32 lines
1.2 KiB
C
32 lines
1.2 KiB
C
/*
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* Linear search algorithm, generalized from Knuth (6.1) Algorithm Q.
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*
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* This version no longer has anything to do with Knuth's Algorithm Q,
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* which first copies the new element into the table, then looks for it.
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* The assumption there was that the cost of checking for the end of the
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* table before each comparison outweighed the cost of the comparison, which
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* isn't true when an arbitrary comparison function must be called and when the
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* copy itself takes a significant number of cycles.
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* Actually, it has now reverted to Algorithm S, which is "simpler."
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*/
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typedef char *POINTER;
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extern POINTER memcpy();
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POINTER
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lsearch(key, base, nelp, width, compar)
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register POINTER key; /* Key to be located */
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register POINTER base; /* Beginning of table */
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unsigned *nelp; /* Pointer to current table size */
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register unsigned width; /* Width of an element (bytes) */
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int (*compar)(); /* Comparison function */
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{
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register POINTER next = base + *nelp * width; /* End of table */
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for ( ; base < next; base += width)
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if ((*compar)(key, base) == 0)
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return (base); /* Key found */
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++*nelp; /* Not found, add to table */
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return (memcpy(base, key, (int)width)); /* base now == next */
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}
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