Merge e4b4bf33ab into 1881a9bccb

2016-11-17 07:01:06 +00:00 · 2016-11-17 07:01:06 +00:00 · c5b8fcb38d
parent 1881a9bccb e4b4bf33ab
commit c5b8fcb38d
14 changed files with 883 additions and 2235 deletions
--- a/.pullapprove.yml
+++ b/.pullapprove.yml
@ -0,0 +1,9 @@
+approve_by_comment: true
+approve_regex: ^LGTM
+reject_regex: ^Rejected
+reset_on_push: true
+reviewers:
+  members:
+    - ggaaooppeenngg
+  name: pullapprove
+  required: 1
--- a/.travis.yml
+++ b/.travis.yml
@ -0,0 +1,13 @@
+language: go
+
+go:
+  - tip
+
+before_script:
+  - go get github.com/axw/gocov/gocov
+  - go get github.com/mattn/goveralls
+  - if ! go get code.google.com/p/go.tools/cmd/cover; then go get golang.org/x/tools/cmd/cover; fi
+
+script:
+  - $HOME/gopath/bin/goveralls -service=travis-ci
+
--- a/4
+++ b/4
@ -1,8 +1,10 @@
-This is a list of people who have contributed code to go-cache. They, or their
+This is a list of people who have contributed code to cachemap. They, or their
 employers, are the copyright holders of the contributed code. Contributed code
 is subject to the license restrictions listed in LICENSE (as they were when the
 code was contributed.)

+Peng Gao <peng.gao.dut@gmail.com>
 Dustin Sallings <dustin@spy.net>
 Jason Mooberry <jasonmoo@me.com>
 Sergey Shepelev <temotor@gmail.com>
+Peng Gao <peng.gao.dut@gmail.com>
--- a/1
+++ b/1
@ -1,4 +1,5 @@
 Copyright (c) 2012-2015 Patrick Mylund Nielsen and the go-cache contributors
+Copyright (c) 2016 Peng Gao and cachemap contributors

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
--- a/README.md
+++ b/README.md
@ -1,28 +1,38 @@
-# go-cache
+[![Build Status](https://travis-ci.org/ggaaooppeenngg/cachemap.svg?branch=master)](https://travis-ci.org/ggaaooppeenngg/cachemap)
+[![Coverage Status](https://coveralls.io/repos/github/ggaaooppeenngg/cachemap/badge.svg?branch=sharded-dev)](https://coveralls.io/github/ggaaooppeenngg/cachemap?branch=sharded-dev)
+[![Go Report Card](https://goreportcard.com/badge/github.com/ggaaooppeenngg/cachemap)](https://goreportcard.com/report/github.com/ggaaooppeenngg/cachemap)
+[![GoDoc](https://godoc.org/github.com/ggaaooppeenngg/cachemap?status.svg)](https://godoc.org/github.com/ggaaooppeenngg/cachemap)
+# cachemap

-go-cache is an in-memory key:value store/cache similar to memcached that is
+cachemap is an in-memory key:value store/cache similar to memcached that is
 suitable for applications running on a single machine. Its major advantage is
-that, being essentially a thread-safe `map[string]interface{}` with expiration
-times, it doesn't need to serialize or transmit its contents over the network.
+that, being essentially a thread-safe map with expirationtimes, it doesn't
+need to serialize or transmit its contents over the network.

 Any object can be stored, for a given duration or forever, and the cache can be
 safely used by multiple goroutines.

-Although go-cache isn't meant to be used as a persistent datastore, the entire
+Although cachemap isn't meant to be used as a persistent datastore, the entire
 cache can be saved to and loaded from a file (using `c.Items()` to retrieve the
 items map to serialize, and `NewFrom()` to create a cache from a deserialized
 one) to recover from downtime quickly. (See the docs for `NewFrom()` for caveats.)

+### Notice
+
+This is a repo in development, so I leave a implementation with suffix "\_tpl" in `*.go` and the real generator main package in `cachemap` directory,to generate a template for generic usage in main package, you can try to run script like `cat cache.go | sed 's/ValueType_tpl/{{.ValueType}}/g'  | sed 's/New_tpl/New{{.ValueType}}Cache/g' | sed 's/Attr_tpl/{{.ValueType}}CacheAttr/g' | sed 's/Item_tpl/{{.ValueType}}Item/g' |sed 's/Cache_tpl/{{.ValueType}}Cache/g'|sed 's/cache_tpl/{{.ValueType}}cache/g' | sed 's/package\ cache/package\ {{.PackageName}} /g' | sed 's|// MARK_Numberic_tpl_begin|{{ if call .IsNumberic .RealType }}|g' | sed 's|// MARK_Numberic_tpl_end|{{end}}|g' > cachemap/cache.tmpl` to replace "\_tpl" suffix with golang template variables in the main package.
+
 ### Installation

-`go get github.com/patrickmn/go-cache`
+`go get github.com/ggaaooppeenngg/cachemap`

 ### Usage

+run `cachemap -k string -v string`
+
 ```go
 	import (
 		"fmt"
-		"github.com/patrickmn/go-cache"
+		"github.com/ggaaooppeengg/cachemap"
 		"time"
 	)

@ -102,6 +112,30 @@ one) to recover from downtime quickly. (See the docs for `NewFrom()` for caveats
 	}
 ```

-### Reference
+### Benchmark

-`godoc` or [http://godoc.org/github.com/patrickmn/go-cache](http://godoc.org/github.com/patrickmn/go-cache)
+| benchmark\package                                   | go-cache              | cachemap             |
+|-----------------------------------------------------|-----------------------|----------------------|
+| BenchmarkCacheGetExpiring-v                         | 30000000,46.3 ns/op   | 20000000,43.4 ns/op  |
+| BenchmarkCacheGetNotExpiring-v                      | 50000000,29.6 ns/op   | 50000000,29.6 ns/op  |
+| BenchmarkRWMutexMapGet-x                            | 50000000,26.7 ns/op   | 50000000,26.6 ns/op  |
+| BenchmarkRWMutexInterfaceMapGetStruct-x             | 20000000,75.1 ns/op   | 20000000,66.1 ns/op  |
+| BenchmarkRWMutexInterfaceMapGetString-x             | 20000000,75.3 ns/op   | 20000000,67.6 ns/op  |
+| BenchmarkCacheGetConcurrentExpiring-v               | 20000000,67.8 ns/op   | 20000000,68.9 ns/op  |
+| BenchmarkCacheGetConcurrentNotExpiring-v            | 20000000,69.2 ns/op   | 20000000,68.6 ns/op  |
+| BenchmarkRWMutexMapGetConcurrent-x                  | 30000000,57.4 ns/op   | 20000000,64.7 ns/op  |
+| BenchmarkCacheGetManyConcurrentExpiring-v           | 100000000,68.0 ns/op  | 100000000,66.7 ns/op |
+| BenchmarkCacheGetManyConcurrentNotExpiring-v        | 2000000000,68.3 ns/op | 20000000,69.3 ns/op  |
+| BenchmarkCacheSetExpiring-4                         | 10000000,173 ns/op    | 20000000,91.4 ns/op  |
+| BenchmarkCacheSetNotExpiring-4                      | 10000000,123 ns/op    | 20000000,100 ns/op   |
+| BenchmarkRWMutexMapSet-4                            | 20000000,88.5 ns/op   | 20000000,74.5 ns/op  |
+| BenchmarkCacheSetDelete-4                           | 5000000,257 ns/op     | 10000000,151 ns/op   |
+| BenchmarkRWMutexMapSetDelete-4                      | 10000000,180 ns/op    | 10000000,154 ns/op   |
+| BenchmarkCacheSetDeleteSingleLock-4                 | 10000000,211 ns/op    | 20000000,118 ns/op   |
+| BenchmarkRWMutexMapSetDeleteSingleLock-4            | 10000000,142 ns/op    | 20000000,118 ns/op   |
+| BenchmarkIncrementInt-4                             | 10000000,167 ns/op    |                      |
+| BenchmarkDeleteExpiredLoop-4                        | 500,2584384 ns/op     | 1000,2173019 ns/op   |
+| BenchmarkShardedCacheGetExpiring-4                  | 20000000,79.5 ns/op   | 20000000,67.9 ns/op  |
+| BenchmarkShardedCacheGetNotExpiring-4               | 30000000,59.3 ns/op   | 20000000,49.9 ns/op  |
+| BenchmarkShardedCacheGetManyConcurrentExpiring-4    | 2000000000,52.4 ns/op | 10000000,75.8 ns/op  |
+| BenchmarkShardedCacheGetManyConcurrentNotExpiring-4 | 100000000,68.2 ns/op  | 20000000,75.8 ns/op  |
--- a/cache.go
+++ b/cache.go
--- a/cache_test.go
+++ b/cache_test.go
--- a/cachemap/cache.tmpl
+++ b/cachemap/cache.tmpl
@ -0,0 +1,312 @@
+package {{.PackageName}} 
+
+// The package is used as a template, don't use it directly!
+
+import (
+	"fmt"
+	"runtime"
+	"sync"
+	"time"
+)
+
+// Attr is cachmap attribute
+type {{.ValueType}}CacheAttr struct {
+	// An (optional) function that is called with the key and value when an
+	// item is evicted from the cache. (Including when it is deleted manually, but
+	// not when it is overwritten.) Set to nil to disable.
+	OnEvicted func(k string, v {{.ValueType}})
+
+	DefaultCleanupInterval time.Duration // Default clean interval, this is a time interval to cleanup expired items
+	DefaultExpiration      time.Duration // Default expiration duration
+	Size                   int64         // Initial size of map
+}
+
+// Item struct
+type {{.ValueType}}Item struct {
+	Object     {{.ValueType}}
+	Expiration int64
+}
+
+// Expired returns true if the item has expired.
+func (item {{.ValueType}}Item) Expired() bool {
+	return item.Expiration != 0 && time.Now().UnixNano() > item.Expiration
+}
+
+// Cache struct
+type {{.ValueType}}Cache struct {
+	*{{.ValueType}}cache
+	// If this is confusing, see the comment at the bottom of New()
+}
+
+type {{.ValueType}}cache struct {
+	defaultExpiration time.Duration
+	items             map[string]{{.ValueType}}Item
+	mu                sync.RWMutex
+	onEvicted         func(string, {{.ValueType}})
+	stop              chan bool
+}
+
+// Add an item to the cache, replacing any existing item. If the duration is 0
+// (DefaultExpiration), the cache's default expiration time is used. If it is -1
+// (NoExpiration), the item never expires.
+func (c *{{.ValueType}}cache) Set(k string, x {{.ValueType}}, d time.Duration) {
+	// "Inlining" of set
+	var e int64
+	if d == DefaultExpiration {
+		d = c.defaultExpiration
+	}
+	if d > 0 {
+		e = time.Now().Add(d).UnixNano()
+	}
+	c.mu.Lock()
+	c.items[k] = {{.ValueType}}Item{
+		Object:     x,
+		Expiration: e,
+	}
+	// TODO: Calls to mu.Unlock are currently not deferred because defer
+	// adds ~200 ns (as of go1.)
+	c.mu.Unlock()
+}
+
+func (c *{{.ValueType}}cache) set(k string, x {{.ValueType}}, d time.Duration) {
+	var e int64
+	if d == DefaultExpiration {
+		d = c.defaultExpiration
+	}
+	if d > 0 {
+		e = time.Now().Add(d).UnixNano()
+	}
+	c.items[k] = {{.ValueType}}Item{
+		Object:     x,
+		Expiration: e,
+	}
+}
+
+// Add an item to the cache only if an item doesn't already exist for the given
+// key, or if the existing item has expired. Returns an error otherwise.
+func (c *{{.ValueType}}cache) Add(k string, x {{.ValueType}}, d time.Duration) error {
+	c.mu.Lock()
+	_, found := c.get(k)
+	if found {
+		c.mu.Unlock()
+		return fmt.Errorf("Item %s already exists", k)
+	}
+	c.set(k, x, d)
+	c.mu.Unlock()
+	return nil
+}
+
+// Set a new value for the cache key only if it already exists, and the existing
+// item hasn't expired. Returns an error otherwise.
+func (c *{{.ValueType}}cache) Replace(k string, x {{.ValueType}}, d time.Duration) error {
+	c.mu.Lock()
+	_, found := c.get(k)
+	if !found {
+		c.mu.Unlock()
+		return fmt.Errorf("Item %s doesn't exist", k)
+	}
+	c.set(k, x, d)
+	c.mu.Unlock()
+	return nil
+}
+
+// Get an item from the cache. Returns the item or nil, and a bool indicating
+// whether the key was found.
+func (c *{{.ValueType}}cache) Get(k string) ({{.ValueType}}, bool) {
+	c.mu.RLock()
+	// "Inlining" of get and Expired
+	item, found := c.items[k]
+	// TODO: inline time.Now implementation
+	if !found || item.Expiration > 0 && time.Now().UnixNano() > item.Expiration {
+		c.mu.RUnlock()
+		return {{.ZeroValue}}, false
+	}
+	c.mu.RUnlock()
+	return item.Object, true
+}
+
+func (c *{{.ValueType}}cache) get(k string) (*{{.ValueType}}, bool) {
+	item, found := c.items[k]
+	if !found || item.Expiration > 0 && time.Now().UnixNano() > item.Expiration {
+		return nil, false
+	}
+	return &item.Object, true
+}
+
+{{ if call .IsNumberic .RealType }}
+
+// Increment an item of type int, int8, int16, int32, int64, uintptr, uint,
+// uint8, uint32, or uint64, float32 or float64 by n. Returns an error if the
+// item's value is not an integer, if it was not found, or if it is not
+// possible to increment it by n. To retrieve the incremented value, use one
+// of the specialized methods, e.g. IncrementInt64.
+func (c *{{.ValueType}}cache) Increment(k string, n {{.ValueType}}) error {
+	c.mu.Lock()
+	v, found := c.items[k]
+	if !found || v.Expired() {
+		c.mu.Unlock()
+		return fmt.Errorf("Item %s not found", k)
+	}
+	v.Object += n
+	c.items[k] = v
+	c.mu.Unlock()
+	return nil
+}
+
+// Decrement an item of type int, int8, int16, int32, int64, uintptr, uint,
+// uint8, uint32, or uint64, float32 or float64 by n. Returns an error if the
+// item's value is not an integer, if it was not found, or if it is not
+// possible to decrement it by n. To retrieve the decremented value, use one
+// of the specialized methods, e.g. DecrementInt64.
+func (c *{{.ValueType}}cache) Decrement(k string, n {{.ValueType}}) error {
+	// TODO: Implement Increment and Decrement more cleanly.
+	// (Cannot do Increment(k, n*-1) for uints.)
+	c.mu.Lock()
+	v, found := c.items[k]
+	if !found || v.Expired() {
+		c.mu.Unlock()
+		return fmt.Errorf("Item not found")
+	}
+	v.Object -= n
+	c.items[k] = v
+	c.mu.Unlock()
+	return nil
+}
+
+{{end}}
+
+// Delete an item from the cache. Does nothing if the key is not in the cache.
+func (c *{{.ValueType}}cache) Delete(k string) {
+	// fast path
+	if c.onEvicted == nil {
+		c.mu.Lock()
+		c.deleteFast(k)
+		c.mu.Unlock()
+		return
+	}
+	// slow path
+	c.mu.Lock()
+	v, evicted := c.delete(k)
+	c.mu.Unlock()
+	if evicted {
+		c.onEvicted(k, v)
+	}
+}
+
+func (c *{{.ValueType}}cache) delete(k string) ({{.ValueType}}, bool) {
+	if v, found := c.items[k]; found {
+		delete(c.items, k)
+		return v.Object, true
+	}
+	return {{.ZeroValue}}, false
+}
+
+func (c *{{.ValueType}}cache) deleteFast(k string) {
+	delete(c.items, k)
+}
+
+// Delete all expired items from the cache.
+func (c *{{.ValueType}}cache) DeleteExpired() {
+	var evictedItems []struct{
+		key string
+		value {{.ValueType}}
+	}
+	now := time.Now().UnixNano()
+	// fast path
+	if c.onEvicted == nil {
+		c.mu.Lock()
+		for k, v := range c.items {
+			// "Inlining" of expired
+			if v.Expiration > 0 && now > v.Expiration {
+				c.deleteFast(k)
+			}
+		}
+		c.mu.Unlock()
+		return
+	}
+	// slow path
+	c.mu.Lock()
+	for k, v := range c.items {
+		// "Inlining" of expired
+		if v.Expiration > 0 && now > v.Expiration {
+			ov, evicted := c.delete(k)
+			if evicted {
+				evictedItems = append(evictedItems, struct{
+					key string
+					value {{.ValueType}}
+				}{k, ov})
+			}
+		}
+	}
+	c.mu.Unlock()
+	for _, v := range evictedItems {
+		c.onEvicted(v.key, v.value)
+	}
+}
+
+// Returns the number of items in the cache. This may include items that have
+// expired, but have not yet been cleaned up. Equivalent to len(c.Items()).
+func (c *{{.ValueType}}cache) ItemCount() int {
+	c.mu.RLock()
+	n := len(c.items)
+	c.mu.RUnlock()
+	return n
+}
+
+// Delete all items from the cache.
+func (c *{{.ValueType}}cache) Flush() {
+	c.mu.Lock()
+	c.items = map[string]{{.ValueType}}Item{}
+	c.mu.Unlock()
+}
+
+// _ *{{.ValueType}}cache is used as a namespace, so that "stopJanitor" will not conflicts for the name.
+func (_ *{{.ValueType}}cache) stopJanitor(c *{{.ValueType}}Cache) {
+	c.stop <- true
+}
+
+func (c *{{.ValueType}}cache) runJanitor(ci time.Duration) {
+	c.stop = make(chan bool)
+	go func() {
+		ticker := time.NewTicker(ci)
+		for {
+			select {
+			case <-ticker.C:
+				c.DeleteExpired()
+			case <-c.stop:
+				ticker.Stop()
+				return
+			}
+		}
+	}()
+
+}
+
+// New Returns a new cache with a given default expiration duration and
+// cleanup interval. If the expiration duration is less than one
+// (or NoExpiration), the items in the cache never expire (by default),
+// and must be deleted manually. If the cleanup interval is less than one,
+// expired items are not deleted from the cache before calling c.DeleteExpired().
+//
+func New{{.ValueType}}Cache(attr {{.ValueType}}CacheAttr) *{{.ValueType}}Cache {
+	items := make(map[string]{{.ValueType}}Item, attr.Size)
+	if attr.DefaultExpiration == 0 {
+		attr.DefaultExpiration = -1
+	}
+	c := &{{.ValueType}}cache{
+		defaultExpiration: attr.DefaultExpiration,
+		items:             items,
+	}
+	c.onEvicted = attr.OnEvicted
+	// This trick ensures that the janitor goroutine (which--granted it
+	// was enabled--is running DeleteExpired on c forever) does not keep
+	// the returned C object from being garbage collected. When it is
+	// garbage collected, the finalizer stops the janitor goroutine, after
+	// which c can be collected.
+	C := &{{.ValueType}}Cache{c}
+	if attr.DefaultCleanupInterval > 0 {
+		c.runJanitor(attr.DefaultCleanupInterval)
+		runtime.SetFinalizer(C, c.stopJanitor)
+	}
+	return C
+}
--- a/cachemap/const.tmpl
+++ b/cachemap/const.tmpl
@ -0,0 +1,17 @@
+package {{.PackageName}}
+
+import (
+	"time"
+)
+
+// To avoid redecleration, put common code in this file.
+
+const (
+	// NoExpiration is for use with functions that take no expiration time.
+	NoExpiration time.Duration = -1
+	// DefaultExpiration is for use with functions that take an
+	// expiration time. Equivalent to passing in the same expiration
+	// duration as was given to New() when the cache was
+	// created (e.g. 5 minutes.)
+	DefaultExpiration time.Duration = 0
+)
--- a/cachemap/main.go
+++ b/cachemap/main.go
@ -0,0 +1,193 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"os"
+	"path"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"text/template"
+)
+
+func fatal(v ...interface{}) {
+	fmt.Fprintln(os.Stderr, v...)
+	os.Exit(1)
+}
+
+func packageDir() string {
+	_, filename, _, ok := runtime.Caller(0)
+	if !ok {
+		panic("No caller information")
+	}
+	return path.Dir(filename)
+}
+
+// TODO: parse type if type is also not builtin type.
+// find literal value of type.
+func findInGenDecl(genDecl *ast.GenDecl, valueName string) string {
+	for _, spec := range genDecl.Specs {
+		valueSpec, ok := spec.(*ast.TypeSpec)
+		if ok {
+			if ok && valueSpec.Name.Name == valueName {
+				indent, ok := valueSpec.Type.(*ast.Ident)
+				if ok {
+					return indent.Name
+				} else {
+					// For other types like StructType
+					return valueName
+				}
+			}
+		}
+	}
+	return ""
+}
+
+func findInDecl(decl ast.Decl, valueName string) string {
+	genDecl, ok := decl.(*ast.GenDecl)
+	if ok {
+		g := findInGenDecl(genDecl, valueName)
+		if g != "" {
+			return g
+		}
+	}
+	return ""
+}
+
+// zeroValue returns literal zero value.
+func zeroValue(s string) string {
+	// TODO: support func type.
+	switch s {
+	case "bool":
+		return "false"
+	case "string":
+		return "\"\""
+	case "int", "uint", "int64", "uint64", "uint32", "int32", "int16",
+		"uint16", "int8", "uint8", "byte", "rune", "float64", "float32",
+		"complex64", "complex32", "uintptr":
+		return "0"
+	default:
+		if s[0] == '*' || // Pointer
+			strings.Index(s, "map") == 0 || // map
+			strings.Index(s, "chan") == 0 || // chan
+			strings.Index(s, "[]") == 0 || // slice
+			strings.Index(s, "func") == 0 { // func
+			return "nil"
+		}
+		return s + "{}"
+	}
+}
+
+var builtinTypes = []string{
+	"bool",
+	"string",
+
+	"int", "int8", "int16", "int32", "int64", // numbericType
+	"uint", "uint8", "uint16", "uint32", "uint64", "uintptr",
+	"float32", "float64",
+	"complex64", "complex128",
+	"byte",
+	"rune",
+}
+
+func isNumberic(s string) bool {
+	for _, v := range builtinTypes[2:] { // 2 is beginning of numberic types in builtinTypes.
+		if v == s {
+			return true
+		}
+	}
+	return false
+}
+
+func isBuiltin(s string) bool {
+	for _, v := range builtinTypes {
+		if v == s {
+			return true
+		}
+	}
+	return false
+}
+
+func main() {
+	keyType := flag.String("k", "", "key type")
+	valueType := flag.String("v", "", "value type")
+	flag.Parse()
+	if *keyType == "" {
+		fatal("key empty")
+	}
+	if *valueType == "" {
+		fatal("value empty")
+	}
+	fset := token.NewFileSet()
+	pkgs, err := parser.ParseDir(fset, ".", nil, parser.ParseComments)
+	if err != nil {
+		fatal(err)
+	}
+	packageName := "main"
+	typeName := ""
+FIND:
+	for name, pkg := range pkgs {
+		packageName = name
+		for _, f := range pkg.Files {
+			for _, decl := range f.Decls {
+				typeName = findInDecl(decl, *valueType)
+				if typeName != "" {
+					break FIND
+				}
+			}
+		}
+	}
+	if typeName == "" && !isBuiltin(*valueType) {
+		fatal(fmt.Errorf("found no definition of %s in files\n", *valueType))
+	}
+	if typeName == "" {
+		typeName = *valueType
+	}
+	zeroTypeValue := zeroValue(typeName)
+	f, err := os.OpenFile(fmt.Sprintf("%s2%s_cachemap.go", *keyType, *valueType), os.O_TRUNC|os.O_WRONLY|os.O_CREATE, 0644)
+	if err != nil {
+		fatal(err)
+	}
+	defer f.Close()
+	tpl, err := template.New("cache.tmpl").ParseFiles(filepath.Join(packageDir(), "cache.tmpl"))
+	if err != nil {
+		fatal(err)
+	}
+	if !isBuiltin(*valueType) {
+		*valueType = strings.Title(*valueType)
+	}
+	err = tpl.Execute(
+		f,
+		map[string]interface{}{
+			"ValueType":   *valueType,
+			"RealType":    typeName,
+			"PackageName": packageName,
+			"Cache":       fmt.Sprintf("String2%sCache", *valueType),
+			"ZeroValue":   zeroTypeValue,
+			"IsNumberic":  isNumberic,
+		},
+	)
+	if err != nil {
+		fatal(err)
+	}
+	constFile, err := os.OpenFile(fmt.Sprintf("cachemap_const.go"), os.O_TRUNC|os.O_WRONLY|os.O_CREATE, 0644)
+	if err != nil {
+		fatal(err)
+	}
+	defer constFile.Close()
+	constTpl, err := template.New("const.tmpl").ParseFiles(filepath.Join(packageDir(), "const.tmpl"))
+	if err != nil {
+		fatal(err)
+	}
+	err = constTpl.Execute(constFile,
+		map[string]interface{}{
+			"PackageName": packageName,
+		})
+	if err != nil {
+		fatal(err)
+	}
+}
--- a/const.go
+++ b/const.go
@ -0,0 +1,17 @@
+package cache
+
+import (
+	"time"
+)
+
+// To avoid redecleration errors, put common code in this file.
+
+const (
+	// NoExpiration is for use with functions that take no expiration time.
+	NoExpiration time.Duration = -1
+	// DefaultExpiration is for use with functions that take an
+	// expiration time. Equivalent to passing in the same expiration
+	// duration as was given to New() when the cache was
+	// created (e.g. 5 minutes.)
+	DefaultExpiration time.Duration = 0
+)
--- a/sharded.go
+++ b/sharded.go
@ -26,7 +26,7 @@ type unexportedShardedCache struct {
 type shardedCache struct {
 	seed    uint32
 	m       uint32
-	cs      []*cache
+	cs      []*cache_tpl
 	janitor *shardedJanitor
 }

@ -62,35 +62,31 @@ func djb33(seed uint32, k string) uint32 {
 	return d ^ (d >> 16)
 }

-func (sc *shardedCache) bucket(k string) *cache {
+func (sc *shardedCache) bucket(k string) *cache_tpl {
 	return sc.cs[djb33(sc.seed, k)%sc.m]
 }

-func (sc *shardedCache) Set(k string, x interface{}, d time.Duration) {
+func (sc *shardedCache) Set(k string, x ValueType_tpl, d time.Duration) {
 	sc.bucket(k).Set(k, x, d)
 }

-func (sc *shardedCache) Add(k string, x interface{}, d time.Duration) error {
+func (sc *shardedCache) Add(k string, x ValueType_tpl, d time.Duration) error {
 	return sc.bucket(k).Add(k, x, d)
 }

-func (sc *shardedCache) Replace(k string, x interface{}, d time.Duration) error {
+func (sc *shardedCache) Replace(k string, x ValueType_tpl, d time.Duration) error {
 	return sc.bucket(k).Replace(k, x, d)
 }

-func (sc *shardedCache) Get(k string) (interface{}, bool) {
+func (sc *shardedCache) Get(k string) (ValueType_tpl, bool) {
 	return sc.bucket(k).Get(k)
 }

-func (sc *shardedCache) Increment(k string, n int64) error {
+func (sc *shardedCache) Increment(k string, n ValueType_tpl) error {
 	return sc.bucket(k).Increment(k, n)
 }

-func (sc *shardedCache) IncrementFloat(k string, n float64) error {
-	return sc.bucket(k).IncrementFloat(k, n)
-}
-
-func (sc *shardedCache) Decrement(k string, n int64) error {
+func (sc *shardedCache) Decrement(k string, n ValueType_tpl) error {
 	return sc.bucket(k).Decrement(k, n)
 }

@ -109,12 +105,9 @@ func (sc *shardedCache) DeleteExpired() {
 // fields of the items should be checked. Note that explicit synchronization
 // is needed to use a cache and its corresponding Items() return values at
 // the same time, as the maps are shared.
-func (sc *shardedCache) Items() []map[string]Item {
-	res := make([]map[string]Item, len(sc.cs))
-	for i, v := range sc.cs {
-		res[i] = v.Items()
-	}
-	return res
+// TODO: 不准备暴露这个接口,使用者不应该知道底层的数据.
+func (sc *shardedCache) items() []map[string]Item_tpl {
+	return nil
 }

 func (sc *shardedCache) Flush() {
@ -166,12 +159,12 @@ func newShardedCache(n int, de time.Duration) *shardedCache {
 	sc := &shardedCache{
 		seed: seed,
 		m:    uint32(n),
-		cs:   make([]*cache, n),
+		cs:   make([]*cache_tpl, n),
 	}
 	for i := 0; i < n; i++ {
-		c := &cache{
+		c := &cache_tpl{
 			defaultExpiration: de,
-			items:             map[string]Item{},
+			items:             map[string]Item_tpl{},
 		}
 		sc.cs[i] = c
 	}
--- a/sharded_test.go
+++ b/sharded_test.go
@ -29,7 +29,7 @@ var shardedKeys = []string{
 func TestShardedCache(t *testing.T) {
 	tc := unexportedNewSharded(DefaultExpiration, 0, 13)
 	for _, v := range shardedKeys {
-		tc.Set(v, "value", DefaultExpiration)
+		tc.Set(v, ValueType_tpl(1), DefaultExpiration)
 	}
 }

@ -44,7 +44,7 @@ func BenchmarkShardedCacheGetNotExpiring(b *testing.B) {
 func benchmarkShardedCacheGet(b *testing.B, exp time.Duration) {
 	b.StopTimer()
 	tc := unexportedNewSharded(exp, 0, 10)
-	tc.Set("foobarba", "zquux", DefaultExpiration)
+	tc.Set("foobarba", ValueType_tpl(1), DefaultExpiration)
 	b.StartTimer()
 	for i := 0; i < b.N; i++ {
 		tc.Get("foobarba")
@ -65,17 +65,18 @@ func benchmarkShardedCacheGetManyConcurrent(b *testing.B, exp time.Duration) {
 	tsc := unexportedNewSharded(exp, 0, 20)
 	keys := make([]string, n)
 	for i := 0; i < n; i++ {
-		k := "foo" + strconv.Itoa(n)
+		k := "foo" + strconv.Itoa(i)
 		keys[i] = k
-		tsc.Set(k, "bar", DefaultExpiration)
+		tsc.Set(k, ValueType_tpl(1), DefaultExpiration)
 	}
 	each := b.N / n
 	wg := new(sync.WaitGroup)
 	wg.Add(n)
 	for _, v := range keys {
+		x := v
 		go func() {
 			for j := 0; j < each; j++ {
-				tsc.Get(v)
+				tsc.Get(x)
 			}
 			wg.Done()
 		}()
--- a/valtyp.go
+++ b/valtyp.go
@ -0,0 +1,3 @@
+package cache
+
+type ValueType_tpl int