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model.go
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model.go
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// Copyright 2024 The PipeCD Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package model
import (
"math/rand"
"time"
"unsafe"
)
var randomSrc = rand.NewSource(time.Now().UnixNano())
const (
letterIdxBits = 6 // 6 bits to represent a letter index
letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
letterIdxMax = 63 / letterIdxBits // Number of letter indices fitting in 63 bits
letterBytes = "abcdefghijklmnopqrstuvwxyz0123456789"
)
// GenerateRandomString makes a random string with the given length.
// This implementation was referenced from the link below.
// https://stackoverflow.com/questions/22892120/how-to-generate-a-random-string-of-a-fixed-length-in-go
func GenerateRandomString(n int) string {
b := make([]byte, n)
// A src.Int63() generates 63 random bits, enough for letterIdxMax characters.
for i, cache, remain := n-1, randomSrc.Int63(), letterIdxMax; i >= 0; {
if remain == 0 {
cache, remain = randomSrc.Int63(), letterIdxMax
}
if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
b[i] = letterBytes[idx]
i--
}
cache >>= letterIdxBits
remain--
}
return *(*string)(unsafe.Pointer(&b))
}