avcodec/mqcenc: Add ff_mqc_flush_to()

This is needed to separate the end padding from the bitstream, allowing
to end it multiple times without disturbing it.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mqc.h

@@ -59,6 +59,7 @@ int ff_mqc_length(MqcState *mqc);
 
 /** flush the encoder [returns number of bytes encoded] */
 int ff_mqc_flush(MqcState *mqc);
+int ff_mqc_flush_to(MqcState *mqc, uint8_t *dst, int *dst_len);
 
 /* decoder */
 

libavcodec/mqcenc.c

@@ -25,6 +25,7 @@
  * @author Kamil Nowosad
  */
 
+#include "libavutil/avassert.h"
 #include "mqc.h"
 
 static void byteout(MqcState *mqc)
@@ -117,3 +118,23 @@ int ff_mqc_flush(MqcState *mqc)
         mqc->bp++;
     return mqc->bp - mqc->bpstart;
 }
+
+int ff_mqc_flush_to(MqcState *mqc, uint8_t *dst, int *dst_len)
+{
+    int len;
+    MqcState mqc2 = *mqc;
+    mqc2.bpstart=
+    mqc2.bp = dst;
+    *mqc2.bp = *mqc->bp;
+    ff_mqc_flush(&mqc2);
+    *dst_len = mqc2.bp - dst;
+    if (mqc->bp < mqc->bpstart) {
+        av_assert1(mqc->bpstart - mqc->bp == 1);
+        av_assert1(*dst_len > 0);
+        av_assert1(mqc->bp[0] == 0 && dst[0] == 0);
+        (*dst_len) --;
+        memmove(dst, dst+1, *dst_len);
+        return mqc->bp - mqc->bpstart + 1 + *dst_len;
+    }
+    return mqc->bp - mqc->bpstart + *dst_len;
+}