51 lines
1,001 B
C
51 lines
1,001 B
C
/* bsearch(3)
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*
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* Author: Terrence Holm Aug. 1988
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*
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*
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* Performs a binary search for a given <key> within a sorted
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* table. The table contains <count> entries of size <width>
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* and starts at <base>.
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*
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* Entries are compared using keycmp( key, entry ), each argument
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* is a (char *), the function returns an int < 0, = 0 or > 0
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* according to the order of the two arguments.
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*
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* Bsearch(3) returns a pointer to the matching entry, if found,
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* otherwise NULL is returned.
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*/
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#define NULL (char *) 0
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char *bsearch( key, base, count, width, keycmp )
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char *key;
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char *base;
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unsigned int count;
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unsigned int width;
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int (*keycmp)();
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{
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char *mid_point;
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int cmp;
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while ( count > 0 )
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{
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mid_point = base + width * (count >> 1);
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cmp = (*keycmp)( key, mid_point );
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if ( cmp == 0 )
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return( mid_point );
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if ( cmp < 0 )
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count >>= 1;
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else
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{
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base = mid_point + width;
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count = (count - 1) >> 1;
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}
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}
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return( NULL );
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}
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