search for undamaged headers

Originally committed as revision 2970 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/nut.c

@@ -90,6 +90,7 @@ typedef struct {
     int64_t packet_size_pos;
     int64_t last_frame_start[3];
     FrameCode frame_code[256];
+    int stream_count;
     StreamContext *stream;
 } NUTContext;
 
@@ -328,6 +329,39 @@ static int get_length(uint64_t val){
     return 7; //not reached
 }
 
+static uint64_t find_any_startcode(ByteIOContext *bc, int64_t pos){
+    uint64_t state=0;
+    
+    if(pos >= 0)
+        url_fseek(bc, pos, SEEK_SET); //note, this may fail if the stream isnt seekable, but that shouldnt matter, as in this case we simply start where we are currently
+
+    while(bytes_left(bc)){
+        state= (state<<8) | get_byte(bc);
+        if((state>>56) != 'N')
+            continue;
+        switch(state){
+        case MAIN_STARTCODE:
+        case STREAM_STARTCODE:
+        case KEYFRAME_STARTCODE:
+        case INFO_STARTCODE:
+        case INDEX_STARTCODE:
+            return state;
+        }
+    }
+    return 0;
+}
+
+static int find_startcode(ByteIOContext *bc, uint64_t code, int64_t pos){
+    for(;;){
+        uint64_t startcode= find_any_startcode(bc, pos);
+        if(startcode == code)
+            return 0;
+        else if(startcode == 0)
+            return -1;
+        pos=-1;
+    }
+}
+
 #ifdef CONFIG_ENCODERS
 static int put_v(ByteIOContext *bc, uint64_t val)
 {
@@ -763,28 +797,21 @@ static int nut_probe(AVProbeData *p)
     return 0;
 }
 
-static int nut_read_header(AVFormatContext *s, AVFormatParameters *ap)
-{
-    NUTContext *nut = s->priv_data;
+static int decode_main_header(NUTContext *nut){
+    AVFormatContext *s= nut->avf;
     ByteIOContext *bc = &s->pb;
     uint64_t tmp;
-    int cur_stream, nb_streams, i, j;
-
-    nut->avf= s;
-    
-    av_set_pts_info(s, 60, 1, AV_TIME_BASE);
+    int i, j;
     
-    /* main header */
-    tmp = get_be64(bc);
-    if (tmp != MAIN_STARTCODE)
-	av_log(s, AV_LOG_ERROR, "damaged? startcode!=1 (%Ld)\n", tmp);
     get_packetheader(nut, bc, 8, 1);
 
     tmp = get_v(bc);
-    if (tmp != 1)
+    if (tmp != 1){
 	av_log(s, AV_LOG_ERROR, "bad version (%Ld)\n", tmp);
+        return -1;
+    }
     
-    nb_streams = get_v(bc);
+    nut->stream_count = get_v(bc);
     get_v(bc); //checksum threshold
 
     for(i=0; i<256;){
@@ -811,7 +838,7 @@ static int nut_read_header(AVFormatContext *s, AVFormatParameters *ap)
         }
 
         for(j=0; j<count; j++,i++){
-            if(tmp_stream > nb_streams + 1){
+            if(tmp_stream > nut->stream_count + 1){
                 av_log(s, AV_LOG_ERROR, "illegal stream number\n");
                 return -1;
             }
@@ -836,21 +863,22 @@ static int nut_read_header(AVFormatContext *s, AVFormatParameters *ap)
         return -1;
     }
 
-    s->bit_rate = 0;
-
-    nut->stream = av_malloc(sizeof(StreamContext)*nb_streams);
+    return 0;
+}
 
-    /* stream header */
-    for (cur_stream = 0; cur_stream < nb_streams; cur_stream++)
-    {
-	int class, nom, denom;
+static int decode_stream_header(NUTContext *nut){
+    AVFormatContext *s= nut->avf;
+    ByteIOContext *bc = &s->pb;
+    int class, nom, denom, stream_id, i;
+    uint64_t tmp;
     AVStream *st;
     
-	tmp = get_be64(bc);
-	if (tmp != STREAM_STARTCODE)
-	    av_log(s, AV_LOG_ERROR, "damaged? startcode!=1 (%Ld)\n", tmp);
     get_packetheader(nut, bc, 8, 1);
-	st = av_new_stream(s, get_v(bc));
+    stream_id= get_v(bc);
+    if(stream_id >= nut->stream_count || s->streams[stream_id])
+        return -1;
+    
+    st = av_new_stream(s, stream_id);
     if (!st)
         return AVERROR_NOMEM;
     class = get_v(bc);
@@ -877,11 +905,11 @@ static int nut_read_header(AVFormatContext *s, AVFormatParameters *ap)
     get_v(bc); /* language code */
     nom = get_v(bc);
     denom = get_v(bc);
-	nut->stream[cur_stream].msb_timestamp_shift = get_v(bc);
+    nut->stream[stream_id].msb_timestamp_shift = get_v(bc);
     for(i=0; i<3; i++)
-		nut->stream[cur_stream].initial_pts_predictor[i]= get_v(bc);
+            nut->stream[stream_id].initial_pts_predictor[i]= get_v(bc);
     for(i=0; i<2; i++)
-		nut->stream[cur_stream].initial_size_predictor[i]= get_v(bc);
+            nut->stream[stream_id].initial_size_predictor[i]= get_v(bc);
     get_byte(bc); /* flags */
 
     /* codec specific data headers */
@@ -909,15 +937,18 @@ static int nut_read_header(AVFormatContext *s, AVFormatParameters *ap)
         st->codec.channels = get_v(bc);
     }
     if(check_checksum(bc)){
-            av_log(s, AV_LOG_ERROR, "Stream header %d checksum missmatch\n", cur_stream);
+        av_log(s, AV_LOG_ERROR, "Stream header %d checksum missmatch\n", stream_id);
         return -1;
     }
-        nut->stream[cur_stream].rate_num= nom;
-        nut->stream[cur_stream].rate_den= denom;
-    }
+    nut->stream[stream_id].rate_num= nom;
+    nut->stream[stream_id].rate_den= denom;
+    return 0;
+}
+
+static int decode_info_header(NUTContext *nut){
+    AVFormatContext *s= nut->avf;
+    ByteIOContext *bc = &s->pb;
     
-    tmp = get_be64(bc);
-    if (tmp == INFO_STARTCODE){
     get_packetheader(nut, bc, 8, 1);
 
     for(;;){
@@ -961,9 +992,69 @@ static int nut_read_header(AVFormatContext *s, AVFormatParameters *ap)
     }
     if(check_checksum(bc)){
         av_log(s, AV_LOG_ERROR, "Info header checksum missmatch\n");
+        return -1;
+    }
+    return 0;
+}
+
+static int nut_read_header(AVFormatContext *s, AVFormatParameters *ap)
+{
+    NUTContext *nut = s->priv_data;
+    ByteIOContext *bc = &s->pb;
+    int64_t pos;
+    int inited_stream_count;
+
+    nut->avf= s;
+    
+    av_set_pts_info(s, 60, 1, AV_TIME_BASE);
+
+    /* main header */
+    pos=0;
+    for(;;){
+        if (find_startcode(bc, MAIN_STARTCODE, pos)<0){
+            av_log(s, AV_LOG_ERROR, "no main startcode found\n");
+            return -1;
+        }
+        pos= url_ftell(bc);
+        if(decode_main_header(nut) >= 0)
+            break;
+    }
+    
+    
+    s->bit_rate = 0;
+
+    nut->stream = av_malloc(sizeof(StreamContext)*nut->stream_count);
+
+    /* stream headers */
+    pos=0;
+    for(inited_stream_count=0; inited_stream_count < nut->stream_count;){
+        if (find_startcode(bc, STREAM_STARTCODE, pos)<0){
+            av_log(s, AV_LOG_ERROR, "not all stream headers found\n");
+            return -1;
+        }
+        pos= url_ftell(bc);
+        if(decode_stream_header(nut) >= 0)
+            inited_stream_count++;
+    }
+
+    /* info headers */
+    pos=0;
+    for(;;){
+        uint64_t startcode= find_any_startcode(bc, pos);
+        pos= url_ftell(bc);
+
+        if(startcode==0){
+            av_log(s, AV_LOG_ERROR, "EOF before video frames\n");
+            return -1;
+        }else if(startcode == KEYFRAME_STARTCODE){
+            url_fseek(bc, -8, SEEK_CUR); //FIXME
+            break;
+        }else if(startcode != INFO_STARTCODE){
+            continue;
+        }
+
+        decode_info_header(nut);
     }
-    }else
-        url_fseek(bc, -8, SEEK_CUR);
 
     return 0;
 }