From 2c0951e80af5bc9238dd7036e7a90a93be6ebabe Mon Sep 17 00:00:00 2001
From: old-tom <892955278@qq.com>
Date: Fri, 22 Dec 2023 14:56:26 +0800
Subject: [PATCH] first commit

---
 README.md         |  0
 cache.go          | 18 +++++++++
 fifo/fifo.go      | 97 +++++++++++++++++++++++++++++++++++++++++++++++
 fifo/fifo_test.go | 10 +++++
 go.mod            |  5 +++
 go.sum            |  2 +
 len.go            | 41 ++++++++++++++++++++
 7 files changed, 173 insertions(+)
 create mode 100644 README.md
 create mode 100644 cache.go
 create mode 100644 fifo/fifo.go
 create mode 100644 fifo/fifo_test.go
 create mode 100644 go.mod
 create mode 100644 go.sum
 create mode 100644 len.go

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..e69de29
diff --git a/cache.go b/cache.go
new file mode 100644
index 0000000..78e2283
--- /dev/null
+++ b/cache.go
@@ -0,0 +1,18 @@
+package cache
+
+type Cache interface {
+	// Set 设置/添加一个缓存，如果 key 存在，用新值覆盖旧值
+	Set(key string, value any)
+	// Get 通过 key 获取一个缓存值
+	Get(Key string) any
+	// Del 通过 key 删除一个缓存值
+	Del(Key string)
+	// DelOldest 删除最“无用”的一个缓存值
+	DelOldest()
+	// Len 获取缓存已存在的记录数
+	Len() int
+}
+
+type Value interface {
+	Len() int
+}
diff --git a/fifo/fifo.go b/fifo/fifo.go
new file mode 100644
index 0000000..da0bccc
--- /dev/null
+++ b/fifo/fifo.go
@@ -0,0 +1,97 @@
+package fifo
+
+import (
+	"cache"
+	"container/list"
+)
+
+/**
+ * 先进先出缓存
+ */
+type fifo struct {
+	// 缓存最大容量
+	maxBytes int
+	// 当一个 entry 从缓存中移除时调用该回调函数，默认为 nil
+	onEvicted func(key string, value any)
+	//已使用的字节数，只包括值，key 不算
+	usedBytes int
+	//缓存容器,存放entry
+	ll *list.List
+	//指针容器
+	cache map[string]*list.Element
+}
+
+func New(maxBytes int, onEvicted func(key string, value any)) cache.Cache {
+	return &fifo{
+		maxBytes:  maxBytes,
+		onEvicted: onEvicted,
+		ll:        list.New(),
+		cache:     make(map[string]*list.Element),
+	}
+}
+
+// Set 往 Cache 尾部增加一个元素（如果已经存在，则放入尾部，并修改值）
+func (f *fifo) Set(key string, value any) {
+	//元素存在
+	if e, ok := f.cache[key]; ok {
+		f.ll.MoveToBack(e)
+		en := e.Value.(*entry)
+		f.usedBytes = f.usedBytes - cache.CalcLen(en.value) + cache.CalcLen(value)
+		en.value = value
+	} else {
+		en := &entry{key, value}
+		e := f.ll.PushBack(en)
+		f.cache[key] = e
+		f.usedBytes += en.Len()
+		//元素容量校验
+		if f.CheckOverFlow() {
+			f.DelOldest()
+		}
+	}
+}
+
+// CheckOverFlow 校验容量是否溢出
+func (f *fifo) CheckOverFlow() bool {
+	return f.maxBytes > 0 && f.usedBytes > f.maxBytes
+}
+func (f *fifo) Get(key string) any {
+	if e, ok := f.cache[key]; ok {
+		return e.Value.(*entry).value
+	}
+	return nil
+}
+func (f *fifo) Del(key string) {
+	if e, ok := f.cache[key]; ok {
+		f.removeElement(e)
+	}
+}
+func (f *fifo) DelOldest() {
+	//删除列表头部元素
+	f.removeElement(f.ll.Front())
+}
+func (f *fifo) Len() int {
+	return f.ll.Len()
+}
+
+// removeElement 删除元素
+func (f *fifo) removeElement(e *list.Element) {
+	if e == nil {
+		return
+	}
+	f.ll.Remove(e)
+	en := e.Value.(*entry)
+	f.usedBytes -= en.Len()
+	delete(f.cache, en.key)
+	if f.onEvicted != nil {
+		f.onEvicted(en.key, en.value)
+	}
+}
+
+type entry struct {
+	key   string
+	value any
+}
+
+func (e *entry) Len() int {
+	return cache.CalcLen(e.value)
+}
diff --git a/fifo/fifo_test.go b/fifo/fifo_test.go
new file mode 100644
index 0000000..05b3bd7
--- /dev/null
+++ b/fifo/fifo_test.go
@@ -0,0 +1,10 @@
+package fifo_test
+
+import (
+	"github.com/matryer/is"
+	"testing"
+)
+
+func TestFifo(t *testing.T) {
+	is.New()
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..e573f5a
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,5 @@
+module cache
+
+go 1.21.5
+
+require github.com/matryer/is v1.4.1
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..f95502a
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,2 @@
+github.com/matryer/is v1.4.1 h1:55ehd8zaGABKLXQUe2awZ99BD/PTc2ls+KV/dXphgEQ=
+github.com/matryer/is v1.4.1/go.mod h1:8I/i5uYgLzgsgEloJE1U6xx5HkBQpAZvepWuujKwMRU=
diff --git a/len.go b/len.go
new file mode 100644
index 0000000..8b55e2a
--- /dev/null
+++ b/len.go
@@ -0,0 +1,41 @@
+package cache
+
+import (
+	"fmt"
+	"runtime"
+)
+
+func CalcLen(value any) int {
+	var n int
+	switch v := value.(type) {
+	case Value:
+		n = v.Len()
+	case string:
+		if runtime.GOARCH == "amd64" {
+			n = 16 + len(v)
+		} else {
+			n = 8 + len(v)
+		}
+	case bool, uint8, int8:
+		n = 1
+	case int16, uint16:
+		n = 2
+	case int32, uint32, float32:
+		n = 4
+	case int64, uint64, float64:
+		n = 8
+	case int, uint:
+		if runtime.GOARCH == "amd64" {
+			n = 8
+		} else {
+			n = 4
+		}
+	case complex64:
+		n = 8
+	case complex128:
+		n = 16
+	default:
+		panic(fmt.Sprintf("%T is not implement cache.Value", value))
+	}
+	return n
+}