You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
71 rivejä
1.9 KiB
71 rivejä
1.9 KiB
// 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 <atomic>
|
|
#include <cassert>
|
|
#include <cstddef>
|
|
#include <cstdint>
|
|
#include <vector>
|
|
|
|
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.
|
|
size_t MemoryUsage() const {
|
|
return memory_usage_.load(std::memory_order_relaxed);
|
|
}
|
|
|
|
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_;
|
|
|
|
// Total memory usage of the arena.
|
|
//
|
|
// TODO(costan): This member is accessed via atomics, but the others are
|
|
// accessed without any locking. Is this OK?
|
|
std::atomic<size_t> memory_usage_;
|
|
|
|
// 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_
|