53 lines
1.3 KiB
Go
53 lines
1.3 KiB
Go
// Package base62 provides utilities for working with base62 strings.
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// base62 strings will only contain characters: 0-9, a-z, A-Z
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package base62
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import (
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"crypto/rand"
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"io"
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uuid "github.com/hashicorp/go-uuid"
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)
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const (
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charset = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
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csLen = byte(len(charset))
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)
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// Random generates a random string using base-62 characters.
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// Resulting entropy is ~5.95 bits/character.
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func Random(length int) (string, error) {
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return RandomWithReader(length, rand.Reader)
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}
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// RandomWithReader generates a random string using base-62 characters and a given reader.
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// Resulting entropy is ~5.95 bits/character.
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func RandomWithReader(length int, reader io.Reader) (string, error) {
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if length == 0 {
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return "", nil
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}
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output := make([]byte, 0, length)
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// Request a bit more than length to reduce the chance
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// of needing more than one batch of random bytes
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batchSize := length + length/4
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for {
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buf, err := uuid.GenerateRandomBytesWithReader(batchSize, reader)
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if err != nil {
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return "", err
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}
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for _, b := range buf {
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// Avoid bias by using a value range that's a multiple of 62
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if b < (csLen * 4) {
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output = append(output, charset[b%csLen])
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if len(output) == length {
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return string(output), nil
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}
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}
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}
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}
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}
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