libavformat/aviobuf: keep track of the original buffer-size and restore it after…

libavformat/aviobuf: keep track of the original buffer-size and restore it after probe/ensure-seekback
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/avio.h

@@ -146,6 +146,13 @@ typedef struct AVIOContext {
      * This field is internal to libavformat and access from outside is not allowed.
      */
     int writeout_count;
+
+    /**
+     * Original buffer size
+     * used internally after probing and ensure seekback to reset the buffer size
+     * This field is internal to libavformat and access from outside is not allowed.
+     */
+    int orig_buffer_size;
 } AVIOContext;
 
 /* unbuffered I/O */

libavformat/aviobuf.c

@@ -78,6 +78,7 @@ int ffio_init_context(AVIOContext *s,
                   int64_t (*seek)(void *opaque, int64_t offset, int whence))
 {
     s->buffer      = buffer;
+    s->orig_buffer_size =
     s->buffer_size = buffer_size;
     s->buf_ptr     = buffer;
     s->opaque      = opaque;
@@ -434,14 +435,14 @@ static void fill_buffer(AVIOContext *s)
     }
 
     /* make buffer smaller in case it ended up large after probing */
-    if (s->read_packet && s->buffer_size > max_buffer_size) {
+    if (s->read_packet && s->orig_buffer_size && s->buffer_size > s->orig_buffer_size) {
         if (dst == s->buffer) {
-            ffio_set_buf_size(s, max_buffer_size);
+            ffio_set_buf_size(s, s->orig_buffer_size);
 
             s->checksum_ptr = dst = s->buffer;
         }
-        av_assert0(len >= max_buffer_size);
-        len = max_buffer_size;
+        av_assert0(len >= s->orig_buffer_size);
+        len = s->orig_buffer_size;
     }
 
     if (s->read_packet)
@@ -792,6 +793,7 @@ int ffio_set_buf_size(AVIOContext *s, int buf_size)
 
     av_free(s->buffer);
     s->buffer = buffer;
+    s->orig_buffer_size =
     s->buffer_size = buf_size;
     s->buf_ptr = buffer;
     url_resetbuf(s, s->write_flag ? AVIO_FLAG_WRITE : AVIO_FLAG_READ);