Merge branch 'jk/perf-no-dups'
[git/git.git] / compat / qsort.c
CommitLineData
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1#include "../git-compat-util.h"
2
3/*
4 * A merge sort implementation, simplified from the qsort implementation
5 * by Mike Haertel, which is a part of the GNU C Library.
6 */
7
8static void msort_with_tmp(void *b, size_t n, size_t s,
9 int (*cmp)(const void *, const void *),
10 char *t)
11{
12 char *tmp;
13 char *b1, *b2;
14 size_t n1, n2;
15
16 if (n <= 1)
17 return;
18
19 n1 = n / 2;
20 n2 = n - n1;
21 b1 = b;
22 b2 = (char *)b + (n1 * s);
23
24 msort_with_tmp(b1, n1, s, cmp, t);
25 msort_with_tmp(b2, n2, s, cmp, t);
26
27 tmp = t;
28
29 while (n1 > 0 && n2 > 0) {
30 if (cmp(b1, b2) <= 0) {
31 memcpy(tmp, b1, s);
32 tmp += s;
33 b1 += s;
34 --n1;
35 } else {
36 memcpy(tmp, b2, s);
37 tmp += s;
38 b2 += s;
39 --n2;
40 }
41 }
42 if (n1 > 0)
43 memcpy(tmp, b1, n1 * s);
44 memcpy(b, t, (n - n2) * s);
45}
46
47void git_qsort(void *b, size_t n, size_t s,
48 int (*cmp)(const void *, const void *))
49{
50a6c8ef 50 const size_t size = st_mult(n, s);
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51 char buf[1024];
52
53 if (size < sizeof(buf)) {
54 /* The temporary array fits on the small on-stack buffer. */
55 msort_with_tmp(b, n, s, cmp, buf);
56 } else {
57 /* It's somewhat large, so malloc it. */
040a6551 58 char *tmp = xmalloc(size);
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59 msort_with_tmp(b, n, s, cmp, tmp);
60 free(tmp);
61 }
62}