[FFmpeg-cvslog] avcodec/rangecoder: Add and test ff_rac_check_termination()

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Sun Dec 23 14:17:11 2018 +0100| [b6c2c589041cd99c5bf4117d13708ab010f97bd1] | committer: Michael Niedermayer

avcodec/rangecoder: Add and test ff_rac_check_termination()

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=b6c2c589041cd99c5bf4117d13708ab010f97bd1
---

 libavcodec/rangecoder.c       | 19 +++++++++++++++++++
 libavcodec/rangecoder.h       |  9 +++++++++
 libavcodec/tests/rangecoder.c |  7 +++++--
 3 files changed, 33 insertions(+), 2 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;
+}
diff --git a/libavcodec/rangecoder.h b/libavcodec/rangecoder.h
index 4495f6df1a..4d4ca4d526 100644
--- a/libavcodec/rangecoder.h
+++ b/libavcodec/rangecoder.h
@@ -57,6 +57,15 @@ void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size);
  */
 int ff_rac_terminate(RangeCoder *c, int version);
 
+/**
+ * Check if at the current position there is a valid looking termination
+ * @param version version 0 requires the decoder to know the data size in bytes
+ *                version 1 needs about 1 bit more space but does not need to
+ *                          carry the size from encoder to decoder
+ * @returns negative AVERROR code on error or non negative.
+ */
+int ff_rac_check_termination(RangeCoder *c, int version);
+
 void ff_build_rac_states(RangeCoder *c, int factor, int max_p);
 
 static inline void renorm_encoder(RangeCoder *c)
diff --git a/libavcodec/tests/rangecoder.c b/libavcodec/tests/rangecoder.c
index 3fd07ed9a9..b6edc1493f 100644
--- a/libavcodec/tests/rangecoder.c
+++ b/libavcodec/tests/rangecoder.c
@@ -60,8 +60,11 @@ int main(void)
                     av_log(NULL, AV_LOG_ERROR, "rac failure at %d pass %d version %d\n", i, p, version);
                     return 1;
                 }
-            if(version)
-                get_rac(&c, (uint8_t[]) { 129 });
+
+            if (ff_rac_check_termination(&c, version) < 0) {
+                av_log(NULL, AV_LOG_ERROR, "rac failure at termination pass %d version %d\n", p, version);
+                return 1;
+            }
             if (c.bytestream - c.bytestream_start - actual_length != version) {
                 av_log(NULL, AV_LOG_ERROR, "rac failure at pass %d version %d\n", p, version);
                 return 1;