实现缓存策略的部分功能

internal/caches/file_writer.go

@@ -0,0 +1,77 @@
+package caches
+
+import (
+	"os"
+	"sync"
+)
+
+type FileWriter struct {
+	rawWriter  *os.File
+	key        string
+	size       int64
+	expiredAt  int64
+	locker     *sync.RWMutex
+	isReleased bool
+}
+
+func NewFileWriter(rawWriter *os.File, key string, expiredAt int64, locker *sync.RWMutex) *FileWriter {
+	return &FileWriter{
+		key:       key,
+		rawWriter: rawWriter,
+		expiredAt: expiredAt,
+		locker:    locker,
+	}
+}
+
+// 写入数据
+func (this *FileWriter) Write(data []byte) (n int, err error) {
+	n, err = this.rawWriter.Write(data)
+	this.size += int64(n)
+	if err != nil {
+		_ = this.rawWriter.Close()
+		_ = os.Remove(this.rawWriter.Name())
+		this.Release()
+	}
+	return
+}
+
+// 关闭
+func (this *FileWriter) Close() error {
+	// 写入结束符
+	_, err := this.rawWriter.WriteString("\n$$$")
+	if err != nil {
+		_ = os.Remove(this.rawWriter.Name())
+	}
+
+	this.Release()
+
+	return err
+}
+
+// 丢弃
+func (this *FileWriter) Discard() error {
+	err := os.Remove(this.rawWriter.Name())
+	this.Release()
+	return err
+}
+
+func (this *FileWriter) Size() int64 {
+	return this.size
+}
+
+func (this *FileWriter) ExpiredAt() int64 {
+	return this.expiredAt
+}
+
+func (this *FileWriter) Key() string {
+	return this.key
+}
+
+// 释放锁，一定要调用
+func (this *FileWriter) Release() {
+	if this.isReleased {
+		return
+	}
+	this.isReleased = true
+	this.locker.Unlock()
+}