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#2386 trying a new static lookup table for numberOfOnes()

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Tony Hagale 2014-03-19 16:26:45 -05:00
parent 07742f54a7
commit 5f94e44cde
1 changed files with 16 additions and 8 deletions
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24
libraries/shared/src/SharedUtil.cpp
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@ -130,14 +130,22 @@ void outputBits(unsigned char byte, QDebug* continuedDebug) {
} }
int numberOfOnes(unsigned char byte) { int numberOfOnes(unsigned char byte) {
return (byte >> 7)
+ ((byte >> 6) & 1) static const unsigned char nbits[256] = {
+ ((byte >> 5) & 1) 0,1,1,2,1,2,2,3,1,2,2,3,2,3,3,4,1,2,2,3,2,3,3,4,2,3,3,
+ ((byte >> 4) & 1) 4,3,4,4,5,1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,2,3,3,4,3,4,
+ ((byte >> 3) & 1) 4,5,3,4,4,5,4,5,5,6,1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,2,
+ ((byte >> 2) & 1) 3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,2,3,3,4,3,4,4,5,3,4,4,5,
+ ((byte >> 1) & 1) 4,5,5,6,3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,1,2,2,3,2,3,3,
+ (byte & 1); 4,2,3,3,4,3,4,4,5,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,2,3,
3,4,3,4,4,5,3,4,4,5,4,5,5,6,3,4,4,5,4,5,5,6,4,5,5,6,5,
6,6,7,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,3,4,4,5,4,5,5,6,
4,5,5,6,5,6,6,7,3,4,4,5,4,5,5,6,4,5,5,6,5,6,6,7,4,5,5,
6,5,6,6,7,5,6,6,7,6,7,7,8
};
return nbits[(unsigned char) byte];
} }
bool oneAtBit(unsigned char byte, int bitIndex) { bool oneAtBit(unsigned char byte, int bitIndex) {