mirror of
https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake.git
synced 2025-10-13 11:11:30 -04:00
d99f31d881
https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/merge_requests/154#note_2919109 Still ignoring the io.ErrShortBuffer at the callers, which retains current behavior.
408 lines
12 KiB
Go
408 lines
12 KiB
Go
package encapsulation
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import (
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"bytes"
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"io"
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"math/rand"
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"testing"
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)
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// Return a byte slice with non-trivial contents.
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func pseudorandomBuffer(n int) []byte {
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source := rand.NewSource(0)
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p := make([]byte, n)
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for i := 0; i < len(p); i++ {
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p[i] = byte(source.Int63() & 0xff)
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}
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return p
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}
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func mustWriteData(w io.Writer, p []byte) int {
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n, err := WriteData(w, p)
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if err != nil {
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panic(err)
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}
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return n
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}
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func mustWritePadding(w io.Writer, n int) int {
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n, err := WritePadding(w, n)
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if err != nil {
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panic(err)
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}
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return n
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}
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// Test that ReadData(WriteData()) recovers the original data.
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func TestRoundtrip(t *testing.T) {
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// Test above and below interesting thresholds.
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for _, i := range []int{
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0x00, 0x01,
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0x3e, 0x3f, 0x40, 0x41,
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0xfe, 0xff, 0x100, 0x101,
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0x1ffe, 0x1fff, 0x2000, 0x2001,
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0xfffe, 0xffff, 0x10000, 0x10001,
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0xffffe, 0xfffff,
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} {
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original := pseudorandomBuffer(i)
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var enc bytes.Buffer
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n, err := WriteData(&enc, original)
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if err != nil {
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t.Fatalf("size %d, WriteData returned error %v", i, err)
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}
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if enc.Len() != n {
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t.Fatalf("size %d, returned length was %d, written length was %d",
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i, n, enc.Len())
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}
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inverse := make([]byte, i)
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n, err = ReadData(&enc, inverse)
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if err != nil {
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t.Fatalf("size %d, ReadData returned error %v", i, err)
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}
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if !bytes.Equal(inverse[:n], original) {
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t.Fatalf("size %d, got <%x>, expected <%x>", i, inverse[:n], original)
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}
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}
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}
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// Test that WritePadding writes exactly as much as requested.
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func TestPaddingLength(t *testing.T) {
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// Test above and below interesting thresholds. WritePadding also gets
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// values above 0xfffff, the maximum value of a single length prefix.
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for _, i := range []int{
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0x00, 0x01,
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0x3f, 0x40, 0x41, 0x42,
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0xff, 0x100, 0x101, 0x102,
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0x2000, 0x2001, 0x2002, 0x2003,
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0x10000, 0x10001, 0x10002, 0x10003,
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0x100001, 0x100002, 0x100003, 0x100004,
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} {
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var enc bytes.Buffer
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n, err := WritePadding(&enc, i)
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if err != nil {
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t.Fatalf("size %d, WritePadding returned error %v", i, err)
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}
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if n != i {
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t.Fatalf("requested %d bytes, returned %d", i, n)
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}
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if enc.Len() != n {
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t.Fatalf("requested %d bytes, wrote %d bytes", i, enc.Len())
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}
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}
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}
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// Test that ReadData skips over padding.
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func TestSkipPadding(t *testing.T) {
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var data = [][]byte{{}, {}, []byte("hello"), {}, []byte("world")}
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var enc bytes.Buffer
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mustWritePadding(&enc, 10)
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mustWritePadding(&enc, 100)
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mustWriteData(&enc, data[0])
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mustWriteData(&enc, data[1])
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mustWritePadding(&enc, 10)
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mustWriteData(&enc, data[2])
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mustWriteData(&enc, data[3])
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mustWritePadding(&enc, 10)
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mustWriteData(&enc, data[4])
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mustWritePadding(&enc, 10)
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mustWritePadding(&enc, 10)
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for i, expected := range data {
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var actual [10]byte
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n, err := ReadData(&enc, actual[:])
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if err != nil {
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t.Fatalf("slice %d, got error %v, expected %v", i, err, nil)
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}
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if !bytes.Equal(actual[:n], expected) {
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t.Fatalf("slice %d, got <%x>, expected <%x>", i, actual[:n], expected)
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}
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}
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n, err := ReadData(&enc, nil)
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if n != 0 || err != io.EOF {
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t.Fatalf("got (%v, %v), expected (%v, %v)", n, err, 0, io.EOF)
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}
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}
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// Test that EOF before a length prefix returns io.EOF.
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func TestEOF(t *testing.T) {
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n, err := ReadData(bytes.NewReader(nil), nil)
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if n != 0 || err != io.EOF {
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t.Fatalf("got (%v, %v), expected (%v, %v)", n, err, 0, io.EOF)
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}
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}
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// Test that an EOF while reading a length prefix, or while reading the
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// subsequent data/padding, returns io.ErrUnexpectedEOF.
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func TestUnexpectedEOF(t *testing.T) {
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for _, test := range [][]byte{
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{0x40}, // expecting a second length byte
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{0xc0}, // expecting a second length byte
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{0x41, 0x80}, // expecting a third length byte
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{0xc1, 0x80}, // expecting a third length byte
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{0x02}, // expecting 2 bytes of padding
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{0x82}, // expecting 2 bytes of data
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{0x02, 'X'}, // expecting 1 byte of padding
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{0x82, 'X'}, // expecting 1 byte of data
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{0x41, 0x00}, // expecting 128 bytes of padding
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{0xc1, 0x00}, // expecting 128 bytes of data
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{0x41, 0x00, 'X'}, // expecting 127 bytes of padding
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{0xc1, 0x00, 'X'}, // expecting 127 bytes of data
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{0x41, 0x80, 0x00}, // expecting 32768 bytes of padding
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{0xc1, 0x80, 0x00}, // expecting 32768 bytes of data
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{0x41, 0x80, 0x00, 'X'}, // expecting 32767 bytes of padding
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{0xc1, 0x80, 0x00, 'X'}, // expecting 32767 bytes of data
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} {
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n, err := ReadData(bytes.NewReader(test), nil)
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if n != 0 || err != io.ErrUnexpectedEOF {
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t.Fatalf("<%x> got (%v, %v), expected (%v, %v)", test, n, err, 0, io.ErrUnexpectedEOF)
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}
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}
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}
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// Test that length encodings that are longer than they could be are still
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// interpreted.
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func TestNonMinimalLengthEncoding(t *testing.T) {
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for _, test := range []struct {
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enc []byte
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expected []byte
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}{
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{[]byte{0x81, 'X'}, []byte("X")},
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{[]byte{0xc0, 0x01, 'X'}, []byte("X")},
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{[]byte{0xc0, 0x80, 0x01, 'X'}, []byte("X")},
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} {
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var p [10]byte
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n, err := ReadData(bytes.NewReader(test.enc), p[:])
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if err != nil {
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t.Fatalf("<%x> got error %v, expected %v", test.enc, err, nil)
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}
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if !bytes.Equal(p[:n], test.expected) {
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t.Fatalf("<%x> got <%x>, expected <%x>", test.enc, p[:n], test.expected)
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}
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}
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}
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// Test that ReadData only reads up to 3 bytes of length prefix.
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func TestReadLimits(t *testing.T) {
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// Test the maximum length that's possible with 3 bytes of length
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// prefix.
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maxLength := (0x3f << 14) | (0x7f << 7) | 0x7f
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data := bytes.Repeat([]byte{'X'}, maxLength)
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prefix := []byte{0xff, 0xff, 0x7f} // encodes 0xfffff
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var p [0xfffff]byte
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n, err := ReadData(bytes.NewReader(append(prefix, data...)), p[:])
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if err != nil {
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t.Fatalf("got error %v, expected %v", err, nil)
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}
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if !bytes.Equal(p[:n], data) {
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t.Fatalf("got %d bytes unequal to %d bytes", len(p), len(data))
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}
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// Test a 4-byte prefix.
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prefix = []byte{0xc0, 0xc0, 0x80, 0x80} // encodes 0x100000
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data = bytes.Repeat([]byte{'X'}, maxLength+1)
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n, err = ReadData(bytes.NewReader(append(prefix, data...)), nil)
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if n != 0 || err != ErrTooLong {
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t.Fatalf("got (%v, %v), expected (%v, %v)", n, err, 0, ErrTooLong)
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}
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// Test that 4 bytes don't work, even when they encode an integer that
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// would fix in 3 bytes.
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prefix = []byte{0xc0, 0x80, 0x80, 0x80} // encodes 0x0
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data = []byte{}
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n, err = ReadData(bytes.NewReader(append(prefix, data...)), nil)
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if n != 0 || err != ErrTooLong {
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t.Fatalf("got (%v, %v), expected (%v, %v)", n, err, 0, ErrTooLong)
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}
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// Do the same tests with padding lengths.
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data = []byte("hello")
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prefix = []byte{0x7f, 0xff, 0x7f} // encodes 0xfffff
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padding := bytes.Repeat([]byte{'X'}, maxLength)
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enc := bytes.NewBuffer(append(prefix, padding...))
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mustWriteData(enc, data)
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n, err = ReadData(enc, p[:])
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if err != nil {
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t.Fatalf("got error %v, expected %v", err, nil)
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}
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if !bytes.Equal(p[:n], data) {
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t.Fatalf("got <%x>, expected <%x>", p[:n], data)
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}
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prefix = []byte{0x40, 0xc0, 0x80, 0x80} // encodes 0x100000
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padding = bytes.Repeat([]byte{'X'}, maxLength+1)
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enc = bytes.NewBuffer(append(prefix, padding...))
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mustWriteData(enc, data)
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n, err = ReadData(enc, nil)
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if n != 0 || err != ErrTooLong {
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t.Fatalf("got (%v, %v), expected (%v, %v)", n, err, 0, ErrTooLong)
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}
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prefix = []byte{0x40, 0x80, 0x80, 0x80} // encodes 0x0
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padding = []byte{}
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enc = bytes.NewBuffer(append(prefix, padding...))
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mustWriteData(enc, data)
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n, err = ReadData(enc, nil)
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if n != 0 || err != ErrTooLong {
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t.Fatalf("got (%v, %v), expected (%v, %v)", n, err, 0, ErrTooLong)
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}
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}
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// Test that WriteData and WritePadding only accept lengths that can be encoded
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// in up to 3 bytes of length prefix.
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func TestWriteLimits(t *testing.T) {
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maxLength := (0x3f << 14) | (0x7f << 7) | 0x7f
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var enc bytes.Buffer
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n, err := WriteData(&enc, bytes.Repeat([]byte{'X'}, maxLength))
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if n != maxLength+3 || err != nil {
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t.Fatalf("got (%d, %v), expected (%d, %v)", n, err, maxLength, nil)
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}
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enc.Reset()
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n, err = WriteData(&enc, bytes.Repeat([]byte{'X'}, maxLength+1))
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if n != 0 || err != ErrTooLong {
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t.Fatalf("got (%d, %v), expected (%d, %v)", n, err, 0, ErrTooLong)
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}
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// Padding gets an extra 3 bytes because the prefix is counted as part
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// of the length.
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enc.Reset()
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n, err = WritePadding(&enc, maxLength+3)
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if n != maxLength+3 || err != nil {
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t.Fatalf("got (%d, %v), expected (%d, %v)", n, err, maxLength+3, nil)
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}
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// Writing a too-long padding is okay because WritePadding will break it
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// into smaller chunks.
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enc.Reset()
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n, err = WritePadding(&enc, maxLength+4)
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if n != maxLength+4 || err != nil {
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t.Fatalf("got (%d, %v), expected (%d, %v)", n, err, maxLength+4, nil)
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}
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}
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// Test that WritePadding panics when given a negative length.
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func TestNegativeLength(t *testing.T) {
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for _, n := range []int{-1, ^0} {
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var enc bytes.Buffer
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panicked, nn, err := testNegativeLengthSub(t, &enc, n)
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if !panicked {
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t.Fatalf("WritePadding(%d) returned (%d, %v) instead of panicking", n, nn, err)
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}
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}
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}
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// Calls WritePadding(w, n) and augments the return value with a flag indicating
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// whether the call panicked.
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func testNegativeLengthSub(t *testing.T, w io.Writer, n int) (panicked bool, nn int, err error) {
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defer func() {
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if r := recover(); r != nil {
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panicked = true
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}
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}()
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t.Helper()
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nn, err = WritePadding(w, n)
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return false, n, err
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}
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// Test that MaxDataForSize panics when given a 0 length.
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func TestMaxDataForSizeZero(t *testing.T) {
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defer func() {
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if r := recover(); r == nil {
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t.Fatal("didn't panic")
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}
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}()
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MaxDataForSize(0)
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}
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// Test thresholds of available sizes for MaxDataForSize.
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func TestMaxDataForSize(t *testing.T) {
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for _, test := range []struct {
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size int
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expected int
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}{
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{0x01, 0x00},
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{0x02, 0x01},
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{0x3f, 0x3e},
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{0x40, 0x3e},
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{0x41, 0x3f},
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{0x1fff, 0x1ffd},
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{0x2000, 0x1ffd},
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{0x2001, 0x1ffe},
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{0xfffff, 0xffffc},
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{0x100000, 0xffffc},
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{0x100001, 0xffffc},
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{0x7fffffff, 0xffffc},
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} {
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max := MaxDataForSize(test.size)
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if max != test.expected {
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t.Fatalf("size %d, got %d, expected %d", test.size, max, test.expected)
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}
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}
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}
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// Test that ReadData truncates the data when the destination slice is too
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// short.
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func TestReadDataTruncate(t *testing.T) {
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var enc bytes.Buffer
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mustWriteData(&enc, []byte("12345678"))
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mustWriteData(&enc, []byte("abcdefgh"))
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var p [4]byte
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// First ReadData should return truncated "1234".
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n, err := ReadData(&enc, p[:])
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if err != io.ErrShortBuffer {
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t.Fatalf("got error %v, expected %v", err, io.ErrShortBuffer)
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}
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if !bytes.Equal(p[:n], []byte("1234")) {
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t.Fatalf("got <%x>, expected <%x>", p[:n], []byte("1234"))
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}
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// Second ReadData should return truncated "abcd", not the rest of
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// "12345678".
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n, err = ReadData(&enc, p[:])
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if err != io.ErrShortBuffer {
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t.Fatalf("got error %v, expected %v", err, io.ErrShortBuffer)
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}
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if !bytes.Equal(p[:n], []byte("abcd")) {
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t.Fatalf("got <%x>, expected <%x>", p[:n], []byte("abcd"))
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}
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// Last ReadData should give io.EOF.
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n, err = ReadData(&enc, p[:])
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if err != io.EOF {
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t.Fatalf("got error %v, expected %v", err, io.EOF)
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}
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}
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// Test that even when the result is truncated, ReadData fills the provided
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// buffer as much as possible (and not stop at the boundary of an internal Read,
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// say).
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func TestReadDataTruncateFull(t *testing.T) {
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pr, pw := io.Pipe()
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go func() {
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// Send one data chunk that will be delivered across two Read
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// calls.
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pw.Write([]byte{0x8a, 'h', 'e', 'l', 'l', 'o'})
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pw.Write([]byte{'w', 'o', 'r', 'l', 'd'})
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}()
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var p [8]byte
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n, err := ReadData(pr, p[:])
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if err != io.ErrShortBuffer {
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t.Fatalf("got error %v, expected %v", err, io.ErrShortBuffer)
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}
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// Should not stop after "hello".
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if !bytes.Equal(p[:n], []byte("hellowor")) {
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t.Fatalf("got <%x>, expected <%x>", p[:n], []byte("hellowor"))
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}
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}
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// Benchmark the ReadData function when reading from a stream of data packets of
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// different sizes.
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func BenchmarkReadData(b *testing.B) {
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pr, pw := io.Pipe()
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go func() {
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for {
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for length := 0; length < 128; length++ {
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WriteData(pw, paddingBuffer[:length])
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}
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}
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}()
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var p [128]byte
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for i := 0; i < b.N; i++ {
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_, err := ReadData(pr, p[:])
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if err != nil {
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b.Fatal(err)
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}
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}
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}
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