33 lines
780 B
C
33 lines
780 B
C
/*
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* Binary search algorithm, generalized from Knuth (6.2.1) Algorithm B.
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*
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*/
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typedef char *POINTER;
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POINTER
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bsearch(key, base, nel, width, compar)
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POINTER key; /* Key to be located */
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POINTER base; /* Beginning of table */
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unsigned nel; /* Number of elements in the table */
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unsigned width; /* Width of an element (bytes) */
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int (*compar)(); /* Comparison function */
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{
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int two_width = width + width;
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POINTER last = base + width * (nel - 1); /* Last element in table */
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while (last >= base) {
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register POINTER p = base + width * ((last - base)/two_width);
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register int res = (*compar)(key, p);
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if (res == 0)
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return (p); /* Key found */
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if (res < 0)
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last = p - width;
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else
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base = p + width;
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}
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return ((POINTER) 0); /* Key not found */
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}
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