fb13942b1e
You can read random bytes from Reader without exhausting entropy. Signed-off-by: Alexander Morozov <lk4d4@docker.com>
61 lines
1 KiB
Go
61 lines
1 KiB
Go
package random
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import (
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"io"
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"math/rand"
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"sync"
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"time"
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)
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// Rand is a global *rand.Rand instance, which initilized with NewSource() source.
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var Rand = rand.New(NewSource())
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// Reader is a global, shared instance of a pseudorandom bytes generator.
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// It doesn't consume entropy.
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var Reader io.Reader = &reader{rnd: Rand}
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// copypaste from standard math/rand
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type lockedSource struct {
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lk sync.Mutex
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src rand.Source
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}
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func (r *lockedSource) Int63() (n int64) {
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r.lk.Lock()
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n = r.src.Int63()
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r.lk.Unlock()
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return
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}
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func (r *lockedSource) Seed(seed int64) {
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r.lk.Lock()
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r.src.Seed(seed)
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r.lk.Unlock()
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}
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// NewSource returns math/rand.Source safe for concurrent use and initialized
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// with current unix-nano timestamp
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func NewSource() rand.Source {
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return &lockedSource{
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src: rand.NewSource(time.Now().UnixNano()),
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}
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}
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type reader struct {
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rnd *rand.Rand
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}
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func (r *reader) Read(b []byte) (int, error) {
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i := 0
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for {
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val := r.rnd.Int63()
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for val > 0 {
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b[i] = byte(val)
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i++
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if i == len(b) {
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return i, nil
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}
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val >>= 8
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}
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}
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}
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