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// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package rand_test
import (
"bytes"
"crypto/rand"
"fmt"
"io"
"math/big"
mathrand "math/rand"
"testing"
"time"
)
// https://golang.org/issue/6849.
func TestPrimeSmall(t *testing.T) {
for n := 2; n < 10; n++ {
p, err := rand.Prime(rand.Reader, n)
if err != nil {
t.Fatalf("Can't generate %d-bit prime: %v", n, err)
}
if p.BitLen() != n {
t.Fatalf("%v is not %d-bit", p, n)
}
if !p.ProbablyPrime(32) {
t.Fatalf("%v is not prime", p)
}
}
}
// Test that passing bits < 2 causes Prime to return nil, error
func TestPrimeBitsLt2(t *testing.T) {
if p, err := rand.Prime(rand.Reader, 1); p != nil || err == nil {
t.Errorf("Prime should return nil, error when called with bits < 2")
}
}
func TestPrimeNondeterministic(t *testing.T) {
r := mathrand.New(mathrand.NewSource(42))
p0, err := rand.Prime(r, 32)
if err != nil {
t.Fatal(err)
}
for i := 0; i < 128; i++ {
r.Seed(42)
p, err := rand.Prime(r, 32)
if err != nil {
t.Fatal(err)
}
if p.Cmp(p0) != 0 {
return
}
}
t.Error("Prime always generated the same prime given the same input")
}
func TestInt(t *testing.T) {
// start at 128 so the case of (max.BitLen() % 8) == 0 is covered
for n := 128; n < 140; n++ {
b := new(big.Int).SetInt64(int64(n))
if i, err := rand.Int(rand.Reader, b); err != nil {
t.Fatalf("Can't generate random value: %v, %v", i, err)
}
}
}
type countingReader struct {
r io.Reader
n int
}
func (r *countingReader) Read(p []byte) (n int, err error) {
n, err = r.r.Read(p)
r.n += n
return n, err
}
// Test that Int reads only the necessary number of bytes from the reader for
// max at each bit length
func TestIntReads(t *testing.T) {
for i := 0; i < 32; i++ {
max := int64(1 << uint64(i))
t.Run(fmt.Sprintf("max=%d", max), func(t *testing.T) {
reader := &countingReader{r: rand.Reader}
_, err := rand.Int(reader, big.NewInt(max))
if err != nil {
t.Fatalf("Can't generate random value: %d, %v", max, err)
}
expected := (i + 7) / 8
if reader.n != expected {
t.Errorf("Int(reader, %d) should read %d bytes, but it read: %d", max, expected, reader.n)
}
})
}
}
// Test that Int does not mask out valid return values
func TestIntMask(t *testing.T) {
for max := 1; max <= 256; max++ {
t.Run(fmt.Sprintf("max=%d", max), func(t *testing.T) {
for i := 0; i < max; i++ {
if testing.Short() && i == 0 {
i = max - 1
}
var b bytes.Buffer
b.WriteByte(byte(i))
n, err := rand.Int(&b, big.NewInt(int64(max)))
if err != nil {
t.Fatalf("Can't generate random value: %d, %v", max, err)
}
if n.Int64() != int64(i) {
t.Errorf("Int(reader, %d) should have returned value of %d, but it returned: %v", max, i, n)
}
}
})
}
}
func testIntPanics(t *testing.T, b *big.Int) {
defer func() {
if err := recover(); err == nil {
t.Errorf("Int should panic when called with max <= 0: %v", b)
}
}()
rand.Int(rand.Reader, b)
}
// Test that passing a new big.Int as max causes Int to panic
func TestIntEmptyMaxPanics(t *testing.T) {
b := new(big.Int)
testIntPanics(t, b)
}
// Test that passing a negative value as max causes Int to panic
func TestIntNegativeMaxPanics(t *testing.T) {
b := new(big.Int).SetInt64(int64(-1))
testIntPanics(t, b)
}
func BenchmarkPrime(b *testing.B) {
r := mathrand.New(mathrand.NewSource(time.Now().UnixNano()))
for i := 0; i < b.N; i++ {
rand.Prime(r, 1024)
}
}
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