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utils.h: only define WEBP_NEED_LOG_TABLE_8BIT when needed

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Change-Id: I6ba7a4288034decc5235f07013bd7877545a8b61
This commit is contained in:
James Zern 2018-11-16 01:45:08 -08:00
parent 9f4d4a3f49
commit 41521aed47
1 changed files with 13 additions and 13 deletions
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26
src/utils/utils.h
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@ -107,19 +107,6 @@ static WEBP_INLINE void PutLE32(uint8_t* const data, uint32_t val) {
PutLE16(data + 2, (int)(val >> 16)); PutLE16(data + 2, (int)(val >> 16));
} }
// Returns 31 ^ clz(n) = log2(n). This is the default C-implementation, either
// based on table or not. Can be used as fallback if clz() is not available.
#define WEBP_NEED_LOG_TABLE_8BIT
extern const uint8_t WebPLogTable8bit[256];
static WEBP_INLINE int WebPLog2FloorC(uint32_t n) {
int log_value = 0;
while (n >= 256) {
log_value += 8;
n >>= 8;
}
return log_value + WebPLogTable8bit[n];
}
// Returns (int)floor(log2(n)). n must be > 0. // Returns (int)floor(log2(n)). n must be > 0.
// use GNU builtins where available. // use GNU builtins where available.
#if defined(__GNUC__) && \ #if defined(__GNUC__) && \
@ -138,6 +125,19 @@ static WEBP_INLINE int BitsLog2Floor(uint32_t n) {
return first_set_bit; return first_set_bit;
} }
#else // default: use the C-version. #else // default: use the C-version.
// Returns 31 ^ clz(n) = log2(n). This is the default C-implementation, either
// based on table or not. Can be used as fallback if clz() is not available.
#define WEBP_NEED_LOG_TABLE_8BIT
extern const uint8_t WebPLogTable8bit[256];
static WEBP_INLINE int WebPLog2FloorC(uint32_t n) {
int log_value = 0;
while (n >= 256) {
log_value += 8;
n >>= 8;
}
return log_value + WebPLogTable8bit[n];
}
static WEBP_INLINE int BitsLog2Floor(uint32_t n) { return WebPLog2FloorC(n); } static WEBP_INLINE int BitsLog2Floor(uint32_t n) { return WebPLog2FloorC(n); }
#endif #endif