chore: import upstream snapshot with attribution

src/butil/thread_local_inl.h

@@ -0,0 +1,53 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+// Date: Tue Sep 16 12:39:12 CST 2014
+
+#ifndef BUTIL_THREAD_LOCAL_INL_H
+#define BUTIL_THREAD_LOCAL_INL_H
+
+namespace butil {
+
+namespace detail {
+
+template <typename T>
+class ThreadLocalHelper {
+public:
+    inline static T* get() {
+        if (__builtin_expect(value != NULL, 1)) {
+            return value;
+        }
+        value = new (std::nothrow) T;
+        if (value != NULL) {
+            butil::thread_atexit(delete_object<T>, value);
+        }
+        return value;
+    }
+    static BAIDU_THREAD_LOCAL T* value;
+};
+
+template <typename T> BAIDU_THREAD_LOCAL T* ThreadLocalHelper<T>::value = NULL;
+
+}  // namespace detail
+
+template <typename T> inline T* get_thread_local() {
+    return detail::ThreadLocalHelper<T>::get();
+}
+
+}  // namespace butil
+
+#endif  // BUTIL_THREAD_LOCAL_INL_H