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34 lines
901 B
34 lines
901 B
package indieauth |
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import ( |
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"math/rand" |
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"time" |
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"unsafe" |
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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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var src = rand.NewSource(time.Now().UnixNano()) |
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func randString(n int) string { |
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b := make([]byte, n) |
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// A src.Int63() generates 63 random bits, enough for letterIdxMax characters! |
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for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; { |
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if remain == 0 { |
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cache, remain = src.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)(unsafe.Pointer(&b)) // nolint:gosec |
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}
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