зеркало из https://github.com/github/ruby.git
50 строки
689 B
C
50 строки
689 B
C
/* ffs.c - find first set bit */
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/* ffs() is defined by Single Unix Specification. */
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#include "ruby.h"
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int ffs(int arg)
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{
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unsigned int x = (unsigned int)arg;
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int r;
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if (x == 0)
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return 0;
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r = 1;
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#if 32 < SIZEOF_INT * CHAR_BIT
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if ((x & 0xffffffff) == 0) {
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x >>= 32;
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r += 32;
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}
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#endif
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if ((x & 0xffff) == 0) {
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x >>= 16;
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r += 16;
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}
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if ((x & 0xff) == 0) {
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x >>= 8;
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r += 8;
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}
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if ((x & 0xf) == 0) {
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x >>= 4;
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r += 4;
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}
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if ((x & 0x3) == 0) {
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x >>= 2;
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r += 2;
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}
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if ((x & 0x1) == 0) {
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x >>= 1;
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r += 1;
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}
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return r;
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}
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