Re: [FFmpeg-devel] [PATCH 1/2] libavutil: add av_zhb

2015-03-17 Thread Reimar Döffinger 
On 17.03.2015, at 05:08, James Almer jamr...@gmail.com wrote:

 Signed-off-by: James Almer jamr...@gmail.com
 ---
 Better name (av_zero_high_bits?) and doxygen welcome.

Maybe av_wrap_intp2? (to align with clip function naming)
Or av_mod_p2?
Essentially it does a modulo with a power of 2.
Otherwise clear high bits seems a more natural name than zero.
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Re: [FFmpeg-devel] [PATCH 1/2] libavutil: add av_zhb

2015-03-17 Thread James Almer 
On 17/03/15 5:28 AM, Reimar Döffinger wrote:
 On 17.03.2015, at 05:08, James Almer jamr...@gmail.com wrote:
 
 Signed-off-by: James Almer jamr...@gmail.com
 ---
 Better name (av_zero_high_bits?) and doxygen welcome.
 
 Maybe av_wrap_intp2? (to align with clip function naming)
 Or av_mod_p2?
 Essentially it does a modulo with a power of 2.
 Otherwise clear high bits seems a more natural name than zero.

Well, the bmi2 instruction uses zero http://www.felixcloutier.com/x86/BZHI.html
Nonetheless, i like av_mod_p2 more than av_zhb, so unless someone else suggests 
something else I'll resend the set using that name.
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[FFmpeg-devel] [PATCH 1/2] libavutil: add av_zhb

2015-03-16 Thread James Almer 
Signed-off-by: James Almer jamr...@gmail.com
---
Better name (av_zero_high_bits?) and doxygen welcome.

 libavutil/common.h | 14 ++
 1 file changed, 14 insertions(+)

diff --git a/libavutil/common.h b/libavutil/common.h
index 852c1de..2ee5a98 100644
--- a/libavutil/common.h
+++ b/libavutil/common.h
@@ -301,6 +301,17 @@ static av_always_inline av_const int 
av_popcount64_c(uint64_t x)
 return av_popcount((uint32_t)x) + av_popcount((uint32_t)(x  32));
 }
 
+/**
+ * Zero high bits from a starting from bit position p
+ * @param  a value to clip
+ * @param  p bit position to clip at
+ * @return clipped value
+ */
+static av_always_inline av_const unsigned av_zhb_c(unsigned a, unsigned p)
+{
+return a  ((1  p) - 1);
+}
+
 #define MKTAG(a,b,c,d) ((a) | ((b)  8) | ((c)  16) | ((unsigned)(d)  24))
 #define MKBETAG(a,b,c,d) ((d) | ((c)  8) | ((b)  16) | ((unsigned)(a)  
24))
 
@@ -484,3 +495,6 @@ static av_always_inline av_const int 
av_popcount64_c(uint64_t x)
 #ifndef av_popcount64
 #   define av_popcount64av_popcount64_c
 #endif
+#ifndef av_zhb
+#   define av_zhb   av_zhb_c
+#endif
-- 
2.3.2

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