source.go

package gopherng

import (
	"encoding/binary"
	"fmt"
)

// PseudorandomSource is a pseudorandom source implementing both rand.Source
// and rand.Source64, and can be used to initialize a rand.Rand.
type PseudorandomSource struct {
	randReader *PseudorandomReader
}

// NewSource returns a new Source for the given seed. See NewReader() for
// seeding details.
func NewSource(seed []byte) *PseudorandomSource {
	return &PseudorandomSource{
		randReader: NewReader(seed),
	}
}

// Int63 returns an int64 from the internal PseudorandomReader.
func (s *PseudorandomSource) Int63() int64 {
	v := int64(s.Uint64())
	if v < 0 {
		v *= -1
	}
	return v
}

// Seed exists to be compatible with rand.Source, but is not implemented and
// will panic if called. It should not be needed for use with rand.Rand
// methods.
func (s *PseudorandomSource) Seed(seed int64) {
	panic(fmt.Errorf("Seed not supported for gopherng PseudorandomSource"))
}

// Uint64 returns a uint64 from the internal PseudorandomReader.
func (s *PseudorandomSource) Uint64() uint64 {
	r := make([]byte, 8)
	if _, err := s.randReader.Read(r); err != nil {
		panic(fmt.Errorf("unexpected reader error: %w", err))
	}
	return binary.LittleEndian.Uint64(r)
}