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Diffstat (limited to '')
| -rw-r--r-- | dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/rand/rand.go | 372 |
1 files changed, 372 insertions, 0 deletions
diff --git a/dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/rand/rand.go b/dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/rand/rand.go new file mode 100644 index 0000000..ee6161b --- /dev/null +++ b/dependencies/pkg/mod/golang.org/x/exp@v0.0.0-20220613132600-b0d781184e0d/rand/rand.go @@ -0,0 +1,372 @@ +// Copyright 2009 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Package rand implements pseudo-random number generators. +// +// Random numbers are generated by a Source. Top-level functions, such as +// Float64 and Int, use a default shared Source that produces a deterministic +// sequence of values each time a program is run. Use the Seed function to +// initialize the default Source if different behavior is required for each run. +// The default Source, a LockedSource, is safe for concurrent use by multiple +// goroutines, but Sources created by NewSource are not. However, Sources are small +// and it is reasonable to have a separate Source for each goroutine, seeded +// differently, to avoid locking. +// +// For random numbers suitable for security-sensitive work, see the crypto/rand +// package. +package rand + +import "sync" + +// A Source represents a source of uniformly-distributed +// pseudo-random int64 values in the range [0, 1<<64). +type Source interface { + Uint64() uint64 + Seed(seed uint64) +} + +// NewSource returns a new pseudo-random Source seeded with the given value. +func NewSource(seed uint64) Source { + var rng PCGSource + rng.Seed(seed) + return &rng +} + +// A Rand is a source of random numbers. +type Rand struct { + src Source + + // readVal contains remainder of 64-bit integer used for bytes + // generation during most recent Read call. + // It is saved so next Read call can start where the previous + // one finished. + readVal uint64 + // readPos indicates the number of low-order bytes of readVal + // that are still valid. + readPos int8 +} + +// New returns a new Rand that uses random values from src +// to generate other random values. +func New(src Source) *Rand { + return &Rand{src: src} +} + +// Seed uses the provided seed value to initialize the generator to a deterministic state. +// Seed should not be called concurrently with any other Rand method. +func (r *Rand) Seed(seed uint64) { + if lk, ok := r.src.(*LockedSource); ok { + lk.seedPos(seed, &r.readPos) + return + } + + r.src.Seed(seed) + r.readPos = 0 +} + +// Uint64 returns a pseudo-random 64-bit integer as a uint64. +func (r *Rand) Uint64() uint64 { return r.src.Uint64() } + +// Int63 returns a non-negative pseudo-random 63-bit integer as an int64. +func (r *Rand) Int63() int64 { return int64(r.src.Uint64() &^ (1 << 63)) } + +// Uint32 returns a pseudo-random 32-bit value as a uint32. +func (r *Rand) Uint32() uint32 { return uint32(r.Uint64() >> 32) } + +// Int31 returns a non-negative pseudo-random 31-bit integer as an int32. +func (r *Rand) Int31() int32 { return int32(r.Uint64() >> 33) } + +// Int returns a non-negative pseudo-random int. +func (r *Rand) Int() int { + u := uint(r.Uint64()) + return int(u << 1 >> 1) // clear sign bit. +} + +const maxUint64 = (1 << 64) - 1 + +// Uint64n returns, as a uint64, a pseudo-random number in [0,n). +// It is guaranteed more uniform than taking a Source value mod n +// for any n that is not a power of 2. +func (r *Rand) Uint64n(n uint64) uint64 { + if n&(n-1) == 0 { // n is power of two, can mask + if n == 0 { + panic("invalid argument to Uint64n") + } + return r.Uint64() & (n - 1) + } + // If n does not divide v, to avoid bias we must not use + // a v that is within maxUint64%n of the top of the range. + v := r.Uint64() + if v > maxUint64-n { // Fast check. + ceiling := maxUint64 - maxUint64%n + for v >= ceiling { + v = r.Uint64() + } + } + + return v % n +} + +// Int63n returns, as an int64, a non-negative pseudo-random number in [0,n). +// It panics if n <= 0. +func (r *Rand) Int63n(n int64) int64 { + if n <= 0 { + panic("invalid argument to Int63n") + } + return int64(r.Uint64n(uint64(n))) +} + +// Int31n returns, as an int32, a non-negative pseudo-random number in [0,n). +// It panics if n <= 0. +func (r *Rand) Int31n(n int32) int32 { + if n <= 0 { + panic("invalid argument to Int31n") + } + // TODO: Avoid some 64-bit ops to make it more efficient on 32-bit machines. + return int32(r.Uint64n(uint64(n))) +} + +// Intn returns, as an int, a non-negative pseudo-random number in [0,n). +// It panics if n <= 0. +func (r *Rand) Intn(n int) int { + if n <= 0 { + panic("invalid argument to Intn") + } + // TODO: Avoid some 64-bit ops to make it more efficient on 32-bit machines. + return int(r.Uint64n(uint64(n))) +} + +// Float64 returns, as a float64, a pseudo-random number in [0.0,1.0). +func (r *Rand) Float64() float64 { + // There is one bug in the value stream: r.Int63() may be so close + // to 1<<63 that the division rounds up to 1.0, and we've guaranteed + // that the result is always less than 1.0. + // + // We tried to fix this by mapping 1.0 back to 0.0, but since float64 + // values near 0 are much denser than near 1, mapping 1 to 0 caused + // a theoretically significant overshoot in the probability of returning 0. + // Instead of that, if we round up to 1, just try again. + // Getting 1 only happens 1/2⁵³ of the time, so most clients + // will not observe it anyway. +again: + f := float64(r.Uint64n(1<<53)) / (1 << 53) + if f == 1.0 { + goto again // resample; this branch is taken O(never) + } + return f +} + +// Float32 returns, as a float32, a pseudo-random number in [0.0,1.0). +func (r *Rand) Float32() float32 { + // We do not want to return 1.0. + // This only happens 1/2²⁴ of the time (plus the 1/2⁵³ of the time in Float64). +again: + f := float32(r.Float64()) + if f == 1 { + goto again // resample; this branch is taken O(very rarely) + } + return f +} + +// Perm returns, as a slice of n ints, a pseudo-random permutation of the integers [0,n). +func (r *Rand) Perm(n int) []int { + m := make([]int, n) + // In the following loop, the iteration when i=0 always swaps m[0] with m[0]. + // A change to remove this useless iteration is to assign 1 to i in the init + // statement. But Perm also effects r. Making this change will affect + // the final state of r. So this change can't be made for compatibility + // reasons for Go 1. + for i := 0; i < n; i++ { + j := r.Intn(i + 1) + m[i] = m[j] + m[j] = i + } + return m +} + +// Shuffle pseudo-randomizes the order of elements. +// n is the number of elements. Shuffle panics if n < 0. +// swap swaps the elements with indexes i and j. +func (r *Rand) Shuffle(n int, swap func(i, j int)) { + if n < 0 { + panic("invalid argument to Shuffle") + } + + // Fisher-Yates shuffle: https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle + // Shuffle really ought not be called with n that doesn't fit in 32 bits. + // Not only will it take a very long time, but with 2³¹! possible permutations, + // there's no way that any PRNG can have a big enough internal state to + // generate even a minuscule percentage of the possible permutations. + // Nevertheless, the right API signature accepts an int n, so handle it as best we can. + i := n - 1 + for ; i > 1<<31-1-1; i-- { + j := int(r.Int63n(int64(i + 1))) + swap(i, j) + } + for ; i > 0; i-- { + j := int(r.Int31n(int32(i + 1))) + swap(i, j) + } +} + +// Read generates len(p) random bytes and writes them into p. It +// always returns len(p) and a nil error. +// Read should not be called concurrently with any other Rand method unless +// the underlying source is a LockedSource. +func (r *Rand) Read(p []byte) (n int, err error) { + if lk, ok := r.src.(*LockedSource); ok { + return lk.Read(p, &r.readVal, &r.readPos) + } + return read(p, r.src, &r.readVal, &r.readPos) +} + +func read(p []byte, src Source, readVal *uint64, readPos *int8) (n int, err error) { + pos := *readPos + val := *readVal + rng, _ := src.(*PCGSource) + for n = 0; n < len(p); n++ { + if pos == 0 { + if rng != nil { + val = rng.Uint64() + } else { + val = src.Uint64() + } + pos = 8 + } + p[n] = byte(val) + val >>= 8 + pos-- + } + *readPos = pos + *readVal = val + return +} + +/* + * Top-level convenience functions + */ + +var globalRand = New(&LockedSource{src: *NewSource(1).(*PCGSource)}) + +// Type assert that globalRand's source is a LockedSource whose src is a PCGSource. +var _ PCGSource = globalRand.src.(*LockedSource).src + +// Seed uses the provided seed value to initialize the default Source to a +// deterministic state. If Seed is not called, the generator behaves as +// if seeded by Seed(1). +// Seed, unlike the Rand.Seed method, is safe for concurrent use. +func Seed(seed uint64) { globalRand.Seed(seed) } + +// Int63 returns a non-negative pseudo-random 63-bit integer as an int64 +// from the default Source. +func Int63() int64 { return globalRand.Int63() } + +// Uint32 returns a pseudo-random 32-bit value as a uint32 +// from the default Source. +func Uint32() uint32 { return globalRand.Uint32() } + +// Uint64 returns a pseudo-random 64-bit value as a uint64 +// from the default Source. +func Uint64() uint64 { return globalRand.Uint64() } + +// Int31 returns a non-negative pseudo-random 31-bit integer as an int32 +// from the default Source. +func Int31() int32 { return globalRand.Int31() } + +// Int returns a non-negative pseudo-random int from the default Source. +func Int() int { return globalRand.Int() } + +// Int63n returns, as an int64, a non-negative pseudo-random number in [0,n) +// from the default Source. +// It panics if n <= 0. +func Int63n(n int64) int64 { return globalRand.Int63n(n) } + +// Int31n returns, as an int32, a non-negative pseudo-random number in [0,n) +// from the default Source. +// It panics if n <= 0. +func Int31n(n int32) int32 { return globalRand.Int31n(n) } + +// Intn returns, as an int, a non-negative pseudo-random number in [0,n) +// from the default Source. +// It panics if n <= 0. +func Intn(n int) int { return globalRand.Intn(n) } + +// Float64 returns, as a float64, a pseudo-random number in [0.0,1.0) +// from the default Source. +func Float64() float64 { return globalRand.Float64() } + +// Float32 returns, as a float32, a pseudo-random number in [0.0,1.0) +// from the default Source. +func Float32() float32 { return globalRand.Float32() } + +// Perm returns, as a slice of n ints, a pseudo-random permutation of the integers [0,n) +// from the default Source. +func Perm(n int) []int { return globalRand.Perm(n) } + +// Shuffle pseudo-randomizes the order of elements using the default Source. +// n is the number of elements. Shuffle panics if n < 0. +// swap swaps the elements with indexes i and j. +func Shuffle(n int, swap func(i, j int)) { globalRand.Shuffle(n, swap) } + +// Read generates len(p) random bytes from the default Source and +// writes them into p. It always returns len(p) and a nil error. +// Read, unlike the Rand.Read method, is safe for concurrent use. +func Read(p []byte) (n int, err error) { return globalRand.Read(p) } + +// NormFloat64 returns a normally distributed float64 in the range +// [-math.MaxFloat64, +math.MaxFloat64] with +// standard normal distribution (mean = 0, stddev = 1) +// from the default Source. +// To produce a different normal distribution, callers can +// adjust the output using: +// +// sample = NormFloat64() * desiredStdDev + desiredMean +func NormFloat64() float64 { return globalRand.NormFloat64() } + +// ExpFloat64 returns an exponentially distributed float64 in the range +// (0, +math.MaxFloat64] with an exponential distribution whose rate parameter +// (lambda) is 1 and whose mean is 1/lambda (1) from the default Source. +// To produce a distribution with a different rate parameter, +// callers can adjust the output using: +// +// sample = ExpFloat64() / desiredRateParameter +func ExpFloat64() float64 { return globalRand.ExpFloat64() } + +// LockedSource is an implementation of Source that is concurrency-safe. +// A Rand using a LockedSource is safe for concurrent use. +// +// The zero value of LockedSource is valid, but should be seeded before use. +type LockedSource struct { + lk sync.Mutex + src PCGSource +} + +func (s *LockedSource) Uint64() (n uint64) { + s.lk.Lock() + n = s.src.Uint64() + s.lk.Unlock() + return +} + +func (s *LockedSource) Seed(seed uint64) { + s.lk.Lock() + s.src.Seed(seed) + s.lk.Unlock() +} + +// seedPos implements Seed for a LockedSource without a race condiiton. +func (s *LockedSource) seedPos(seed uint64, readPos *int8) { + s.lk.Lock() + s.src.Seed(seed) + *readPos = 0 + s.lk.Unlock() +} + +// Read implements Read for a LockedSource. +func (s *LockedSource) Read(p []byte, readVal *uint64, readPos *int8) (n int, err error) { + s.lk.Lock() + n, err = read(p, &s.src, readVal, readPos) + s.lk.Unlock() + return +} |