/*

 * 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 <string.h>

#include "libavutil/attributes.h"

#include "libavutil/intreadwrite.h"

#include "libavutil/mem.h"

#include "avcodec.h"

#include "parser_internal.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)

{

    int i;

    int8_t *start;

    static const uint8_t valid_pu_types[] = {

        0x00, 0x10, 0x20, 0x30, 0x08, 0x48, 0xC8, 0xE8, 0x0A, 0x0C, 0x0D, 0x0E,

        0x4C, 0x09, 0xCC, 0x88, 0xCB

    };

    if (offset < 0 || pc->index - 13 < offset)

        return 0;

    start = pc->buffer + offset;

    pu->pu_type = start[4];

    pu->next_pu_offset = AV_RB32(start + 5);

    pu->prev_pu_offset = AV_RB32(start + 9);

    /* Check for valid parse code */

    for (i = 0; i < 17; i++)

        if (valid_pu_types[i] == pu->pu_type)

            break;

    if (i == 17)

        return 0;

    if (pu->pu_type == 0x10 && pu->next_pu_offset == 0x00)

        pu->next_pu_offset = 13; /* The length of a parse info header */

    /* Check if the parse offsets are somewhat sane */

    if ((pu->next_pu_offset && pu->next_pu_offset < 13) ||

        (pu->prev_pu_offset && pu->prev_pu_offset < 13))

        return 0;

    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) {

        memmove(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));

        if (!new_buffer)

            return AVERROR(ENOMEM);

        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);

        if (!new_buffer)

            return AVERROR(ENOMEM);

        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 < pc->dirac_unit_size + 13LL + 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 && pu1.prev_pu_offset >= 13) {

            uint8_t *cur_pu = pc->buffer +

                              pc->index - 13 - pu1.prev_pu_offset;

            int64_t pts = AV_RB32(cur_pu + 13);

            if (s->last_pts == 0 && s->last_dts == 0)

                s->dts = pts - 1;

            else if (s->last_dts != AV_NOPTS_VALUE)

                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 av_cold void dirac_parse_close(AVCodecParserContext *s)

{

    DiracParseContext *pc = s->priv_data;

    if (pc->buffer_size > 0)

        av_freep(&pc->buffer);

}

const FFCodecParser ff_dirac_parser = {

    PARSER_CODEC_LIST(AV_CODEC_ID_DIRAC),

    .priv_data_size = sizeof(DiracParseContext),

    .parse          = dirac_parse,

    .close          = dirac_parse_close,

};