diff options
author | Pieter Wuille <sipa@ulyssis.org> | 2013-08-20 14:17:45 +0200 |
---|---|---|
committer | Pieter Wuille <sipa@ulyssis.org> | 2013-08-20 14:17:45 +0200 |
commit | cb1e39f0a35cc2b36fb748c26f69cd27e0ed5332 (patch) | |
tree | dd1437e5bb46fbfe1c2bdf7a5bfbfe608761f67d /util/arena.cc | |
download | bitcoin-cb1e39f0a35cc2b36fb748c26f69cd27e0ed5332.tar.xz |
Squashed 'src/leveldb/' content from commit a02ddf9
git-subtree-dir: src/leveldb
git-subtree-split: a02ddf9b14d145e88185ee209ab8b01d8826663a
Diffstat (limited to 'util/arena.cc')
-rw-r--r-- | util/arena.cc | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/util/arena.cc b/util/arena.cc new file mode 100644 index 0000000000..9551d6a3a2 --- /dev/null +++ b/util/arena.cc @@ -0,0 +1,68 @@ +// 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. + +#include "util/arena.h" +#include <assert.h> + +namespace leveldb { + +static const int kBlockSize = 4096; + +Arena::Arena() { + blocks_memory_ = 0; + alloc_ptr_ = NULL; // First allocation will allocate a block + alloc_bytes_remaining_ = 0; +} + +Arena::~Arena() { + for (size_t i = 0; i < blocks_.size(); i++) { + delete[] blocks_[i]; + } +} + +char* Arena::AllocateFallback(size_t bytes) { + if (bytes > kBlockSize / 4) { + // Object is more than a quarter of our block size. Allocate it separately + // to avoid wasting too much space in leftover bytes. + char* result = AllocateNewBlock(bytes); + return result; + } + + // We waste the remaining space in the current block. + alloc_ptr_ = AllocateNewBlock(kBlockSize); + alloc_bytes_remaining_ = kBlockSize; + + char* result = alloc_ptr_; + alloc_ptr_ += bytes; + alloc_bytes_remaining_ -= bytes; + return result; +} + +char* Arena::AllocateAligned(size_t bytes) { + const int align = sizeof(void*); // We'll align to pointer size + assert((align & (align-1)) == 0); // Pointer size should be a power of 2 + size_t current_mod = reinterpret_cast<uintptr_t>(alloc_ptr_) & (align-1); + size_t slop = (current_mod == 0 ? 0 : align - current_mod); + size_t needed = bytes + slop; + char* result; + if (needed <= alloc_bytes_remaining_) { + result = alloc_ptr_ + slop; + alloc_ptr_ += needed; + alloc_bytes_remaining_ -= needed; + } else { + // AllocateFallback always returned aligned memory + result = AllocateFallback(bytes); + } + assert((reinterpret_cast<uintptr_t>(result) & (align-1)) == 0); + return result; +} + +char* Arena::AllocateNewBlock(size_t block_bytes) { + char* result = new char[block_bytes]; + blocks_memory_ += block_bytes; + blocks_.push_back(result); + return result; +} + +} // namespace leveldb |