Add AVSEEK_FORCE flag to indicate that the code should attempt to seek

by any means.

Originally committed as revision 22557 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/avio.c

@@ -202,7 +202,7 @@ int64_t url_seek(URLContext *h, int64_t pos, int whence)
 
     if (!h->prot->url_seek)
         return AVERROR(EPIPE);
-    ret = h->prot->url_seek(h, pos, whence);
+    ret = h->prot->url_seek(h, pos, whence & ~AVSEEK_FORCE);
     return ret;
 }
 

libavformat/avio.h

@@ -192,6 +192,14 @@ int64_t av_url_read_seek(URLContext *h, int stream_index,
  */
 #define AVSEEK_SIZE 0x10000
 
+/**
+ * Oring this flag as into the "whence" parameter to a seek function causes it to
+ * seek by any means (like reopening and linear reading) or other normally unreasonble
+ * means that can be extreemly slow.
+ * This may be ignored by the seek code.
+ */
+#define AVSEEK_FORCE 0x20000
+
 typedef struct URLProtocol {
     const char *name;
     int (*url_open)(URLContext *h, const char *url, int flags);

libavformat/aviobuf.c

@@ -150,8 +150,9 @@ int64_t url_fseek(ByteIOContext *s, int64_t offset, int whence)
         offset1 >= 0 && offset1 <= (s->buf_end - s->buffer)) {
         /* can do the seek inside the buffer */
         s->buf_ptr = s->buffer + offset1;
-    } else if(s->is_streamed && !s->write_flag &&
-              offset1 >= 0 && offset1 < (s->buf_end - s->buffer) + (1<<16)){
+    } else if(s->is_streamed && !s->write_flag && offset1 >= 0 &&
+              (   offset1 < (s->buf_end - s->buffer) + (1<<16)
+               || (whence & AVSEEK_FORCE))){
         while(s->pos < offset && !s->eof_reached)
             fill_buffer(s);
         if (s->eof_reached)