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121 lines
2.4 KiB
121 lines
2.4 KiB
package common
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import (
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crand "crypto/rand"
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"encoding/hex"
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"math/rand"
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"time"
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)
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const (
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strChars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" // 62 characters
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)
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func init() {
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// Seed math/rand with "secure" int64
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b := CRandBytes(8)
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var seed uint64
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for i := 0; i < 8; i++ {
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seed |= uint64(b[i])
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seed <<= 8
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}
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rand.Seed(int64(seed))
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}
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// Constructs an alphanumeric string of given length.
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func RandStr(length int) string {
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chars := []byte{}
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MAIN_LOOP:
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for {
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val := rand.Int63()
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for i := 0; i < 10; i++ {
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v := int(val & 0x3f) // rightmost 6 bits
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if v >= 62 { // only 62 characters in strChars
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val >>= 6
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continue
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} else {
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chars = append(chars, strChars[v])
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if len(chars) == length {
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break MAIN_LOOP
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}
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val >>= 6
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}
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}
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}
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return string(chars)
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}
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func RandUInt16() uint16 {
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return uint16(rand.Uint32() & (1<<16 - 1))
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}
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func RandUInt32() uint32 {
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return rand.Uint32()
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}
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func RandUInt64() uint64 {
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return uint64(rand.Uint32())<<32 + uint64(rand.Uint32())
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}
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// Distributed pseudo-exponentially to test for various cases
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func RandUInt16Exp() uint16 {
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bits := rand.Uint32() % 16
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if bits == 0 {
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return 0
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}
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n := uint16(1 << (bits - 1))
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n += uint16(rand.Int31()) & ((1 << (bits - 1)) - 1)
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return n
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}
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// Distributed pseudo-exponentially to test for various cases
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func RandUInt32Exp() uint32 {
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bits := rand.Uint32() % 32
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if bits == 0 {
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return 0
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}
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n := uint32(1 << (bits - 1))
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n += uint32(rand.Int31()) & ((1 << (bits - 1)) - 1)
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return n
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}
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// Distributed pseudo-exponentially to test for various cases
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func RandUInt64Exp() uint64 {
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bits := rand.Uint32() % 64
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if bits == 0 {
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return 0
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}
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n := uint64(1 << (bits - 1))
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n += uint64(rand.Int63()) & ((1 << (bits - 1)) - 1)
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return n
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}
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func RandTime() time.Time {
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return time.Unix(int64(RandUInt64Exp()), 0)
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}
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func RandBytes(n int) []byte {
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bs := make([]byte, n)
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for i := 0; i < n; i++ {
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bs[i] = byte(rand.Intn(256))
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}
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return bs
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}
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//-----------------------------------------------------------------------------
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// CRand* methods are crypto safe.
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func CRandBytes(numBytes int) []byte {
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b := make([]byte, numBytes)
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_, err := crand.Read(b)
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if err != nil {
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panic(err)
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}
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return b
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}
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// RandHex(24) gives 96 bits of randomness, strong enough for most purposes.
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func CRandHex(numDigits int) string {
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return hex.EncodeToString(CRandBytes(numDigits / 2))
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}
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