Add strchrnul.

Bug: http://b/18374026
Change-Id: Iea923309c090a51a2d41c5a83320ab3789f40f1c

libc/Android.mk

@@ -214,6 +214,7 @@ libc_bionic_ndk_src_files := \
     bionic/socket.cpp \
     bionic/stat.cpp \
     bionic/statvfs.cpp \
+    bionic/strchrnul.cpp \
     bionic/strerror.cpp \
     bionic/strerror_r.cpp \
     bionic/strsignal.cpp \

libc/bionic/strchrnul.cpp

@@ -0,0 +1,22 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+extern "C" const char* strchrnul(const char* s, int ch) {
+  while (*s && *s != ch) {
+    ++s;
+  }
+  return s;
+}

libc/include/string.h

@@ -53,6 +53,14 @@ extern void*  memmem(const void *, size_t, const void *, size_t) __purefunc;
 
 extern char*  strchr(const char *, int) __purefunc;
 extern char* __strchr_chk(const char *, int, size_t);
+#if defined(__USE_GNU)
+#if defined(__cplusplus)
+extern "C++" char* strchrnul(char*, int) __RENAME(strchrnul) __purefunc;
+extern "C++" const char* strchrnul(const char*, int) __RENAME(strchrnul) __purefunc;
+#else
+char* strchrnul(const char*, int) __purefunc;
+#endif
+#endif
 
 extern char*  strrchr(const char *, int) __purefunc;
 extern char* __strrchr_chk(const char *, int, size_t);

libc/libc.map

@@ -1342,6 +1342,7 @@ LIBC_N {
     __write_chk;
     getgrgid_r;
     getgrnam_r;
+    strchrnul;
 } LIBC;
 
 LIBC_PRIVATE {

tests/string_test.cpp

@@ -454,6 +454,13 @@ TEST(string, strchr) {
   }
 }
 
+TEST(string, strchrnul) {
+  const char* s = "01234222";
+  EXPECT_TRUE(strchrnul(s, '2') == &s[2]);
+  EXPECT_TRUE(strchrnul(s, '8') == (s + strlen(s)));
+  EXPECT_TRUE(strchrnul(s, '\0') == (s + strlen(s)));
+}
+
 TEST(string, strcmp) {
   StringTestState<char> state(SMALL);
   for (size_t i = 1; i < state.n; i++) {