From 07b1c388bae416a749ceb7d143ac33c3d27e4a53 Mon Sep 17 00:00:00 2001
From: huangzj <Huangzj@123>
Date: Mon, 13 Jul 2020 15:07:56 +0800
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---
 readme.md            |  2 ++
 test/HashMod_test.go | 27 ++++++++++++++++++++++++++
 util/HashModUtil.go  | 46 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 75 insertions(+)
 create mode 100644 test/HashMod_test.go
 create mode 100644 util/HashModUtil.go

diff --git a/readme.md b/readme.md
index 8112c33..6317a4e 100644
--- a/readme.md
+++ b/readme.md
@@ -26,6 +26,8 @@
 
 2020/7/8: 增加读取json文件方法及其单测类
 
+2020/7/13: 增加计算获取字符串哈希值的方法(这个是之前用于做分表系统的方法，搬到这边来看一下)
+
 # mod vendor模式加载包
 通过go mod的方式加载的github上面的包会有报红的问题，但是包本身是可以运行的，这样就是会有一个问题，如果你想要点击去看方法的内容，没办法做到
 
diff --git a/test/HashMod_test.go b/test/HashMod_test.go
new file mode 100644
index 0000000..41d7c03
--- /dev/null
+++ b/test/HashMod_test.go
@@ -0,0 +1,27 @@
+/*
+ *  @Author : huangzj
+ *  @Time : 2020/7/13 11:33
+ *  @Description：
+ */
+
+package test
+
+import (
+	"Go-Tool/util"
+	"fmt"
+	"testing"
+)
+
+//不同方式获取哈希值，结果相差挺大，从输出的结果可以非常直观的看出
+func TestHashMode(t *testing.T) {
+	fmt.Println(util.UseBigIntMod("3213444658987654", 9999999))
+	//因为big.Int只能接受大数，所以如果这边传入字符串没办法转换成功，会发生报错
+	//fmt.Println(util.UseBigIntMod("asdsadasdasdas", 20))
+	fmt.Println(util.Mod("3213444658987654", 9999999))
+	fmt.Println(util.Crc32Mode("3213444658987654", 9999999))
+
+	fmt.Println()
+
+	fmt.Println(util.Mod("asdsadasdasdas", 9999999))
+	fmt.Println(util.Crc32Mode("asdsadasdasdas", 9999999))
+}
diff --git a/util/HashModUtil.go b/util/HashModUtil.go
new file mode 100644
index 0000000..8f77146
--- /dev/null
+++ b/util/HashModUtil.go
@@ -0,0 +1,46 @@
+//通过hash算法获取字符串对应的哈希值
+package util
+
+import (
+	"bytes"
+	"hash/crc32"
+	"math/big"
+)
+
+func bigInt(s string) (*big.Int, bool) {
+	bInt := new(big.Int)
+	return bInt.SetString(s, 10)
+}
+
+func UseBigIntMod(s string, mod int) int64 {
+	b, br := bigInt(s)
+	if !br {
+		panic("该方法只可用于大数mod计算")
+	}
+
+	result := b.Mod(b, new(big.Int).SetInt64(int64(mod)))
+	return result.Int64()
+}
+
+func calBytesSum(s string) int {
+	var sum int
+	for _, b1 := range bytes.NewBufferString(s).Bytes() {
+		sum = sum + int(b1)
+	}
+
+	return sum
+}
+
+func Mod(s string, mod int) int {
+	sum := calBytesSum(s)
+	return sum % mod
+}
+
+func crc32Change(s string) uint32 {
+	return crc32.ChecksumIEEE([]byte(s))
+}
+
+func Crc32Mode(s string, mod int) int {
+	u := crc32Change(s)
+	return int(u) % mod
+}