55 lines
1.7 KiB
C
55 lines
1.7 KiB
C
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#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 & 0x55555555) + ((w >> 1) & 0x55555555);
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res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
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res = (res & 0x0F0F0F0F) + ((res >> 4) & 0x0F0F0F0F);
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res = (res & 0x00FF00FF) + ((res >> 8) & 0x00FF00FF);
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return (res & 0x0000FFFF) + ((res >> 16) & 0x0000FFFF);
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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 & 0x5555) + ((w >> 1) & 0x5555);
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res = (res & 0x3333) + ((res >> 2) & 0x3333);
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res = (res & 0x0F0F) + ((res >> 4) & 0x0F0F);
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return (res & 0x00FF) + ((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 & 0x55) + ((w >> 1) & 0x55);
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res = (res & 0x33) + ((res >> 2) & 0x33);
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return (res & 0x0F) + ((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;
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res = (w & 0x5555555555555555ul) + ((w >> 1) & 0x5555555555555555ul);
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res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul);
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res = (res & 0x0F0F0F0F0F0F0F0Ful) + ((res >> 4) & 0x0F0F0F0F0F0F0F0Ful);
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res = (res & 0x00FF00FF00FF00FFul) + ((res >> 8) & 0x00FF00FF00FF00FFul);
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res = (res & 0x0000FFFF0000FFFFul) + ((res >> 16) & 0x0000FFFF0000FFFFul);
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return (res & 0x00000000FFFFFFFFul) + ((res >> 32) & 0x00000000FFFFFFFFul);
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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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