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+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#ifndef STORAGE_LEVELDB_UTIL_ARENA_H_
+#define STORAGE_LEVELDB_UTIL_ARENA_H_
+
+#include <vector>
+#include <assert.h>
+#include <stddef.h>
+#include <stdint.h>
+
+namespace leveldb {
+
+class Arena {
+ public:
+ Arena();
+ ~Arena();
+
+ // Return a pointer to a newly allocated memory block of "bytes" bytes.
+ char* Allocate(size_t bytes);
+
+ // Allocate memory with the normal alignment guarantees provided by malloc
+ char* AllocateAligned(size_t bytes);
+
+ // Returns an estimate of the total memory usage of data allocated
+ // by the arena (including space allocated but not yet used for user
+ // allocations).
+ size_t MemoryUsage() const {
+ return blocks_memory_ + blocks_.capacity() * sizeof(char*);
+ }
+
+ private:
+ char* AllocateFallback(size_t bytes);
+ char* AllocateNewBlock(size_t block_bytes);
+
+ // Allocation state
+ char* alloc_ptr_;
+ size_t alloc_bytes_remaining_;
+
+ // Array of new[] allocated memory blocks
+ std::vector<char*> blocks_;
+
+ // Bytes of memory in blocks allocated so far
+ size_t blocks_memory_;
+
+ // No copying allowed
+ Arena(const Arena&);
+ void operator=(const Arena&);
+};
+
+inline char* Arena::Allocate(size_t bytes) {
+ // The semantics of what to return are a bit messy if we allow
+ // 0-byte allocations, so we disallow them here (we don't need
+ // them for our internal use).
+ assert(bytes > 0);
+ if (bytes <= alloc_bytes_remaining_) {
+ char* result = alloc_ptr_;
+ alloc_ptr_ += bytes;
+ alloc_bytes_remaining_ -= bytes;
+ return result;
+ }
+ return AllocateFallback(bytes);
+}
+
+} // namespace leveldb
+
+#endif // STORAGE_LEVELDB_UTIL_ARENA_H_