/*
  * 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
  */
 
 #include "config.h"
 #include "libavutil/avassert.h"
 
 #include "libavcodec/avcodec.h"
 #include "libavcodec/bytestream.h"
 #include "libavformat/avformat.h"
 
 
 typedef struct IOContext {
     int64_t pos;
     int64_t filesize;
     uint8_t *fuzz;
     int fuzz_size;
 } IOContext;
 
 int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size);
 
 static void error(const char *err)
 {
     fprintf(stderr, "%s", err);
     exit(1);
 }
 
 static int io_read(void *opaque, uint8_t *buf, int buf_size)
 {
     IOContext *c = opaque;
     int size = FFMIN(buf_size, c->fuzz_size);
 
     if (!c->fuzz_size) {
         c->filesize = FFMIN(c->pos, c->filesize);
         return AVERROR_EOF;
     }
 
     memcpy(buf, c->fuzz, size);
     c->fuzz      += size;
     c->fuzz_size -= size;
     c->pos       += size;
     c->filesize   = FFMAX(c->filesize, c->pos);
 
     return size;
 }
 
 static int64_t io_seek(void *opaque, int64_t offset, int whence)
 {
     IOContext *c = opaque;
 
     if (whence == SEEK_CUR) {
         if (offset > INT64_MAX - c->pos)
             return -1;
         offset += c->pos;
     } else if (whence == SEEK_END) {
         if (offset > INT64_MAX - c->filesize)
             return -1;
         offset += c->filesize;

     } else if (whence == AVSEEK_SIZE) {
         return c->filesize;

     }
     if (offset < 0 || offset > c->filesize)
         return -1;
     c->pos = offset;
     return 0;
 }
 
 // Ensure we don't loop forever
 const uint32_t maxiteration = 8096;
 
 static const uint64_t FUZZ_TAG = 0x4741542D5A5A5546ULL;
 
 int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     const uint64_t fuzz_tag = FUZZ_TAG;
     uint32_t it = 0;
     AVFormatContext *avfmt = avformat_alloc_context();
     AVPacket pkt;
     char filename[1025] = {0};
     AVIOContext *fuzzed_pb = NULL;
     uint8_t *io_buffer;
     int io_buffer_size = 32768;
     int64_t filesize   = size;
     IOContext opaque;
     static int c;
     int seekable = 0;
     int ret;
 
     if (!c) {
         av_register_all();
         avcodec_register_all();
         av_log_set_level(AV_LOG_PANIC);
         c=1;
     }
 
     if (!avfmt)
         error("Failed avformat_alloc_context()");
 
     if (size > 2048) {
         GetByteContext gbc;
         memcpy (filename, data + size - 1024, 1024);
         bytestream2_init(&gbc, data + size - 2048, 1024);
         size -= 2048;
 
         io_buffer_size = bytestream2_get_le32(&gbc) & 0xFFFFFFF;
         seekable       = bytestream2_get_byte(&gbc) & 1;
         filesize       = bytestream2_get_le64(&gbc) & 0x7FFFFFFFFFFFFFFF;
     }
     io_buffer = av_malloc(io_buffer_size);
     if (!io_buffer)
         error("Failed to allocate io_buffer");
 
     opaque.filesize = filesize;
     opaque.pos      = 0;
     opaque.fuzz     = data;
     opaque.fuzz_size= size;
     fuzzed_pb = avio_alloc_context(io_buffer, io_buffer_size, 0, &opaque,
                                    io_read, NULL, seekable ? io_seek : NULL);
     if (!fuzzed_pb)
         error("avio_alloc_context failed");
 
     avfmt->pb = fuzzed_pb;
 
     ret = avformat_open_input(&avfmt, filename, NULL, NULL);
     if (ret < 0) {
         av_freep(&fuzzed_pb->buffer);
         av_freep(&fuzzed_pb);
         avformat_free_context(avfmt);
         return 0;
     }
 
     ret = avformat_find_stream_info(avfmt, NULL);
 
     av_init_packet(&pkt);
 
     //TODO, test seeking
 
     for(it = 0; it < maxiteration; it++) {
         ret = av_read_frame(avfmt, &pkt);
         if (ret < 0)
             break;
         av_packet_unref(&pkt);
     }
 end:
     av_freep(&fuzzed_pb->buffer);
     av_freep(&fuzzed_pb);
     avformat_close_input(&avfmt);
 
     return 0;
 }