63 lines
1.1 KiB
C
63 lines
1.1 KiB
C
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#include "../git-compat-util.h"
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/*
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* A merge sort implementation, simplified from the qsort implementation
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* by Mike Haertel, which is a part of the GNU C Library.
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*/
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static void msort_with_tmp(void *b, size_t n, size_t s,
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int (*cmp)(const void *, const void *),
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char *t)
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{
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char *tmp;
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char *b1, *b2;
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size_t n1, n2;
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if (n <= 1)
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return;
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n1 = n / 2;
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n2 = n - n1;
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b1 = b;
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b2 = (char *)b + (n1 * s);
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msort_with_tmp(b1, n1, s, cmp, t);
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msort_with_tmp(b2, n2, s, cmp, t);
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tmp = t;
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while (n1 > 0 && n2 > 0) {
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if (cmp(b1, b2) <= 0) {
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memcpy(tmp, b1, s);
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tmp += s;
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b1 += s;
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--n1;
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} else {
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memcpy(tmp, b2, s);
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tmp += s;
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b2 += s;
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--n2;
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}
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}
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if (n1 > 0)
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memcpy(tmp, b1, n1 * s);
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memcpy(b, t, (n - n2) * s);
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}
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void git_qsort(void *b, size_t n, size_t s,
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int (*cmp)(const void *, const void *))
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{
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const size_t size = n * s;
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char buf[1024];
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if (size < sizeof(buf)) {
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/* The temporary array fits on the small on-stack buffer. */
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msort_with_tmp(b, n, s, cmp, buf);
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} else {
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/* It's somewhat large, so malloc it. */
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char *tmp = malloc(size);
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msort_with_tmp(b, n, s, cmp, tmp);
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free(tmp);
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}
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}
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