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Generate random string in Go
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| BenchmarkRandomStringA-4 2000000 702 ns/op | |
| BenchmarkRandomStringB-4 10000000 120 ns/op | |
| BenchmarkRandomStringC-4 20000000 115 ns/op | |
| BenchmarkRandomStringD-4 10000000 121 ns/op |
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| func RandomStringA(n int) string { | |
| const letters = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-" | |
| b := make([]byte, n) | |
| lenLetters := len(letters) | |
| for i := 0; i < n; i++ { | |
| b[i] = letters[rand.Intn(lenLetters)] | |
| } | |
| return string(b) | |
| } | |
| func RandomStringB(rng *rand.Rand, n int) string { | |
| const letters = `0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-` | |
| b := make([]byte, ((n+9)/10)*10) | |
| for i := 0; i < n; i += 10 { | |
| rn := rng.Uint64() | |
| b[i+0] = letters[(rn&0x0FC0000000000000)>>54] | |
| b[i+1] = letters[(rn&0x003F000000000000)>>48] | |
| b[i+2] = letters[(rn&0x0000FC0000000000)>>42] | |
| b[i+3] = letters[(rn&0x000003F000000000)>>36] | |
| b[i+4] = letters[(rn&0x0000000FC0000000)>>30] | |
| b[i+5] = letters[(rn&0x000000003F000000)>>24] | |
| b[i+6] = letters[(rn&0x0000000000FC0000)>>18] | |
| b[i+7] = letters[(rn&0x000000000003F000)>>12] | |
| b[i+8] = letters[(rn&0x0000000000000FC0)>>6] | |
| b[i+9] = letters[(rn&0x000000000000003F)>>0] | |
| } | |
| return string(b[:n]) | |
| } | |
| func RandomStringC(rng *rand.Rand, n int) string { | |
| // extract 10 letters — 60 bits of entropy — for each pseudo-random uint64 | |
| const K = 10 | |
| const L = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-" | |
| b := make([]byte, ((n+K-1)/K)*K) | |
| for i := 0; i < n; i += K { | |
| rn := rng.Uint64() | |
| for j := 0; j < K; j++ { | |
| b[i+j] = L[rn&0x3F] | |
| rn >>= 6 | |
| } | |
| } | |
| return string(b[:n]) | |
| } | |
| func RandomStringD(rng *rand.Rand, n int) string { | |
| const letterBytes = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-" | |
| const ( | |
| letterIdxBits = 6 // 6 bits to represent a letter index | |
| letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits | |
| letterIdxMax = 63 / letterIdxBits // # of letter indices fitting in 63 bits | |
| ) | |
| b := make([]byte, n) | |
| // A src.Int63() generates 63 random bits, enough for letterIdxMax characters! | |
| for i, cache, remain := n-1, rng.Int63(), letterIdxMax; i >= 0; { | |
| if remain == 0 { | |
| cache, remain = rng.Int63(), letterIdxMax | |
| } | |
| idx := int(cache & letterIdxMask) | |
| b[i] = letterBytes[idx] | |
| i-- | |
| cache >>= letterIdxBits | |
| remain-- | |
| } | |
| return string(b) | |
| } |
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