56 lines
1.7 KiB
Go
56 lines
1.7 KiB
Go
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// Package uniuri generates random strings good for use in URIs to identify
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// unique objects.
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//
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// Example usage:
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//
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// s := uniuri.New() // s is now "apHCJBl7L1OmC57n"
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//
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// A standard string created by New() is 16 bytes in length and consists of
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// Latin upper and lowercase letters, and numbers (from the set of 62 allowed
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// characters), which means that it has ~95 bits of entropy. To get more
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// entropy, you can use NewLen(UUIDLen), which returns 20-byte string, giving
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// ~119 bits of entropy, or any other desired length.
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//
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// Functions read from crypto/rand random source, and panic if they fail to
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// read from it.
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package uniuri
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import "crypto/rand"
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const (
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// Standard length of uniuri string to achive ~95 bits of entropy.
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StdLen = 16
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// Length of uniurl string to achive ~119 bits of entropy, closest
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// to what can be losslessly converted to UUIDv4 (122 bits).
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UUIDLen = 20
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)
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// Standard characters allowed in uniuri string.
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var StdChars = []byte("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890")
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// New returns a new random string with the standard length and standard
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// characters.
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func New() string {
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return NewLenChars(StdLen, StdChars)
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}
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// NewLen returns a new random string with the provided length and standard
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// characters.
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func NewLen(length int) string {
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return NewLenChars(length, StdChars)
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}
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// NewLenChars returns a new random string with the provided length and byte
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// slice of allowed characters (maximum 256).
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func NewLenChars(length int, chars []byte) string {
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b := make([]byte, length)
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if _, err := rand.Reader.Read(b); err != nil {
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panic("error reading from random source: " + err.String())
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}
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alen := byte(len(chars))
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for i, c := range b {
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b[i] = chars[c%alen]
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}
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return string(b)
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}
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