From 49d5fc2662a5e671a51009e5b40a1311a9f440ee Mon Sep 17 00:00:00 2001
From: Petrichor <390983386@qq.com>
Date: Wed, 6 Apr 2022 11:14:55 +0800
Subject: [PATCH] =?UTF-8?q?=E2=9C=A8=20feat:=20Day4=20=E4=B8=80=E8=87=B4?=
 =?UTF-8?q?=E6=80=A7=E5=93=88=E5=B8=8C?=
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---
 consistenthash/consistenthash.go      | 39 +++++++++++++++++++-
 consistenthash/consistenthash_test.go | 53 +++++++++++++++++++++++++++
 2 files changed, 90 insertions(+), 2 deletions(-)
 create mode 100644 consistenthash/consistenthash_test.go

diff --git a/consistenthash/consistenthash.go b/consistenthash/consistenthash.go
index 65c7e87..964fb2a 100644
--- a/consistenthash/consistenthash.go
+++ b/consistenthash/consistenthash.go
@@ -1,12 +1,18 @@
 package consistenthash
 
-import "hash/crc32"
+import (
+	"fmt"
+	"hash/crc32"
+	"sort"
+	"strconv"
+)
 
 type Hash func(data []byte) uint32
 
+// Map constains all hashed keys
 type Map struct {
 	hash     Hash
-	replicas int            //虚拟节点倍数
+	replicas int            // 虚拟节点倍数
 	keys     []int          // 哈希环
 	hashMap  map[int]string // 虚拟节点与真实节点的映射表，键是哈希值，值是真实节点的名称
 }
@@ -22,3 +28,32 @@ func New(replicas int, fn Hash) *Map {
 	}
 	return m
 }
+
+// Add adds some keys to the hash.
+// 传入真实节点名称
+func (m *Map) Add(keys ...string) {
+	for _, key := range keys {
+		for i := 0; i < m.replicas; i++ {
+			hash := int(m.hash([]byte(strconv.Itoa(i) + key)))
+			fmt.Printf("key: %v, i: %v, hash: %v\n", key, i, hash)
+			m.keys = append(m.keys, hash)
+			m.hashMap[hash] = key
+		}
+	}
+	sort.Ints(m.keys)
+}
+
+func(m *Map) Get(key string) string {
+	if len(m.keys) == 0 {
+		return ""
+	}
+
+	// 计算 key 的哈希值
+	hash := int(m.hash([]byte(key)))
+	// 顺时针找到第一个匹配的虚拟节点的下标 idx，从 m.keys 中获取对应的哈希值
+	idx := sort.Search(len(m.keys), func(i int) bool {
+		return m.keys[i] >= hash
+	})
+	// 得到真实节点
+	return m.hashMap[m.keys[idx%len(m.keys)]]
+}
\ No newline at end of file
diff --git a/consistenthash/consistenthash_test.go b/consistenthash/consistenthash_test.go
new file mode 100644
index 0000000..ec4e1ca
--- /dev/null
+++ b/consistenthash/consistenthash_test.go
@@ -0,0 +1,53 @@
+package consistenthash
+
+import (
+	"strconv"
+	"testing"
+)
+
+func TestHashing(t *testing.T) {
+	hash := New(3, func(key []byte) uint32 {
+		i, _ := strconv.Atoi(string(key))
+		return uint32(i)
+	})
+
+	// 哈希值: 2, 4, 6, 12, 14, 16, 22, 24, 26
+	hash.Add("6", "4", "2")
+	// fmt.Printf("%+v\n", hash)
+	// &{hash:0x77f740 replicas:3
+	//	 keys:[2 4 6 12 14 16 22 24 26]
+	//   hashMap:map[2:2 4:4 6:6 12:2 14:4 16:6 22:2 24:4 26:6]}
+
+	testCases := map[string]string{
+		"2":  "2",
+		"11": "2",
+		"23": "4",
+		"27": "2",
+	}
+
+	for k, v := range testCases {
+		if hash.Get(k) != v {
+			t.Errorf("Asking for %s, should have yielded %s", k, v)
+		}
+	}
+
+	hash.Add("8")
+	// fmt.Printf("%+v\n", hash)
+	// &{hash:0x5af740 replicas:3
+	//	 keys:[2 4 6 8 12 14 16 18 22 24 26 28]
+	//   hashMap:map[2:2 4:4 6:6 8:8 12:2 14:4 16:6 18:8 22:2 24:4 26:6 28:8]}
+
+	testCases["27"] = "8"
+
+	for k, v := range testCases {
+		if hash.Get(k) != v {
+			t.Errorf("Asking for %s, should have yielded %s", k, v)
+		}
+	}
+
+	// hash.Add("9", "10", "11", "12", "233")
+	// fmt.Printf("%+v\n", hash)
+	// &{hash:0xf1f740 replicas:3
+	// keys:[2 4 6 8 9 10 11 12 12 14 16 18 19 22 24 26 28 29 110 111 112 210 211 212]
+	// hashMap:map[2:2 4:4 6:6 8:8 9:9 10:10 11:11 12:12 14:4 16:6 18:8 19:9 22:2 24:4 26:6 28:8 29:9 110:10 111:11 112:12 210:10 211:11 212:12]}
+}