From bf07d813f6c88b5a76980f321cf7272d799c4216 Mon Sep 17 00:00:00 2001
From: Peter Meerwald <pmeerw@pmeerw.net>
Date: Fri, 20 Feb 2015 01:35:33 +0100
Subject: [PATCH] libavutil: Add av_clip_intp2
there already is a function, av_clip_uintp2() that clips a signed integer
to an unsigned power-of-two range, i.e. 0,2^p-1
this patch adds a function av_clip_intp2() that clips a signed integer
to a signed power-of-two range, i.e. -(2^p),(2^p-1)
the new function can be used as a special case for av_clip(), e.g.
av_clip(x, -8192, 8191) can be rewritten as av_clip_intp2(x, 13)
there are ARM instructions, usat and ssat resp., which map nicely to these
functions (see next patch)
Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
---
libavutil/common.h | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/libavutil/common.h b/libavutil/common.h
index eb40e12990..3265f9cca4 100644
--- a/libavutil/common.h
+++ b/libavutil/common.h
@@ -152,6 +152,20 @@ static av_always_inline av_const int32_t av_clipl_int32_c(int64_t a)
else return a;
}
+/**
+ * Clip a signed integer into the -(2^p),(2^p-1) range.
+ * @param a value to clip
+ * @param p bit position to clip at
+ * @return clipped value
+ */
+static av_always_inline av_const int av_clip_intp2_c(int a, int p)
+{
+ if ((a + (1 << p)) & ~((1 << (p + 1)) - 1))
+ return (a >> 31) ^ ((1 << p) - 1);
+ else
+ return a;
+}
+
/**
* Clip a signed integer to an unsigned power of two range.
* @param a value to clip
@@ -386,6 +400,9 @@ static av_always_inline av_const int av_popcount64_c(uint64_t x)
#ifndef av_clipl_int32
# define av_clipl_int32 av_clipl_int32_c
#endif
+#ifndef av_clip_intp2
+# define av_clip_intp2 av_clip_intp2_c
+#endif
#ifndef av_clip_uintp2
# define av_clip_uintp2 av_clip_uintp2_c
#endif