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Fifo cache implementation.

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Vladimir Byko-Ianko 2018-03-30 18:07:17 +03:00 • committed by Tatiana Yan
parent 62bffec3f9
commit fe036cbb13
3 changed files with 61 additions and 0 deletions
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1
base/CMakeLists.txt
View file

@ -23,6 +23,7 @@ set(
dfa_helpers.hpp
exception.cpp
exception.hpp
fifo_cache.hpp
get_time.hpp
gmtime.cpp
gmtime.hpp

56
base/fifo_cache.hpp Normal file
View file

@ -0,0 +1,56 @@
#pragma once
#include "base/assert.hpp"
#include <cstddef>
#include <functional>
#include <list>
#include <unordered_map>
template<class Key, class Value>
class FifoCache
{
template <typename K, typename V> friend class FifoCacheTest;
public:
using Loader = std::function<void(Key const & key, Value & value)>;
/// \param capacity maximum size of the cache in number of items.
/// \param loader Function which is called if it's necessary to load a new item for the cache.
FifoCache(size_t capacity, Loader const & loader) : m_capacity(capacity), m_loader(loader) {}
/// \brief Loads value, if it's necessary, by |key| with |m_loader|, puts it to cache and
/// returns the reference to the value to |m_map|.
Value const & GetValue(const Key & key)
{
auto const it = m_map.find(key);
if (it != m_map.cend())
return it->second;
if (Size() >= m_capacity)
Evict();
m_list.push_front(key);
auto & v = m_map[key];
m_loader(key, v);
return (m_map[key] = v);
}
private:
void Evict()
{
auto const i = --m_list.end();
m_map.erase(*i);
m_list.erase(i);
}
size_t Size() const { return m_map.size(); }
std::unordered_map<Key, Value> m_map;
// @TODO(bykoianko) Consider using a structure like boost/circular_buffer instead of list
// but with handling overwriting shift. We need it to know to remove overwritten key from |m_map|.
std::list<Key> m_list;
size_t m_capacity;
Loader m_loader;
};

4
xcode/base/base.xcodeproj/project.pbxproj
View file

@ -56,6 +56,7 @@
3D74EF151F8B902C0081202C /* bwt.hpp in Headers */ = {isa = PBXBuildFile; fileRef = 3D74EF0F1F8B902C0081202C /* bwt.hpp */; };
3D7815731F3A145F0068B6AC /* task_loop.hpp in Headers */ = {isa = PBXBuildFile; fileRef = 3D7815711F3A145F0068B6AC /* task_loop.hpp */; };
3D78157B1F3D89EC0068B6AC /* waiter.hpp in Headers */ = {isa = PBXBuildFile; fileRef = 3D78157A1F3D89EC0068B6AC /* waiter.hpp */; };
564BB445206E89ED00BDD211 /* fifo_cache.hpp in Headers */ = {isa = PBXBuildFile; fileRef = 564BB444206E89ED00BDD211 /* fifo_cache.hpp */; };
56B1A0741E69DE4D00395022 /* random.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 56B1A0711E69DE4D00395022 /* random.cpp */; };
56B1A0751E69DE4D00395022 /* random.hpp in Headers */ = {isa = PBXBuildFile; fileRef = 56B1A0721E69DE4D00395022 /* random.hpp */; };
56B1A0761E69DE4D00395022 /* small_set.hpp in Headers */ = {isa = PBXBuildFile; fileRef = 56B1A0731E69DE4D00395022 /* small_set.hpp */; };
@ -188,6 +189,7 @@
3D74EF0F1F8B902C0081202C /* bwt.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = bwt.hpp; sourceTree = "<group>"; };
3D7815711F3A145F0068B6AC /* task_loop.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = task_loop.hpp; sourceTree = "<group>"; };
3D78157A1F3D89EC0068B6AC /* waiter.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = waiter.hpp; sourceTree = "<group>"; };
564BB444206E89ED00BDD211 /* fifo_cache.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = fifo_cache.hpp; sourceTree = "<group>"; };
56B1A0711E69DE4D00395022 /* random.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = random.cpp; sourceTree = "<group>"; };
56B1A0721E69DE4D00395022 /* random.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = random.hpp; sourceTree = "<group>"; };
56B1A0731E69DE4D00395022 /* small_set.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = small_set.hpp; sourceTree = "<group>"; };
@ -350,6 +352,7 @@
675341791A3F57BF00A0A8C3 /* base */ = {
isa = PBXGroup;
children = (
564BB444206E89ED00BDD211 /* fifo_cache.hpp */,
675341851A3F57E400A0A8C3 /* array_adapters.hpp */,
675341861A3F57E400A0A8C3 /* assert.hpp */,
675341871A3F57E400A0A8C3 /* base.cpp */,
@ -526,6 +529,7 @@
6753420B1A3F57E400A0A8C3 /* threaded_container.hpp in Headers */,
672DD4C21E0425600078E13C /* condition.hpp in Headers */,
672DD4C41E0425600078E13C /* newtype.hpp in Headers */,
564BB445206E89ED00BDD211 /* fifo_cache.hpp in Headers */,
672DD4C31E0425600078E13C /* mem_trie.hpp in Headers */,
672DD4C61E0425600078E13C /* range_iterator.hpp in Headers */,
F6F8E3C91EF846CE00F2DE8F /* worker_thread.hpp in Headers */,