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-rw-r--r--compat/qsort.c62
1 files changed, 62 insertions, 0 deletions
diff --git a/compat/qsort.c b/compat/qsort.c
new file mode 100644
index 0000000..d93dce2
--- /dev/null
+++ b/compat/qsort.c
@@ -0,0 +1,62 @@
+#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);
+ }
+}