git/compat/qsort_s.c
René Scharfe 04ee8b875b compat: add qsort_s()
The function qsort_s() was introduced with C11 Annex K; it provides the
ability to pass a context pointer to the comparison function, supports
the convention of using a NULL pointer for an empty array and performs a
few safety checks.

Add an implementation based on compat/qsort.c for platforms that lack a
native standards-compliant qsort_s() (i.e. basically everyone).  It
doesn't perform the full range of possible checks: It uses size_t
instead of rsize_t and doesn't check nmemb and size against RSIZE_MAX
because we probably don't have the restricted size type defined.  For
the same reason it returns int instead of errno_t.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-01-23 11:02:34 -08:00

70 lines
1.3 KiB
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.
* Added context pointer, safety checks and return value.
*/
static void msort_with_tmp(void *b, size_t n, size_t s,
int (*cmp)(const void *, const void *, void *),
char *t, void *ctx)
{
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, ctx);
msort_with_tmp(b2, n2, s, cmp, t, ctx);
tmp = t;
while (n1 > 0 && n2 > 0) {
if (cmp(b1, b2, ctx) <= 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);
}
int git_qsort_s(void *b, size_t n, size_t s,
int (*cmp)(const void *, const void *, void *), void *ctx)
{
const size_t size = st_mult(n, s);
char buf[1024];
if (!n)
return 0;
if (!b || !cmp)
return -1;
if (size < sizeof(buf)) {
/* The temporary array fits on the small on-stack buffer. */
msort_with_tmp(b, n, s, cmp, buf, ctx);
} else {
/* It's somewhat large, so malloc it. */
char *tmp = xmalloc(size);
msort_with_tmp(b, n, s, cmp, tmp, ctx);
free(tmp);
}
return 0;
}