormatContext *s, int64_t filesize, int64_t duration)

 {
     int i;

     MP3DecContext *mp3 = s->priv_data;

     int fast_seek = s->flags & AVFMT_FLAG_FAST_SEEK;
     int fill_index = (mp3->usetoc || fast_seek) && duration > 0;

 
     if (!filesize &&
         !(filesize = avio_size(s->pb))) {
         av_log(s, AV_LOG_WARNING, "Cannot determine file size, skipping TOC table.\n");

         fill_index = 0;

     }
 
     for (i = 0; i < XING_TOC_COUNT; i++) {
         uint8_t b = avio_r8(s->pb);

         if (fill_index)

             av_add_index_entry(s->streams[0],

                            av_rescale(b, filesize, 256),

                            av_rescale(i, duration, XING_TOC_COUNT),
                            0, 0, AVINDEX_KEYFRAME);
     }

     if (fill_index)
         mp3->xing_toc = 1;

 }
 

 static void mp3_parse_info_tag(AVFormatContext *s, AVStream *st,

                                MPADecodeHeader *c, uint32_t spf)

 {

 #define LAST_BITS(k, n) ((k) & ((1 << (n)) - 1))
 #define MIDDLE_BITS(k, m, n) LAST_BITS((k) >> (m), ((n) - (m)))
 
     uint16_t crc;

     uint32_t v;

 
     char version[10];
 
     uint32_t peak   = 0;
     int32_t  r_gain = INT32_MIN, a_gain = INT32_MIN;
 

     MP3DecContext *mp3 = s->priv_data;

     static const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};

     uint64_t fsize = avio_size(s->pb);

     fsize = fsize >= avio_tell(s->pb) ? fsize - avio_tell(s->pb) : 0;

     /* Check for Xing / Info tag */

     avio_skip(s->pb, xing_offtbl[c->lsf == 1][c->nb_channels == 1]);

     v = avio_rb32(s->pb);

     mp3->is_cbr = v == MKBETAG('I', 'n', 'f', 'o');

     if (v != MKBETAG('X', 'i', 'n', 'g') && !mp3->is_cbr)
         return;
 
     v = avio_rb32(s->pb);
     if (v & XING_FLAG_FRAMES)
         mp3->frames = avio_rb32(s->pb);
     if (v & XING_FLAG_SIZE)

         mp3->header_filesize = avio_rb32(s->pb);

     if (fsize && mp3->header_filesize) {
         uint64_t min, delta;
         min = FFMIN(fsize, mp3->header_filesize);
         delta = FFMAX(fsize, mp3->header_filesize) - min;
         if (fsize > mp3->header_filesize && delta > min >> 4) {
             mp3->frames = 0;

             av_log(s, AV_LOG_WARNING,
                    "invalid concatenated file detected - using bitrate for duration\n");

         } else if (delta > min >> 4) {
             av_log(s, AV_LOG_WARNING,
                    "filesize and duration do not match (growing file?)\n");
         }
     }

     if (v & XING_FLAG_TOC)

         read_xing_toc(s, mp3->header_filesize, av_rescale_q(mp3->frames,

                                        (AVRational){spf, c->sample_rate},
                                        st->time_base));

     /* VBR quality */

     if (v & XING_FLAC_QSCALE)
         avio_rb32(s->pb);

     /* Encoder short version string */
     memset(version, 0, sizeof(version));
     avio_read(s->pb, version, 9);
 
     /* Info Tag revision + VBR method */
     avio_r8(s->pb);
 
     /* Lowpass filter value */
     avio_r8(s->pb);
 
     /* ReplayGain peak */
     v    = avio_rb32(s->pb);
     peak = av_rescale(v, 100000, 1 << 23);
 
     /* Radio ReplayGain */
     v = avio_rb16(s->pb);
 
     if (MIDDLE_BITS(v, 13, 15) == 1) {
         r_gain = MIDDLE_BITS(v, 0, 8) * 10000;
 
         if (v & (1 << 9))
             r_gain *= -1;
     }
 
     /* Audiophile ReplayGain */
     v = avio_rb16(s->pb);
 
     if (MIDDLE_BITS(v, 13, 15) == 2) {
         a_gain = MIDDLE_BITS(v, 0, 8) * 10000;
 
         if (v & (1 << 9))
             a_gain *= -1;
     }
 
     /* Encoding flags + ATH Type */
     avio_r8(s->pb);
 
     /* if ABR {specified bitrate} else {minimal bitrate} */
     avio_r8(s->pb);
 
     /* Encoder delays */

     v= avio_rb24(s->pb);
     if(AV_RB32(version) == MKBETAG('L', 'A', 'M', 'E')

         || AV_RB32(version) == MKBETAG('L', 'a', 'v', 'f')
         || AV_RB32(version) == MKBETAG('L', 'a', 'v', 'c')
     ) {

 
         mp3->start_pad = v>>12;
         mp3->  end_pad = v&4095;

         st->start_skip_samples = mp3->start_pad + 528 + 1;

         if (mp3->frames) {
             st->first_discard_sample = -mp3->end_pad + 528 + 1 + mp3->frames * (int64_t)spf;
             st->last_discard_sample = mp3->frames * (int64_t)spf;
         }

         if (!st->start_time)

             st->start_time = av_rescale_q(st->start_skip_samples,

                                             (AVRational){1, c->sample_rate},
                                             st->time_base);
         av_log(s, AV_LOG_DEBUG, "pad %d %d\n", mp3->start_pad, mp3->  end_pad);
     }

 
     /* Misc */
     avio_r8(s->pb);
 
     /* MP3 gain */
     avio_r8(s->pb);
 
     /* Preset and surround info */
     avio_rb16(s->pb);
 
     /* Music length */
     avio_rb32(s->pb);
 
     /* Music CRC */
     avio_rb16(s->pb);
 
     /* Info Tag CRC */
     crc = ffio_get_checksum(s->pb);
     v   = avio_rb16(s->pb);
 
     if (v == crc) {
         ff_replaygain_export_raw(st, r_gain, peak, a_gain, 0);
         av_dict_set(&st->metadata, "encoder", version, 0);

     }

 }
 
 static void mp3_parse_vbri_tag(AVFormatContext *s, AVStream *st, int64_t base)
 {
     uint32_t v;
     MP3DecContext *mp3 = s->priv_data;

 
     /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */

     avio_seek(s->pb, base + 4 + 32, SEEK_SET);

     v = avio_rb32(s->pb);

     if (v == MKBETAG('V', 'B', 'R', 'I')) {

         /* Check tag version */

         if (avio_rb16(s->pb) == 1) {

             /* skip delay and quality */

             avio_skip(s->pb, 4);

             mp3->header_filesize = avio_rb32(s->pb);

             mp3->frames = avio_rb32(s->pb);

         }
     }

 }

 
 /**
  * Try to find Xing/Info/VBRI tags and compute duration from info therein
  */
 static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
 {
     uint32_t v, spf;
     MPADecodeHeader c;
     int vbrtag_size = 0;

     MP3DecContext *mp3 = s->priv_data;

     int ret;

     ffio_init_checksum(s->pb, ff_crcA001_update, 0);
 

     v = avio_rb32(s->pb);

     ret = avpriv_mpegaudio_decode_header(&c, v);
     if (ret < 0)
         return ret;
     else if (ret == 0)

         vbrtag_size = c.frame_size;
     if(c.layer != 3)
         return -1;
 

     spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
 

     mp3->frames = 0;

     mp3->header_filesize   = 0;

     mp3_parse_info_tag(s, st, &c, spf);

     mp3_parse_vbri_tag(s, st, base);

     if (!mp3->frames && !mp3->header_filesize)

         return -1;
 
     /* Skip the vbr tag frame */

     avio_seek(s->pb, base + vbrtag_size, SEEK_SET);

     if (mp3->frames)
         st->duration = av_rescale_q(mp3->frames, (AVRational){spf, c.sample_rate},

                                     st->time_base);

     if (mp3->header_filesize && mp3->frames && !mp3->is_cbr)

         st->codecpar->bit_rate = av_rescale(mp3->header_filesize, 8 * c.sample_rate, mp3->frames * (int64_t)spf);

     return 0;
 }
 

 static int mp3_read_header(AVFormatContext *s)

 {

     MP3DecContext *mp3 = s->priv_data;

     AVStream *st;
     int64_t off;

     int ret;

     int i;

     st = avformat_new_stream(s, NULL);

     if (!st)
         return AVERROR(ENOMEM);
 

     st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
     st->codecpar->codec_id = AV_CODEC_ID_MP3;

     st->need_parsing = AVSTREAM_PARSE_FULL_RAW;

     st->start_time = 0;
 
     // lcm of all mp3 sample rates

     avpriv_set_pts_info(st, 64, 1, 14112000);

     s->pb->maxsize = -1;

     off = avio_tell(s->pb);

     if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))

         ff_id3v1_read(s);
 

     if(s->pb->seekable)
         mp3->filesize = avio_size(s->pb);
 

     if (mp3_parse_vbr_tags(s, st, off) < 0)

         avio_seek(s->pb, off, SEEK_SET);

     ret = ff_replaygain_export(st, s->metadata);
     if (ret < 0)
         return ret;
 

     off = avio_tell(s->pb);
     for (i = 0; i < 64 * 1024; i++) {

         uint32_t header, header2;
         int frame_size;

         if (!(i&1023))
             ffio_ensure_seekback(s->pb, i + 1024 + 4);

         frame_size = check(s->pb, off + i, &header);
         if (frame_size > 0) {

             ret = avio_seek(s->pb, off, SEEK_SET);
             if (ret < 0)
                 return ret;

             ffio_ensure_seekback(s->pb, i + 1024 + frame_size + 4);

             ret = check(s->pb, off + i + frame_size, &header2);
             if (ret >= 0 &&

                 (header & SAME_HEADER_MASK) == (header2 & SAME_HEADER_MASK))
             {

                 av_log(s, i > 0 ? AV_LOG_INFO : AV_LOG_VERBOSE, "Skipping %d bytes of junk at %"PRId64".\n", i, off);

                 ret = avio_seek(s->pb, off + i, SEEK_SET);
                 if (ret < 0)
                     return ret;

                 break;

             } else if (ret == CHECK_SEEK_FAILED) {
                 av_log(s, AV_LOG_ERROR, "Invalid frame size (%d): Could not seek to %"PRId64".\n", frame_size, off + i + frame_size);
                 return AVERROR(EINVAL);

             }

         } else if (frame_size == CHECK_SEEK_FAILED) {
             av_log(s, AV_LOG_ERROR, "Failed to read frame size: Could not seek to %"PRId64".\n", (int64_t) (i + 1024 + frame_size + 4));
             return AVERROR(EINVAL);

         }

         ret = avio_seek(s->pb, off, SEEK_SET);
         if (ret < 0)
             return ret;

     }
 

     // the seek index is relative to the end of the xing vbr headers
     for (i = 0; i < st->nb_index_entries; i++)
         st->index_entries[i].pos += avio_tell(s->pb);
 

     /* the parameters will be extracted from the compressed bitstream */
     return 0;
 }
 
 #define MP3_PACKET_SIZE 1024
 
 static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
 {

     MP3DecContext *mp3 = s->priv_data;

     int ret, size;

     int64_t pos;

 
     size= MP3_PACKET_SIZE;

     pos = avio_tell(s->pb);
     if(mp3->filesize > ID3v1_TAG_SIZE && pos < mp3->filesize)
         size= FFMIN(size, mp3->filesize - pos);

 
     ret= av_get_packet(s->pb, pkt, size);
     if (ret <= 0) {

         if(ret<0)
             return ret;
         return AVERROR_EOF;

     }

     pkt->flags &= ~AV_PKT_FLAG_CORRUPT;

     pkt->stream_index = 0;

     return ret;
 }
 

 #define SEEK_WINDOW 4096

 static int check(AVIOContext *pb, int64_t pos, uint32_t *ret_header)

 {

     int64_t ret = avio_seek(pb, pos, SEEK_SET);

     uint8_t header_buf[4];

     unsigned header;
     MPADecodeHeader sd;
     if (ret < 0)

         return CHECK_SEEK_FAILED;
 
     ret = avio_read(pb, &header_buf[0], 4);

     /* We should always find four bytes for a valid mpa header. */
     if (ret < 4)

         return CHECK_SEEK_FAILED;

     header = AV_RB32(&header_buf[0]);

     if (ff_mpa_check_header(header) < 0)

         return CHECK_WRONG_HEADER;

     if (avpriv_mpegaudio_decode_header(&sd, header) == 1)

         return CHECK_WRONG_HEADER;

     if (ret_header)
         *ret_header = header;

     return sd.frame_size;
 }
 

 static int64_t mp3_sync(AVFormatContext *s, int64_t target_pos, int flags)

 {

     int dir = (flags&AVSEEK_FLAG_BACKWARD) ? -1 : 1;

     int64_t best_pos;

     int best_score, i, j;
     int64_t ret;

     avio_seek(s->pb, FFMAX(target_pos - SEEK_WINDOW, 0), SEEK_SET);
     ret = avio_seek(s->pb, target_pos, SEEK_SET);

     if (ret < 0)
         return ret;

 #define MIN_VALID 3

     best_pos = target_pos;

     best_score = 999;

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

         int64_t pos = target_pos + (dir > 0 ? i - SEEK_WINDOW/4 : -i);

         int64_t candidate = -1;
         int score = 999;

 
         if (pos < 0)
             continue;
 

         for(j=0; j<MIN_VALID; j++) {

             ret = check(s->pb, pos, NULL);

             if(ret < 0) {
                 if (ret == CHECK_WRONG_HEADER) {
                     break;
                 } else if (ret == CHECK_SEEK_FAILED) {
                     av_log(s, AV_LOG_ERROR, "Could not seek to %"PRId64".\n", pos);
                     return AVERROR(EINVAL);
                 }
             }

             if ((target_pos - pos)*dir <= 0 && abs(MIN_VALID/2-j) < score) {

                 candidate = pos;
                 score = abs(MIN_VALID/2-j);
             }

             pos += ret;

         }

         if (best_score > score && j == MIN_VALID) {
             best_pos = candidate;
             best_score = score;
             if(score == 0)
                 break;
         }

     }

     return avio_seek(s->pb, best_pos, SEEK_SET);
 }
 
 static int mp3_seek(AVFormatContext *s, int stream_index, int64_t timestamp,
                     int flags)
 {
     MP3DecContext *mp3 = s->priv_data;
     AVIndexEntry *ie, ie1;
     AVStream *st = s->streams[0];
     int64_t best_pos;

     int fast_seek = s->flags & AVFMT_FLAG_FAST_SEEK;

     int64_t filesize = mp3->header_filesize;

     if (filesize <= 0) {
         int64_t size = avio_size(s->pb);
         if (size > 0 && size > s->internal->data_offset)
             filesize = size - s->internal->data_offset;
     }
 

     if (mp3->xing_toc && (mp3->usetoc || (fast_seek && !mp3->is_cbr))) {
         int64_t ret = av_index_search_timestamp(st, timestamp, flags);
 
         // NOTE: The MP3 TOC is not a precise lookup table. Accuracy is worse
         // for bigger files.
         av_log(s, AV_LOG_WARNING, "Using MP3 TOC to seek; may be imprecise.\n");
 

         if (ret < 0)
             return ret;
 
         ie = &st->index_entries[ret];

     } else if (fast_seek && st->duration > 0 && filesize > 0) {
         if (!mp3->is_cbr)
             av_log(s, AV_LOG_WARNING, "Using scaling to seek VBR MP3; may be imprecise.\n");
 
         ie = &ie1;
         timestamp = av_clip64(timestamp, 0, st->duration);
         ie->timestamp = timestamp;
         ie->pos       = av_rescale(timestamp, filesize, st->duration) + s->internal->data_offset;

     } else {

         return -1; // generic index code

     }
 

     best_pos = mp3_sync(s, ie->pos, flags);

     if (best_pos < 0)
         return best_pos;

     if (mp3->is_cbr && ie == &ie1 && mp3->frames) {

         int frame_duration = av_rescale(st->duration, 1, mp3->frames);
         ie1.timestamp = frame_duration * av_rescale(best_pos - s->internal->data_offset, mp3->frames, mp3->header_filesize);
     }
 

     ff_update_cur_dts(s, st, ie->timestamp);
     return 0;

 }
 

 static const AVOption options[] = {

     { "usetoc", "use table of contents", offsetof(MP3DecContext, usetoc), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, AV_OPT_FLAG_DECODING_PARAM},

     { NULL },
 };
 
 static const AVClass demuxer_class = {
     .class_name = "mp3",
     .item_name  = av_default_item_name,
     .option     = options,
     .version    = LIBAVUTIL_VERSION_INT,
     .category   = AV_CLASS_CATEGORY_DEMUXER,
 };
 

 AVInputFormat ff_mp3_demuxer = {

     .name           = "mp3",

     .long_name      = NULL_IF_CONFIG_SMALL("MP2/3 (MPEG audio layer 2/3)"),

     .read_probe     = mp3_read_probe,
     .read_header    = mp3_read_header,
     .read_packet    = mp3_read_packet,

     .read_seek      = mp3_seek,

     .priv_data_size = sizeof(MP3DecContext),

     .flags          = AVFMT_GENERIC_INDEX,

     .extensions     = "mp2,mp3,m2a,mpa", /* XXX: use probe */

     .priv_class     = &demuxer_class,

 };