Commit f8732c55 authored by Junio C Hamano's avatar Junio C Hamano

Merge branch 'bd/qsort'

* bd/qsort:
  compat: Add simplified merge sort implementation from glibc
parents 2ac4b4b2 43fe901b
......@@ -137,6 +137,10 @@ all::
# Define THREADED_DELTA_SEARCH if you have pthreads and wish to exploit
# parallel delta searching when packing objects.
#
# Define INTERNAL_QSORT to use Git's implementation of qsort(), which
# is a simplified version of the merge sort used in glibc. This is
# recommended if Git triggers O(n^2) behavior in your platform's qsort().
#
GIT-VERSION-FILE: .FORCE-GIT-VERSION-FILE
@$(SHELL_PATH) ./GIT-VERSION-GEN
......@@ -722,6 +726,10 @@ ifdef NO_MEMMEM
COMPAT_CFLAGS += -DNO_MEMMEM
COMPAT_OBJS += compat/memmem.o
endif
ifdef INTERNAL_QSORT
COMPAT_CFLAGS += -DINTERNAL_QSORT
COMPAT_OBJS += compat/qsort.o
endif
ifdef THREADED_DELTA_SEARCH
BASIC_CFLAGS += -DTHREADED_DELTA_SEARCH
......
#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_qsort(void *b, size_t n, size_t s,
int (*cmp)(const void *, const void *))
{
const size_t size = n * s;
char buf[1024];
if (size < sizeof(buf)) {
/* The temporary array fits on the small on-stack buffer. */
msort_with_tmp(b, n, s, cmp, buf);
} else {
/* It's somewhat large, so malloc it. */
char *tmp = malloc(size);
msort_with_tmp(b, n, s, cmp, tmp);
free(tmp);
}
}
......@@ -426,4 +426,10 @@ static inline int strtol_i(char const *s, int base, int *result)
return 0;
}
#ifdef INTERNAL_QSORT
void git_qsort(void *base, size_t nmemb, size_t size,
int(*compar)(const void *, const void *));
#define qsort git_qsort
#endif
#endif
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