forked from vikunja/vikunja
53 lines
1.7 KiB
Go
53 lines
1.7 KiB
Go
// Vikunja is a to-do list application to facilitate your life.
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// Copyright 2018-2021 Vikunja and contributors. All rights reserved.
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public Licensee as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public Licensee for more details.
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//
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// You should have received a copy of the GNU Affero General Public Licensee
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// along with this program. If not, see <https://www.gnu.org/licenses/>.
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package utils
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import (
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"math/rand"
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"time"
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)
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func init() {
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rand.Seed(time.Now().UnixNano())
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}
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const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
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const (
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letterIdxBits = 6 // 6 bits to represent a letter index
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letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
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letterIdxMax = 63 / letterIdxBits // # of letter indices fitting in 63 bits
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)
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// MakeRandomString return a random string
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func MakeRandomString(n int) string {
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b := make([]byte, n)
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// A rand.Int63() generates 63 random bits, enough for letterIdxMax letters!
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for i, cache, remain := n-1, rand.Int63(), letterIdxMax; i >= 0; {
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if remain == 0 {
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cache, remain = rand.Int63(), letterIdxMax
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}
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if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
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b[i] = letterBytes[idx]
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i--
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}
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cache >>= letterIdxBits
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remain--
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}
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return string(b)
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}
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