Support memory alignment tests for string_benchmark.cpp

Test: Manually verify that benchmark times are similar and add a unit test.
Change-Id: Idaaeb4c8c3629f797ffd8d0c86c8d7b7b9653181
diff --git a/benchmarks/util.h b/benchmarks/util.h
new file mode 100644
index 0000000..bd3d515
--- /dev/null
+++ b/benchmarks/util.h
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2017 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.
+ */
+
+#ifndef _BIONIC_BENCHMARKS_UTIL_H_
+#define _BIONIC_BENCHMARKS_UTIL_H_
+
+#include <vector>
+
+// This function returns a pointer less than 2 * alignment + or_mask bytes into the array.
+char *GetAlignedMemory(char *orig_ptr, size_t alignment, size_t or_mask);
+
+char *GetAlignedPtr(std::vector<char>* buf, size_t alignment, size_t nbytes);
+
+char *GetAlignedPtrFilled(std::vector<char>* buf, size_t alignment, size_t nbytes, char fill_byte);
+
+bool LockToCPU(int cpu_to_lock);
+
+#endif // _BIONIC_BENCHMARKS_UTIL_H