1// Copyright 2013 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package rand_test
6
7import (
8	"bytes"
9	"crypto/rand"
10	"fmt"
11	"io"
12	"math/big"
13	mathrand "math/rand"
14	"testing"
15	"time"
16)
17
18// https://golang.org/issue/6849.
19func TestPrimeSmall(t *testing.T) {
20	for n := 2; n < 10; n++ {
21		p, err := rand.Prime(rand.Reader, n)
22		if err != nil {
23			t.Fatalf("Can't generate %d-bit prime: %v", n, err)
24		}
25		if p.BitLen() != n {
26			t.Fatalf("%v is not %d-bit", p, n)
27		}
28		if !p.ProbablyPrime(32) {
29			t.Fatalf("%v is not prime", p)
30		}
31	}
32}
33
34// Test that passing bits < 2 causes Prime to return nil, error
35func TestPrimeBitsLt2(t *testing.T) {
36	if p, err := rand.Prime(rand.Reader, 1); p != nil || err == nil {
37		t.Errorf("Prime should return nil, error when called with bits < 2")
38	}
39}
40
41func TestInt(t *testing.T) {
42	// start at 128 so the case of (max.BitLen() % 8) == 0 is covered
43	for n := 128; n < 140; n++ {
44		b := new(big.Int).SetInt64(int64(n))
45		if i, err := rand.Int(rand.Reader, b); err != nil {
46			t.Fatalf("Can't generate random value: %v, %v", i, err)
47		}
48	}
49}
50
51type countingReader struct {
52	r io.Reader
53	n int
54}
55
56func (r *countingReader) Read(p []byte) (n int, err error) {
57	n, err = r.r.Read(p)
58	r.n += n
59	return n, err
60}
61
62// Test that Int reads only the necessary number of bytes from the reader for
63// max at each bit length
64func TestIntReads(t *testing.T) {
65	for i := 0; i < 32; i++ {
66		max := int64(1 << uint64(i))
67		t.Run(fmt.Sprintf("max=%d", max), func(t *testing.T) {
68			reader := &countingReader{r: rand.Reader}
69
70			_, err := rand.Int(reader, big.NewInt(max))
71			if err != nil {
72				t.Fatalf("Can't generate random value: %d, %v", max, err)
73			}
74			expected := (i + 7) / 8
75			if reader.n != expected {
76				t.Errorf("Int(reader, %d) should read %d bytes, but it read: %d", max, expected, reader.n)
77			}
78		})
79	}
80}
81
82// Test that Int does not mask out valid return values
83func TestIntMask(t *testing.T) {
84	for max := 1; max <= 256; max++ {
85		t.Run(fmt.Sprintf("max=%d", max), func(t *testing.T) {
86			for i := 0; i < max; i++ {
87				var b bytes.Buffer
88				b.WriteByte(byte(i))
89				n, err := rand.Int(&b, big.NewInt(int64(max)))
90				if err != nil {
91					t.Fatalf("Can't generate random value: %d, %v", max, err)
92				}
93				if n.Int64() != int64(i) {
94					t.Errorf("Int(reader, %d) should have returned value of %d, but it returned: %v", max, i, n)
95				}
96			}
97		})
98	}
99}
100
101func testIntPanics(t *testing.T, b *big.Int) {
102	defer func() {
103		if err := recover(); err == nil {
104			t.Errorf("Int should panic when called with max <= 0: %v", b)
105		}
106	}()
107	rand.Int(rand.Reader, b)
108}
109
110// Test that passing a new big.Int as max causes Int to panic
111func TestIntEmptyMaxPanics(t *testing.T) {
112	b := new(big.Int)
113	testIntPanics(t, b)
114}
115
116// Test that passing a negative value as max causes Int to panic
117func TestIntNegativeMaxPanics(t *testing.T) {
118	b := new(big.Int).SetInt64(int64(-1))
119	testIntPanics(t, b)
120}
121
122func BenchmarkPrime(b *testing.B) {
123	r := mathrand.New(mathrand.NewSource(time.Now().UnixNano()))
124	for i := 0; i < b.N; i++ {
125		rand.Prime(r, 1024)
126	}
127}
128