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