From 826cf0c61c2e0712914f986e756d1fdef56f9c5c Mon Sep 17 00:00:00 2001
From: Justin Raymond <justin.raymond.14@gmail.com>
Date: Sat, 10 Mar 2018 11:10:19 -0500
Subject: [PATCH 1/3] implement strrchr

---
 src/string/src/lib.rs  | 13 +++++++++++--
 tests/Makefile         |  1 +
 tests/string/strrchr.c | 22 ++++++++++++++++++++++
 3 files changed, 34 insertions(+), 2 deletions(-)
 create mode 100644 tests/string/strrchr.c

diff --git a/src/string/src/lib.rs b/src/string/src/lib.rs
index a3d454fe7e..bbb1a53c69 100644
--- a/src/string/src/lib.rs
+++ b/src/string/src/lib.rs
@@ -223,8 +223,17 @@ pub extern "C" fn strpbrk(s1: *const c_char, s2: *const c_char) -> *mut c_char {
 }
 
 #[no_mangle]
-pub extern "C" fn strrchr(s: *const c_char, c: c_int) -> *mut c_char {
-    unimplemented!();
+pub unsafe extern "C" fn strrchr(s: *const c_char, c: c_int) -> *mut c_char {
+    let len = strlen(s) as isize;
+    let c = c as i8;
+    let mut i = len - 1;
+    while *s.offset(i) != 0 && i >= 0 {
+        if *s.offset(i) == c {
+            return s.offset(i) as *mut c_char;
+        }
+        i -= 1;
+    }
+    ptr::null_mut()
 }
 
 #[no_mangle]
diff --git a/tests/Makefile b/tests/Makefile
index 0726ba101b..8ca12a9a8d 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -25,6 +25,7 @@ BINS=\
 	sprintf \
 	stdlib/strtol \
 	string/strncmp \
+	string/strrchr \
 	unlink \
 	write
 
diff --git a/tests/string/strrchr.c b/tests/string/strrchr.c
new file mode 100644
index 0000000000..7edc98040b
--- /dev/null
+++ b/tests/string/strrchr.c
@@ -0,0 +1,22 @@
+#include <string.h>
+#include <stdio.h>
+
+
+int main(int argc, char* argv[]) {
+  char s0[] = "hello, world";
+  char* ptr = strrchr(s0, 'l');
+  if (ptr != &s0[10]) {
+    printf("%p != %p\n", ptr, &s0[10]);
+    printf("strrchr FAIL , exit with status code %d\n", 1);
+    return 1;
+  }
+  char s1[] = "";
+  ptr = strrchr(s1, 'a');
+  if (ptr != NULL) {
+    printf("%p != 0\n", ptr);
+    printf("strrchr FAIL, exit with status code %d\n", 1);
+    return 1;
+  }
+  printf("strrch PASS, exiting with status code %d\n", 0);
+  return 0;
+}

From 23a409204f3619499546b7f9f72433eddc0ac21f Mon Sep 17 00:00:00 2001
From: Justin Raymond <justin.raymond.14@gmail.com>
Date: Sat, 10 Mar 2018 12:36:42 -0500
Subject: [PATCH 2/3] Update .gitignore

---
 tests/.gitignore | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tests/.gitignore b/tests/.gitignore
index 929fcc62d7..c5a743e74f 100644
--- a/tests/.gitignore
+++ b/tests/.gitignore
@@ -32,6 +32,7 @@
 /string/strncmp
 /string/strcspn
 /string/strchr
+/string/strrchr
 /string/strspn
 /unlink
 /write

From 63ee4de1627e3cbbc87bddc9b631217da9cb15ef Mon Sep 17 00:00:00 2001
From: Justin Raymond <justin.raymond.14@gmail.com>
Date: Sat, 10 Mar 2018 12:39:30 -0500
Subject: [PATCH 3/3] Update lib.rs

---
 src/string/src/lib.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/string/src/lib.rs b/src/string/src/lib.rs
index 81e15e819f..962c8f761d 100644
--- a/src/string/src/lib.rs
+++ b/src/string/src/lib.rs
@@ -259,7 +259,7 @@ pub unsafe extern "C" fn strrchr(s: *const c_char, c: c_int) -> *mut c_char {
     let len = strlen(s) as isize;
     let c = c as i8;
     let mut i = len - 1;
-    while *s.offset(i) != 0 && i >= 0 {
+    while i >= 0 {
         if *s.offset(i) == c {
             return s.offset(i) as *mut c_char;
         }