encoding/binary: support for varint encoding

R=rsc, r, nigeltao, r, dsymonds
CC=golang-dev
https://golang.org/cl/5146048

1 files changed, 175 insertions, 0 deletions

diff --git a/src/pkg/encoding/binary/varint_test.go b/src/pkg/encoding/binary/varint_test.go
new file mode 100644
index 0000000000..a85aceeeac
--- /dev/null
+++ b/src/pkg/encoding/binary/varint_test.go
@@ -0,0 +1,175 @@
+// Copyright 2011 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 binary
+
+import (
+	"bytes"
+	"os"
+	"testing"
+)
+
+func testConstant(t *testing.T, w uint, max int) {
+	n := -PutUvarint(nil, 1<<w-1)
+	if n != max {
+		t.Errorf("MaxVarintLen%d = %d; want %d", w, max, n)
+	}
+}
+
+func TestConstants(t *testing.T) {
+	testConstant(t, 16, MaxVarintLen16)
+	testConstant(t, 32, MaxVarintLen32)
+	testConstant(t, 64, MaxVarintLen64)
+}
+
+func testVarint(t *testing.T, x int64) {
+	var buf1 [10]byte
+	n := PutVarint(buf1[:], x)
+	y, m := Varint(buf1[0:n])
+	if x != y {
+		t.Errorf("Varint(%d): got %d", x, y)
+	}
+	if n != m {
+		t.Errorf("Varint(%d): got n = %d; want %d", x, m, n)
+	}
+
+	var buf2 bytes.Buffer
+	err := WriteVarint(&buf2, x)
+	if err != nil {
+		t.Errorf("WriteVarint(%d): %s", x, err)
+	}
+	if n != buf2.Len() {
+		t.Errorf("WriteVarint(%d): got n = %d; want %d", x, buf2.Len(), n)
+	}
+	y, err = ReadVarint(&buf2)
+	if err != nil {
+		t.Errorf("ReadVarint(%d): %s", x, err)
+	}
+	if x != y {
+		t.Errorf("ReadVarint(%d): got %d", x, y)
+	}
+}
+
+func testUvarint(t *testing.T, x uint64) {
+	var buf1 [10]byte
+	n := PutUvarint(buf1[:], x)
+	y, m := Uvarint(buf1[0:n])
+	if x != y {
+		t.Errorf("Uvarint(%d): got %d", x, y)
+	}
+	if n != m {
+		t.Errorf("Uvarint(%d): got n = %d; want %d", x, m, n)
+	}
+
+	var buf2 bytes.Buffer
+	err := WriteUvarint(&buf2, x)
+	if err != nil {
+		t.Errorf("WriteUvarint(%d): %s", x, err)
+	}
+	if n != buf2.Len() {
+		t.Errorf("WriteUvarint(%d): got n = %d; want %d", x, buf2.Len(), n)
+	}
+	y, err = ReadUvarint(&buf2)
+	if err != nil {
+		t.Errorf("ReadUvarint(%d): %s", x, err)
+	}
+	if x != y {
+		t.Errorf("ReadUvarint(%d): got %d", x, y)
+	}
+}
+
+var tests = []int64{
+	-1 << 63,
+	-1<<63 + 1,
+	-1,
+	0,
+	1,
+	2,
+	10,
+	20,
+	63,
+	64,
+	65,
+	127,
+	128,
+	129,
+	255,
+	256,
+	257,
+	1<<63 - 1,
+}
+
+func TestVarint(t *testing.T) {
+	for _, x := range tests {
+		testVarint(t, x)
+		testVarint(t, -x)
+	}
+	for x := int64(0x7); x != 0; x <<= 1 {
+		testVarint(t, x)
+		testVarint(t, -x)
+	}
+}
+
+func TestUvarint(t *testing.T) {
+	for _, x := range tests {
+		testUvarint(t, uint64(x))
+	}
+	for x := uint64(0x7); x != 0; x <<= 1 {
+		testUvarint(t, x)
+	}
+}
+
+func TestBufferTooSmall(t *testing.T) {
+	for i := 0; i < 10; i++ {
+		buf := make([]byte, i)
+		x := uint64(1) << (uint(i) * 7)
+		n0 := -i
+		if i == 0 {
+			n0 = -1 // encoding 0 takes one byte
+		}
+		if n := PutUvarint(buf, x); n != n0 {
+			t.Errorf("PutUvarint([%d]byte, %d): got n = %d; want %d", len(buf), x, n, n0)
+		}
+	}
+
+	buf := []byte{0x80, 0x80, 0x80, 0x80}
+	for i := 0; i <= len(buf); i++ {
+		buf := buf[0:i]
+		x, n := Uvarint(buf)
+		if x != 0 || n != 0 {
+			t.Errorf("Uvarint(%v): got x = %d, n = %d", buf, x, n)
+		}
+
+		x, err := ReadUvarint(bytes.NewBuffer(buf))
+		if x != 0 || err != os.EOF {
+			t.Errorf("ReadUvarint(%v): got x = %d, err = %s", buf, x, err)
+		}
+	}
+}
+
+func testOverflow(t *testing.T, buf []byte, n0 int, err0 os.Error) {
+	x, n := Uvarint(buf)
+	if x != 0 || n != n0 {
+		t.Errorf("Uvarint(%v): got x = %d, n = %d; want 0, %d", buf, x, n, n0)
+	}
+
+	x, err := ReadUvarint(bytes.NewBuffer(buf))
+	if x != 0 || err != err0 {
+		t.Errorf("ReadUvarint(%v): got x = %d, err = %s; want 0, %s", buf, x, err, err0)
+	}
+}
+
+func TestOverflow(t *testing.T) {
+	testOverflow(t, []byte{0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x2}, -10, overflow)
+	testOverflow(t, []byte{0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x1, 0, 0}, -13, overflow)
+}
+
+func TestNonCanonicalZero(t *testing.T) {
+	buf := []byte{0x80, 0x80, 0x80, 0}
+	x, n := Uvarint(buf)
+	if x != 0 || n != 4 {
+		t.Errorf("Uvarint(%v): got x = %d, n = %d; want 0, 4", buf, x, n)
+
+	}
+}