mirror of https://github.com/coder/coder.git
208 lines
3.8 KiB
Go
208 lines
3.8 KiB
Go
package cryptorand
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import (
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"crypto/rand"
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"encoding/binary"
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"time"
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"golang.org/x/xerrors"
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)
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// Most of this code is inspired by math/rand, so shares similar
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// functions and implementations, but uses crypto/rand to generate
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// random Int63 data.
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// Int64 returns a non-negative random 63-bit integer as a int64.
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func Int63() (int64, error) {
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var i int64
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err := binary.Read(rand.Reader, binary.BigEndian, &i)
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if err != nil {
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return 0, xerrors.Errorf("read binary: %w", err)
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}
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if i < 0 {
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return -i, nil
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}
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return i, nil
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}
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// Uint64 returns a random 64-bit integer as a uint64.
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func Uint64() (uint64, error) {
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upper, err := Int63()
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if err != nil {
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return 0, xerrors.Errorf("read upper: %w", err)
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}
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lower, err := Int63()
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if err != nil {
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return 0, xerrors.Errorf("read lower: %w", err)
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}
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return uint64(lower)>>31 | uint64(upper)<<32, nil
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}
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// Int31 returns a non-negative random 31-bit integer as a int32.
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func Int31() (int32, error) {
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i, err := Int63()
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if err != nil {
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return 0, err
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}
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return int32(i >> 32), nil
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}
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// Uint32 returns a 32-bit value as a uint32.
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func Uint32() (uint32, error) {
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i, err := Int63()
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if err != nil {
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return 0, err
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}
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return uint32(i >> 31), nil
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}
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// Int returns a non-negative random integer as a int.
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func Int() (int, error) {
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i, err := Int63()
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if err != nil {
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return 0, err
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}
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if i < 0 {
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return int(-i), nil
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}
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return int(i), nil
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}
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// Int63n returns a non-negative random integer in [0,max) as a int64.
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func Int63n(max int64) (int64, error) {
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if max <= 0 {
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panic("invalid argument to Int63n")
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}
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trueMax := int64((1 << 63) - 1 - (1<<63)%uint64(max))
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i, err := Int63()
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if err != nil {
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return 0, err
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}
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for i > trueMax {
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i, err = Int63()
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if err != nil {
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return 0, err
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}
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}
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return i % max, nil
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}
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// Int31n returns a non-negative integer in [0,max) as a int32.
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func Int31n(max int32) (int32, error) {
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i, err := Uint32()
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if err != nil {
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return 0, err
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}
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return UnbiasedModulo32(i, max)
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}
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// UnbiasedModulo32 uniformly modulos v by n over a sufficiently large data
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// set, regenerating v if necessary. n must be > 0. All input bits in v must be
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// fully random, you cannot cast a random uint8/uint16 for input into this
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// function.
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//
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//nolint:varnamelen
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func UnbiasedModulo32(v uint32, n int32) (int32, error) {
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prod := uint64(v) * uint64(n)
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low := uint32(prod)
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if low < uint32(n) {
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thresh := uint32(-n) % uint32(n)
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for low < thresh {
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var err error
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v, err = Uint32()
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if err != nil {
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return 0, err
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}
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prod = uint64(v) * uint64(n)
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low = uint32(prod)
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}
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}
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return int32(prod >> 32), nil
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}
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// Intn returns a non-negative integer in [0,max) as a int.
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func Intn(max int) (int, error) {
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if max <= 0 {
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panic("n must be a positive nonzero number")
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}
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if max <= 1<<31-1 {
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i, err := Int31n(int32(max))
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if err != nil {
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return 0, err
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}
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return int(i), nil
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}
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i, err := Int63n(int64(max))
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if err != nil {
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return 0, err
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}
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return int(i), nil
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}
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// Float64 returns a random number in [0.0,1.0) as a float64.
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func Float64() (float64, error) {
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again:
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i, err := Int63n(1 << 53)
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if err != nil {
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return 0, err
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}
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f := (float64(i) / (1 << 53))
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if f == 1 {
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goto again
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}
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return f, nil
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}
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// Float32 returns a random number in [0.0,1.0) as a float32.
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func Float32() (float32, error) {
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again:
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i, err := Float64()
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if err != nil {
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return 0, err
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}
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f := float32(i)
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if f == 1 {
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goto again
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}
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return f, nil
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}
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// Bool returns a random true/false value as a bool.
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func Bool() (bool, error) {
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i, err := Uint64()
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if err != nil {
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return false, err
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}
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// True if the least significant bit is 1
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return i&1 == 1, nil
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}
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// Duration returns a random time.Duration value
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func Duration() (time.Duration, error) {
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i, err := Int63()
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if err != nil {
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return time.Duration(0), err
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}
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return time.Duration(i), nil
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}
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