[PATCH] global: provide memrchr implementation for macOS

[Markus Mayer]

macOS doesn't come with a memrchr() of its own, so let's provide an
implementation it can use.

memrchr.c was taken from Apple's own open source site.

https://opensource.apple.com/source/sudo/sudo-87.80.2/sudo/lib/util/memrchr.c

It was minimally modified, so it would work for cgit:

- Removed #include "sudo_compat.h"
- Renamed function from sudo_memrchr() to memrchr()

Signed-off-by: Markus Mayer <code at mmayer.net>
---

I sent this a few days ago already, but it looks like it didn't make it
to the mailig list. Let's give it another shot.

 cgit.h    |  4 ++++
 cgit.mk   |  9 +++++++++
 memrchr.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 62 insertions(+)
 create mode 100644 memrchr.c

diff --git a/cgit.h b/cgit.h
index 7ec46b4..1b2f712 100644
--- a/cgit.h
+++ b/cgit.h
@@ -395,4 +395,8 @@ extern char *expand_macros(const char *txt);
 
 extern char *get_mimetype_for_filename(const char *filename);
 
+#ifdef NEED_MEMRCHR
+extern void *memrchr(const void *s, int c, size_t n);
+#endif
+
 #endif /* CGIT_H */
diff --git a/cgit.mk b/cgit.mk
index 3fcc1ca..f85018c 100644
--- a/cgit.mk
+++ b/cgit.mk
@@ -63,10 +63,19 @@ ifeq ($(uname_S),Linux)
 	HAVE_LINUX_SENDFILE = YesPlease
 endif
 
+ifeq ($(uname_S),Darwin)
+	IS_DARWIN = yes
+endif
+
 ifdef HAVE_LINUX_SENDFILE
 	CGIT_CFLAGS += -DHAVE_LINUX_SENDFILE
 endif
 
+ifdef IS_DARWIN
+	CGIT_CFLAGS += -DNEED_MEMRCHR
+	CGIT_OBJ_NAMES += memrchr.o
+endif
+
 CGIT_OBJ_NAMES += cgit.o
 CGIT_OBJ_NAMES += cache.o
 CGIT_OBJ_NAMES += cmd.o
diff --git a/memrchr.c b/memrchr.c
new file mode 100644
index 0000000..46ec17f
--- /dev/null
+++ b/memrchr.c
@@ -0,0 +1,49 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2007, 2010-2014
+ *	Todd C. Miller <Todd.Miller at sudo.ws>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * This is an open source non-commercial project. Dear PVS-Studio, please check it.
+ * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+ */
+
+#include <config.h>
+
+#ifndef HAVE_MEMRCHR
+
+#include <sys/types.h>
+
+/*
+ * Reverse memchr()
+ * Find the last occurrence of 'c' in the buffer 's' of size 'n'.
+ */
+void *
+memrchr(const void *s, int c, size_t n)
+{
+    const unsigned char *cp;
+
+    if (n != 0) {
+	cp = (unsigned char *)s + n;
+	do {
+	    if (*(--cp) == (unsigned char)c)
+		return (void *)cp;
+	} while (--n != 0);
+    }
+    return (void *)0;
+}
+#endif /* HAVE_MEMRCHR */
-- 
2.26.0