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 5 package rand_test 6 7 import ( 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. 19 func 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 35 func 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 41 func 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 51 type countingReader struct { 52 r io.Reader 53 n int 54 } 55 56 func (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 64 func 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 83 func 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 } 100 101 func 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 111 func 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 117 func TestIntNegativeMaxPanics(t *testing.T) { 118 b := new(big.Int).SetInt64(int64(-1)) 119 testIntPanics(t, b) 120 } 121 122 func 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
