30 lines
623 B
Go
30 lines
623 B
Go
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package utils
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import (
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"crypto/rand"
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"encoding/binary"
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)
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// Rand is a wrapper around crypto/rand that adds some convenience functions known from math/rand.
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type Rand struct {
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buf [4]byte
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}
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func (r *Rand) Int31() int32 {
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rand.Read(r.buf[:])
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return int32(binary.BigEndian.Uint32(r.buf[:]) & ^uint32(1<<31))
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}
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// copied from the standard library math/rand implementation of Int63n
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func (r *Rand) Int31n(n int32) int32 {
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if n&(n-1) == 0 { // n is power of two, can mask
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return r.Int31() & (n - 1)
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}
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max := int32((1 << 31) - 1 - (1<<31)%uint32(n))
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v := r.Int31()
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for v > max {
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v = r.Int31()
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}
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return v % n
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}
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