/*

 * APNG demuxer

 * Copyright (c) 2014 Benoit Fouet

 *

 * 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

 * APNG demuxer.

 * @see https://wiki.mozilla.org/APNG_Specification

 * @see http://www.w3.org/TR/PNG

 */

#include "avformat.h"

#include "avio_internal.h"

#include "demux.h"

#include "internal.h"

#include "libavutil/imgutils.h"

#include "libavutil/intreadwrite.h"

#include "libavutil/mem.h"

#include "libavutil/opt.h"

#include "libavcodec/apng.h"

#include "libavcodec/png.h"

#include "libavcodec/bytestream.h"

#define DEFAULT_APNG_FPS 15

typedef struct APNGDemuxContext {

    const AVClass *class;

    int max_fps;

    int default_fps;

    int pkt_duration;

    int is_key_frame;

    /*

     * loop options

     */

    int ignore_loop;

    uint32_t num_frames;

    uint32_t num_play;

    uint32_t cur_loop;

} APNGDemuxContext;

/*

 * To be a valid APNG file, we mandate, in this order:

 *     PNGSIG

 *     IHDR

 *     ...

 *     acTL

 *     ...

 *     IDAT

 */

static int apng_probe(const AVProbeData *p)

{

    GetByteContext gb;

    int state = 0;

    uint32_t len, tag;

    bytestream2_init(&gb, p->buf, p->buf_size);

    if (bytestream2_get_be64(&gb) != PNGSIG)

        return 0;

    for (;;) {

        len = bytestream2_get_be32(&gb);

        if (len > 0x7fffffff)

            return 0;

        tag = bytestream2_get_le32(&gb);

        /* we don't check IDAT size, as this is the last tag

         * we check, and it may be larger than the probe buffer */

        if (tag != MKTAG('I', 'D', 'A', 'T') &&

            len + 4 > bytestream2_get_bytes_left(&gb))

            return 0;

        switch (tag) {

        case MKTAG('I', 'H', 'D', 'R'):

            if (len != 13)

                return 0;

            if (av_image_check_size(bytestream2_get_be32(&gb), bytestream2_get_be32(&gb), 0, NULL))

                return 0;

            bytestream2_skip(&gb, 9);

            state++;

            break;

        case MKTAG('a', 'c', 'T', 'L'):

            if (state != 1 ||

                len != 8 ||

                bytestream2_get_be32(&gb) == 0) /* 0 is not a valid value for number of frames */

                return 0;

            bytestream2_skip(&gb, 8);

            state++;

            break;

        case MKTAG('I', 'D', 'A', 'T'):

            if (state != 2)

                return 0;

            goto end;

        default:

            /* skip other tags */

            bytestream2_skip(&gb, len + 4);

            break;

        }

    }

end:

    return AVPROBE_SCORE_MAX;

}

static int append_extradata(AVCodecParameters *par, AVIOContext *pb, int len)

{

    int previous_size = par->extradata_size;

    int new_size, ret;

    uint8_t *new_extradata;

    if (len > INT_MAX - AV_INPUT_BUFFER_PADDING_SIZE - previous_size)

        return AVERROR_INVALIDDATA;

    new_size = previous_size + len;

    new_extradata = av_realloc(par->extradata, new_size + AV_INPUT_BUFFER_PADDING_SIZE);

    if (!new_extradata)

        return AVERROR(ENOMEM);

    memset(new_extradata + new_size, 0, AV_INPUT_BUFFER_PADDING_SIZE);

    par->extradata = new_extradata;

    par->extradata_size = new_size;

    if ((ret = ffio_read_size(pb, par->extradata + previous_size, len)) < 0)

        return ret;

    return previous_size;

}

static int apng_read_header(AVFormatContext *s)

{

    APNGDemuxContext *ctx = s->priv_data;

    AVIOContext *pb = s->pb;

    uint32_t len, tag;

    AVStream *st;

    int acTL_found = 0;

    int64_t ret;

    /* verify PNGSIG */

    if (avio_rb64(pb) != PNGSIG)

        return AVERROR_INVALIDDATA;

    /* parse IHDR (must be first chunk) */

    len = avio_rb32(pb);

    tag = avio_rl32(pb);

    if (len != 13 || tag != MKTAG('I', 'H', 'D', 'R'))

        return AVERROR_INVALIDDATA;

    st = avformat_new_stream(s, NULL);

    if (!st)

        return AVERROR(ENOMEM);

    /* set the timebase to something large enough (1/100,000 of second)

     * to hopefully cope with all sane frame durations */

    avpriv_set_pts_info(st, 64, 1, 100000);

    st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;

    st->codecpar->codec_id   = AV_CODEC_ID_APNG;

    st->codecpar->width      = avio_rb32(pb);

    st->codecpar->height     = avio_rb32(pb);

    if ((ret = av_image_check_size(st->codecpar->width, st->codecpar->height, 0, s)) < 0)

        return ret;

    /* extradata will contain every chunk up to the first fcTL (excluded) */

    ret = ff_alloc_extradata(st->codecpar, len + 12);

    if (ret < 0)

        return ret;

    AV_WB32(st->codecpar->extradata,    len);

    AV_WL32(st->codecpar->extradata+4,  tag);

    AV_WB32(st->codecpar->extradata+8,  st->codecpar->width);

    AV_WB32(st->codecpar->extradata+12, st->codecpar->height);

    if ((ret = ffio_read_size(pb, st->codecpar->extradata + 16, 9)) < 0)

        return ret;

    while (1) {

        if (acTL_found && ctx->num_play != 1) {

            int64_t size   = avio_size(pb);

            int64_t offset = avio_tell(pb);

            if (size < 0) {

                return size;

            } else if (offset < 0) {

                return offset;

            } else if ((ret = ffio_ensure_seekback(pb, size - offset)) < 0) {

                av_log(s, AV_LOG_WARNING, "Could not ensure seekback, will not loop\n");

                ctx->num_play = 1;

            }

        }

        if ((ctx->num_play == 1 || !acTL_found) &&

            ((ret = ffio_ensure_seekback(pb, 4 /* len */ + 4 /* tag */)) < 0))

            return ret;

        len = avio_rb32(pb);

        if (len > INT_MAX - 12)

            return AVERROR_INVALIDDATA;

        tag = avio_rl32(pb);

        switch (tag) {

        case MKTAG('a', 'c', 'T', 'L'):

            if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0 ||

                (ret = append_extradata(st->codecpar, pb, len + 12)) < 0)

                return ret;

            acTL_found = 1;

            ctx->num_frames = AV_RB32(st->codecpar->extradata + ret + 8);

            ctx->num_play   = AV_RB32(st->codecpar->extradata + ret + 12);

            av_log(s, AV_LOG_DEBUG, "num_frames: %"PRIu32", num_play: %"PRIu32"\n",

                                    ctx->num_frames, ctx->num_play);

            break;

        case MKTAG('f', 'c', 'T', 'L'):

            if (!acTL_found || len != APNG_FCTL_CHUNK_SIZE) {

                return AVERROR_INVALIDDATA;

            }

            if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0)

                return ret;

            return 0;

        default:

            if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0 ||

                (ret = append_extradata(st->codecpar, pb, len + 12)) < 0)

                return ret;

        }

    }

}

static int decode_fctl_chunk(AVFormatContext *s, APNGDemuxContext *ctx, AVPacket *pkt)

{

    uint32_t sequence_number, width, height, x_offset, y_offset;

    uint16_t delay_num, delay_den;

    uint8_t dispose_op, blend_op;

    sequence_number = avio_rb32(s->pb);

    width           = avio_rb32(s->pb);

    height          = avio_rb32(s->pb);

    x_offset        = avio_rb32(s->pb);

    y_offset        = avio_rb32(s->pb);

    delay_num       = avio_rb16(s->pb);

    delay_den       = avio_rb16(s->pb);

    dispose_op      = avio_r8(s->pb);

    blend_op        = avio_r8(s->pb);

    avio_skip(s->pb, 4); /* crc */

    /* default is hundredths of seconds */

    if (!delay_den)

        delay_den = 100;

    if (!delay_num || (ctx->max_fps && delay_den / delay_num > ctx->max_fps)) {

        delay_num = 1;

        delay_den = ctx->default_fps;

    }

    ctx->pkt_duration = av_rescale_q(delay_num,

                                     (AVRational){ 1, delay_den },

                                     s->streams[0]->time_base);

    av_log(s, AV_LOG_DEBUG, "%s: "

            "sequence_number: %"PRId32", "

            "width: %"PRIu32", "

            "height: %"PRIu32", "

            "x_offset: %"PRIu32", "

            "y_offset: %"PRIu32", "

            "delay_num: %"PRIu16", "

            "delay_den: %"PRIu16", "

            "dispose_op: %d, "

            "blend_op: %d\n",

            __func__,

            sequence_number,

            width,

            height,

            x_offset,

            y_offset,

            delay_num,

            delay_den,

            dispose_op,

            blend_op);

    if (width != s->streams[0]->codecpar->width ||

        height != s->streams[0]->codecpar->height ||

        x_offset != 0 ||

        y_offset != 0) {

        if (sequence_number == 0 ||

            x_offset >= s->streams[0]->codecpar->width ||

            width > s->streams[0]->codecpar->width - x_offset ||

            y_offset >= s->streams[0]->codecpar->height ||

            height > s->streams[0]->codecpar->height - y_offset)

            return AVERROR_INVALIDDATA;

        ctx->is_key_frame = 0;

    } else {

        if (sequence_number == 0 && dispose_op == APNG_DISPOSE_OP_PREVIOUS)

            dispose_op = APNG_DISPOSE_OP_BACKGROUND;

        ctx->is_key_frame = dispose_op == APNG_DISPOSE_OP_BACKGROUND ||

                            blend_op   == APNG_BLEND_OP_SOURCE;

    }

    return 0;

}

static int apng_read_packet(AVFormatContext *s, AVPacket *pkt)

{

    APNGDemuxContext *ctx = s->priv_data;

    int64_t ret;

    int64_t size;

    AVIOContext *pb = s->pb;

    uint32_t len, tag;

    /*

     * fcTL chunk length, in bytes:

     *  4 (length)

     *  4 (tag)

     * 26 (actual chunk)

     *  4 (crc) bytes

     * and needed next:

     *  4 (length)

     *  4 (tag (must be fdAT or IDAT))

     */

    /* if num_play is not 1, then the seekback is already guaranteed */

    if (ctx->num_play == 1 && (ret = ffio_ensure_seekback(pb, 46)) < 0)

        return ret;

    len = avio_rb32(pb);

    tag = avio_rl32(pb);

    if (avio_feof(pb))

        return AVERROR_EOF;

    switch (tag) {

    case MKTAG('f', 'c', 'T', 'L'):

        if (len != APNG_FCTL_CHUNK_SIZE)

            return AVERROR_INVALIDDATA;

        if ((ret = decode_fctl_chunk(s, ctx, pkt)) < 0)

            return ret;

        /* fcTL may be followed by other chunks before fdAT or IDAT */

        len = avio_rb32(pb);

        tag = avio_rl32(pb);

        if (len > 0x7fffffff)

            return AVERROR_INVALIDDATA;

        /* check for empty frame */

        if (tag == MKTAG('f', 'c', 'T', 'L') ||

            tag == MKTAG('I', 'E', 'N', 'D'))

            return AVERROR_INVALIDDATA;

        size = 38 /* fcTL */ + 8 /* len, tag */ + len + 4 /* crc */;

        if (size > INT_MAX)

            return AVERROR(EINVAL);

        if ((ret = avio_seek(pb, -46, SEEK_CUR)) < 0 ||

            (ret = av_append_packet(pb, pkt, size)) < 0)

            return ret;

        if (ctx->num_play == 1 && (ret = ffio_ensure_seekback(pb, 8)) < 0)

            return ret;

        len = avio_rb32(pb);

        tag = avio_rl32(pb);

        while (tag &&

               tag != MKTAG('f', 'c', 'T', 'L') &&

               tag != MKTAG('I', 'E', 'N', 'D')) {

            if (len > 0x7fffffff)

                return AVERROR_INVALIDDATA;

            if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0 ||

                (ret = av_append_packet(pb, pkt, len + 12)) < 0)

                return ret;

            if (ctx->num_play == 1 && (ret = ffio_ensure_seekback(pb, 8)) < 0)

                return ret;

            len = avio_rb32(pb);

            tag = avio_rl32(pb);

        }

        if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0)

            return ret;

        if (ctx->is_key_frame)

            pkt->flags |= AV_PKT_FLAG_KEY;

        pkt->pts = pkt->dts = AV_NOPTS_VALUE;

        pkt->duration = ctx->pkt_duration;

        return ret;

    case MKTAG('I', 'E', 'N', 'D'):

        ctx->cur_loop++;

        if (ctx->ignore_loop || ctx->num_play >= 1 && ctx->cur_loop == ctx->num_play) {

            avio_seek(pb, -8, SEEK_CUR);

            return AVERROR_EOF;

        }

        if ((ret = avio_seek(pb, s->streams[0]->codecpar->extradata_size + 8, SEEK_SET)) < 0)

            return ret;

        return 0;

    default:

        avpriv_request_sample(s, "In-stream tag=%s (0x%08"PRIX32") len=%"PRIu32,

                              av_fourcc2str(tag), tag, len);

        avio_skip(pb, len + 4);

    }

    /* Handle the unsupported yet cases */

    return AVERROR_PATCHWELCOME;

}

static const AVOption options[] = {

    { "ignore_loop", "ignore loop setting"                         , offsetof(APNGDemuxContext, ignore_loop),

      AV_OPT_TYPE_BOOL, { .i64 = 1 }              , 0, 1      , AV_OPT_FLAG_DECODING_PARAM },

    { "max_fps"    , "maximum framerate (0 is no limit)"           , offsetof(APNGDemuxContext, max_fps),

      AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },

    { "default_fps", "default framerate (0 is as fast as possible)", offsetof(APNGDemuxContext, default_fps),

      AV_OPT_TYPE_INT, { .i64 = DEFAULT_APNG_FPS }, 0, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },

    { NULL },

};

static const AVClass demuxer_class = {

    .class_name = "APNG demuxer",

    .item_name  = av_default_item_name,

    .option     = options,

    .version    = LIBAVUTIL_VERSION_INT,

    .category   = AV_CLASS_CATEGORY_DEMUXER,

};

const FFInputFormat ff_apng_demuxer = {

    .p.name         = "apng",

    .p.long_name    = NULL_IF_CONFIG_SMALL("Animated Portable Network Graphics"),

    .p.flags        = AVFMT_GENERIC_INDEX,

    .p.priv_class   = &demuxer_class,

    .priv_data_size = sizeof(APNGDemuxContext),

    .read_probe     = apng_probe,

    .read_header    = apng_read_header,

    .read_packet    = apng_read_packet,

};