mirror of https://github.com/grafana/grafana
bergquist
9 years ago
parent
69d6316512
commit
362162d6fa
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This is a list of people who have contributed code to go-cache. They, or their |
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employers, are the copyright holders of the contributed code. Contributed code |
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is subject to the license restrictions listed in LICENSE (as they were when the |
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code was contributed.) |
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|
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Dustin Sallings <dustin@spy.net> |
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Jason Mooberry <jasonmoo@me.com> |
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Sergey Shepelev <temotor@gmail.com> |
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@ -0,0 +1,19 @@ |
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Copyright (c) 2012-2016 Patrick Mylund Nielsen and the go-cache contributors |
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|
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Permission is hereby granted, free of charge, to any person obtaining a copy |
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of this software and associated documentation files (the "Software"), to deal |
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in the Software without restriction, including without limitation the rights |
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
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copies of the Software, and to permit persons to whom the Software is |
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furnished to do so, subject to the following conditions: |
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|
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The above copyright notice and this permission notice shall be included in |
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all copies or substantial portions of the Software. |
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|
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
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THE SOFTWARE. |
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@ -0,0 +1,107 @@ |
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# go-cache |
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|
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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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|
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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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|
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Although go-cache isn't meant to be used as a persistent datastore, the entire |
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cache can be saved to and loaded from a file (using `c.Items()` to retrieve the |
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items map to serialize, and `NewFrom()` to create a cache from a deserialized |
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one) to recover from downtime quickly. (See the docs for `NewFrom()` for caveats.) |
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|
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### Installation |
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|
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`go get github.com/patrickmn/go-cache` |
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|
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### Usage |
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|
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```go |
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import ( |
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"fmt" |
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"github.com/patrickmn/go-cache" |
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"time" |
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) |
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|
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func main() { |
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|
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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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|
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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", cache.DefaultExpiration) |
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|
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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, cache.NoExpiration) |
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|
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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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|
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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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|
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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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|
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// Want performance? Store pointers! |
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c.Set("foo", &MyStruct, cache.DefaultExpiration) |
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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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|
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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, cache.DefaultExpiration) |
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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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|
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// will print: |
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// 1 |
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// 2 |
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} |
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``` |
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|
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### Reference |
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|
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`godoc` or [http://godoc.org/github.com/patrickmn/go-cache](http://godoc.org/github.com/patrickmn/go-cache) |
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File diff suppressed because it is too large
Load Diff
@ -0,0 +1,192 @@ |
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package cache |
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import ( |
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"crypto/rand" |
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"math" |
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"math/big" |
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insecurerand "math/rand" |
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"os" |
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"runtime" |
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"time" |
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) |
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|
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// This is an experimental and unexported (for now) attempt at making a cache
|
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// with better algorithmic complexity than the standard one, namely by
|
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// preventing write locks of the entire cache when an item is added. As of the
|
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// time of writing, the overhead of selecting buckets results in cache
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// operations being about twice as slow as for the standard cache with small
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// total cache sizes, and faster for larger ones.
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//
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// See cache_test.go for a few benchmarks.
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type unexportedShardedCache struct { |
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*shardedCache |
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} |
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type shardedCache struct { |
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seed uint32 |
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m uint32 |
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cs []*cache |
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janitor *shardedJanitor |
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} |
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|
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// djb2 with better shuffling. 5x faster than FNV with the hash.Hash overhead.
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func djb33(seed uint32, k string) uint32 { |
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var ( |
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l = uint32(len(k)) |
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d = 5381 + seed + l |
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i = uint32(0) |
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) |
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// Why is all this 5x faster than a for loop?
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if l >= 4 { |
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for i < l-4 { |
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d = (d * 33) ^ uint32(k[i]) |
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d = (d * 33) ^ uint32(k[i+1]) |
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d = (d * 33) ^ uint32(k[i+2]) |
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d = (d * 33) ^ uint32(k[i+3]) |
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i += 4 |
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} |
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} |
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switch l - i { |
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case 1: |
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case 2: |
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d = (d * 33) ^ uint32(k[i]) |
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case 3: |
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d = (d * 33) ^ uint32(k[i]) |
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d = (d * 33) ^ uint32(k[i+1]) |
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case 4: |
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d = (d * 33) ^ uint32(k[i]) |
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d = (d * 33) ^ uint32(k[i+1]) |
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d = (d * 33) ^ uint32(k[i+2]) |
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} |
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return d ^ (d >> 16) |
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} |
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func (sc *shardedCache) bucket(k string) *cache { |
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return sc.cs[djb33(sc.seed, k)%sc.m] |
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} |
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func (sc *shardedCache) Set(k string, x interface{}, d time.Duration) { |
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sc.bucket(k).Set(k, x, d) |
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} |
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func (sc *shardedCache) Add(k string, x interface{}, d time.Duration) error { |
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return sc.bucket(k).Add(k, x, d) |
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} |
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func (sc *shardedCache) Replace(k string, x interface{}, d time.Duration) error { |
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return sc.bucket(k).Replace(k, x, d) |
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} |
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func (sc *shardedCache) Get(k string) (interface{}, bool) { |
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return sc.bucket(k).Get(k) |
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} |
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func (sc *shardedCache) Increment(k string, n int64) error { |
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return sc.bucket(k).Increment(k, n) |
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} |
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func (sc *shardedCache) IncrementFloat(k string, n float64) error { |
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return sc.bucket(k).IncrementFloat(k, n) |
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} |
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func (sc *shardedCache) Decrement(k string, n int64) error { |
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return sc.bucket(k).Decrement(k, n) |
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} |
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func (sc *shardedCache) Delete(k string) { |
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sc.bucket(k).Delete(k) |
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} |
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func (sc *shardedCache) DeleteExpired() { |
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for _, v := range sc.cs { |
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v.DeleteExpired() |
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} |
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} |
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|
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// Returns the items in the cache. This may include items that have expired,
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// but have not yet been cleaned up. If this is significant, the Expiration
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// fields of the items should be checked. Note that explicit synchronization
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// is needed to use a cache and its corresponding Items() return values at
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// the same time, as the maps are shared.
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func (sc *shardedCache) Items() []map[string]Item { |
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res := make([]map[string]Item, len(sc.cs)) |
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for i, v := range sc.cs { |
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res[i] = v.Items() |
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} |
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return res |
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} |
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func (sc *shardedCache) Flush() { |
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for _, v := range sc.cs { |
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v.Flush() |
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} |
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} |
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type shardedJanitor struct { |
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Interval time.Duration |
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stop chan bool |
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} |
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func (j *shardedJanitor) Run(sc *shardedCache) { |
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j.stop = make(chan bool) |
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tick := time.Tick(j.Interval) |
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for { |
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select { |
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case <-tick: |
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sc.DeleteExpired() |
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case <-j.stop: |
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return |
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} |
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} |
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} |
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func stopShardedJanitor(sc *unexportedShardedCache) { |
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sc.janitor.stop <- true |
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} |
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func runShardedJanitor(sc *shardedCache, ci time.Duration) { |
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j := &shardedJanitor{ |
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Interval: ci, |
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} |
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sc.janitor = j |
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go j.Run(sc) |
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} |
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func newShardedCache(n int, de time.Duration) *shardedCache { |
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max := big.NewInt(0).SetUint64(uint64(math.MaxUint32)) |
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rnd, err := rand.Int(rand.Reader, max) |
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var seed uint32 |
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if err != nil { |
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os.Stderr.Write([]byte("WARNING: go-cache's newShardedCache failed to read from the system CSPRNG (/dev/urandom or equivalent.) Your system's security may be compromised. Continuing with an insecure seed.\n")) |
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seed = insecurerand.Uint32() |
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} else { |
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seed = uint32(rnd.Uint64()) |
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} |
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sc := &shardedCache{ |
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seed: seed, |
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m: uint32(n), |
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cs: make([]*cache, n), |
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} |
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for i := 0; i < n; i++ { |
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c := &cache{ |
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defaultExpiration: de, |
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items: map[string]Item{}, |
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} |
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sc.cs[i] = c |
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} |
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return sc |
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} |
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func unexportedNewSharded(defaultExpiration, cleanupInterval time.Duration, shards int) *unexportedShardedCache { |
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if defaultExpiration == 0 { |
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defaultExpiration = -1 |
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} |
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sc := newShardedCache(shards, defaultExpiration) |
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SC := &unexportedShardedCache{sc} |
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if cleanupInterval > 0 { |
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runShardedJanitor(sc, cleanupInterval) |
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runtime.SetFinalizer(SC, stopShardedJanitor) |
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} |
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return SC |
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} |
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