type Source … type Source64 … // NewSource returns a new pseudo-random [Source] seeded with the given value. // Unlike the default [Source] used by top-level functions, this source is not // safe for concurrent use by multiple goroutines. // The returned [Source] implements [Source64]. func NewSource(seed int64) Source { … } func newSource(seed int64) *rngSource { … } type Rand … // New returns a new [Rand] that uses random values from src // to generate other random values. func New(src Source) *Rand { … } // 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 int64) { … } // Int63 returns a non-negative pseudo-random 63-bit integer as an int64. func (r *Rand) Int63() int64 { … } // Uint32 returns a pseudo-random 32-bit value as a uint32. func (r *Rand) Uint32() uint32 { … } // Uint64 returns a pseudo-random 64-bit value as a uint64. func (r *Rand) Uint64() uint64 { … } // Int31 returns a non-negative pseudo-random 31-bit integer as an int32. func (r *Rand) Int31() int32 { … } // Int returns a non-negative pseudo-random int. func (r *Rand) Int() int { … } // Int63n returns, as an int64, a non-negative pseudo-random number in the half-open interval [0,n). // It panics if n <= 0. func (r *Rand) Int63n(n int64) int64 { … } // Int31n returns, as an int32, a non-negative pseudo-random number in the half-open interval [0,n). // It panics if n <= 0. func (r *Rand) Int31n(n int32) int32 { … } // int31n returns, as an int32, a non-negative pseudo-random number in the half-open interval [0,n). // n must be > 0, but int31n does not check this; the caller must ensure it. // int31n exists because Int31n is inefficient, but Go 1 compatibility // requires that the stream of values produced by math/rand remain unchanged. // int31n can thus only be used internally, by newly introduced APIs. // // For implementation details, see: // https://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction // https://lemire.me/blog/2016/06/30/fast-random-shuffling func (r *Rand) int31n(n int32) int32 { … } // Intn returns, as an int, a non-negative pseudo-random number in the half-open interval [0,n). // It panics if n <= 0. func (r *Rand) Intn(n int) int { … } // Float64 returns, as a float64, a pseudo-random number in the half-open interval [0.0,1.0). func (r *Rand) Float64() float64 { … } // Float32 returns, as a float32, a pseudo-random number in the half-open interval [0.0,1.0). func (r *Rand) Float32() float32 { … } // Perm returns, as a slice of n ints, a pseudo-random permutation of the integers // in the half-open interval [0,n). func (r *Rand) Perm(n int) []int { … } // 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)) { … } // 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. func (r *Rand) Read(p []byte) (n int, err error) { … } func read(p []byte, src Source, readVal *int64, readPos *int8) (n int, err error) { … } var globalRandGenerator … var randautoseed … var randseednop … // globalRand returns the generator to use for the top-level convenience // functions. func globalRand() *Rand { … } //go:linkname runtime_rand runtime.rand func runtime_rand() uint64 type runtimeSource … func (*runtimeSource) Int63() int64 { … } func (*runtimeSource) Seed(int64) { … } func (*runtimeSource) Uint64() uint64 { … } func (fs *runtimeSource) read(p []byte, readVal *int64, readPos *int8) (n int, err error) { … } // Seed uses the provided seed value to initialize the default Source to a // deterministic state. Seed values that have the same remainder when // divided by 2³¹-1 generate the same pseudo-random sequence. // Seed, unlike the [Rand.Seed] method, is safe for concurrent use. // // If Seed is not called, the generator is seeded randomly at program startup. // // Prior to Go 1.20, the generator was seeded like Seed(1) at program startup. // To force the old behavior, call Seed(1) at program startup. // Alternately, set GODEBUG=randautoseed=0 in the environment // before making any calls to functions in this package. // // Deprecated: As of Go 1.20 there is no reason to call Seed with // a random value. Programs that call Seed with a known value to get // a specific sequence of results should use New(NewSource(seed)) to // obtain a local random generator. // // As of Go 1.24 [Seed] is a no-op. To restore the previous behavior set // GODEBUG=randseednop=0. func Seed(seed int64) { … } // Int63 returns a non-negative pseudo-random 63-bit integer as an int64 // from the default [Source]. func Int63() int64 { … } // Uint32 returns a pseudo-random 32-bit value as a uint32 // from the default [Source]. func Uint32() uint32 { … } // Uint64 returns a pseudo-random 64-bit value as a uint64 // from the default [Source]. func Uint64() uint64 { … } // Int31 returns a non-negative pseudo-random 31-bit integer as an int32 // from the default [Source]. func Int31() int32 { … } // Int returns a non-negative pseudo-random int from the default [Source]. func Int() int { … } // Int63n returns, as an int64, a non-negative pseudo-random number in the half-open interval [0,n) // from the default [Source]. // It panics if n <= 0. func Int63n(n int64) int64 { … } // Int31n returns, as an int32, a non-negative pseudo-random number in the half-open interval [0,n) // from the default [Source]. // It panics if n <= 0. func Int31n(n int32) int32 { … } // Intn returns, as an int, a non-negative pseudo-random number in the half-open interval [0,n) // from the default [Source]. // It panics if n <= 0. func Intn(n int) int { … } // Float64 returns, as a float64, a pseudo-random number in the half-open interval [0.0,1.0) // from the default [Source]. func Float64() float64 { … } // Float32 returns, as a float32, a pseudo-random number in the half-open interval [0.0,1.0) // from the default [Source]. func Float32() float32 { … } // Perm returns, as a slice of n ints, a pseudo-random permutation of the integers // in the half-open interval [0,n) from the default [Source]. func Perm(n int) []int { … } // 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)) { … } // 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. // // Deprecated: For almost all use cases, [crypto/rand.Read] is more appropriate. // If a deterministic source is required, use [math/rand/v2.ChaCha8.Read]. func Read(p []byte) (n int, err error) { … } // 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 { … } // 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 { … } type lockedSource … func (r *lockedSource) Int63() (n int64) { … } func (r *lockedSource) Uint64() (n uint64) { … } func (r *lockedSource) Seed(seed int64) { … } // seedPos implements Seed for a lockedSource without a race condition. func (r *lockedSource) seedPos(seed int64, readPos *int8) { … } // seed seeds the underlying source. // The caller must have locked r.lk. func (r *lockedSource) seed(seed int64) { … } // read implements Read for a lockedSource without a race condition. func (r *lockedSource) read(p []byte, readVal *int64, readPos *int8) (n int, err error) { … }
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