129 lines
4.9 KiB
Plaintext
129 lines
4.9 KiB
Plaintext
go-cache is an in-memory key:value store/cache similar to memcached that is suitable for
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applications running on a single machine. Any object can be stored, for a given duration
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or forever, and the cache can be used safely by multiple goroutines.
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Installation:
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goinstall github.com/pmylund/go-cache
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Usage:
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// Create a cache with a default expiration time of 5 minutes, and which purges
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// expired items every 30 seconds
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c := cache.New(5*time.Minute, 30*time.Second)
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// Set the value of the key "foo" to "bar", with the default expiration time
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c.Set("foo", "bar", 0)
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// Set the value of the key "baz" to "yes", with no expiration time (the item
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// won't be removed until it is re-set, or removed using c.Delete("baz")
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c.Set("baz", "yes", -1)
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// Get the string associated with the key "foo" from the cache
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foo, found := c.Get("foo")
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if found {
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fmt.Println(foo)
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}
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// Since Go is statically typed, and cache values can be anything, type assertion
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// is needed when values are being passed to functions that don't take arbitrary types,
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// (i.e. interface{}). The simplest way to do this for values which will only be used
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// once--e.g. for passing to another function--is:
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foo, found := c.Get("foo")
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if found {
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MyFunction(foo.(string))
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}
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// This gets tedious if the value is used several times in the same function. You
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// might do either of the following instead:
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if x, found := c.Get("foo"); found {
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foo := x.(string)
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...
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}
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// or
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var foo string
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if x, found := c.Get("foo"); found {
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foo = x.(string)
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}
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...
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// foo can then be passed around freely as a string
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// Want performance? Store pointers!
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c.Set("foo", &MyStruct, 0)
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if x, found := c.Get("foo"); found {
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foo := x.(*MyStruct)
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...
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}
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If you store a reference type like a pointer, slice, map or channel, you do not need to
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run Set if you modify the underlying data. The cache does not serialize its data, so if
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you modify a struct whose pointer you've stored in the cache, retrieving that pointer
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with Get will point you to the same data:
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foo := &MyStruct{Num: 1}
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c.Set("foo", foo, 0)
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...
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x, _ := c.Get("foo")
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foo := x.(MyStruct)
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fmt.Println(foo.Num)
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...
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foo.Num++
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...
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x, _ := c.Get("foo")
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foo := x.(MyStruct)
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foo.Println(foo.Num)
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will print:
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1
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2
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Reference:
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func New(de, ci time.Duration) *Cache
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Returns a new cache with a given default expiration duration and default cleanup
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interval. If the expiration duration is less than 1, the items in the cache never
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expire and must be deleted manually. If the cleanup interval is less than one,
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expired items are not deleted from the cache before their next lookup or before
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calling DeleteExpired.
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func (c *Cache) Set(k string, x interface{}, d time.Duration)
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Adds an item to the cache, replacing any existing item. If the duration is 0, the
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cache's default expiration time is used. If it is -1, the item never expires.
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func (c *Cache) Add(k string, x interface{}, d time.Duration) error
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Adds an item to the cache only if an item doesn't already exist for the given key,
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or if the existing item has expired. Returns an error if not.
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func (c *Cache) Replace(k string, x interface{}, d time.Duration) error
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Sets a new value for the cache item only if it already exists. Returns an error if
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it does not.
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func (c *Cache) Get(k string) (interface{}, bool)
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Gets an item from the cache. Returns the item or nil, and a bool indicating whether
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the given key was found in the cache.
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func (c *Cache) Increment(k string, n int64) error
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Increment an item of type int, int8, int16, int32, int64, uintptr, uint, uint8,
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uint32, or uint64, float32 or float64 by n. Returns an error if the item's value
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is not an integer, if it was not found, or if it is not possible to increment it
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by n. Passing a negative number will cause the item to be decremented.
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func (c *Cache) IncrementFloat(k string, n float64) error
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Increment an item of type int, int8, int16, int32, int64, uintptr, uint, uint8,
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uint32, uint64, float32 or float64 by n. Returns an error if the item's value is
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not an integer, if it was not found, or if it is not possible to increment it by
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n. Passing a negative number will cause the item to be decremented.
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func (c *Cache) Decrement(k string, n int64) error
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Decrement an item of type int, int8, int16, int32, int64, uintptr, uint, uint8,
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uint32, or uint64, float32 or float64 by n. Returns an error if the item's value
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is not an integer, if it was not found, or if it is not possible to decrement it
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by n.
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func (c *Cache) Delete(k string)
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Deletes an item from the cache. Does nothing if the item does not exist in the cache.
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func (c *Cache) DeleteExpired()
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Deletes all expired items from the cache.
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func (c *Cache) Flush()
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Deletes all items from the cache.
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