70 lines
1.6 KiB
C
70 lines
1.6 KiB
C
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/*
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* Code adapted from uClibc-0.9.30.3
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*
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* It is therefore covered by the GNU LESSER GENERAL PUBLIC LICENSE
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* Version 2.1, February 1999
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*
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* Wolfgang Denk <wd@denx.de>
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*/
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/* This code is derived from a public domain shell sort routine by
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* Ray Gardner and found in Bob Stout's snippets collection. The
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* original code is included below in an #if 0/#endif block.
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*
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* I modified it to avoid the possibility of overflow in the wgap
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* calculation, as well as to reduce the generated code size with
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* bcc and gcc. */
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#include <linux/types.h>
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#if 0
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#include <assert.h>
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#else
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#define assert(arg)
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#endif
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void qsort(void *base,
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size_t nel,
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size_t width,
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int (*comp)(const void *, const void *))
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{
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size_t wgap, i, j, k;
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char tmp;
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if ((nel > 1) && (width > 0)) {
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assert(nel <= ((size_t)(-1)) / width); /* check for overflow */
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wgap = 0;
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do {
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wgap = 3 * wgap + 1;
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} while (wgap < (nel-1)/3);
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/* From the above, we know that either wgap == 1 < nel or */
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/* ((wgap-1)/3 < (int) ((nel-1)/3) <= (nel-1)/3 ==> wgap < nel. */
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wgap *= width; /* So this can not overflow if wnel doesn't. */
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nel *= width; /* Convert nel to 'wnel' */
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do {
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i = wgap;
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do {
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j = i;
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do {
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register char *a;
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register char *b;
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j -= wgap;
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a = j + ((char *)base);
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b = a + wgap;
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if ((*comp)(a, b) <= 0) {
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break;
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}
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k = width;
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do {
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tmp = *a;
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*a++ = *b;
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*b++ = tmp;
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} while (--k);
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} while (j >= wgap);
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i += width;
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} while (i < nel);
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wgap = (wgap - width)/3;
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} while (wgap);
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}
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}
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