/*
  * 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 "internal.h"
 #include "libavutil/imgutils.h"
 #include "libavutil/intreadwrite.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;
 

     int64_t pkt_pts;
     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(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(AVCodecContext *s, AVIOContext *pb, int len)
 {
     int previous_size = s->extradata_size;
     int new_size, ret;
     uint8_t *new_extradata;
 
     if (previous_size > INT_MAX - len)
         return AVERROR_INVALIDDATA;
 
     new_size = previous_size + len;

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

     if (!new_extradata)
         return AVERROR(ENOMEM);
     s->extradata = new_extradata;
     s->extradata_size = new_size;
 
     if ((ret = avio_read(pb, s->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 = AVERROR_INVALIDDATA;

 
     /* verify PNGSIG */
     if (avio_rb64(pb) != PNGSIG)
         return ret;
 
     /* parse IHDR (must be first chunk) */
     len = avio_rb32(pb);
     tag = avio_rl32(pb);
     if (len != 13 || tag != MKTAG('I', 'H', 'D', 'R'))
         return ret;
 
     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->codec->codec_type = AVMEDIA_TYPE_VIDEO;
     st->codec->codec_id   = AV_CODEC_ID_APNG;
     st->codec->width      = avio_rb32(pb);
     st->codec->height     = avio_rb32(pb);
     if ((ret = av_image_check_size(st->codec->width, st->codec->height, 0, s)) < 0)
         return ret;
 
     /* extradata will contain every chunk up to the first fcTL (excluded) */

     st->codec->extradata = av_malloc(len + 12 + AV_INPUT_BUFFER_PADDING_SIZE);

     if (!st->codec->extradata)
         return AVERROR(ENOMEM);
     st->codec->extradata_size = len + 12;
     AV_WB32(st->codec->extradata,    len);
     AV_WL32(st->codec->extradata+4,  tag);
     AV_WB32(st->codec->extradata+8,  st->codec->width);
     AV_WB32(st->codec->extradata+12, st->codec->height);
     if ((ret = avio_read(pb, st->codec->extradata+16, 9)) < 0)
         goto fail;
 
     while (!avio_feof(pb)) {
         if (acTL_found && ctx->num_play != 1) {
             int64_t size   = avio_size(pb);
             int64_t offset = avio_tell(pb);
             if (size < 0) {
                 ret = size;
                 goto fail;
             } else if (offset < 0) {
                 ret = offset;
                 goto fail;
             } 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))
             goto fail;
 
         len = avio_rb32(pb);
         if (len > 0x7fffffff) {
             ret = AVERROR_INVALIDDATA;
             goto fail;
         }
 
         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->codec, pb, len + 12)) < 0)
                 goto fail;
             acTL_found = 1;
             ctx->num_frames = AV_RB32(st->codec->extradata + ret + 8);
             ctx->num_play   = AV_RB32(st->codec->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) {
                ret = AVERROR_INVALIDDATA;
                goto fail;
             }
             if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0)
                 goto fail;
             return 0;
         default:
             if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0 ||
                 (ret = append_extradata(st->codec, pb, len + 12)) < 0)
                 goto fail;
         }
     }
 
 fail:
     if (st->codec->extradata_size) {
         av_freep(&st->codec->extradata);
         st->codec->extradata_size = 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 || 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",

             __FUNCTION__,

             sequence_number,
             width,
             height,
             x_offset,
             y_offset,
             delay_num,
             delay_den,
             dispose_op,
             blend_op);
 
     if (width != s->streams[0]->codec->width ||
         height != s->streams[0]->codec->height ||
         x_offset != 0 ||
         y_offset != 0) {

         if (sequence_number == 0 ||
             x_offset >= s->streams[0]->codec->width ||
             width > s->streams[0]->codec->width - x_offset ||
             y_offset >= s->streams[0]->codec->height ||
             height > s->streams[0]->codec->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);
     switch (tag) {
     case MKTAG('f', 'c', 'T', 'L'):
         if (len != 26)
             return AVERROR_INVALIDDATA;
 
         if ((ret = decode_fctl_chunk(s, ctx, pkt)) < 0)
             return ret;
 
         /* fcTL must precede fdAT or IDAT */
         len = avio_rb32(pb);
         tag = avio_rl32(pb);
         if (len > 0x7fffffff ||
             tag != MKTAG('f', 'd', 'A', 'T') &&
             tag != MKTAG('I', 'D', 'A', 'T'))
             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 = ctx->pkt_pts;
         pkt->duration = ctx->pkt_duration;
         ctx->pkt_pts += 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]->codec->extradata_size + 8, SEEK_SET)) < 0)
             return ret;
         return 0;
     default:

         {

         char tag_buf[32];

 
         av_get_codec_tag_string(tag_buf, sizeof(tag_buf), tag);
         avpriv_request_sample(s, "In-stream tag=%s (0x%08X) len=%"PRIu32, tag_buf, 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 = DEFAULT_APNG_FPS }, 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,
 };
 
 AVInputFormat ff_apng_demuxer = {
     .name           = "apng",
     .long_name      = NULL_IF_CONFIG_SMALL("Animated Portable Network Graphics"),
     .priv_data_size = sizeof(APNGDemuxContext),
     .read_probe     = apng_probe,
     .read_header    = apng_read_header,
     .read_packet    = apng_read_packet,
     .flags          = AVFMT_GENERIC_INDEX,
     .priv_class     = &demuxer_class,
 };