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👔 up: str - random string gen split non-win and windows implement
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,27 @@ | ||
| //go:build !windows | ||
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| package strutil | ||
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| import ( | ||
| "math/rand" | ||
| "time" | ||
| ) | ||
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| var rn = newRand() | ||
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| func newRand() *rand.Rand { | ||
| return rand.New(rand.NewSource(time.Now().UnixNano())) | ||
| } | ||
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| // buildRandomString 生成随机字符串 | ||
| func buildRandomString(letters string, length int) string { | ||
| // rn := newRand() | ||
| cs := make([]byte, length) | ||
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| lettersN := len(letters) | ||
| for i := 0; i < length; i++ { | ||
| cs[i] = letters[rn.Intn(lettersN)] | ||
| } | ||
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| return Byte2str(cs) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,85 @@ | ||
| //go:build windows | ||
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| package strutil | ||
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| import ( | ||
| "math" | ||
| "math/rand" | ||
| "time" | ||
| "unsafe" | ||
| ) | ||
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| const MaximumCapacity = math.MaxInt>>1 + 1 | ||
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| var rn = rand.NewSource(time.Now().UnixNano()) | ||
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| // nearestPowerOfTwo 返回一个大于等于cap的最近的2的整数次幂，参考java8的hashmap的tableSizeFor函数 | ||
| // - cap 输入参数 | ||
| // | ||
| // 返回一个大于等于cap的最近的2的整数次幂 | ||
| func nearestPowerOfTwo(cap int) int { | ||
| n := cap - 1 | ||
| n |= n >> 1 | ||
| n |= n >> 2 | ||
| n |= n >> 4 | ||
| n |= n >> 8 | ||
| n |= n >> 16 | ||
| if n < 0 { | ||
| return 1 | ||
| } | ||
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| if n >= MaximumCapacity { | ||
| return MaximumCapacity | ||
| } | ||
| return n + 1 | ||
| } | ||
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| // buildRandomString 生成随机字符串 | ||
| // - letters 字符串模板 | ||
| // - length 生成长度 | ||
| // | ||
| // 返回一个指定长度的随机字符串 | ||
| func buildRandomString(letters string, length int) string { | ||
| // 仿照strings.Builder | ||
| // 创建一个长度为 length 的字节切片 | ||
| bytes := make([]byte, length) | ||
| strLength := len(letters) | ||
| if strLength <= 0 { | ||
| return "" | ||
| } | ||
| if strLength == 1 { | ||
| for i := 0; i < length; i++ { | ||
| bytes[i] = letters[0] | ||
| } | ||
| return *(*string)(unsafe.Pointer(&bytes)) | ||
| } | ||
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| // letters的字符需要使用多少个比特位数才能表示完 | ||
| // letterIdBits := int(math.Ceil(math.Log2(strLength))),下面比上面的代码快 | ||
| letterIdBits := int(math.Log2(float64(nearestPowerOfTwo(strLength)))) | ||
| // 最大的字母id掩码 | ||
| var letterIdMask int64 = 1<<letterIdBits - 1 | ||
| // 可用次数的最大值 | ||
| letterIdMax := 63 / letterIdBits | ||
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| // UnixNano: 1607400451937462000 | ||
| // 循环生成随机字符串 | ||
| for i, cache, remain := length-1, rn.Int63(), letterIdMax; i >= 0; { | ||
| // 检查随机数生成器是否用尽所有随机数 | ||
| if remain == 0 { | ||
| cache, remain = rn.Int63(), letterIdMax | ||
| } | ||
| // 从可用字符的字符串中随机选择一个字符 | ||
| if idx := int(cache & letterIdMask); idx < strLength { | ||
| bytes[i] = letters[idx] | ||
| i-- | ||
| } | ||
| // 右移比特位数，为下次选择字符做准备 | ||
| cache >>= letterIdBits | ||
| remain-- | ||
| } | ||
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| // 仿照strings.Builder用unsafe包返回一个字符串，避免拷贝 | ||
| // 将字节切片转换为字符串并返回 | ||
| return *(*string)(unsafe.Pointer(&bytes)) | ||
| } |