99 lines
2.5 KiB
Go
99 lines
2.5 KiB
Go
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package hash32
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/*
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* ***注意***
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*
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* Sum 使用的是[]byte参数；string中文是utf-8编码
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* SumByRune 使用的是[]rune参数；中文使用的是unicode编码
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*
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* 两种参数中文编码不同；同一个string调用两个接口得到的hash是不同的！！！ 这是要特别注意的
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*
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* 对string进行for range操作会自动被[]rune化；一定要注意！！！
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*
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*/
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const shiftBit = 11 // 每个字节移位数(测试经验值11)
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const reverseBit = 32 - shiftBit
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// 快速Hash计算(*** 注意：只取了rune低16位进行hash计算；计算结果与SumByRune不一致 ***)
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func FastSumByRune2(in rune, hs uint32) (out uint32) {
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out = ((hs << shiftBit) | (hs >> reverseBit)) + uint32(byte(in>>8))
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out = ((out << shiftBit) | (out >> reverseBit)) + uint32(byte(in))
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return
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}
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// 快速Hash计算(*** 此计算结果与SumByRune一致 ***)
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func FastSumByRune4(in rune, hs uint32) (out uint32) {
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out = ((hs << shiftBit) | (hs >> reverseBit)) + uint32(byte(in>>24))
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out = ((out << shiftBit) | (out >> reverseBit)) + uint32(byte(in>>16))
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out = ((out << shiftBit) | (out >> reverseBit)) + uint32(byte(in>>8))
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out = ((out << shiftBit) | (out >> reverseBit)) + uint32(byte(in))
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return
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}
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// 原Hash值参数重
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func hsArg(hsOpt ...uint32) (out uint32) {
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out = uint32(0)
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if len(hsOpt) > 0 {
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out = hsOpt[0]
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}
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return
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}
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// Hash计算
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// in - 待hash串
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// hsOpt - 原hash值(在此基础上继续hash)
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func Sum(in []byte, hsOpt ...uint32) (out uint32) {
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out = hsArg(hsOpt...)
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for _, v := range in {
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out = ((out << shiftBit) | (out >> reverseBit)) + uint32(v)
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}
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return
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}
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// Hash计算
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func SumByRune(in rune, hsOpt ...uint32) (out uint32) {
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// rune转[]byte
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inVal := make([]byte, 4)
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inVal[0] = byte(in >> 24)
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inVal[1] = byte(in >> 16)
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inVal[2] = byte(in >> 8)
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inVal[3] = byte(in)
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// *** 经实际测试：不加以下代码运行效率更高 ***
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// 去除前面多余的\x00
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// for {
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// if len(inVal) <= 1 {
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// // 以免全0异常；至少要保留1位
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// break
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// }
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// if inVal[0] == 0 {
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// inVal = inVal[1:]
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// } else {
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// break
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// }
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// }
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// 规避hash冲突，如："N-"与"中"unicode编码均为#4E2D，即会产生hash冲突
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// 若长度>1(即非常规ASCII)，所有字节最高位置1
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// if len(inVal) > 1 {
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// for i := 0; i < len(inVal); i++ {
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// inVal[i] |= 0x80
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// }
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// }
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out = Sum(inVal, hsOpt...)
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return
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}
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// Hash计算
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func SumByRunes(in []rune, hsOpt ...uint32) (out uint32) {
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out = hsArg(hsOpt...)
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for _, v := range in {
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out = SumByRune(v, out)
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}
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return
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}
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