54 lines
1.4 KiB
C
54 lines
1.4 KiB
C
#include <linux/module.h>
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#include <asm/types.h>
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/**
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* hweightN - returns the hamming weight of a N-bit word
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* @x: the word to weigh
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*
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* The Hamming Weight of a number is the total number of bits set in it.
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*/
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unsigned int hweight32(unsigned int w)
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{
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unsigned int res = w - ((w >> 1) & 0x55555555);
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res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
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res = (res + (res >> 4)) & 0x0F0F0F0F;
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res = res + (res >> 8);
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return (res + (res >> 16)) & 0x000000FF;
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}
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EXPORT_SYMBOL(hweight32);
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unsigned int hweight16(unsigned int w)
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{
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unsigned int res = w - ((w >> 1) & 0x5555);
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res = (res & 0x3333) + ((res >> 2) & 0x3333);
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res = (res + (res >> 4)) & 0x0F0F;
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return (res + (res >> 8)) & 0x00FF;
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}
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EXPORT_SYMBOL(hweight16);
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unsigned int hweight8(unsigned int w)
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{
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unsigned int res = w - ((w >> 1) & 0x55);
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res = (res & 0x33) + ((res >> 2) & 0x33);
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return (res + (res >> 4)) & 0x0F;
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}
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EXPORT_SYMBOL(hweight8);
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unsigned long hweight64(__u64 w)
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{
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#if BITS_PER_LONG == 32
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return hweight32((unsigned int)(w >> 32)) + hweight32((unsigned int)w);
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#elif BITS_PER_LONG == 64
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__u64 res = w - ((w >> 1) & 0x5555555555555555ul);
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res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul);
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res = (res + (res >> 4)) & 0x0F0F0F0F0F0F0F0Ful;
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res = res + (res >> 8);
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res = res + (res >> 16);
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return (res + (res >> 32)) & 0x00000000000000FFul;
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#else
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#error BITS_PER_LONG not defined
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#endif
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}
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EXPORT_SYMBOL(hweight64);
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