/*
  * Dirac parser
  *

  * Copyright (c) 2007-2008 Marco Gerards <marco@gnu.org>
  * Copyright (c) 2008 BBC, Anuradha Suraparaju <asuraparaju@gmail.com>

  *
  * 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

  * Dirac Parser
  * @author Marco Gerards <marco@gnu.org>
  */
 

 #include "libavutil/intreadwrite.h"

 #include "parser.h"
 
 #define DIRAC_PARSE_INFO_PREFIX 0x42424344
 
 /**

  * Find the end of the current frame in the bitstream.

  * @return the position of the first byte of the next frame or -1
  */

 typedef struct DiracParseContext {
     int state;
     int is_synced;
     int sync_offset;
     int header_bytes_needed;
     int overread_index;
     int buffer_size;
     int index;
     uint8_t *buffer;
     int dirac_unit_size;
     uint8_t *dirac_unit;
 } DiracParseContext;
 
 static int find_frame_end(DiracParseContext *pc,
                           const uint8_t *buf, int buf_size)

 {
     uint32_t state = pc->state;

     int i = 0;
 
     if (!pc->is_synced) {
         for (i = 0; i < buf_size; i++) {
             state = (state << 8) | buf[i];
             if (state == DIRAC_PARSE_INFO_PREFIX) {
                 state                   = -1;
                 pc->is_synced           = 1;
                 pc->header_bytes_needed = 9;
                 pc->sync_offset         = i;
                 break;

             }
         }
     }
 

     if (pc->is_synced) {
         pc->sync_offset = 0;
         for (; i < buf_size; i++) {
             if (state == DIRAC_PARSE_INFO_PREFIX) {
                 if ((buf_size-i) >= pc->header_bytes_needed) {
                     pc->state = -1;
                     return i + pc->header_bytes_needed;
                 } else {
                     pc->header_bytes_needed = 9-(buf_size-i);
                     break;
                 }
             } else
               state = (state << 8) | buf[i];
         }
     }

     pc->state = state;

     return -1;
 }
 
 typedef struct DiracParseUnit
 {
     int next_pu_offset;
     int prev_pu_offset;
     uint8_t pu_type;
 } DiracParseUnit;
 
 static int unpack_parse_unit(DiracParseUnit *pu, DiracParseContext *pc,
                              int offset)
 {
     uint8_t *start = pc->buffer + offset;
     uint8_t *end   = pc->buffer + pc->index;
     if (start < pc->buffer || (start+13 > end))
         return 0;
     pu->pu_type = start[4];
 
     pu->next_pu_offset = AV_RB32(start+5);
     pu->prev_pu_offset = AV_RB32(start+9);
 
     if (pu->pu_type == 0x10 && pu->next_pu_offset == 0)
         pu->next_pu_offset = 13;
 
     return 1;
 }
 
 static int dirac_combine_frame(AVCodecParserContext *s, AVCodecContext *avctx,
                                int next, const uint8_t **buf, int *buf_size)
 {
     int parse_timing_info = (s->pts == AV_NOPTS_VALUE &&
                              s->dts == AV_NOPTS_VALUE);
     DiracParseContext *pc = s->priv_data;
 
     if (pc->overread_index) {
         memcpy(pc->buffer, pc->buffer + pc->overread_index,
                pc->index - pc->overread_index);
         pc->index -= pc->overread_index;
         pc->overread_index = 0;
         if (*buf_size == 0 && pc->buffer[4] == 0x10) {
             *buf      = pc->buffer;
             *buf_size = pc->index;
             return 0;
         }
     }
 
     if ( next == -1) {
         /* Found a possible frame start but not a frame end */
         void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,
                                            pc->index + (*buf_size -
                                                         pc->sync_offset));
         pc->buffer = new_buffer;
         memcpy(pc->buffer+pc->index, (*buf + pc->sync_offset),
                *buf_size - pc->sync_offset);
         pc->index += *buf_size - pc->sync_offset;
         return -1;
     } else {
         /* Found a possible frame start and a  possible frame end */
         DiracParseUnit pu1, pu;
         void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,
                                            pc->index + next);
         pc->buffer = new_buffer;
         memcpy(pc->buffer + pc->index, *buf, next);
         pc->index += next;

         /* Need to check if we have a valid Parse Unit. We can't go by the
          * sync pattern 'BBCD' alone because arithmetic coding of the residual
          * and motion data can cause the pattern triggering a false start of
          * frame. So check if the previous parse offset of the next parse unit
          * is equal to the next parse offset of the current parse unit then
          * we can be pretty sure that we have a valid parse unit */
         if (!unpack_parse_unit(&pu1, pc, pc->index - 13)                     ||
             !unpack_parse_unit(&pu, pc, pc->index - 13 - pu1.prev_pu_offset) ||
             pu.next_pu_offset != pu1.prev_pu_offset) {
             pc->index -= 9;
             *buf_size = next-9;
             pc->header_bytes_needed = 9;
             return -1;
         }
 
         /* All non-frame data must be accompanied by frame data. This is to
          * ensure that pts is set correctly. So if the current parse unit is
          * not frame data, wait for frame data to come along */
 
         pc->dirac_unit = pc->buffer + pc->index - 13 -
                          pu1.prev_pu_offset - pc->dirac_unit_size;
 
         pc->dirac_unit_size += pu.next_pu_offset;
 
         if ((pu.pu_type&0x08) != 0x08) {
             pc->header_bytes_needed = 9;
             *buf_size = next;
             return -1;
         }
 
         /* Get the picture number to set the pts and dts*/
         if (parse_timing_info) {
             uint8_t *cur_pu = pc->buffer +
                               pc->index - 13 - pu1.prev_pu_offset;
             int pts =  AV_RB32(cur_pu + 13);
             if (s->last_pts == 0 && s->last_dts == 0)
                 s->dts = pts - 1;
             else
                 s->dts = s->last_dts+1;
             s->pts = pts;
             if (!avctx->has_b_frames && (cur_pu[4] & 0x03))
                 avctx->has_b_frames = 1;
         }
         if (avctx->has_b_frames && s->pts == s->dts)

              s->pict_type = AV_PICTURE_TYPE_B;

 
         /* Finally have a complete Dirac data unit */
         *buf      = pc->dirac_unit;
         *buf_size = pc->dirac_unit_size;
 
         pc->dirac_unit_size     = 0;
         pc->overread_index      = pc->index-13;
         pc->header_bytes_needed = 9;
     }
     return next;

 }
 
 static int dirac_parse(AVCodecParserContext *s, AVCodecContext *avctx,
                        const uint8_t **poutbuf, int *poutbuf_size,
                        const uint8_t *buf, int buf_size)
 {

     DiracParseContext *pc = s->priv_data;

     int next;
 

     *poutbuf = NULL;
     *poutbuf_size = 0;
 

     if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
         next = buf_size;

         *poutbuf = buf;
         *poutbuf_size = buf_size;
         /* Assume that data has been packetized into an encapsulation unit. */
     } else {

         next = find_frame_end(pc, buf, buf_size);

         if (!pc->is_synced && next == -1) {
             /* No frame start found yet. So throw away the entire buffer. */
             return buf_size;
         }

         if (dirac_combine_frame(s, avctx, next, &buf, &buf_size) < 0) {

             return buf_size;
         }
     }
 
     *poutbuf = buf;
     *poutbuf_size = buf_size;
     return next;
 }
 

 static void dirac_parse_close(AVCodecParserContext *s)
 {
     DiracParseContext *pc = s->priv_data;
 
     if (pc->buffer_size > 0)
         av_free(pc->buffer);
 }
 

 AVCodecParser ff_dirac_parser = {

     .codec_ids      = { CODEC_ID_DIRAC },
     .priv_data_size = sizeof(DiracParseContext),
     .parser_parse   = dirac_parse,
     .parser_close   = dirac_parse_close,

 };