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204 lines
8.1 KiB
Plaintext
204 lines
8.1 KiB
Plaintext
go-cache is an in-memory key:value store/cache similar to memcached that is
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suitable for applications running on a single machine. Its major advantage is
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that, being essentially a thread-safe map[string]interface{} with expiration
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times, it doesn't need to serialize or transmit its contents over the network.
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Any object can be stored, for a given duration or forever, and the cache can be
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safely used by multiple goroutines.
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Although go-cache isn't meant to be used as a persistent datastore, the entire
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cache may be saved to and loaded from a file (or any io.Reader/Writer) to
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recover from downtime quickly.
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== Installation
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go get github.com/pmylund/go-cache
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== Usage
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import "github.com/pmylund/go-cache"
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// Create a cache with a default expiration time of 5 minutes, and which
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// purges 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 42, with no expiration time
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// (the item won't be removed until it is re-set, or removed using
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// c.Delete("baz")
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c.Set("baz", 42, -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
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// assertion is needed when values are being passed to functions that don't
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// take arbitrary types, (i.e. interface{}). The simplest way to do this for
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// values which will only be used once--e.g. for passing to another
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// 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.
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// You 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
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// do not need to run Set if you modify the underlying data. The cached
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// reference points to the same memory, so if you modify a struct whose
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// pointer you've stored in the cache, retrieving that pointer with Get will
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// 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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Return a new cache with a given default expiration duration and cleanup
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interval. If the expiration duration is less than 1, the items in the cache
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never expire (by default), and must be deleted manually. If the cleanup
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interval is less than one, expired items are not deleted from the cache
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before their next lookup or before calling DeleteExpired.
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func (c *Cache) Set(k string, x interface{}, d time.Duration)
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Add an item to the cache, replacing any existing item. If the duration is
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0, the cache's default expiration time is used. If it is -1, the item never
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expires.
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func (c *Cache) Add(k string, x interface{}, d time.Duration) error
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Add an item to the cache only if an item doesn't already exist for the
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given key, 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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Set a new value for the cache key only if it already exists. Returns an
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error if it does not.
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func (c *Cache) Get(k string) (interface{}, bool)
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Get an item from the cache. Returns the item or nil, and a bool indicating
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whether the key was found.
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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,
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uint8, uint32, or uint64, float32 or float64 by n. Returns an error if the
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item's value is not an integer, if it was not found, or if it is not
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possible to increment it by n. To retrieve the incremented value, use one
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of the specialized methods, e.g. IncrementInt64.
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func (c *Cache) IncrementFloat(k string, n float64) error
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Increment an item of type float32 or float64 by n. Returns an error if the
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item's value is not floating point, if it was not found, or if it is not
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possible to increment it by n.
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func (c *Cache) IncrementInt(k string, n int) (int, error)
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func (c *Cache) IncrementInt8(k string, n int8) (int8, error)
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func (c *Cache) IncrementInt16(k string, n int16) (int16, error)
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func (c *Cache) IncrementInt32(k string, n int32) (int32, error)
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func (c *Cache) IncrementInt64(k string, n int64) (int64, error)
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func (c *Cache) IncrementUint(k string, n uint) (uint, error)
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func (c *Cache) IncrementUint8(k string, n uint8) (uint8, error)
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func (c *Cache) IncrementUint16(k string, n uint16) (uint16, error)
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func (c *Cache) IncrementUint32(k string, n uint32) (uint32, error)
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func (c *Cache) IncrementUint64(k string, n uint64) (uint64, error)
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func (c *Cache) IncrementFloat32(k string, n float32) (float32, error)
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func (c *Cache) IncrementFloat64(k string, n float64) (float64, error)
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Increment an item of the specified type by n. Returns an error if the item's
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value is not of that type, or if it was not found. If there is no error, the
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incremented value is returned.
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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,
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uint8, uint32, or uint64, float32 or float64 by n. Returns an error if the
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item's value is not an integer, if it was not found, or if it is not
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possible to decrement it by n.
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func (c *Cache) DecrementFloat(k string, n float64) error
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Decrement an item of type float32 or float64 by n. Returns an error if the
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item's value is floating point, if it was not found, or if it is not
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possible to decrement it by n.
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func (c *Cache) DecrementInt(k string, n int) (int, error)
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func (c *Cache) DecrementInt8(k string, n int8) (int8, error)
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func (c *Cache) DecrementInt16(k string, n int16) (int16, error)
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func (c *Cache) DecrementInt32(k string, n int32) (int32, error)
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func (c *Cache) DecrementInt64(k string, n int64) (int64, error)
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func (c *Cache) DecrementUint(k string, n uint) (uint, error)
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func (c *Cache) DecrementUintptr(k string, n uintptr) (uintptr, error)
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func (c *Cache) DecrementUint8(k string, n uint8) (uint8, error)
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func (c *Cache) DecrementUint16(k string, n uint16) (uint16, error)
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func (c *Cache) DecrementUint32(k string, n uint32) (uint32, error)
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func (c *Cache) DecrementUint64(k string, n uint64) (uint64, error)
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func (c *Cache) DecrementFloat32(k string, n float32) (float32, error)
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func (c *Cache) DecrementFloat64(k string, n float64) (float64, error)
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Decrement an item of the specified type by n. Returns an error if the item's
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value is not of that type, or if it was not found. If there is no error, the
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decremented value is returned.
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func (c *Cache) Delete(k string)
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Delete an item from the cache. Does nothing if the key does not exist in the
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cache.
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func (c *Cache) DeleteExpired()
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Delete all expired items from the cache.
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func (c *Cache) ItemCount()
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Returns the number of items in the cache. This may include items that have
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expired, but have not yet been cleaned up.
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func (c *Cache) Flush()
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Delete all items from the cache.
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func (c *Cache) Save(w io.Writer) error
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Write the cache's items (using Gob) to an io.Writer. Returns an error if
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the serialization fails, e.g. because there are unserializable objects like
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channels in the cache.
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func (c *Cache) SaveFile(fname string) error
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Save the cache's items to the given filename, creating the file if it
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doesn't exist, and overwriting it if it does.
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func (c *Cache) Load(r io.Reader) error
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Add (Gob-serialized) cache items from an io.Reader, excluding any items
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with keys that already exist in the current cache.
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func (c *Cache) LoadFile(fname string) error
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Loads and adds cache items from the given filename, excluding any items
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with keys that already exist in the current cache.
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