[PATCH] compat: add memrchr()

[Jonathan Nieder <jrnieder@gmail.com>]

Reimplement another handy convenience function from glibc.  memrchr()
searches from the end of a memory area for a particular character.  It
is similar to strrchr() but takes a length argument and is
binary-safe.

The whole-directory rename detection patch could use this to find the
last directory separator in a (possibly truncated) pathname.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
Yann Dirson wrote:

> * memrchr() implementation for portability

Something like this?  Untested.

 git-compat-util.h |   16 ++++++++++++++++
 1 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/git-compat-util.h b/git-compat-util.h
index 2af8d3e..6f1020e 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -366,6 +366,9 @@ extern int git_vsnprintf(char *str, size_t maxsize,
 #define HAVE_STRCHRNUL
 #define HAVE_MEMPCPY
 #endif
+#if __GLIBC_PREREQ(2, 2)
+#define HAVE_MEMRCHR
+#endif
 #endif
 
 #ifndef HAVE_STRCHRNUL
@@ -386,6 +389,19 @@ static inline void *gitmempcpy(void *dest, const void *src, size_t n)
 }
 #endif
 
+#ifndef HAVE_MEMRCHR
+#define memrchr gitmemrchr
+static inline void *gitmemrchr(const void *s, int c, size_t n)
+{
+	const char *p = s;
+	p += n;
+	while (p != s)
+		if (*--p == c)
+			return p;
+	return NULL;
+}
+#endif
+
 extern void release_pack_memory(size_t, int);
 
 typedef void (*try_to_free_t)(size_t);
-- 
1.7.2.3