/*
  * "NUT" Container Format demuxer
  * Copyright (c) 2004-2006 Michael Niedermayer
  * Copyright (c) 2003 Alex Beregszaszi
  *
  * 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 <strings.h>

 #include "libavutil/avstring.h"

 #include "libavutil/bswap.h"

 #include "libavutil/dict.h"

 #include "libavutil/tree.h"

 #include "avio_internal.h"

 #include "nut.h"
 
 #undef NDEBUG
 #include <assert.h>
 

 #if FF_API_MAX_STREAMS

 #define NUT_MAX_STREAMS MAX_STREAMS
 #else
 #define NUT_MAX_STREAMS 256    /* arbitrary sanity check value */
 #endif
 

 static int get_str(AVIOContext *bc, char *string, unsigned int maxlen){

     unsigned int len= ffio_read_varlen(bc);

 
     if(len && maxlen)

         avio_read(bc, string, FFMIN(len, maxlen));

     while(len > maxlen){

         avio_r8(bc);

         len--;
     }
 
     if(maxlen)
         string[FFMIN(len, maxlen-1)]= 0;
 
     if(maxlen == len)
         return -1;
     else
         return 0;
 }
 

 static int64_t get_s(AVIOContext *bc){

     int64_t v = ffio_read_varlen(bc) + 1;

 
     if (v&1) return -(v>>1);
     else     return  (v>>1);
 }
 

 static uint64_t get_fourcc(AVIOContext *bc){

     unsigned int len= ffio_read_varlen(bc);

     if     (len==2) return avio_rl16(bc);
     else if(len==4) return avio_rl32(bc);

     else            return -1;
 }
 
 #ifdef TRACE

 static inline uint64_t get_v_trace(AVIOContext *bc, char *file, char *func, int line){

     uint64_t v= ffio_read_varlen(bc);

     av_log(NULL, AV_LOG_DEBUG, "get_v %5"PRId64" / %"PRIX64" in %s %s:%d\n", v, v, file, func, line);

     return v;
 }
 

 static inline int64_t get_s_trace(AVIOContext *bc, char *file, char *func, int line){

     int64_t v= get_s(bc);
 

     av_log(NULL, AV_LOG_DEBUG, "get_s %5"PRId64" / %"PRIX64" in %s %s:%d\n", v, v, file, func, line);

     return v;
 }
 

 static inline uint64_t get_vb_trace(AVIOContext *bc, char *file, char *func, int line){

     uint64_t v= get_vb(bc);
 

     av_log(NULL, AV_LOG_DEBUG, "get_vb %5"PRId64" / %"PRIX64" in %s %s:%d\n", v, v, file, func, line);

     return v;
 }

 #define ffio_read_varlen(bc)  get_v_trace(bc, __FILE__, __PRETTY_FUNCTION__, __LINE__)

 #define get_s(bc)  get_s_trace(bc, __FILE__, __PRETTY_FUNCTION__, __LINE__)
 #define get_vb(bc)  get_vb_trace(bc, __FILE__, __PRETTY_FUNCTION__, __LINE__)
 #endif
 

 static int get_packetheader(NUTContext *nut, AVIOContext *bc, int calculate_checksum, uint64_t startcode)

 {

     int64_t size;

 //    start= avio_tell(bc) - 8;

     startcode= av_be2ne64(startcode);

     startcode= ff_crc04C11DB7_update(0, (uint8_t*)&startcode, 8);

     ffio_init_checksum(bc, ff_crc04C11DB7_update, startcode);

     size= ffio_read_varlen(bc);

     if(size > 4096)

         avio_rb32(bc);

     if(ffio_get_checksum(bc) && size > 4096)

         return -1;

     ffio_init_checksum(bc, calculate_checksum ? ff_crc04C11DB7_update : NULL, 0);

 
     return size;
 }
 

 static uint64_t find_any_startcode(AVIOContext *bc, int64_t pos){

     uint64_t state=0;
 
     if(pos >= 0)

         avio_seek(bc, pos, SEEK_SET); //note, this may fail if the stream is not seekable, but that should not matter, as in this case we simply start where we currently are

 
     while(!url_feof(bc)){

         state= (state<<8) | avio_r8(bc);

         if((state>>56) != 'N')
             continue;
         switch(state){
         case MAIN_STARTCODE:
         case STREAM_STARTCODE:
         case SYNCPOINT_STARTCODE:
         case INFO_STARTCODE:
         case INDEX_STARTCODE:
             return state;
         }
     }
 
     return 0;
 }
 
 /**

  * Find the given startcode.

  * @param code the startcode
  * @param pos the start position of the search, or -1 if the current position

  * @return the position of the startcode or -1 if not found

  */

 static int64_t find_startcode(AVIOContext *bc, uint64_t code, int64_t pos){

     for(;;){
         uint64_t startcode= find_any_startcode(bc, pos);
         if(startcode == code)

             return avio_tell(bc) - 8;

         else if(startcode == 0)
             return -1;
         pos=-1;
     }
 }
 
 static int nut_probe(AVProbeData *p){
     int i;
     uint64_t code= 0;
 
     for (i = 0; i < p->buf_size; i++) {
         code = (code << 8) | p->buf[i];
         if (code == MAIN_STARTCODE)
             return AVPROBE_SCORE_MAX;
     }
     return 0;
 }
 
 #define GET_V(dst, check) \

     tmp= ffio_read_varlen(bc);\

     if(!(check)){\
         av_log(s, AV_LOG_ERROR, "Error " #dst " is (%"PRId64")\n", tmp);\
         return -1;\
     }\
     dst= tmp;
 

 static int skip_reserved(AVIOContext *bc, int64_t pos){

     pos -= avio_tell(bc);

     if(pos<0){

         avio_seek(bc, pos, SEEK_CUR);

         return -1;
     }else{
         while(pos--)

             avio_r8(bc);

         return 0;
     }
 }
 
 static int decode_main_header(NUTContext *nut){
     AVFormatContext *s= nut->avf;

     AVIOContext *bc = s->pb;

     uint64_t tmp, end;
     unsigned int stream_count;

     int i, j, tmp_stream, tmp_mul, tmp_pts, tmp_size, count, tmp_res, tmp_head_idx;

     end= get_packetheader(nut, bc, 1, MAIN_STARTCODE);

     end += avio_tell(bc);

 
     GET_V(tmp              , tmp >=2 && tmp <= 3)

     GET_V(stream_count     , tmp > 0 && tmp <= NUT_MAX_STREAMS)

     nut->max_distance = ffio_read_varlen(bc);

     if(nut->max_distance > 65536){
         av_log(s, AV_LOG_DEBUG, "max_distance %d\n", nut->max_distance);
         nut->max_distance= 65536;
     }
 
     GET_V(nut->time_base_count, tmp>0 && tmp<INT_MAX / sizeof(AVRational))
     nut->time_base= av_malloc(nut->time_base_count * sizeof(AVRational));
 
     for(i=0; i<nut->time_base_count; i++){
         GET_V(nut->time_base[i].num, tmp>0 && tmp<(1ULL<<31))
         GET_V(nut->time_base[i].den, tmp>0 && tmp<(1ULL<<31))

         if(av_gcd(nut->time_base[i].num, nut->time_base[i].den) != 1){

             av_log(s, AV_LOG_ERROR, "time base invalid\n");

             return AVERROR_INVALIDDATA;

         }
     }
     tmp_pts=0;
     tmp_mul=1;
     tmp_stream=0;

     tmp_head_idx= 0;

     for(i=0; i<256;){

         int tmp_flags = ffio_read_varlen(bc);
         int tmp_fields= ffio_read_varlen(bc);

         if(tmp_fields>0) tmp_pts   = get_s(bc);

         if(tmp_fields>1) tmp_mul   = ffio_read_varlen(bc);
         if(tmp_fields>2) tmp_stream= ffio_read_varlen(bc);
         if(tmp_fields>3) tmp_size  = ffio_read_varlen(bc);

         else             tmp_size  = 0;

         if(tmp_fields>4) tmp_res   = ffio_read_varlen(bc);

         else             tmp_res   = 0;

         if(tmp_fields>5) count     = ffio_read_varlen(bc);

         else             count     = tmp_mul - tmp_size;

         if(tmp_fields>6) get_s(bc);

         if(tmp_fields>7) tmp_head_idx= ffio_read_varlen(bc);

         while(tmp_fields-- > 8)

            ffio_read_varlen(bc);

 
         if(count == 0 || i+count > 256){
             av_log(s, AV_LOG_ERROR, "illegal count %d at %d\n", count, i);

             return AVERROR_INVALIDDATA;

         }
         if(tmp_stream >= stream_count){
             av_log(s, AV_LOG_ERROR, "illegal stream number\n");

             return AVERROR_INVALIDDATA;

         }
 
         for(j=0; j<count; j++,i++){
             if (i == 'N') {
                 nut->frame_code[i].flags= FLAG_INVALID;
                 j--;
                 continue;
             }
             nut->frame_code[i].flags           = tmp_flags ;
             nut->frame_code[i].pts_delta       = tmp_pts   ;
             nut->frame_code[i].stream_id       = tmp_stream;
             nut->frame_code[i].size_mul        = tmp_mul   ;
             nut->frame_code[i].size_lsb        = tmp_size+j;
             nut->frame_code[i].reserved_count  = tmp_res   ;

             nut->frame_code[i].header_idx      = tmp_head_idx;

         }
     }
     assert(nut->frame_code['N'].flags == FLAG_INVALID);
 

     if(end > avio_tell(bc) + 4){

         int rem= 1024;
         GET_V(nut->header_count, tmp<128U)
         nut->header_count++;
         for(i=1; i<nut->header_count; i++){
             GET_V(nut->header_len[i], tmp>0 && tmp<256);
             rem -= nut->header_len[i];
             if(rem < 0){
                 av_log(s, AV_LOG_ERROR, "invalid elision header\n");

                 return AVERROR_INVALIDDATA;

             }
             nut->header[i]= av_malloc(nut->header_len[i]);

             avio_read(bc, nut->header[i], nut->header_len[i]);

         }
         assert(nut->header_len[0]==0);
     }
 

     if(skip_reserved(bc, end) || ffio_get_checksum(bc)){

         av_log(s, AV_LOG_ERROR, "main header checksum mismatch\n");

         return AVERROR_INVALIDDATA;

     }
 
     nut->stream = av_mallocz(sizeof(StreamContext)*stream_count);
     for(i=0; i<stream_count; i++){
         av_new_stream(s, i);
     }
 
     return 0;
 }
 
 static int decode_stream_header(NUTContext *nut){
     AVFormatContext *s= nut->avf;

     AVIOContext *bc = s->pb;

     StreamContext *stc;

     int class, stream_id;

     uint64_t tmp, end;
     AVStream *st;
 

     end= get_packetheader(nut, bc, 1, STREAM_STARTCODE);

     end += avio_tell(bc);

     GET_V(stream_id, tmp < s->nb_streams && !nut->stream[tmp].time_base);

     stc= &nut->stream[stream_id];
 
     st = s->streams[stream_id];
     if (!st)

         return AVERROR(ENOMEM);

     class = ffio_read_varlen(bc);

     tmp = get_fourcc(bc);
     st->codec->codec_tag= tmp;
     switch(class)
     {
         case 0:

             st->codec->codec_type = AVMEDIA_TYPE_VIDEO;

             st->codec->codec_id = av_codec_get_id(
                 (const AVCodecTag * const []) { ff_codec_bmp_tags, ff_nut_video_tags, 0 },
                 tmp);

             break;
         case 1:

             st->codec->codec_type = AVMEDIA_TYPE_AUDIO;

             st->codec->codec_id = ff_codec_get_id(ff_codec_wav_tags, tmp);

             break;
         case 2:

             st->codec->codec_type = AVMEDIA_TYPE_SUBTITLE;

             st->codec->codec_id = ff_codec_get_id(ff_nut_subtitle_tags, tmp);

             break;

         case 3:

             st->codec->codec_type = AVMEDIA_TYPE_DATA;

             break;
         default:

             av_log(s, AV_LOG_ERROR, "unknown stream class (%d)\n", class);

             return -1;
     }

     if(class<3 && st->codec->codec_id == CODEC_ID_NONE)

         av_log(s, AV_LOG_ERROR, "Unknown codec tag '0x%04x' for stream number %d\n",
                (unsigned int)tmp, stream_id);

     GET_V(stc->time_base_id    , tmp < nut->time_base_count);
     GET_V(stc->msb_pts_shift   , tmp < 16);

     stc->max_pts_distance= ffio_read_varlen(bc);

     GET_V(stc->decode_delay    , tmp < 1000); //sanity limit, raise this if Moore's law is true

     st->codec->has_b_frames= stc->decode_delay;

     ffio_read_varlen(bc); //stream flags

 
     GET_V(st->codec->extradata_size, tmp < (1<<30));
     if(st->codec->extradata_size){
         st->codec->extradata= av_mallocz(st->codec->extradata_size + FF_INPUT_BUFFER_PADDING_SIZE);

         avio_read(bc, st->codec->extradata, st->codec->extradata_size);

     }
 

     if (st->codec->codec_type == AVMEDIA_TYPE_VIDEO){

         GET_V(st->codec->width , tmp > 0)
         GET_V(st->codec->height, tmp > 0)

         st->sample_aspect_ratio.num= ffio_read_varlen(bc);
         st->sample_aspect_ratio.den= ffio_read_varlen(bc);

         if((!st->sample_aspect_ratio.num) != (!st->sample_aspect_ratio.den)){
             av_log(s, AV_LOG_ERROR, "invalid aspect ratio %d/%d\n", st->sample_aspect_ratio.num, st->sample_aspect_ratio.den);

             return -1;
         }

         ffio_read_varlen(bc); /* csp type */

     }else if (st->codec->codec_type == AVMEDIA_TYPE_AUDIO){

         GET_V(st->codec->sample_rate , tmp > 0)

         ffio_read_varlen(bc); // samplerate_den

         GET_V(st->codec->channels, tmp > 0)
     }

     if(skip_reserved(bc, end) || ffio_get_checksum(bc)){

         av_log(s, AV_LOG_ERROR, "stream header %d checksum mismatch\n", stream_id);

         return -1;
     }

     stc->time_base= &nut->time_base[stc->time_base_id];
     av_set_pts_info(s->streams[stream_id], 63, stc->time_base->num, stc->time_base->den);

     return 0;
 }
 

 static void set_disposition_bits(AVFormatContext* avf, char* value, int stream_id){
     int flag = 0, i;
     for (i=0; ff_nut_dispositions[i].flag; ++i) {
         if (!strcmp(ff_nut_dispositions[i].str, value))
             flag = ff_nut_dispositions[i].flag;
     }
     if (!flag)
         av_log(avf, AV_LOG_INFO, "unknown disposition type '%s'\n", value);
     for (i = 0; i < avf->nb_streams; ++i)
         if (stream_id == i || stream_id == -1)
             avf->streams[i]->disposition |= flag;
 }
 

 static int decode_info_header(NUTContext *nut){
     AVFormatContext *s= nut->avf;

     AVIOContext *bc = s->pb;

     uint64_t tmp, chapter_start, chapter_len;
     unsigned int stream_id_plus1, count;

     int chapter_id, i;
     int64_t value, end;

     char name[256], str_value[1024], type_str[256];

     const char *type;

     AVChapter *chapter= NULL;

     AVStream *st= NULL;

     AVDictionary **metadata = NULL;

     end= get_packetheader(nut, bc, 1, INFO_STARTCODE);

     end += avio_tell(bc);

 
     GET_V(stream_id_plus1, tmp <= s->nb_streams)
     chapter_id   = get_s(bc);

     chapter_start= ffio_read_varlen(bc);
     chapter_len  = ffio_read_varlen(bc);
     count        = ffio_read_varlen(bc);

 
     if(chapter_id && !stream_id_plus1){
         int64_t start= chapter_start / nut->time_base_count;

         chapter= ff_new_chapter(s, chapter_id,
                                 nut->time_base[chapter_start % nut->time_base_count],
                                 start, start + chapter_len, NULL);

         metadata = &chapter->metadata;
     } else if(stream_id_plus1) {

         st= s->streams[stream_id_plus1 - 1];

         metadata = &st->metadata;
     } else
         metadata = &s->metadata;

     for(i=0; i<count; i++){
         get_str(bc, name, sizeof(name));
         value= get_s(bc);
         if(value == -1){
             type= "UTF-8";
             get_str(bc, str_value, sizeof(str_value));
         }else if(value == -2){

             get_str(bc, type_str, sizeof(type_str));
             type= type_str;

             get_str(bc, str_value, sizeof(str_value));
         }else if(value == -3){
             type= "s";
             value= get_s(bc);
         }else if(value == -4){
             type= "t";

             value= ffio_read_varlen(bc);

         }else if(value < -4){
             type= "r";
             get_s(bc);
         }else{
             type= "v";
         }
 

         if (stream_id_plus1 > s->nb_streams) {

             av_log(s, AV_LOG_ERROR, "invalid stream id for info packet\n");
             continue;
         }
 

         if(!strcmp(type, "UTF-8")){

             if(chapter_id==0 && !strcmp(name, "Disposition")) {

                 set_disposition_bits(s, str_value, stream_id_plus1 - 1);

                 continue;
             }

             if(metadata && strcasecmp(name,"Uses")
                && strcasecmp(name,"Depends") && strcasecmp(name,"Replaces"))

                 av_dict_set(metadata, name, str_value, 0);

         }

     }
 

     if(skip_reserved(bc, end) || ffio_get_checksum(bc)){

         av_log(s, AV_LOG_ERROR, "info header checksum mismatch\n");

         return -1;
     }
     return 0;
 }
 

 static int decode_syncpoint(NUTContext *nut, int64_t *ts, int64_t *back_ptr){

     AVFormatContext *s= nut->avf;

     AVIOContext *bc = s->pb;

     int64_t end, tmp;

     nut->last_syncpoint_pos= avio_tell(bc)-8;

     end= get_packetheader(nut, bc, 1, SYNCPOINT_STARTCODE);

     end += avio_tell(bc);

     tmp= ffio_read_varlen(bc);
     *back_ptr= nut->last_syncpoint_pos - 16*ffio_read_varlen(bc);

     if(*back_ptr < 0)
         return -1;

     ff_nut_reset_ts(nut, nut->time_base[tmp % nut->time_base_count], tmp / nut->time_base_count);

     if(skip_reserved(bc, end) || ffio_get_checksum(bc)){

         av_log(s, AV_LOG_ERROR, "sync point checksum mismatch\n");

         return -1;
     }

 
     *ts= tmp / s->nb_streams * av_q2d(nut->time_base[tmp % s->nb_streams])*AV_TIME_BASE;

     ff_nut_add_sp(nut, nut->last_syncpoint_pos, *back_ptr, *ts);

     return 0;
 }
 

 static int find_and_decode_index(NUTContext *nut){
     AVFormatContext *s= nut->avf;

     AVIOContext *bc = s->pb;

     uint64_t tmp, end;
     int i, j, syncpoint_count;

     int64_t filesize= avio_size(bc);

     int64_t *syncpoints;
     int8_t *has_keyframe;

     int ret= -1;

     avio_seek(bc, filesize-12, SEEK_SET);
     avio_seek(bc, filesize-avio_rb64(bc), SEEK_SET);

     if(avio_rb64(bc) != INDEX_STARTCODE){

         av_log(s, AV_LOG_ERROR, "no index at the end\n");
         return -1;
     }
 

     end= get_packetheader(nut, bc, 1, INDEX_STARTCODE);

     end += avio_tell(bc);

     ffio_read_varlen(bc); //max_pts

     GET_V(syncpoint_count, tmp < INT_MAX/8 && tmp > 0)
     syncpoints= av_malloc(sizeof(int64_t)*syncpoint_count);
     has_keyframe= av_malloc(sizeof(int8_t)*(syncpoint_count+1));
     for(i=0; i<syncpoint_count; i++){

         syncpoints[i] = ffio_read_varlen(bc);

         if(syncpoints[i] <= 0)
             goto fail;

         if(i)
             syncpoints[i] += syncpoints[i-1];
     }
 
     for(i=0; i<s->nb_streams; i++){
         int64_t last_pts= -1;
         for(j=0; j<syncpoint_count;){

             uint64_t x= ffio_read_varlen(bc);

             int type= x&1;
             int n= j;
             x>>=1;
             if(type){
                 int flag= x&1;
                 x>>=1;
                 if(n+x >= syncpoint_count + 1){
                     av_log(s, AV_LOG_ERROR, "index overflow A\n");

                     goto fail;

                 }
                 while(x--)
                     has_keyframe[n++]= flag;
                 has_keyframe[n++]= !flag;
             }else{
                 while(x != 1){
                     if(n>=syncpoint_count + 1){
                         av_log(s, AV_LOG_ERROR, "index overflow B\n");

                         goto fail;

                     }
                     has_keyframe[n++]= x&1;
                     x>>=1;
                 }
             }
             if(has_keyframe[0]){
                 av_log(s, AV_LOG_ERROR, "keyframe before first syncpoint in index\n");

                 goto fail;

             }
             assert(n<=syncpoint_count+1);

             for(; j<n && j<syncpoint_count; j++){

                 if(has_keyframe[j]){

                     uint64_t B, A= ffio_read_varlen(bc);

                     if(!A){

                         A= ffio_read_varlen(bc);
                         B= ffio_read_varlen(bc);

                         //eor_pts[j][i] = last_pts + A + B
                     }else
                         B= 0;
                     av_add_index_entry(
                         s->streams[i],
                         16*syncpoints[j-1],
                         last_pts + A,
                         0,
                         0,
                         AVINDEX_KEYFRAME);
                     last_pts += A + B;
                 }
             }
         }
     }
 

     if(skip_reserved(bc, end) || ffio_get_checksum(bc)){

         av_log(s, AV_LOG_ERROR, "index checksum mismatch\n");

         goto fail;

     }

     ret= 0;
 fail:
     av_free(syncpoints);
     av_free(has_keyframe);
     return ret;

 }
 

 static int nut_read_header(AVFormatContext *s, AVFormatParameters *ap)
 {
     NUTContext *nut = s->priv_data;

     AVIOContext *bc = s->pb;

     int64_t pos;

     int initialized_stream_count;

 
     nut->avf= s;
 
     /* main header */
     pos=0;

     do{

         pos= find_startcode(bc, MAIN_STARTCODE, pos)+1;
         if (pos<0+1){

             av_log(s, AV_LOG_ERROR, "No main startcode found.\n");

             return AVERROR_INVALIDDATA;

         }

     }while(decode_main_header(nut) < 0);

 
     /* stream headers */
     pos=0;

     for(initialized_stream_count=0; initialized_stream_count < s->nb_streams;){

         pos= find_startcode(bc, STREAM_STARTCODE, pos)+1;
         if (pos<0+1){

             av_log(s, AV_LOG_ERROR, "Not all stream headers found.\n");

             return AVERROR_INVALIDDATA;

         }
         if(decode_stream_header(nut) >= 0)

             initialized_stream_count++;

     }
 
     /* info headers */
     pos=0;
     for(;;){
         uint64_t startcode= find_any_startcode(bc, pos);

         pos= avio_tell(bc);

 
         if(startcode==0){
             av_log(s, AV_LOG_ERROR, "EOF before video frames\n");

             return AVERROR_INVALIDDATA;

         }else if(startcode == SYNCPOINT_STARTCODE){
             nut->next_startcode= startcode;
             break;
         }else if(startcode != INFO_STARTCODE){
             continue;
         }
 
         decode_info_header(nut);
     }
 

     s->data_offset= pos-8;
 

     if(bc->seekable){

         int64_t orig_pos= avio_tell(bc);

         find_and_decode_index(nut);

         avio_seek(bc, orig_pos, SEEK_SET);

     }
     assert(nut->next_startcode == SYNCPOINT_STARTCODE);
 

     ff_metadata_conv_ctx(s, NULL, ff_nut_metadata_conv);
 

     return 0;
 }
 

 static int decode_frame_header(NUTContext *nut, int64_t *pts, int *stream_id, uint8_t *header_idx, int frame_code){

     AVFormatContext *s= nut->avf;

     AVIOContext *bc = s->pb;

     StreamContext *stc;
     int size, flags, size_mul, pts_delta, i, reserved_count;
     uint64_t tmp;
 

     if(avio_tell(bc) > nut->last_syncpoint_pos + nut->max_distance){
         av_log(s, AV_LOG_ERROR, "Last frame must have been damaged %"PRId64" > %"PRId64" + %d\n", avio_tell(bc), nut->last_syncpoint_pos, nut->max_distance);

         return AVERROR_INVALIDDATA;

     }
 
     flags          = nut->frame_code[frame_code].flags;
     size_mul       = nut->frame_code[frame_code].size_mul;
     size           = nut->frame_code[frame_code].size_lsb;
     *stream_id     = nut->frame_code[frame_code].stream_id;
     pts_delta      = nut->frame_code[frame_code].pts_delta;
     reserved_count = nut->frame_code[frame_code].reserved_count;

     *header_idx    = nut->frame_code[frame_code].header_idx;

 
     if(flags & FLAG_INVALID)

         return AVERROR_INVALIDDATA;

     if(flags & FLAG_CODED)

         flags ^= ffio_read_varlen(bc);

     if(flags & FLAG_STREAM_ID){
         GET_V(*stream_id, tmp < s->nb_streams)
     }
     stc= &nut->stream[*stream_id];
     if(flags&FLAG_CODED_PTS){

         int coded_pts= ffio_read_varlen(bc);

 //FIXME check last_pts validity?
         if(coded_pts < (1<<stc->msb_pts_shift)){

             *pts=ff_lsb2full(stc, coded_pts);

         }else
             *pts=coded_pts - (1<<stc->msb_pts_shift);
     }else
         *pts= stc->last_pts + pts_delta;
     if(flags&FLAG_SIZE_MSB){

         size += size_mul*ffio_read_varlen(bc);

     }

     if(flags&FLAG_MATCH_TIME)
         get_s(bc);

     if(flags&FLAG_HEADER_IDX)

         *header_idx= ffio_read_varlen(bc);

     if(flags&FLAG_RESERVED)

         reserved_count= ffio_read_varlen(bc);

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

         ffio_read_varlen(bc);

 
     if(*header_idx >= (unsigned)nut->header_count){
         av_log(s, AV_LOG_ERROR, "header_idx invalid\n");

         return AVERROR_INVALIDDATA;

     }
     if(size > 4096)
         *header_idx=0;
     size -= nut->header_len[*header_idx];
 

     if(flags&FLAG_CHECKSUM){

         avio_rb32(bc); //FIXME check this

     }else if(size > 2*nut->max_distance || FFABS(stc->last_pts - *pts) > stc->max_pts_distance){

         av_log(s, AV_LOG_ERROR, "frame size > 2max_distance and no checksum\n");

         return AVERROR_INVALIDDATA;

     }
 
     stc->last_pts= *pts;

     stc->last_flags= flags;

 
     return size;
 }
 
 static int decode_frame(NUTContext *nut, AVPacket *pkt, int frame_code){
     AVFormatContext *s= nut->avf;

     AVIOContext *bc = s->pb;

     int size, stream_id, discard;

     int64_t pts, last_IP_pts;

     StreamContext *stc;

     uint8_t header_idx;

     size= decode_frame_header(nut, &pts, &stream_id, &header_idx, frame_code);

     if(size < 0)

         return size;

     stc= &nut->stream[stream_id];
 
     if (stc->last_flags & FLAG_KEY)
         stc->skip_until_key_frame=0;

     discard= s->streams[ stream_id ]->discard;
     last_IP_pts= s->streams[ stream_id ]->last_IP_pts;

     if(  (discard >= AVDISCARD_NONKEY && !(stc->last_flags & FLAG_KEY))

        ||(discard >= AVDISCARD_BIDIR && last_IP_pts != AV_NOPTS_VALUE && last_IP_pts > pts)

        || discard >= AVDISCARD_ALL

        || stc->skip_until_key_frame){

         avio_skip(bc, size);

         return 1;
     }
 

     av_new_packet(pkt, size + nut->header_len[header_idx]);
     memcpy(pkt->data, nut->header[header_idx], nut->header_len[header_idx]);

     pkt->pos= avio_tell(bc); //FIXME

     avio_read(bc, pkt->data + nut->header_len[header_idx], size);

     pkt->stream_index = stream_id;

     if (stc->last_flags & FLAG_KEY)

         pkt->flags |= AV_PKT_FLAG_KEY;

     pkt->pts = pts;
 
     return 0;
 }
 
 static int nut_read_packet(AVFormatContext *s, AVPacket *pkt)
 {
     NUTContext *nut = s->priv_data;

     AVIOContext *bc = s->pb;

     int i, frame_code=0, ret, skip;

     int64_t ts, back_ptr;

 
     for(;;){

         int64_t pos= avio_tell(bc);

         uint64_t tmp= nut->next_startcode;
         nut->next_startcode=0;
 
         if(tmp){
             pos-=8;
         }else{

             frame_code = avio_r8(bc);

             if(url_feof(bc))
                 return -1;

             if(frame_code == 'N'){
                 tmp= frame_code;
                 for(i=1; i<8; i++)

                     tmp = (tmp<<8) + avio_r8(bc);

             }
         }
         switch(tmp){
         case MAIN_STARTCODE:
         case STREAM_STARTCODE:
         case INDEX_STARTCODE:

             skip= get_packetheader(nut, bc, 0, tmp);

             avio_skip(bc, skip);

             break;
         case INFO_STARTCODE:
             if(decode_info_header(nut)<0)
                 goto resync;
             break;
         case SYNCPOINT_STARTCODE:

             if(decode_syncpoint(nut, &ts, &back_ptr)<0)

                 goto resync;

             frame_code = avio_r8(bc);

         case 0:
             ret= decode_frame(nut, pkt, frame_code);
             if(ret==0)
                 return 0;
             else if(ret==1) //ok but discard packet
                 break;
         default:
 resync:
 av_log(s, AV_LOG_DEBUG, "syncing from %"PRId64"\n", pos);

             tmp= find_any_startcode(bc, nut->last_syncpoint_pos+1);

             if(tmp==0)

                 return AVERROR_INVALIDDATA;

 av_log(s, AV_LOG_DEBUG, "sync\n");
             nut->next_startcode= tmp;
         }
     }
 }
 

 static int64_t nut_read_timestamp(AVFormatContext *s, int stream_index, int64_t *pos_arg, int64_t pos_limit){
     NUTContext *nut = s->priv_data;

     AVIOContext *bc = s->pb;

     int64_t pos, pts, back_ptr;

 av_log(s, AV_LOG_DEBUG, "read_timestamp(X,%d,%"PRId64",%"PRId64")\n", stream_index, *pos_arg, pos_limit);
 
     pos= *pos_arg;
     do{
         pos= find_startcode(bc, SYNCPOINT_STARTCODE, pos)+1;
         if(pos < 1){
             assert(nut->next_startcode == 0);

             av_log(s, AV_LOG_ERROR, "read_timestamp failed.\n");

             return AV_NOPTS_VALUE;
         }

     }while(decode_syncpoint(nut, &pts, &back_ptr) < 0);

     *pos_arg = pos-1;
     assert(nut->last_syncpoint_pos == *pos_arg);
 

     av_log(s, AV_LOG_DEBUG, "return %"PRId64" %"PRId64"\n", pts,back_ptr );

     if     (stream_index == -1) return pts;
     else if(stream_index == -2) return back_ptr;
 
 assert(0);

 }
 

 static int read_seek(AVFormatContext *s, int stream_index, int64_t pts, int flags){
     NUTContext *nut = s->priv_data;
     AVStream *st= s->streams[stream_index];

     Syncpoint dummy={.ts= pts*av_q2d(st->time_base)*AV_TIME_BASE};
     Syncpoint nopts_sp= {.ts= AV_NOPTS_VALUE, .back_ptr= AV_NOPTS_VALUE};
     Syncpoint *sp, *next_node[2]= {&nopts_sp, &nopts_sp};

     int64_t pos, pos2, ts;

     int i;

     if(st->index_entries){
         int index= av_index_search_timestamp(st, pts, flags);
         if(index<0)
             return -1;
 
         pos2= st->index_entries[index].pos;
         ts  = st->index_entries[index].timestamp;
     }else{

         av_tree_find(nut->syncpoints, &dummy, (void *) ff_nut_sp_pts_cmp,
                      (void **) next_node);

         av_log(s, AV_LOG_DEBUG, "%"PRIu64"-%"PRIu64" %"PRId64"-%"PRId64"\n", next_node[0]->pos, next_node[1]->pos,

                                                     next_node[0]->ts , next_node[1]->ts);
         pos= av_gen_search(s, -1, dummy.ts, next_node[0]->pos, next_node[1]->pos, next_node[1]->pos,
                                             next_node[0]->ts , next_node[1]->ts, AVSEEK_FLAG_BACKWARD, &ts, nut_read_timestamp);
 
         if(!(flags & AVSEEK_FLAG_BACKWARD)){
             dummy.pos= pos+16;
             next_node[1]= &nopts_sp;

             av_tree_find(nut->syncpoints, &dummy, (void *) ff_nut_sp_pos_cmp,
                          (void **) next_node);

             pos2= av_gen_search(s, -2, dummy.pos, next_node[0]->pos     , next_node[1]->pos, next_node[1]->pos,
                                                 next_node[0]->back_ptr, next_node[1]->back_ptr, flags, &ts, nut_read_timestamp);
             if(pos2>=0)
                 pos= pos2;

             //FIXME dir but I think it does not matter

         }
         dummy.pos= pos;

         sp= av_tree_find(nut->syncpoints, &dummy, (void *) ff_nut_sp_pos_cmp,
                          NULL);

 
         assert(sp);
         pos2= sp->back_ptr  - 15;

     }
     av_log(NULL, AV_LOG_DEBUG, "SEEKTO: %"PRId64"\n", pos2);

     pos= find_startcode(s->pb, SYNCPOINT_STARTCODE, pos2);

     avio_seek(s->pb, pos, SEEK_SET);

     av_log(NULL, AV_LOG_DEBUG, "SP: %"PRId64"\n", pos);

     if(pos2 > pos || pos2 + 15 < pos){

         av_log(NULL, AV_LOG_ERROR, "no syncpoint at backptr pos\n");
     }

     for(i=0; i<s->nb_streams; i++)
         nut->stream[i].skip_until_key_frame=1;
 

     return 0;
 }
 

 static int nut_read_close(AVFormatContext *s)
 {
     NUTContext *nut = s->priv_data;

     int i;

 
     av_freep(&nut->time_base);
     av_freep(&nut->stream);

     ff_nut_free_sp(nut);

     for(i = 1; i < nut->header_count; i++)
         av_freep(&nut->header[i]);

 
     return 0;
 }
 

 #if CONFIG_NUT_DEMUXER

 AVInputFormat ff_nut_demuxer = {

     "nut",

     NULL_IF_CONFIG_SMALL("NUT format"),

     sizeof(NUTContext),
     nut_probe,
     nut_read_header,
     nut_read_packet,
     nut_read_close,

     read_seek,

     .extensions = "nut",

     .codec_tag = (const AVCodecTag * const []) { ff_codec_bmp_tags, ff_nut_video_tags, ff_codec_wav_tags, ff_nut_subtitle_tags, 0 },

 };
 #endif