The rationale for this function is reflected in the documentation for
it, and is copied here:
Clip a double value into the long long amin-amax range.
This function is needed because conversion of floating point to integers when
it does not fit in the integer's representation does not necessarily saturate
correctly (usually converted to a cvttsd2si on x86) which saturates numbers
> INT64_MAX to INT64_MIN. The standard marks such conversions as undefined
behavior, allowing this sort of mathematically bogus conversions. This provides
a safe alternative that is slower obviously but assures safety and better
mathematical behavior.
API:
@param a value to clip
@param amin minimum value of the clip range
@param amax maximum value of the clip range
@return clipped value
Note that a priori if one can guarantee from the calling side that the
double is in range, it is safe to simply do an explicit/implicit cast,
and that will be far faster. However, otherwise this function should be
used.
avutil minor version is bumped.
Reviewed-by: Ronald S. Bultje <rsbul...@gmail.com>
Signed-off-by: Ganesh Ajjanagadde <gajjanaga...@gmail.com>
---
libavutil/common.h | 30 ++++++++++++++++++++++++++++++
libavutil/version.h | 2 +-
2 files changed, 31 insertions(+), 1 deletion(-)
diff --git a/libavutil/common.h b/libavutil/common.h
index 6f0f582..f4687ab 100644
--- a/libavutil/common.h
+++ b/libavutil/common.h
@@ -298,6 +298,33 @@ static av_always_inline av_const double av_clipd_c(double
a, double amin, double
else return a;
}
+/**
+ * Clip and convert a double value into the long long amin-amax range.
+ * This function is needed because conversion of floating point to integers
when
+ * it does not fit in the integer's representation does not necessarily
saturate
+ * correctly (usually converted to a cvttsd2si on x86) which saturates numbers
+ * > INT64_MAX to INT64_MIN. The standard marks such conversions as undefined
+ * behavior, allowing this sort of mathematically bogus conversions. This
provides
+ * a safe alternative that is slower obviously but assures safety and better
+ * mathematical behavior.
+ * @param a value to clip
+ * @param amin minimum value of the clip range
+ * @param amax maximum value of the clip range
+ * @return clipped value
+ */
+static av_always_inline av_const int64_t av_rint64_clip_c(double a, int64_t
amin, int64_t amax)
+{
+#if defined(HAVE_AV_CONFIG_H) && defined(ASSERT_LEVEL) && ASSERT_LEVEL >= 2
+ if (amin > amax) abort();
+#endif
+ // INT64_MAX+1,INT64_MIN are exactly representable as IEEE doubles
+ if (a >= 9223372036854775808.0 || llrint(a) >= amax)
+ return amax;
+ if (a <= -9223372036854775808.0 || llrint(a) <= amin)
+ return amin;
+ return llrint(a);
+}
+
/** Compute ceil(log2(x)).
* @param x value used to compute ceil(log2(x))
* @return computed ceiling of log2(x)
@@ -511,6 +538,9 @@ static av_always_inline av_const int
av_popcount64_c(uint64_t x)
#ifndef av_clipd
# define av_clipd av_clipd_c
#endif
+#ifndef av_rint64_clip
+# define av_rint64_clip av_rint64_clip_c
+#endif
#ifndef av_popcount
# define av_popcount av_popcount_c
#endif
diff --git a/libavutil/version.h b/libavutil/version.h
index 909f9a6..bcad658 100644
--- a/libavutil/version.h
+++ b/libavutil/version.h
@@ -56,7 +56,7 @@
*/
#define LIBAVUTIL_VERSION_MAJOR 55
-#define LIBAVUTIL_VERSION_MINOR 5
+#define LIBAVUTIL_VERSION_MINOR 6
#define LIBAVUTIL_VERSION_MICRO 100
#define LIBAVUTIL_VERSION_INT AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
--
2.6.2
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
