From a1de0ef8a1eb442a12ec16cb40b1a37c881fe2be Mon Sep 17 00:00:00 2001
From: Andrii Zymohliad <azymohliad@protonmail.com>
Date: Mon, 12 Mar 2018 14:55:02 +0800
Subject: [PATCH] Implement strstr(), add strstr test

---
 src/string/src/lib.rs               | 18 ++++++++++++++++--
 tests/Makefile                      |  1 +
 tests/expected/string/strstr.stderr |  0
 tests/expected/string/strstr.stdout |  3 +++
 tests/string/strstr.c               | 18 ++++++++++++++++++
 5 files changed, 38 insertions(+), 2 deletions(-)
 create mode 100644 tests/expected/string/strstr.stderr
 create mode 100644 tests/expected/string/strstr.stdout
 create mode 100644 tests/string/strstr.c

diff --git a/src/string/src/lib.rs b/src/string/src/lib.rs
index ca56dff001..04b8c93bcd 100644
--- a/src/string/src/lib.rs
+++ b/src/string/src/lib.rs
@@ -299,8 +299,22 @@ pub unsafe extern "C" fn strspn(s1: *const c_char, s2: *const c_char) -> c_ulong
 }
 
 #[no_mangle]
-pub extern "C" fn strstr(s1: *const c_char, s2: *const c_char) -> *mut c_char {
-    unimplemented!();
+pub unsafe extern "C" fn strstr(s1: *const c_char, s2: *const c_char) -> *mut c_char {
+    let mut i = 0;
+    while *s1.offset(i) != 0 {
+        let mut j = 0;
+        while *s2.offset(j) != 0 && *s1.offset(j + i) != 0 {
+            if *s2.offset(j) != *s1.offset(j + i) {
+                break;
+            }
+            j += 1;
+            if *s2.offset(j) == 0 {
+                return s1.offset(i) as *mut c_char;
+            }
+        }
+        i += 1;
+    }
+    ptr::null_mut()
 }
 
 #[no_mangle]
diff --git a/tests/Makefile b/tests/Makefile
index a252889605..ecd259335b 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -27,6 +27,7 @@ EXPECT_BINS=\
 	string/strchr \
 	string/strrchr \
 	string/strspn \
+	string/strstr \
 	unlink \
 	write
 
diff --git a/tests/expected/string/strstr.stderr b/tests/expected/string/strstr.stderr
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/tests/expected/string/strstr.stdout b/tests/expected/string/strstr.stdout
new file mode 100644
index 0000000000..e978edff7f
--- /dev/null
+++ b/tests/expected/string/strstr.stdout
@@ -0,0 +1,3 @@
+rust
+libc we trust
+NULL
diff --git a/tests/string/strstr.c b/tests/string/strstr.c
new file mode 100644
index 0000000000..1f6796a2f1
--- /dev/null
+++ b/tests/string/strstr.c
@@ -0,0 +1,18 @@
+#include <string.h>
+#include <stdio.h>
+
+int main(int argc, char* argv[]) {
+    // should be "rust"
+    char* str1 = strstr("In relibc we trust", "rust");
+    printf("%s\n", (str1) ? str1 : "NULL"); 
+
+    // should be "libc we trust"
+    char* str2 = strstr("In relibc we trust", "libc");
+    printf("%s\n", (str2) ? str2 : "NULL"); 
+
+    // should be "NULL"
+    char* str3 = strstr("In relibc we trust", "bugs");
+    printf("%s\n", (str3) ? str3 : "NULL"); 
+
+    return 0;
+}