From 9094cb29bffde1e7dc5c4699028b02c70788d0e6 Mon Sep 17 00:00:00 2001
From: dudaodong <lanliddd.2007@163.com>
Date: Mon, 22 Aug 2022 15:21:30 +0800
Subject: [PATCH] feat: add new HashMap data structure

---
 datastructure/hashmap/hashmap.go | 69 ++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)
 create mode 100644 datastructure/hashmap/hashmap.go

diff --git a/datastructure/hashmap/hashmap.go b/datastructure/hashmap/hashmap.go
new file mode 100644
index 0000000..a7b401c
--- /dev/null
+++ b/datastructure/hashmap/hashmap.go
@@ -0,0 +1,69 @@
+// Copyright 2021 dudaodong@gmail.com. All rights reserved.
+// Use of this source code is governed by MIT license
+
+// Package datastructure implements some data structure. eg. list, linklist, stack, queue, tree, graph.
+package datastructure
+
+import (
+	"fmt"
+	"hash/fnv"
+)
+
+var defaultMapCapacity uint64 = 1 << 10
+
+type mapNode struct {
+	key   any
+	value any
+	next  *mapNode
+}
+
+//HashMap implements a hash map
+type HashMap struct {
+	capacity uint64
+	size     uint64
+	table    []*mapNode
+}
+
+// NewHashMap return a HashMap instance
+func NewHashMap() *HashMap {
+	return &HashMap{
+		capacity: defaultMapCapacity,
+		table:    make([]*mapNode, defaultMapCapacity),
+	}
+}
+
+// NewHashMapWithCapacity return a HashMap instance with given size and capacity
+func NewHashMapWithCapacity(size, capacity uint64) *HashMap {
+	return &HashMap{
+		size:     size,
+		capacity: capacity,
+		table:    make([]*mapNode, capacity),
+	}
+}
+
+// Get return the value of given key in hash map
+func (hm *HashMap) Get(key any) any {
+	hashValue := hm.hash(key)
+	node := hm.table[hashValue]
+	if node != nil {
+		return node.value
+	}
+
+	return nil
+}
+
+func (hm *HashMap) hash(key any) uint64 {
+	h := fnv.New64a()
+	_, _ = h.Write([]byte(fmt.Sprintf("%v", key)))
+
+	hashValue := h.Sum64()
+
+	return (hm.capacity - 1) & (hashValue ^ (hashValue >> 16))
+}
+
+func newMapNode(key any, value any) *mapNode {
+	return &mapNode{
+		key:   key,
+		value: value,
+	}
+}