avcodec/put_bits: Relax requirements to rebase PutBitContext

The earlier requirement was for the new buffer to be bigger than the old
one. This has been relaxed to only demand that the new buffer can hold
all the data written so far. This is in preparation for further commits.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/put_bits.h

@@ -61,17 +61,25 @@ static inline void init_put_bits(PutBitContext *s, uint8_t *buffer,
     s->bit_buf      = 0;
 }
 
+/**
+ * @return the total number of bits written to the bitstream.
+ */
+static inline int put_bits_count(PutBitContext *s)
+{
+    return (s->buf_ptr - s->buf) * 8 + 32 - s->bit_left;
+}
+
 /**
  * Rebase the bit writer onto a reallocated buffer.
  *
  * @param buffer the buffer where to put bits
  * @param buffer_size the size in bytes of buffer,
- *                    must be larger than the previous size
+ *                    must be large enough to hold everything written so far
  */
 static inline void rebase_put_bits(PutBitContext *s, uint8_t *buffer,
                                    int buffer_size)
 {
-    av_assert0(8*buffer_size > s->size_in_bits);
+    av_assert0(8*buffer_size >= put_bits_count(s));
 
     s->buf_end = buffer + buffer_size;
     s->buf_ptr = buffer + (s->buf_ptr - s->buf);
@@ -79,14 +87,6 @@ static inline void rebase_put_bits(PutBitContext *s, uint8_t *buffer,
     s->size_in_bits = 8 * buffer_size;
 }
 
-/**
- * @return the total number of bits written to the bitstream.
- */
-static inline int put_bits_count(PutBitContext *s)
-{
-    return (s->buf_ptr - s->buf) * 8 + 32 - s->bit_left;
-}
-
 /**
  * @return the number of bits available in the bitstream.
  */