Added pyext/thread_unsafe_shared_ptr.h

1 files changed, 104 insertions, 0 deletions

diff --git a/python/google/protobuf/pyext/thread_unsafe_shared_ptr.h b/python/google/protobuf/pyext/thread_unsafe_shared_ptr.h
new file mode 100644
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+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// ThreadUnsafeSharedPtr<T> is the same as shared_ptr<T> without the locking
+// overhread (and thread-safety).
+#ifndef GOOGLE_PROTOBUF_PYTHON_CPP_THREAD_UNSAFE_SHARED_PTR_H__
+#define GOOGLE_PROTOBUF_PYTHON_CPP_THREAD_UNSAFE_SHARED_PTR_H__
+
+#include <algorithm>
+#include <utility>
+
+#include <google/protobuf/stubs/logging.h>
+#include <google/protobuf/stubs/common.h>
+
+namespace google {
+namespace protobuf {
+namespace python {
+
+template <typename T>
+class ThreadUnsafeSharedPtr {
+ public:
+  // Takes ownership.
+  explicit ThreadUnsafeSharedPtr(T* ptr)
+      : ptr_(ptr), refcount_(ptr ? new RefcountT(1) : nullptr) {
+  }
+
+  ThreadUnsafeSharedPtr(const ThreadUnsafeSharedPtr& other)
+      : ThreadUnsafeSharedPtr(nullptr) {
+    *this = other;
+  }
+
+  ThreadUnsafeSharedPtr& operator=(const ThreadUnsafeSharedPtr& other) {
+    if (other.refcount_ == refcount_) {
+      return *this;
+    }
+    this->~ThreadUnsafeSharedPtr();
+    ptr_ = other.ptr_;
+    refcount_ = other.refcount_;
+    if (refcount_) {
+      ++*refcount_;
+    }
+    return *this;
+  }
+
+  ~ThreadUnsafeSharedPtr() {
+    if (refcount_ == nullptr) {
+      GOOGLE_DCHECK(ptr_ == nullptr);
+      return;
+    }
+    if (--*refcount_ == 0) {
+      delete refcount_;
+      delete ptr_;
+    }
+  }
+
+  void reset(T* ptr = nullptr) { *this = ThreadUnsafeSharedPtr(ptr); }
+
+  T* get() { return ptr_; }
+  const T* get() const { return ptr_; }
+
+  void swap(ThreadUnsafeSharedPtr& other) {
+    using std::swap;
+    swap(ptr_, other.ptr_);
+    swap(refcount_, other.refcount_);
+  }
+
+ private:
+  typedef int RefcountT;
+  T* ptr_;
+  RefcountT* refcount_;
+};
+
+}  // namespace python
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_PYTHON_CPP_THREAD_UNSAFE_SHARED_PTR_H__