新增 cache

pkg/services/cache.go

@@ -1,7 +1,97 @@
 package services
 
+import (
+	"errors"
+	"io"
+	"sync"
+	"time"
+)
+
 type Cache interface {
-	Put(key string, value []byte) error
-	Get(key string) ([]byte, error)
-	Delete(key string) error
+	Put(key string, reader io.Reader) error
+	Get(key string) (io.ReadSeekCloser, error)
+	Delete(pattern string) error
+	io.Closer
+}
+
+var ErrCacheOutOfMemory = errors.New("内容无法被缓存，超过最大限定值")
+
+type CacheMemory struct {
+	l       sync.RWMutex
+	data    map[string][]byte
+	maxAge  time.Duration
+	sizeGl  int
+	sizeOne int
+
+	current int
+	cache   []byte
+	ordered []string
+}
+
+func NewCacheMemory(maxUsage, maxGlobalUsage int) *CacheMemory {
+	return &CacheMemory{
+		data:    make(map[string][]byte),
+		l:       sync.RWMutex{},
+		sizeGl:  maxGlobalUsage,
+		sizeOne: maxUsage,
+
+		cache:   make([]byte, maxUsage+1),
+		ordered: make([]string, 0),
+	}
+}
+
+func (c *CacheMemory) Put(key string, reader io.Reader) error {
+	c.l.Lock()
+	defer c.l.Unlock()
+	size, err := io.ReadAtLeast(reader, c.cache, 0)
+	if err != nil {
+		return err
+	}
+	if size == len(c.cache) {
+		return ErrCacheOutOfMemory
+	}
+	needed := c.sizeGl - c.current + size
+	if needed < 0 {
+		// 清理旧的内容
+		count := 0
+		for i, k := range c.ordered {
+			needed += len(c.data[k])
+			if needed > 0 {
+				break
+			}
+			count = i + 1
+		}
+
+		if needed < 0 {
+			// 清理全部内容也无法留出空间
+			return ErrCacheOutOfMemory
+		}
+		for _, s := range c.ordered[:count] {
+			delete(c.data, s)
+			c.current -= len(c.data)
+		}
+		c.ordered = c.ordered[count:]
+	}
+
+	dest := make([]byte, size)
+	copy(dest, c.cache[:size])
+	c.data[key] = dest
+	c.ordered = append(c.ordered, key)
+	c.current += len(dest)
+	return nil
+}
+
+func (c *CacheMemory) Get(key string) (io.ReadSeekCloser, error) {
+	//TODO implement me
+	panic("implement me")
+}
+
+func (c *CacheMemory) Delete(key string) error {
+	//TODO implement me
+	panic("implement me")
+}
+
+func (c *CacheMemory) Close() error {
+	//TODO implement me
+	panic("implement me")
 }