mirror of
https://github.com/git/git.git
synced 2024-11-28 04:23:30 +08:00
b80741e5b9
Like in the previous patch for compat/qsort_s.c, remove the optimization of using an on-stack buffer to avoid small allocations. This ensures maximum alignment for the array elements and simplifies the code a bit. The performance impact for the current callers is unlikely to be noticeable: * compat/mingw.c::make_environment_block() uses ALLOC_ARRAY and ALLOC_GROW several times already, so another allocation of up to 1KB should not matter much. * diffcore-rename.c::diffcore_rename_extended() is called once per diff or twice per merge, and those require allocations for each object and more already. * merge-ort.c::detect_and_process_renames() is called once per merge. It's responsible for the two per-merge diffcore_rename_extended() calls mentioned above as well, though. So this is possibly the most impacted caller. Per-object allocations are likely to dwarf the additional small allocations in git_stable_qsort(), though. Signed-off-by: René Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
57 lines
986 B
C
57 lines
986 B
C
#include "git-compat-util.h"
|
|
|
|
/*
|
|
* A merge sort implementation, simplified from the qsort implementation
|
|
* by Mike Haertel, which is a part of the GNU C Library.
|
|
*/
|
|
|
|
static void msort_with_tmp(void *b, size_t n, size_t s,
|
|
int (*cmp)(const void *, const void *),
|
|
char *t)
|
|
{
|
|
char *tmp;
|
|
char *b1, *b2;
|
|
size_t n1, n2;
|
|
|
|
if (n <= 1)
|
|
return;
|
|
|
|
n1 = n / 2;
|
|
n2 = n - n1;
|
|
b1 = b;
|
|
b2 = (char *)b + (n1 * s);
|
|
|
|
msort_with_tmp(b1, n1, s, cmp, t);
|
|
msort_with_tmp(b2, n2, s, cmp, t);
|
|
|
|
tmp = t;
|
|
|
|
while (n1 > 0 && n2 > 0) {
|
|
if (cmp(b1, b2) <= 0) {
|
|
memcpy(tmp, b1, s);
|
|
tmp += s;
|
|
b1 += s;
|
|
--n1;
|
|
} else {
|
|
memcpy(tmp, b2, s);
|
|
tmp += s;
|
|
b2 += s;
|
|
--n2;
|
|
}
|
|
}
|
|
if (n1 > 0)
|
|
memcpy(tmp, b1, n1 * s);
|
|
memcpy(b, t, (n - n2) * s);
|
|
}
|
|
|
|
void git_stable_qsort(void *b, size_t n, size_t s,
|
|
int (*cmp)(const void *, const void *))
|
|
{
|
|
const size_t size = st_mult(n, s);
|
|
char *tmp;
|
|
|
|
tmp = xmalloc(size);
|
|
msort_with_tmp(b, n, s, cmp, tmp);
|
|
free(tmp);
|
|
}
|