package common import ( crand "crypto/rand" "math/rand" "time" ) const ( strChars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" // 62 characters ) func init() { b := cRandBytes(8) var seed uint64 for i := 0; i < 8; i++ { seed |= uint64(b[i]) seed <<= 8 } rand.Seed(int64(seed)) } // Constructs an alphanumeric string of given length. func RandStr(length int) string { chars := []byte{} MAIN_LOOP: for { val := rand.Int63() for i := 0; i < 10; i++ { v := int(val & 0x3f) // rightmost 6 bits if v >= 62 { // only 62 characters in strChars val >>= 6 continue } else { chars = append(chars, strChars[v]) if len(chars) == length { break MAIN_LOOP } val >>= 6 } } } return string(chars) } func RandUint16() uint16 { return uint16(rand.Uint32() & (1<<16 - 1)) } func RandUint32() uint32 { return rand.Uint32() } func RandUint64() uint64 { return uint64(rand.Uint32())<<32 + uint64(rand.Uint32()) } func RandUint() uint { return uint(rand.Int()) } func RandInt16() int16 { return int16(rand.Uint32() & (1<<16 - 1)) } func RandInt32() int32 { return int32(rand.Uint32()) } func RandInt64() int64 { return int64(rand.Uint32())<<32 + int64(rand.Uint32()) } func RandInt() int { return rand.Int() } // Distributed pseudo-exponentially to test for various cases func RandUint16Exp() uint16 { bits := rand.Uint32() % 16 if bits == 0 { return 0 } n := uint16(1 << (bits - 1)) n += uint16(rand.Int31()) & ((1 << (bits - 1)) - 1) return n } // Distributed pseudo-exponentially to test for various cases func RandUint32Exp() uint32 { bits := rand.Uint32() % 32 if bits == 0 { return 0 } n := uint32(1 << (bits - 1)) n += uint32(rand.Int31()) & ((1 << (bits - 1)) - 1) return n } // Distributed pseudo-exponentially to test for various cases func RandUint64Exp() uint64 { bits := rand.Uint32() % 64 if bits == 0 { return 0 } n := uint64(1 << (bits - 1)) n += uint64(rand.Int63()) & ((1 << (bits - 1)) - 1) return n } func RandFloat32() float32 { return rand.Float32() } func RandTime() time.Time { return time.Unix(int64(RandUint64Exp()), 0) } func RandBytes(n int) []byte { bs := make([]byte, n) for i := 0; i < n; i++ { bs[i] = byte(rand.Intn(256)) } return bs } // NOTE: This relies on the os's random number generator. // For real security, we should salt that with some seed. // See github.com/tendermint/go-crypto for a more secure reader. func cRandBytes(numBytes int) []byte { b := make([]byte, numBytes) _, err := crand.Read(b) if err != nil { PanicCrisis(err) } return b }