From 929f9cbdff08090a222495db7db601f164cebb8c Mon Sep 17 00:00:00 2001
From: liaogang <liaogang@baidu.com>
Date: Mon, 3 Jul 2017 19:52:04 +0800
Subject: [PATCH] ENH: Add Metadata for memory block

---
 paddle/memory/detail/metadata.cc | 62 ++++++++++++++++++++++++++++++++
 paddle/memory/detail/metadata.h  | 53 +++++++++++++++++++++++++++
 2 files changed, 115 insertions(+)
 create mode 100644 paddle/memory/detail/metadata.cc
 create mode 100644 paddle/memory/detail/metadata.h

diff --git a/paddle/memory/detail/metadata.cc b/paddle/memory/detail/metadata.cc
new file mode 100644
index 0000000000..4607cd8512
--- /dev/null
+++ b/paddle/memory/detail/metadata.cc
@@ -0,0 +1,62 @@
+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.
+
+   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. */
+
+#include "paddle/memory/detail/metadata.h"
+
+#include <functional>
+
+namespace paddle {
+namespace memory {
+namespace detail {
+
+Metadata::Metadata(MemoryBlock::Type t, size_t i, size_t s, size_t ts,
+                   MemoryBlock* l, MemoryBlock* r)
+    : type(t),
+      index(i),
+      size(s),
+      total_size(ts),
+      left_buddy(l),
+      right_buddy(r) {}
+
+template <class T>
+inline void hash_combine(std::size_t& seed, const T& v) {
+  std::hash<T> hasher;
+  seed ^= hasher(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+}
+
+inline size_t hash(const Metadata* metadata, size_t initial_seed) {
+  size_t seed = initial_seed;
+
+  hash_combine(seed, (size_t)metadata->type);
+  hash_combine(seed, metadata->index);
+  hash_combine(seed, metadata->size);
+  hash_combine(seed, metadata->total_size);
+  hash_combine(seed, metadata->left_buddy);
+  hash_combine(seed, metadata->right_buddy);
+
+  return seed;
+}
+
+void Metadata::update_guards() {
+  guard_begin = hash(this, 1);
+  guard_end = hash(this, 2);
+}
+
+bool Metadata::check_guards() const {
+  return guard_begin == hash(this, 1) && guard_end == hash(this, 2);
+}
+
+}  // namespace detail
+}  // namespace memory
+}  // namespace paddle
diff --git a/paddle/memory/detail/metadata.h b/paddle/memory/detail/metadata.h
new file mode 100644
index 0000000000..ddb826571b
--- /dev/null
+++ b/paddle/memory/detail/metadata.h
@@ -0,0 +1,53 @@
+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.
+
+   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. */
+
+#pragma once
+
+#include "paddle/memory/detail/memory_block.h"
+
+#include <stddef.h>
+
+namespace paddle {
+namespace memory {
+namespace detail {
+
+class Metadata {
+ public:
+  Metadata(MemoryBlock::Type t, size_t i, size_t s, size_t ts, MemoryBlock* l,
+           MemoryBlock* r);
+
+ public:
+  /*! \brief Update the guards when metadata is changed */
+  void update_guards();
+
+  /*! \brief Check consistency to previous modification */
+  bool check_guards() const;
+
+ public:
+  // TODO(gangliao): compress this
+  // clang-format off
+  size_t            guard_begin = 0;
+  MemoryBlock::Type type        = MemoryBlock::INVALID_CHUNK;
+  size_t            index       = 0;
+  size_t            size        = 0;
+  size_t            total_size  = 0;
+  MemoryBlock*      left_buddy  = nullptr;
+  MemoryBlock*      right_buddy = nullptr;
+  size_t            guard_end   = 0;
+  // clang-format on
+};
+
+}  // namespace detail
+}  // namespace memory
+}  // namespace paddle
-- 
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