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

 #include "libavutil/dict.h"

 #include "libavutil/mathematics.h"

 #include "avformat.h"

 #include "internal.h"

 #include "id3v2.h"
 #include "id3v1.h"
 #include "libavcodec/mpegaudiodecheader.h"
 

 #define XING_FLAG_FRAMES 0x01
 #define XING_FLAG_SIZE   0x02

 #define XING_FLAG_TOC    0x04
 
 #define XING_TOC_COUNT 100

 typedef struct {
     int64_t filesize;

     int64_t header_filesize;

     int xing_toc;

     int start_pad;
     int end_pad;

     int is_cbr;

 } MP3DecContext;

 /* mp3 read */
 
 static int mp3_read_probe(AVProbeData *p)
 {
     int max_frames, first_frames = 0;
     int fsize, frames, sample_rate;
     uint32_t header;

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

     AVCodecContext avctx;
 
     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++) {
             header = AV_RB32(buf2);

             fsize = avpriv_mpa_decode_header(&avctx, header, &sample_rate, &sample_rate, &sample_rate, &sample_rate);

             if(fsize < 0)
                 break;
             buf2 += fsize;
         }
         max_frames = FFMAX(max_frames, frames);
         if(buf == buf0)
             first_frames= frames;
     }
     // keep this in sync with ac3 probe, both need to avoid
     // issues with MPEG-files!
     if   (first_frames>=4) return AVPROBE_SCORE_MAX/2+1;

     else if(max_frames>200)return AVPROBE_SCORE_MAX/2;

     else if(max_frames>=4) return AVPROBE_SCORE_MAX/4;

     else if(ff_id3v2_match(buf0, ID3v2_DEFAULT_MAGIC) && 2*ff_id3v2_tag_len(buf0) >= p->buf_size)
                            return AVPROBE_SCORE_MAX/8;

     else if(max_frames>=1) 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;

 
     if (!filesize &&
         !(filesize = avio_size(s->pb))) {
         av_log(s, AV_LOG_WARNING, "Cannot determine file size, skipping TOC table.\n");
         return;
     }
 
     for (i = 0; i < XING_TOC_COUNT; i++) {
         uint8_t b = avio_r8(s->pb);
 
         av_add_index_entry(s->streams[0],
                            av_rescale(b, filesize, 256),
                            av_rescale(i, duration, XING_TOC_COUNT),
                            0, 0, AVINDEX_KEYFRAME);
     }

     mp3->xing_toc = 1;

 }
 

 /**
  * 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)
 {

     MP3DecContext *mp3 = s->priv_data;

     uint32_t v, spf;
     unsigned frames = 0; /* Total number of frames in file */
     unsigned size = 0; /* Total number of bytes in the stream */
     const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
     MPADecodeHeader c;
     int vbrtag_size = 0;

     int is_cbr;

     v = avio_rb32(s->pb);

     if(ff_mpa_check_header(v) < 0)
       return -1;
 

     if (avpriv_mpegaudio_decode_header(&c, v) == 0)

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

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

     /* Check for Xing / Info tag */

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

     v = avio_rb32(s->pb);

     is_cbr = v == MKBETAG('I', 'n', 'f', 'o');
     if (v == MKBETAG('X', 'i', 'n', 'g') || is_cbr) {

         v = avio_rb32(s->pb);

         if(v & XING_FLAG_FRAMES)

             frames = avio_rb32(s->pb);

         if(v & XING_FLAG_SIZE)

             size = avio_rb32(s->pb);

         if (v & XING_FLAG_TOC && frames)
             read_xing_toc(s, size, av_rescale_q(frames, (AVRational){spf, c.sample_rate},
                                     st->time_base));

         if(v & 8)
             avio_skip(s->pb, 4);
 
         v = avio_rb32(s->pb);

         if(v == MKBETAG('L', 'A', 'M', 'E') || v == MKBETAG('L', 'a', 'v', 'f')) {

             avio_skip(s->pb, 21-4);
             v= avio_rb24(s->pb);
             mp3->start_pad = v>>12;
             mp3->  end_pad = v&4095;
             st->skip_samples = mp3->start_pad + 528 + 1;
             av_log(s, AV_LOG_DEBUG, "pad %d %d\n", mp3->start_pad, mp3->  end_pad);
         }

     }
 
     /* 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);

             size = avio_rb32(s->pb);

             frames = avio_rb32(s->pb);

         }
     }
 
     if(!frames && !size)
         return -1;
 
     /* Skip the vbr tag frame */

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

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

     if (size && frames && !is_cbr)

         st->codec->bit_rate = av_rescale(size, 8 * c.sample_rate, frames * (int64_t)spf);
 

     mp3->is_cbr          = is_cbr;
     mp3->header_filesize = size;
 

     return 0;
 }
 

 static int mp3_read_header(AVFormatContext *s)

 {

     MP3DecContext *mp3 = s->priv_data;

     AVStream *st;
     int64_t off;
 

     st = avformat_new_stream(s, NULL);

     if (!st)
         return AVERROR(ENOMEM);
 
     st->codec->codec_type = AVMEDIA_TYPE_AUDIO;

     st->codec->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);

 
     /* 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;

     if (ret >= ID3v1_TAG_SIZE &&

         memcmp(&pkt->data[ret - ID3v1_TAG_SIZE], "TAG", 3) == 0)
         ret -= ID3v1_TAG_SIZE;
 

     /* note: we need to modify the packet size here to handle the last
        packet */
     pkt->size = ret;
     return ret;
 }
 

 static int check(AVFormatContext *s, int64_t pos)
 {
     int64_t ret = avio_seek(s->pb, pos, SEEK_SET);
     unsigned header;
     MPADecodeHeader sd;
     if (ret < 0)
         return ret;
     header = avio_rb32(s->pb);
     if (ff_mpa_check_header(header) < 0)
         return -1;
     if (avpriv_mpegaudio_decode_header(&sd, header) == 1)
         return -1;
     return sd.frame_size;
 }
 

 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 ret  = av_index_search_timestamp(st, timestamp, flags);

     int i, j;

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

     if (mp3->is_cbr && st->duration > 0 && mp3->header_filesize > s->data_offset) {
         int64_t filesize = avio_size(s->pb);
         int64_t duration;
         if (filesize <= s->data_offset)
             filesize = mp3->header_filesize;
         filesize -= s->data_offset;
         duration = av_rescale(st->duration, filesize, mp3->header_filesize - s->data_offset);
         ie = &ie1;
         timestamp = av_clip64(timestamp, 0, duration);
         ie->timestamp = timestamp;
         ie->pos       = av_rescale(timestamp, filesize, duration) + s->data_offset;
     } else if (mp3->xing_toc) {
         if (ret < 0)
             return ret;
 
         ie = &st->index_entries[ret];
     } else {

         st->skip_samples = timestamp <= 0 ? mp3->start_pad + 528 + 1 : 0;
 
         return -1;
     }
 

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

 #define MIN_VALID 3
     for(i=0; i<4096; i++) {

         int64_t pos = ie->pos + i*dir;

         for(j=0; j<MIN_VALID; j++) {
             ret = check(s, pos);
             if(ret < 0)
                 break;
             pos += ret;

         }

         if(j==MIN_VALID)
             break;

     }

     if(j!=MIN_VALID)
         i=0;

     ret = avio_seek(s->pb, ie->pos + i*dir, SEEK_SET);

     if (ret < 0)
         return ret;
     ff_update_cur_dts(s, st, ie->timestamp);
     st->skip_samples = ie->timestamp <= 0 ? mp3->start_pad + 528 + 1 : 0;
     return 0;

 }
 

 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", /* XXX: use probe */

 };