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43 lines
720 B
43 lines
720 B
3 months ago
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/*
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* UCW Library -- Find Highest Set Bit
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*
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* (c) 1997-2005 Martin Mares <mj@ucw.cz>
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*
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* This software may be freely distributed and used according to the terms
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* of the GNU Lesser General Public License.
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*/
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#include <ucw/lib.h>
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#include <ucw/bitops.h>
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int
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bit_fls(u32 x)
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{
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uint l;
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if (!x)
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return -1;
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l = 0;
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if (x & 0xffff0000) { l += 16; x &= 0xffff0000; }
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if (x & 0xff00ff00) { l += 8; x &= 0xff00ff00; }
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if (x & 0xf0f0f0f0) { l += 4; x &= 0xf0f0f0f0; }
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if (x & 0xcccccccc) { l += 2; x &= 0xcccccccc; }
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if (x & 0xaaaaaaaa) l++;
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return l;
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}
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#ifdef TEST
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#include <stdio.h>
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int main(void)
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{
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uint i;
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while (scanf("%x", &i) == 1)
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printf("%d\n", bit_fls(i));
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return 0;
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}
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#endif
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