mirror of
https://github.com/facebook/rocksdb.git
synced 2024-12-04 20:02:50 +00:00
6c50fe1ec9
Summary: When building RocksDB on VS2015, an error shows up with hash_map.h(39): error C2719: 'value': formal parameter with requested alignment of 8 won't be aligned Making the reference a reference can solve the problem, and there isn't a reason we can't do that, at least for the current use of the hash map. Pull Request resolved: https://github.com/facebook/rocksdb/pull/6567 Test Plan: See CI tests pass. Reviewed By: pdillinger Differential Revision: D20548543 fbshipit-source-id: 255b55d74cf68a0b324e6f504c56608a97ea6276
68 lines
1.9 KiB
C++
68 lines
1.9 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
|
|
// This source code is licensed under both the GPLv2 (found in the
|
|
// COPYING file in the root directory) and Apache 2.0 License
|
|
// (found in the LICENSE.Apache file in the root directory).
|
|
//
|
|
|
|
#pragma once
|
|
|
|
#include <algorithm>
|
|
#include <array>
|
|
#include <utility>
|
|
|
|
#include "util/autovector.h"
|
|
|
|
namespace ROCKSDB_NAMESPACE {
|
|
|
|
// This is similar to std::unordered_map, except that it tries to avoid
|
|
// allocating or deallocating memory as much as possible. With
|
|
// std::unordered_map, an allocation/deallocation is made for every insertion
|
|
// or deletion because of the requirement that iterators remain valid even
|
|
// with insertions or deletions. This means that the hash chains will be
|
|
// implemented as linked lists.
|
|
//
|
|
// This implementation uses autovector as hash chains insteads.
|
|
//
|
|
template <typename K, typename V, size_t size = 128>
|
|
class HashMap {
|
|
std::array<autovector<std::pair<K, V>, 1>, size> table_;
|
|
|
|
public:
|
|
bool Contains(K key) {
|
|
auto& bucket = table_[key % size];
|
|
auto it = std::find_if(
|
|
bucket.begin(), bucket.end(),
|
|
[key](const std::pair<K, V>& p) { return p.first == key; });
|
|
return it != bucket.end();
|
|
}
|
|
|
|
void Insert(K key, const V& value) {
|
|
auto& bucket = table_[key % size];
|
|
bucket.push_back({key, value});
|
|
}
|
|
|
|
void Delete(K key) {
|
|
auto& bucket = table_[key % size];
|
|
auto it = std::find_if(
|
|
bucket.begin(), bucket.end(),
|
|
[key](const std::pair<K, V>& p) { return p.first == key; });
|
|
if (it != bucket.end()) {
|
|
auto last = bucket.end() - 1;
|
|
if (it != last) {
|
|
*it = *last;
|
|
}
|
|
bucket.pop_back();
|
|
}
|
|
}
|
|
|
|
V& Get(K key) {
|
|
auto& bucket = table_[key % size];
|
|
auto it = std::find_if(
|
|
bucket.begin(), bucket.end(),
|
|
[key](const std::pair<K, V>& p) { return p.first == key; });
|
|
return it->second;
|
|
}
|
|
};
|
|
|
|
} // namespace ROCKSDB_NAMESPACE
|