/*
  * Copyright (c) 2012 Justin Ruggles
  *

  * 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
  */
 
 /**
  * @file
  * Vorbis audio parser
  *
  * Determines the duration for each packet.
  */
 
 #include "get_bits.h"
 #include "parser.h"
 #include "xiph.h"
 #include "vorbis_parser.h"
 
 static int parse_id_header(AVCodecContext *avctx, VorbisParseContext *s,
                            const uint8_t *buf, int buf_size)
 {
     /* Id header should be 30 bytes */
     if (buf_size < 30) {
         av_log(avctx, AV_LOG_ERROR, "Id header is too short\n");
         return AVERROR_INVALIDDATA;
     }
 
     /* make sure this is the Id header */
     if (buf[0] != 1) {
         av_log(avctx, AV_LOG_ERROR, "Wrong packet type in Id header\n");
         return AVERROR_INVALIDDATA;
     }
 
     /* check for header signature */
     if (memcmp(&buf[1], "vorbis", 6)) {
         av_log(avctx, AV_LOG_ERROR, "Invalid packet signature in Id header\n");
         return AVERROR_INVALIDDATA;
     }
 
     if (!(buf[29] & 0x1)) {
         av_log(avctx, AV_LOG_ERROR, "Invalid framing bit in Id header\n");
         return AVERROR_INVALIDDATA;
     }
 
     s->blocksize[0] = 1 << (buf[28] & 0xF);
     s->blocksize[1] = 1 << (buf[28] >>  4);
 
     return 0;
 }
 
 static int parse_setup_header(AVCodecContext *avctx, VorbisParseContext *s,
                               const uint8_t *buf, int buf_size)
 {
     GetBitContext gb, gb0;
     uint8_t *rev_buf;
     int i, ret = 0;
     int got_framing_bit, mode_count, got_mode_header, last_mode_count = 0;
 
     /* avoid overread */
     if (buf_size < 7) {
         av_log(avctx, AV_LOG_ERROR, "Setup header is too short\n");
         return AVERROR_INVALIDDATA;
     }
 
     /* make sure this is the Setup header */
     if (buf[0] != 5) {
         av_log(avctx, AV_LOG_ERROR, "Wrong packet type in Setup header\n");
         return AVERROR_INVALIDDATA;
     }
 
     /* check for header signature */
     if (memcmp(&buf[1], "vorbis", 6)) {
         av_log(avctx, AV_LOG_ERROR, "Invalid packet signature in Setup header\n");
         return AVERROR_INVALIDDATA;
     }
 
     /* reverse bytes so we can easily read backwards with get_bits() */
     if (!(rev_buf = av_malloc(buf_size))) {
         av_log(avctx, AV_LOG_ERROR, "Out of memory\n");
         return AVERROR(ENOMEM);
     }
     for (i = 0; i < buf_size; i++)
         rev_buf[i] = buf[buf_size - 1 - i];
     init_get_bits(&gb, rev_buf, buf_size * 8);
 
     got_framing_bit = 0;
     while (get_bits_left(&gb) > 97) {
         if (get_bits1(&gb)) {
             got_framing_bit = get_bits_count(&gb);
             break;
         }
     }
     if (!got_framing_bit) {
         av_log(avctx, AV_LOG_ERROR, "Invalid Setup header\n");
         ret = AVERROR_INVALIDDATA;
         goto bad_header;
     }
 
     /* Now we search backwards to find possible valid mode counts. This is not
      * fool-proof because we could have false positive matches and read too
      * far, but there isn't really any way to be sure without parsing through
      * all the many variable-sized fields before the modes. This approach seems
      * to work well in testing, and it is similar to how it is handled in
      * liboggz. */
     mode_count = 0;
     got_mode_header = 0;
     while (get_bits_left(&gb) >= 97) {
         if (get_bits(&gb, 8) > 63 || get_bits(&gb, 16) || get_bits(&gb, 16))
             break;
         skip_bits(&gb, 1);
         mode_count++;
         if (mode_count > 64)
             break;
         gb0 = gb;
         if (get_bits(&gb0, 6) + 1 == mode_count) {
             got_mode_header = 1;
             last_mode_count = mode_count;
         }
     }
     if (!got_mode_header) {
         av_log(avctx, AV_LOG_ERROR, "Invalid Setup header\n");
         ret = AVERROR_INVALIDDATA;
         goto bad_header;
     }
     /* All samples I've seen use <= 2 modes, so ask for a sample if we find
      * more than that, as it is most likely a false positive. If we get any
      * we may need to approach this the long way and parse the whole Setup
      * header, but I hope very much that it never comes to that. */
     if (last_mode_count > 2) {

         avpriv_request_sample(avctx,
                               "%d modes (either a false positive or a "
                               "sample from an unknown encoder)",

                               last_mode_count);
     }
     /* We're limiting the mode count to 63 so that we know that the previous
      * block flag will be in the first packet byte. */
     if (last_mode_count > 63) {
         av_log(avctx, AV_LOG_ERROR, "Unsupported mode count: %d\n",
                last_mode_count);
         ret = AVERROR_INVALIDDATA;
         goto bad_header;
     }
     s->mode_count = mode_count = last_mode_count;
     /* Determine the number of bits required to code the mode and turn that
      * into a bitmask to directly access the mode from the first frame byte. */
     s->mode_mask = ((1 << (av_log2(mode_count - 1) + 1)) - 1) << 1;
     /* The previous window flag is the next bit after the mode */
     s->prev_mask = (s->mode_mask | 0x1) + 1;
 
     init_get_bits(&gb, rev_buf, buf_size * 8);
     skip_bits_long(&gb, got_framing_bit);
     for (i = mode_count - 1; i >= 0; i--) {
         skip_bits_long(&gb, 40);

         s->mode_blocksize[i] = get_bits1(&gb);

     }
 
 bad_header:
     av_free(rev_buf);
     return ret;
 }
 
 int avpriv_vorbis_parse_extradata(AVCodecContext *avctx, VorbisParseContext *s)
 {
     uint8_t *header_start[3];
     int header_len[3];
     int ret;
 
     s->avctx = avctx;
     s->extradata_parsed = 1;
 
     if ((ret = avpriv_split_xiph_headers(avctx->extradata,
                                          avctx->extradata_size, 30,
                                          header_start, header_len)) < 0) {
         av_log(avctx, AV_LOG_ERROR, "Extradata corrupt.\n");
         return ret;
     }
 
     if ((ret = parse_id_header(avctx, s, header_start[0], header_len[0])) < 0)
         return ret;
 
     if ((ret = parse_setup_header(avctx, s, header_start[2], header_len[2])) < 0)
         return ret;
 
     s->valid_extradata = 1;

     s->previous_blocksize = s->blocksize[s->mode_blocksize[0]];

 
     return 0;
 }
 

 int avpriv_vorbis_parse_frame_flags(VorbisParseContext *s, const uint8_t *buf,
                                     int buf_size, int *flags)

 {
     int duration = 0;
 
     if (s->valid_extradata && buf_size > 0) {
         int mode, current_blocksize;
         int previous_blocksize = s->previous_blocksize;
 
         if (buf[0] & 1) {

             /* If the user doesn't care about special packets, it's a bad one. */
             if (!flags)
                 goto bad_packet;
 
             /* Set the flag for which kind of special packet it is. */
             if (buf[0] == 1)
                 *flags |= VORBIS_FLAG_HEADER;
             else if (buf[0] == 3)
                 *flags |= VORBIS_FLAG_COMMENT;
             else
                 goto bad_packet;
 
             /* Special packets have no duration. */
             return 0;
 
 bad_packet:

             av_log(s->avctx, AV_LOG_ERROR, "Invalid packet\n");
             return AVERROR_INVALIDDATA;
         }
         if (s->mode_count == 1)
             mode = 0;
         else
             mode = (buf[0] & s->mode_mask) >> 1;
         if (mode >= s->mode_count) {
             av_log(s->avctx, AV_LOG_ERROR, "Invalid mode in packet\n");
             return AVERROR_INVALIDDATA;
         }

         if(s->mode_blocksize[mode]){

             int flag = !!(buf[0] & s->prev_mask);
             previous_blocksize = s->blocksize[flag];
         }

         current_blocksize     = s->blocksize[s->mode_blocksize[mode]];

         duration              = (previous_blocksize + current_blocksize) >> 2;

         s->previous_blocksize = current_blocksize;
     }
 
     return duration;
 }
 

 int avpriv_vorbis_parse_frame(VorbisParseContext *s, const uint8_t *buf,
                               int buf_size)
 {
     return avpriv_vorbis_parse_frame_flags(s, buf, buf_size, NULL);
 }
 

 void avpriv_vorbis_parse_reset(VorbisParseContext *s)
 {
     if (s->valid_extradata)

         s->previous_blocksize = s->blocksize[0];

 }
 
 #if CONFIG_VORBIS_PARSER
 static int vorbis_parse(AVCodecParserContext *s1, AVCodecContext *avctx,
                         const uint8_t **poutbuf, int *poutbuf_size,
                         const uint8_t *buf, int buf_size)
 {
     VorbisParseContext *s = s1->priv_data;
     int duration;
 
     if (!s->extradata_parsed && avctx->extradata && avctx->extradata_size)
         if (avpriv_vorbis_parse_extradata(avctx, s))
             goto end;
 
     if ((duration = avpriv_vorbis_parse_frame(s, buf, buf_size)) >= 0)
         s1->duration = duration;
 
 end:
     /* always return the full packet. this parser isn't doing any splitting or
        combining, only packet analysis */
     *poutbuf      = buf;
     *poutbuf_size = buf_size;
     return buf_size;
 }
 
 AVCodecParser ff_vorbis_parser = {

     .codec_ids      = { AV_CODEC_ID_VORBIS },

     .priv_data_size = sizeof(VorbisParseContext),
     .parser_parse   = vorbis_parse,
 };
 #endif /* CONFIG_VORBIS_PARSER */