libgo: update to go1.9

    
    Reviewed-on: https://go-review.googlesource.com/63753

From-SVN: r252767

1 files changed, 53 insertions, 0 deletions

diff --git a/libgo/go/crypto/rand/util_test.go b/libgo/go/crypto/rand/util_test.go
index 48a2c3f..685624e 100644
--- a/libgo/go/crypto/rand/util_test.go
+++ b/libgo/go/crypto/rand/util_test.go
@@ -5,7 +5,10 @@
 package rand_test
 
 import (
+	"bytes"
 	"crypto/rand"
+	"fmt"
+	"io"
 	"math/big"
 	mathrand "math/rand"
 	"testing"
@@ -45,6 +48,56 @@ func TestInt(t *testing.T) {
 	}
 }
 
+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++ {
+				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 {