lru

Documentation

Overview

Package cache implements a LRU cache.

The implementation borrows heavily from SmallLRUCache (originally by Nathan Schrenk). The object maintains a doubly-linked list of elements. When an element is accessed, it is promoted to the head of the list. When space is needed, the element at the tail of the list (the least recently used element) is evicted.

Index

• type Cache
  • func New(capacity int64) *Cache
  • func (lru *Cache) Capacity() int64
  • func (lru *Cache) Clear()
  • func (lru *Cache) Delete(key string) bool
  • func (lru *Cache) Evictions() int64
  • func (lru *Cache) Get(key string) (v Value, ok bool)
  • func (lru *Cache) Items() []Item
  • func (lru *Cache) Keys() []string
  • func (lru *Cache) Length() int64
  • func (lru *Cache) Oldest() (oldest time.Time)
  • func (lru *Cache) Peek(key string) (v Value, ok bool)
  • func (lru *Cache) Set(key string, value Value)
  • func (lru *Cache) SetCapacity(capacity int64)
  • func (lru *Cache) SetIfAbsent(key string, value Value)
  • func (lru *Cache) Size() int64
  • func (lru *Cache) Stats() (length, size, capacity, evictions int64, oldest time.Time)
  • func (lru *Cache) StatsJSON() string
• type Item
• type Value

Types

type Cache

type Cache struct {
	// contains filtered or unexported fields
}

Cache is a typical LRU cache implementation. If the cache reaches the capacity, the least recently used item is deleted from the cache. Note the capacity is not the number of items, but the total sum of the Size() of each item.

func New

func New(capacity int64) *Cache

New creates a new empty cache with the given capacity.

func (*Cache) Capacity

func (lru *Cache) Capacity() int64

Capacity returns the cache maximum capacity.

func (*Cache) Clear

func (lru *Cache) Clear()

Clear will clear the entire cache.

func (*Cache) Delete

func (lru *Cache) Delete(key string) bool

Delete removes an entry from the cache, and returns if the entry existed.

func (*Cache) Evictions

func (lru *Cache) Evictions() int64

Evictions returns the eviction count.

func (*Cache) Get

func (lru *Cache) Get(key string) (v Value, ok bool)

Get returns a value from the cache, and marks the entry as most recently used.

func (*Cache) Items

func (lru *Cache) Items() []Item

Items returns all the values for the cache, ordered from most recently used to last recently used.

func (*Cache) Keys

func (lru *Cache) Keys() []string

Keys returns all the keys for the cache, ordered from most recently used to last recently used.

func (*Cache) Length

func (lru *Cache) Length() int64

Length returns how many elements are in the cache

func (*Cache) Oldest

func (lru *Cache) Oldest() (oldest time.Time)

Oldest returns the insertion time of the oldest element in the cache, or a IsZero() time if cache is empty.

func (*Cache) Peek

func (lru *Cache) Peek(key string) (v Value, ok bool)

Peek returns a value from the cache without changing the LRU order.

func (*Cache) Set

func (lru *Cache) Set(key string, value Value)

Set sets a value in the cache.

func (*Cache) SetCapacity

func (lru *Cache) SetCapacity(capacity int64)

SetCapacity will set the capacity of the cache. If the capacity is smaller, and the current cache size exceed that capacity, the cache will be shrank.

func (*Cache) SetIfAbsent

func (lru *Cache) SetIfAbsent(key string, value Value)

SetIfAbsent will set the value in the cache if not present. If the value exists in the cache, we don't set it.

func (*Cache) Size

func (lru *Cache) Size() int64

Size returns the sum of the objects' Size() method.

func (*Cache) Stats

func (lru *Cache) Stats() (length, size, capacity, evictions int64, oldest time.Time)

Stats returns a few stats on the cache.

func (*Cache) StatsJSON

func (lru *Cache) StatsJSON() string

StatsJSON returns stats as a JSON object in a string.

type Item

type Item struct {
	Key   string
	Value Value
}

Item is what is stored in the cache

type Value

type Value interface {
	// Size returns how big this value is. If you want to just track
	// the cache by number of objects, you may return the size as 1.
	Size() int
}

Value is the interface values that go into Cache need to satisfy