avcodec/rangecoder: Add and test ff_rac_check_termination()

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

1 files changed, 19 insertions, 0 deletions

diff --git a/libavcodec/rangecoder.c b/libavcodec/rangecoder.c
index fa7d5526d1..a6a3f082ef 100644
--- a/libavcodec/rangecoder.c
+++ b/libavcodec/rangecoder.c
@@ -121,3 +121,22 @@ int ff_rac_terminate(RangeCoder *c, int version)
 
     return c->bytestream - c->bytestream_start;
 }
+
+int ff_rac_check_termination(RangeCoder *c, int version)
+{
+    if (version == 1) {
+        RangeCoder tmp = *c;
+        get_rac(c, (uint8_t[]) { 129 });
+
+        if (c->bytestream == tmp.bytestream && c->bytestream > c->bytestream_start)
+            tmp.low -= *--tmp.bytestream;
+        tmp.bytestream_end = tmp.bytestream;
+
+        if (get_rac(&tmp, (uint8_t[]) { 129 }))
+            return AVERROR_INVALIDDATA;
+    } else {
+        if (c->bytestream_end != c->bytestream)
+            return AVERROR_INVALIDDATA;
+    }
+    return 0;
+}