1 // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file. See the AUTHORS file for names of contributors.
5 #include "util/arena.h"
10 static const int kBlockSize = 4096;
14 alloc_ptr_ = NULL; // First allocation will allocate a block
15 alloc_bytes_remaining_ = 0;
19 for (size_t i = 0; i < blocks_.size(); i++) {
24 char* Arena::AllocateFallback(size_t bytes) {
25 if (bytes > kBlockSize / 4) {
26 // Object is more than a quarter of our block size. Allocate it separately
27 // to avoid wasting too much space in leftover bytes.
28 char* result = AllocateNewBlock(bytes);
32 // We waste the remaining space in the current block.
33 alloc_ptr_ = AllocateNewBlock(kBlockSize);
34 alloc_bytes_remaining_ = kBlockSize;
36 char* result = alloc_ptr_;
38 alloc_bytes_remaining_ -= bytes;
42 char* Arena::AllocateAligned(size_t bytes) {
43 const int align = (sizeof(void*) > 8) ? sizeof(void*) : 8;
44 assert((align & (align-1)) == 0); // Pointer size should be a power of 2
45 size_t current_mod = reinterpret_cast<uintptr_t>(alloc_ptr_) & (align-1);
46 size_t slop = (current_mod == 0 ? 0 : align - current_mod);
47 size_t needed = bytes + slop;
49 if (needed <= alloc_bytes_remaining_) {
50 result = alloc_ptr_ + slop;
52 alloc_bytes_remaining_ -= needed;
54 // AllocateFallback always returned aligned memory
55 result = AllocateFallback(bytes);
57 assert((reinterpret_cast<uintptr_t>(result) & (align-1)) == 0);
61 char* Arena::AllocateNewBlock(size_t block_bytes) {
62 char* result = new char[block_bytes];
63 blocks_memory_ += block_bytes;
64 blocks_.push_back(result);
68 } // namespace leveldb