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common.encapsulation.encapsulation_test.go Maven / Gradle / Ivy
package encapsulation
import (
"bytes"
"io"
"math/rand"
"testing"
)
// Return a byte slice with non-trivial contents.
func pseudorandomBuffer(n int) []byte {
source := rand.NewSource(0)
p := make([]byte, n)
for i := 0; i < len(p); i++ {
p[i] = byte(source.Int63() & 0xff)
}
return p
}
func mustWriteData(w io.Writer, p []byte) int {
n, err := WriteData(w, p)
if err != nil {
panic(err)
}
return n
}
func mustWritePadding(w io.Writer, n int) int {
n, err := WritePadding(w, n)
if err != nil {
panic(err)
}
return n
}
// Test that ReadData(WriteData()) recovers the original data.
func TestRoundtrip(t *testing.T) {
// Test above and below interesting thresholds.
for _, i := range []int{
0x00, 0x01,
0x3e, 0x3f, 0x40, 0x41,
0xfe, 0xff, 0x100, 0x101,
0x1ffe, 0x1fff, 0x2000, 0x2001,
0xfffe, 0xffff, 0x10000, 0x10001,
0xffffe, 0xfffff,
} {
original := pseudorandomBuffer(i)
var enc bytes.Buffer
n, err := WriteData(&enc, original)
if err != nil {
t.Fatalf("size %d, WriteData returned error %v", i, err)
}
if enc.Len() != n {
t.Fatalf("size %d, returned length was %d, written length was %d",
i, n, enc.Len())
}
inverse, err := ReadData(&enc)
if err != nil {
t.Fatalf("size %d, ReadData returned error %v", i, err)
}
if !bytes.Equal(inverse, original) {
t.Fatalf("size %d, got <%x>, expected <%x>", i, inverse, original)
}
}
}
// Test that WritePadding writes exactly as much as requested.
func TestPaddingLength(t *testing.T) {
// Test above and below interesting thresholds. WritePadding also gets
// values above 0xfffff, the maximum value of a single length prefix.
for _, i := range []int{
0x00, 0x01,
0x3f, 0x40, 0x41, 0x42,
0xff, 0x100, 0x101, 0x102,
0x2000, 0x2001, 0x2002, 0x2003,
0x10000, 0x10001, 0x10002, 0x10003,
0x100001, 0x100002, 0x100003, 0x100004,
} {
var enc bytes.Buffer
n, err := WritePadding(&enc, i)
if err != nil {
t.Fatalf("size %d, WritePadding returned error %v", i, err)
}
if n != i {
t.Fatalf("requested %d bytes, returned %d", i, n)
}
if enc.Len() != n {
t.Fatalf("requested %d bytes, wrote %d bytes", i, enc.Len())
}
}
}
// Test that ReadData skips over padding.
func TestSkipPadding(t *testing.T) {
var data = [][]byte{{}, {}, []byte("hello"), {}, []byte("world")}
var enc bytes.Buffer
mustWritePadding(&enc, 10)
mustWritePadding(&enc, 100)
mustWriteData(&enc, data[0])
mustWriteData(&enc, data[1])
mustWritePadding(&enc, 10)
mustWriteData(&enc, data[2])
mustWriteData(&enc, data[3])
mustWritePadding(&enc, 10)
mustWriteData(&enc, data[4])
mustWritePadding(&enc, 10)
mustWritePadding(&enc, 10)
for i, expected := range data {
actual, err := ReadData(&enc)
if err != nil {
t.Fatalf("slice %d, got error %v, expected %v", i, err, nil)
}
if !bytes.Equal(actual, expected) {
t.Fatalf("slice %d, got <%x>, expected <%x>", i, actual, expected)
}
}
p, err := ReadData(&enc)
if p != nil || err != io.EOF {
t.Fatalf("got (<%x>, %v), expected (%v, %v)", p, err, nil, io.EOF)
}
}
// Test that EOF before a length prefix returns io.EOF.
func TestEOF(t *testing.T) {
p, err := ReadData(bytes.NewReader(nil))
if p != nil || err != io.EOF {
t.Fatalf("got (<%x>, %v), expected (%v, %v)", p, err, nil, io.EOF)
}
}
// Test that an EOF while reading a length prefix, or while reading the
// subsequent data/padding, returns io.ErrUnexpectedEOF.
func TestUnexpectedEOF(t *testing.T) {
for _, test := range [][]byte{
{0x40}, // expecting a second length byte
{0xc0}, // expecting a second length byte
{0x41, 0x80}, // expecting a third length byte
{0xc1, 0x80}, // expecting a third length byte
{0x02}, // expecting 2 bytes of padding
{0x82}, // expecting 2 bytes of data
{0x02, 'X'}, // expecting 1 byte of padding
{0x82, 'X'}, // expecting 1 byte of data
{0x41, 0x00}, // expecting 128 bytes of padding
{0xc1, 0x00}, // expecting 128 bytes of data
{0x41, 0x00, 'X'}, // expecting 127 bytes of padding
{0xc1, 0x00, 'X'}, // expecting 127 bytes of data
{0x41, 0x80, 0x00}, // expecting 32768 bytes of padding
{0xc1, 0x80, 0x00}, // expecting 32768 bytes of data
{0x41, 0x80, 0x00, 'X'}, // expecting 32767 bytes of padding
{0xc1, 0x80, 0x00, 'X'}, // expecting 32767 bytes of data
} {
p, err := ReadData(bytes.NewReader(test))
if p != nil || err != io.ErrUnexpectedEOF {
t.Fatalf("<%x> got (<%x>, %v), expected (%v, %v)", test, p, err, nil, io.ErrUnexpectedEOF)
}
}
}
// Test that length encodings that are longer than they could be are still
// interpreted.
func TestNonMinimalLengthEncoding(t *testing.T) {
for _, test := range []struct {
enc []byte
expected []byte
}{
{[]byte{0x81, 'X'}, []byte("X")},
{[]byte{0xc0, 0x01, 'X'}, []byte("X")},
{[]byte{0xc0, 0x80, 0x01, 'X'}, []byte("X")},
} {
p, err := ReadData(bytes.NewReader(test.enc))
if err != nil {
t.Fatalf("<%x> got error %v, expected %v", test.enc, err, nil)
}
if !bytes.Equal(p, test.expected) {
t.Fatalf("<%x> got <%x>, expected <%x>", test.enc, p, test.expected)
}
}
}
// Test that ReadData only reads up to 3 bytes of length prefix.
func TestReadLimits(t *testing.T) {
// Test the maximum length that's possible with 3 bytes of length
// prefix.
maxLength := (0x3f << 14) | (0x7f << 7) | 0x7f
data := bytes.Repeat([]byte{'X'}, maxLength)
prefix := []byte{0xff, 0xff, 0x7f} // encodes 0xfffff
p, err := ReadData(bytes.NewReader(append(prefix, data...)))
if err != nil {
t.Fatalf("got error %v, expected %v", err, nil)
}
if !bytes.Equal(p, data) {
t.Fatalf("got %d bytes unequal to %d bytes", len(p), len(data))
}
// Test a 4-byte prefix.
prefix = []byte{0xc0, 0xc0, 0x80, 0x80} // encodes 0x100000
data = bytes.Repeat([]byte{'X'}, maxLength+1)
p, err = ReadData(bytes.NewReader(append(prefix, data...)))
if p != nil || err != ErrTooLong {
t.Fatalf("got (<%x>, %v), expected (%v, %v)", p, err, nil, ErrTooLong)
}
// Test that 4 bytes don't work, even when they encode an integer that
// would fix in 3 bytes.
prefix = []byte{0xc0, 0x80, 0x80, 0x80} // encodes 0x0
data = []byte{}
p, err = ReadData(bytes.NewReader(append(prefix, data...)))
if p != nil || err != ErrTooLong {
t.Fatalf("got (<%x>, %v), expected (%v, %v)", p, err, nil, ErrTooLong)
}
// Do the same tests with padding lengths.
data = []byte("hello")
prefix = []byte{0x7f, 0xff, 0x7f} // encodes 0xfffff
padding := bytes.Repeat([]byte{'X'}, maxLength)
enc := bytes.NewBuffer(append(prefix, padding...))
mustWriteData(enc, data)
p, err = ReadData(enc)
if err != nil {
t.Fatalf("got error %v, expected %v", err, nil)
}
if !bytes.Equal(p, data) {
t.Fatalf("got <%x>, expected <%x>", p, data)
}
prefix = []byte{0x40, 0xc0, 0x80, 0x80} // encodes 0x100000
padding = bytes.Repeat([]byte{'X'}, maxLength+1)
enc = bytes.NewBuffer(append(prefix, padding...))
mustWriteData(enc, data)
p, err = ReadData(enc)
if p != nil || err != ErrTooLong {
t.Fatalf("got (<%x>, %v), expected (%v, %v)", p, err, nil, ErrTooLong)
}
prefix = []byte{0x40, 0x80, 0x80, 0x80} // encodes 0x0
padding = []byte{}
enc = bytes.NewBuffer(append(prefix, padding...))
mustWriteData(enc, data)
p, err = ReadData(enc)
if p != nil || err != ErrTooLong {
t.Fatalf("got (<%x>, %v), expected (%v, %v)", p, err, nil, ErrTooLong)
}
}
// Test that WriteData and WritePadding only accept lengths that can be encoded
// in up to 3 bytes of length prefix.
func TestWriteLimits(t *testing.T) {
maxLength := (0x3f << 14) | (0x7f << 7) | 0x7f
var enc bytes.Buffer
n, err := WriteData(&enc, bytes.Repeat([]byte{'X'}, maxLength))
if n != maxLength+3 || err != nil {
t.Fatalf("got (%d, %v), expected (%d, %v)", n, err, maxLength, nil)
}
enc.Reset()
n, err = WriteData(&enc, bytes.Repeat([]byte{'X'}, maxLength+1))
if n != 0 || err != ErrTooLong {
t.Fatalf("got (%d, %v), expected (%d, %v)", n, err, 0, ErrTooLong)
}
// Padding gets an extra 3 bytes because the prefix is counted as part
// of the length.
enc.Reset()
n, err = WritePadding(&enc, maxLength+3)
if n != maxLength+3 || err != nil {
t.Fatalf("got (%d, %v), expected (%d, %v)", n, err, maxLength+3, nil)
}
// Writing a too-long padding is okay because WritePadding will break it
// into smaller chunks.
enc.Reset()
n, err = WritePadding(&enc, maxLength+4)
if n != maxLength+4 || err != nil {
t.Fatalf("got (%d, %v), expected (%d, %v)", n, err, maxLength+4, nil)
}
}
// Test that WritePadding panics when given a negative length.
func TestNegativeLength(t *testing.T) {
for _, n := range []int{-1, ^0} {
var enc bytes.Buffer
panicked, nn, err := testNegativeLengthSub(t, &enc, n)
if !panicked {
t.Fatalf("WritePadding(%d) returned (%d, %v) instead of panicking", n, nn, err)
}
}
}
// Calls WritePadding(w, n) and augments the return value with a flag indicating
// whether the call panicked.
func testNegativeLengthSub(t *testing.T, w io.Writer, n int) (panicked bool, nn int, err error) {
defer func() {
if r := recover(); r != nil {
panicked = true
}
}()
t.Helper()
nn, err = WritePadding(w, n)
return false, n, err
}
// Test that MaxDataForSize panics when given a 0 length.
func TestMaxDataForSizeZero(t *testing.T) {
defer func() {
if r := recover(); r == nil {
t.Fatal("didn't panic")
}
}()
MaxDataForSize(0)
}
// Test thresholds of available sizes for MaxDataForSize.
func TestMaxDataForSize(t *testing.T) {
for _, test := range []struct {
size int
expected int
}{
{0x01, 0x00},
{0x02, 0x01},
{0x3f, 0x3e},
{0x40, 0x3e},
{0x41, 0x3f},
{0x1fff, 0x1ffd},
{0x2000, 0x1ffd},
{0x2001, 0x1ffe},
{0xfffff, 0xffffc},
{0x100000, 0xffffc},
{0x100001, 0xffffc},
{0x7fffffff, 0xffffc},
} {
max := MaxDataForSize(test.size)
if max != test.expected {
t.Fatalf("size %d, got %d, expected %d", test.size, max, test.expected)
}
}
}
