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snappy_test.go
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snappy_test.go
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// Copyright 2011 The Snappy-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 snappy
import (
"bytes"
"encoding/binary"
"flag"
"fmt"
"io"
"io/ioutil"
"math/rand"
"net/http"
"os"
"os/exec"
"path/filepath"
"runtime"
"strings"
"testing"
)
var (
download = flag.Bool("download", false, "If true, download any missing files before running benchmarks")
testdataDir = flag.String("testdataDir", "testdata", "Directory containing the test data")
benchdataDir = flag.String("benchdataDir", "testdata/bench", "Directory containing the benchmark data")
)
// goEncoderShouldMatchCppEncoder is whether to test that the algorithm used by
// Go's encoder matches byte-for-byte what the C++ snappy encoder produces, on
// this GOARCH. There is more than one valid encoding of any given input, and
// there is more than one good algorithm along the frontier of trading off
// throughput for output size. Nonetheless, we presume that the C++ encoder's
// algorithm is a good one and has been tested on a wide range of inputs, so
// matching that exactly should mean that the Go encoder's algorithm is also
// good, without needing to gather our own corpus of test data.
//
// The exact algorithm used by the C++ code is potentially endian dependent, as
// it puns a byte pointer to a uint32 pointer to load, hash and compare 4 bytes
// at a time. The Go implementation is endian agnostic, in that its output is
// the same (as little-endian C++ code), regardless of the CPU's endianness.
//
// Thus, when comparing Go's output to C++ output generated beforehand, such as
// the "testdata/pi.txt.rawsnappy" file generated by C++ code on a little-
// endian system, we can run that test regardless of the runtime.GOARCH value.
//
// When comparing Go's output to dynamically generated C++ output, i.e. the
// result of fork/exec'ing a C++ program, we can run that test only on
// little-endian systems, because the C++ output might be different on
// big-endian systems. The runtime package doesn't export endianness per se,
// but we can restrict this match-C++ test to common little-endian systems.
const goEncoderShouldMatchCppEncoder = runtime.GOARCH == "386" || runtime.GOARCH == "amd64" || runtime.GOARCH == "arm"
func TestMaxEncodedLenOfMaxBlockSize(t *testing.T) {
got := maxEncodedLenOfMaxBlockSize
want := MaxEncodedLen(maxBlockSize)
if got != want {
t.Fatalf("got %d, want %d", got, want)
}
}
func cmp(a, b []byte) error {
if bytes.Equal(a, b) {
return nil
}
if len(a) != len(b) {
return fmt.Errorf("got %d bytes, want %d", len(a), len(b))
}
for i := range a {
if a[i] != b[i] {
return fmt.Errorf("byte #%d: got 0x%02x, want 0x%02x", i, a[i], b[i])
}
}
return nil
}
func roundtrip(b, ebuf, dbuf []byte) error {
d, err := Decode(dbuf, Encode(ebuf, b))
if err != nil {
return fmt.Errorf("decoding error: %v", err)
}
if err := cmp(d, b); err != nil {
return fmt.Errorf("roundtrip mismatch: %v", err)
}
return nil
}
func TestEmpty(t *testing.T) {
if err := roundtrip(nil, nil, nil); err != nil {
t.Fatal(err)
}
}
func TestSmallCopy(t *testing.T) {
for _, ebuf := range [][]byte{nil, make([]byte, 20), make([]byte, 64)} {
for _, dbuf := range [][]byte{nil, make([]byte, 20), make([]byte, 64)} {
for i := 0; i < 32; i++ {
s := "aaaa" + strings.Repeat("b", i) + "aaaabbbb"
if err := roundtrip([]byte(s), ebuf, dbuf); err != nil {
t.Errorf("len(ebuf)=%d, len(dbuf)=%d, i=%d: %v", len(ebuf), len(dbuf), i, err)
}
}
}
}
}
func TestSmallRand(t *testing.T) {
rng := rand.New(rand.NewSource(1))
for n := 1; n < 20000; n += 23 {
b := make([]byte, n)
for i := range b {
b[i] = uint8(rng.Intn(256))
}
if err := roundtrip(b, nil, nil); err != nil {
t.Fatal(err)
}
}
}
func TestSmallRegular(t *testing.T) {
for n := 1; n < 20000; n += 23 {
b := make([]byte, n)
for i := range b {
b[i] = uint8(i%10 + 'a')
}
if err := roundtrip(b, nil, nil); err != nil {
t.Fatal(err)
}
}
}
func TestInvalidVarint(t *testing.T) {
testCases := []struct {
desc string
input string
}{{
"invalid varint, final byte has continuation bit set",
"\xff",
}, {
"invalid varint, value overflows uint64",
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\x00",
}, {
// https://github.com/google/snappy/blob/master/format_description.txt
// says that "the stream starts with the uncompressed length [as a
// varint] (up to a maximum of 2^32 - 1)".
"valid varint (as uint64), but value overflows uint32",
"\x80\x80\x80\x80\x10",
}}
for _, tc := range testCases {
input := []byte(tc.input)
if _, err := DecodedLen(input); err != ErrCorrupt {
t.Errorf("%s: DecodedLen: got %v, want ErrCorrupt", tc.desc, err)
}
if _, err := Decode(nil, input); err != ErrCorrupt {
t.Errorf("%s: Decode: got %v, want ErrCorrupt", tc.desc, err)
}
}
}
func TestDecode(t *testing.T) {
lit40Bytes := make([]byte, 40)
for i := range lit40Bytes {
lit40Bytes[i] = byte(i)
}
lit40 := string(lit40Bytes)
testCases := []struct {
desc string
input string
want string
wantErr error
}{{
`decodedLen=0; valid input`,
"\x00",
"",
nil,
}, {
`decodedLen=3; tagLiteral, 0-byte length; length=3; valid input`,
"\x03" + "\x08\xff\xff\xff",
"\xff\xff\xff",
nil,
}, {
`decodedLen=2; tagLiteral, 0-byte length; length=3; not enough dst bytes`,
"\x02" + "\x08\xff\xff\xff",
"",
ErrCorrupt,
}, {
`decodedLen=3; tagLiteral, 0-byte length; length=3; not enough src bytes`,
"\x03" + "\x08\xff\xff",
"",
ErrCorrupt,
}, {
`decodedLen=40; tagLiteral, 0-byte length; length=40; valid input`,
"\x28" + "\x9c" + lit40,
lit40,
nil,
}, {
`decodedLen=1; tagLiteral, 1-byte length; not enough length bytes`,
"\x01" + "\xf0",
"",
ErrCorrupt,
}, {
`decodedLen=3; tagLiteral, 1-byte length; length=3; valid input`,
"\x03" + "\xf0\x02\xff\xff\xff",
"\xff\xff\xff",
nil,
}, {
`decodedLen=1; tagLiteral, 2-byte length; not enough length bytes`,
"\x01" + "\xf4\x00",
"",
ErrCorrupt,
}, {
`decodedLen=3; tagLiteral, 2-byte length; length=3; valid input`,
"\x03" + "\xf4\x02\x00\xff\xff\xff",
"\xff\xff\xff",
nil,
}, {
`decodedLen=1; tagLiteral, 3-byte length; not enough length bytes`,
"\x01" + "\xf8\x00\x00",
"",
ErrCorrupt,
}, {
`decodedLen=3; tagLiteral, 3-byte length; length=3; valid input`,
"\x03" + "\xf8\x02\x00\x00\xff\xff\xff",
"\xff\xff\xff",
nil,
}, {
`decodedLen=1; tagLiteral, 4-byte length; not enough length bytes`,
"\x01" + "\xfc\x00\x00\x00",
"",
ErrCorrupt,
}, {
`decodedLen=1; tagLiteral, 4-byte length; length=3; not enough dst bytes`,
"\x01" + "\xfc\x02\x00\x00\x00\xff\xff\xff",
"",
ErrCorrupt,
}, {
`decodedLen=4; tagLiteral, 4-byte length; length=3; not enough src bytes`,
"\x04" + "\xfc\x02\x00\x00\x00\xff",
"",
ErrCorrupt,
}, {
`decodedLen=3; tagLiteral, 4-byte length; length=3; valid input`,
"\x03" + "\xfc\x02\x00\x00\x00\xff\xff\xff",
"\xff\xff\xff",
nil,
}, {
`decodedLen=4; tagCopy1, 1 extra length|offset byte; not enough extra bytes`,
"\x04" + "\x01",
"",
ErrCorrupt,
}, {
`decodedLen=4; tagCopy2, 2 extra length|offset bytes; not enough extra bytes`,
"\x04" + "\x02\x00",
"",
ErrCorrupt,
}, {
`decodedLen=4; tagCopy4, 4 extra length|offset bytes; not enough extra bytes`,
"\x04" + "\x03\x00\x00\x00",
"",
ErrCorrupt,
}, {
`decodedLen=4; tagLiteral (4 bytes "abcd"); valid input`,
"\x04" + "\x0cabcd",
"abcd",
nil,
}, {
`decodedLen=13; tagLiteral (4 bytes "abcd"); tagCopy1; length=9 offset=4; valid input`,
"\x0d" + "\x0cabcd" + "\x15\x04",
"abcdabcdabcda",
nil,
}, {
`decodedLen=8; tagLiteral (4 bytes "abcd"); tagCopy1; length=4 offset=4; valid input`,
"\x08" + "\x0cabcd" + "\x01\x04",
"abcdabcd",
nil,
}, {
`decodedLen=8; tagLiteral (4 bytes "abcd"); tagCopy1; length=4 offset=2; valid input`,
"\x08" + "\x0cabcd" + "\x01\x02",
"abcdcdcd",
nil,
}, {
`decodedLen=8; tagLiteral (4 bytes "abcd"); tagCopy1; length=4 offset=1; valid input`,
"\x08" + "\x0cabcd" + "\x01\x01",
"abcddddd",
nil,
}, {
`decodedLen=8; tagLiteral (4 bytes "abcd"); tagCopy1; length=4 offset=0; zero offset`,
"\x08" + "\x0cabcd" + "\x01\x00",
"",
ErrCorrupt,
}, {
`decodedLen=9; tagLiteral (4 bytes "abcd"); tagCopy1; length=4 offset=4; inconsistent dLen`,
"\x09" + "\x0cabcd" + "\x01\x04",
"",
ErrCorrupt,
}, {
`decodedLen=8; tagLiteral (4 bytes "abcd"); tagCopy1; length=4 offset=5; offset too large`,
"\x08" + "\x0cabcd" + "\x01\x05",
"",
ErrCorrupt,
}, {
`decodedLen=7; tagLiteral (4 bytes "abcd"); tagCopy1; length=4 offset=4; length too large`,
"\x07" + "\x0cabcd" + "\x01\x04",
"",
ErrCorrupt,
}, {
`decodedLen=6; tagLiteral (4 bytes "abcd"); tagCopy2; length=2 offset=3; valid input`,
"\x06" + "\x0cabcd" + "\x06\x03\x00",
"abcdbc",
nil,
}, {
`decodedLen=6; tagLiteral (4 bytes "abcd"); tagCopy4; length=2 offset=3; valid input`,
"\x06" + "\x0cabcd" + "\x07\x03\x00\x00\x00",
"abcdbc",
nil,
}}
const (
// notPresentXxx defines a range of byte values [0xa0, 0xc5) that are
// not present in either the input or the output. It is written to dBuf
// to check that Decode does not write bytes past the end of
// dBuf[:dLen].
//
// The magic number 37 was chosen because it is prime. A more 'natural'
// number like 32 might lead to a false negative if, for example, a
// byte was incorrectly copied 4*8 bytes later.
notPresentBase = 0xa0
notPresentLen = 37
)
var dBuf [100]byte
loop:
for i, tc := range testCases {
input := []byte(tc.input)
for _, x := range input {
if notPresentBase <= x && x < notPresentBase+notPresentLen {
t.Errorf("#%d (%s): input shouldn't contain %#02x\ninput: % x", i, tc.desc, x, input)
continue loop
}
}
dLen, n := binary.Uvarint(input)
if n <= 0 {
t.Errorf("#%d (%s): invalid varint-encoded dLen", i, tc.desc)
continue
}
if dLen > uint64(len(dBuf)) {
t.Errorf("#%d (%s): dLen %d is too large", i, tc.desc, dLen)
continue
}
for j := range dBuf {
dBuf[j] = byte(notPresentBase + j%notPresentLen)
}
g, gotErr := Decode(dBuf[:], input)
if got := string(g); got != tc.want || gotErr != tc.wantErr {
t.Errorf("#%d (%s):\ngot %q, %v\nwant %q, %v",
i, tc.desc, got, gotErr, tc.want, tc.wantErr)
continue
}
for j, x := range dBuf {
if uint64(j) < dLen {
continue
}
if w := byte(notPresentBase + j%notPresentLen); x != w {
t.Errorf("#%d (%s): Decode overrun: dBuf[%d] was modified: got %#02x, want %#02x\ndBuf: % x",
i, tc.desc, j, x, w, dBuf)
continue loop
}
}
}
}
func TestDecodeCopy4(t *testing.T) {
dots := strings.Repeat(".", 65536)
input := strings.Join([]string{
"\x89\x80\x04", // decodedLen = 65545.
"\x0cpqrs", // 4-byte literal "pqrs".
"\xf4\xff\xff" + dots, // 65536-byte literal dots.
"\x13\x04\x00\x01\x00", // tagCopy4; length=5 offset=65540.
}, "")
gotBytes, err := Decode(nil, []byte(input))
if err != nil {
t.Fatal(err)
}
got := string(gotBytes)
want := "pqrs" + dots + "pqrs."
if len(got) != len(want) {
t.Fatalf("got %d bytes, want %d", len(got), len(want))
}
if got != want {
for i := 0; i < len(got); i++ {
if g, w := got[i], want[i]; g != w {
t.Fatalf("byte #%d: got %#02x, want %#02x", i, g, w)
}
}
}
}
// TestDecodeLengthOffset tests decoding an encoding of the form literal +
// copy-length-offset + literal. For example: "abcdefghijkl" + "efghij" + "AB".
func TestDecodeLengthOffset(t *testing.T) {
const (
prefix = "abcdefghijklmnopqr"
suffix = "ABCDEFGHIJKLMNOPQR"
// notPresentXxx defines a range of byte values [0xa0, 0xc5) that are
// not present in either the input or the output. It is written to
// gotBuf to check that Decode does not write bytes past the end of
// gotBuf[:totalLen].
//
// The magic number 37 was chosen because it is prime. A more 'natural'
// number like 32 might lead to a false negative if, for example, a
// byte was incorrectly copied 4*8 bytes later.
notPresentBase = 0xa0
notPresentLen = 37
)
var gotBuf, wantBuf, inputBuf [128]byte
for length := 1; length <= 18; length++ {
for offset := 1; offset <= 18; offset++ {
loop:
for suffixLen := 0; suffixLen <= 18; suffixLen++ {
totalLen := len(prefix) + length + suffixLen
inputLen := binary.PutUvarint(inputBuf[:], uint64(totalLen))
inputBuf[inputLen] = tagLiteral + 4*byte(len(prefix)-1)
inputLen++
inputLen += copy(inputBuf[inputLen:], prefix)
inputBuf[inputLen+0] = tagCopy2 + 4*byte(length-1)
inputBuf[inputLen+1] = byte(offset)
inputBuf[inputLen+2] = 0x00
inputLen += 3
if suffixLen > 0 {
inputBuf[inputLen] = tagLiteral + 4*byte(suffixLen-1)
inputLen++
inputLen += copy(inputBuf[inputLen:], suffix[:suffixLen])
}
input := inputBuf[:inputLen]
for i := range gotBuf {
gotBuf[i] = byte(notPresentBase + i%notPresentLen)
}
got, err := Decode(gotBuf[:], input)
if err != nil {
t.Errorf("length=%d, offset=%d; suffixLen=%d: %v", length, offset, suffixLen, err)
continue
}
wantLen := 0
wantLen += copy(wantBuf[wantLen:], prefix)
for i := 0; i < length; i++ {
wantBuf[wantLen] = wantBuf[wantLen-offset]
wantLen++
}
wantLen += copy(wantBuf[wantLen:], suffix[:suffixLen])
want := wantBuf[:wantLen]
for _, x := range input {
if notPresentBase <= x && x < notPresentBase+notPresentLen {
t.Errorf("length=%d, offset=%d; suffixLen=%d: input shouldn't contain %#02x\ninput: % x",
length, offset, suffixLen, x, input)
continue loop
}
}
for i, x := range gotBuf {
if i < totalLen {
continue
}
if w := byte(notPresentBase + i%notPresentLen); x != w {
t.Errorf("length=%d, offset=%d; suffixLen=%d; totalLen=%d: "+
"Decode overrun: gotBuf[%d] was modified: got %#02x, want %#02x\ngotBuf: % x",
length, offset, suffixLen, totalLen, i, x, w, gotBuf)
continue loop
}
}
for _, x := range want {
if notPresentBase <= x && x < notPresentBase+notPresentLen {
t.Errorf("length=%d, offset=%d; suffixLen=%d: want shouldn't contain %#02x\nwant: % x",
length, offset, suffixLen, x, want)
continue loop
}
}
if !bytes.Equal(got, want) {
t.Errorf("length=%d, offset=%d; suffixLen=%d:\ninput % x\ngot % x\nwant % x",
length, offset, suffixLen, input, got, want)
continue
}
}
}
}
}
const (
goldenText = "Mark.Twain-Tom.Sawyer.txt"
goldenCompressed = goldenText + ".rawsnappy"
)
func TestDecodeGoldenInput(t *testing.T) {
tDir := filepath.FromSlash(*testdataDir)
src, err := ioutil.ReadFile(filepath.Join(tDir, goldenCompressed))
if err != nil {
t.Fatalf("ReadFile: %v", err)
}
got, err := Decode(nil, src)
if err != nil {
t.Fatalf("Decode: %v", err)
}
want, err := ioutil.ReadFile(filepath.Join(tDir, goldenText))
if err != nil {
t.Fatalf("ReadFile: %v", err)
}
if err := cmp(got, want); err != nil {
t.Fatal(err)
}
}
func TestEncodeGoldenInput(t *testing.T) {
tDir := filepath.FromSlash(*testdataDir)
src, err := ioutil.ReadFile(filepath.Join(tDir, goldenText))
if err != nil {
t.Fatalf("ReadFile: %v", err)
}
got := Encode(nil, src)
want, err := ioutil.ReadFile(filepath.Join(tDir, goldenCompressed))
if err != nil {
t.Fatalf("ReadFile: %v", err)
}
if err := cmp(got, want); err != nil {
t.Fatal(err)
}
}
func TestExtendMatchGoldenInput(t *testing.T) {
tDir := filepath.FromSlash(*testdataDir)
src, err := ioutil.ReadFile(filepath.Join(tDir, goldenText))
if err != nil {
t.Fatalf("ReadFile: %v", err)
}
for i, tc := range extendMatchGoldenTestCases {
got := extendMatch(src, tc.i, tc.j)
if got != tc.want {
t.Errorf("test #%d: i, j = %5d, %5d: got %5d (= j + %6d), want %5d (= j + %6d)",
i, tc.i, tc.j, got, got-tc.j, tc.want, tc.want-tc.j)
}
}
}
func TestExtendMatch(t *testing.T) {
// ref is a simple, reference implementation of extendMatch.
ref := func(src []byte, i, j int) int {
for ; j < len(src) && src[i] == src[j]; i, j = i+1, j+1 {
}
return j
}
nums := []int{0, 1, 2, 7, 8, 9, 29, 30, 31, 32, 33, 34, 38, 39, 40}
for yIndex := 40; yIndex > 30; yIndex-- {
xxx := bytes.Repeat([]byte("x"), 40)
if yIndex < len(xxx) {
xxx[yIndex] = 'y'
}
for _, i := range nums {
for _, j := range nums {
if i >= j {
continue
}
got := extendMatch(xxx, i, j)
want := ref(xxx, i, j)
if got != want {
t.Errorf("yIndex=%d, i=%d, j=%d: got %d, want %d", yIndex, i, j, got, want)
}
}
}
}
}
const snappytoolCmdName = "cmd/snappytool/snappytool"
func skipTestSameEncodingAsCpp() (msg string) {
if !goEncoderShouldMatchCppEncoder {
return fmt.Sprintf("skipping testing that the encoding is byte-for-byte identical to C++: GOARCH=%s", runtime.GOARCH)
}
if _, err := os.Stat(snappytoolCmdName); err != nil {
return fmt.Sprintf("could not find snappytool: %v", err)
}
return ""
}
func runTestSameEncodingAsCpp(src []byte) error {
got := Encode(nil, src)
cmd := exec.Command(snappytoolCmdName, "-e")
cmd.Stdin = bytes.NewReader(src)
want, err := cmd.Output()
if err != nil {
return fmt.Errorf("could not run snappytool: %v", err)
}
return cmp(got, want)
}
func TestSameEncodingAsCppShortCopies(t *testing.T) {
if msg := skipTestSameEncodingAsCpp(); msg != "" {
t.Skip(msg)
}
src := bytes.Repeat([]byte{'a'}, 20)
for i := 0; i <= len(src); i++ {
if err := runTestSameEncodingAsCpp(src[:i]); err != nil {
t.Errorf("i=%d: %v", i, err)
}
}
}
func TestSameEncodingAsCppLongFiles(t *testing.T) {
if msg := skipTestSameEncodingAsCpp(); msg != "" {
t.Skip(msg)
}
bDir := filepath.FromSlash(*benchdataDir)
failed := false
for i, tf := range testFiles {
if err := downloadBenchmarkFiles(t, tf.filename); err != nil {
t.Fatalf("failed to download testdata: %s", err)
}
data := readFile(t, filepath.Join(bDir, tf.filename))
if n := tf.sizeLimit; 0 < n && n < len(data) {
data = data[:n]
}
if err := runTestSameEncodingAsCpp(data); err != nil {
t.Errorf("i=%d: %v", i, err)
failed = true
}
}
if failed {
t.Errorf("was the snappytool program built against the C++ snappy library version " +
"d53de187 or later, commited on 2016-04-05? See " +
"https://github.com/google/snappy/commit/d53de18799418e113e44444252a39b12a0e4e0cc")
}
}
// TestSlowForwardCopyOverrun tests the "expand the pattern" algorithm
// described in decode_amd64.s and its claim of a 10 byte overrun worst case.
func TestSlowForwardCopyOverrun(t *testing.T) {
const base = 100
for length := 1; length < 18; length++ {
for offset := 1; offset < 18; offset++ {
highWaterMark := base
d := base
l := length
o := offset
// makeOffsetAtLeast8
for o < 8 {
if end := d + 8; highWaterMark < end {
highWaterMark = end
}
l -= o
d += o
o += o
}
// fixUpSlowForwardCopy
a := d
d += l
// finishSlowForwardCopy
for l > 0 {
if end := a + 8; highWaterMark < end {
highWaterMark = end
}
a += 8
l -= 8
}
dWant := base + length
overrun := highWaterMark - dWant
if d != dWant || overrun < 0 || 10 < overrun {
t.Errorf("length=%d, offset=%d: d and overrun: got (%d, %d), want (%d, something in [0, 10])",
length, offset, d, overrun, dWant)
}
}
}
}
// TestEncodeNoiseThenRepeats encodes input for which the first half is very
// incompressible and the second half is very compressible. The encoded form's
// length should be closer to 50% of the original length than 100%.
func TestEncodeNoiseThenRepeats(t *testing.T) {
for _, origLen := range []int{256 * 1024, 2048 * 1024} {
src := make([]byte, origLen)
rng := rand.New(rand.NewSource(1))
firstHalf, secondHalf := src[:origLen/2], src[origLen/2:]
for i := range firstHalf {
firstHalf[i] = uint8(rng.Intn(256))
}
for i := range secondHalf {
secondHalf[i] = uint8(i >> 8)
}
dst := Encode(nil, src)
if got, want := len(dst), origLen*3/4; got >= want {
t.Errorf("origLen=%d: got %d encoded bytes, want less than %d", origLen, got, want)
}
}
}
func TestFramingFormat(t *testing.T) {
// src is comprised of alternating 1e5-sized sequences of random
// (incompressible) bytes and repeated (compressible) bytes. 1e5 was chosen
// because it is larger than maxBlockSize (64k).
src := make([]byte, 1e6)
rng := rand.New(rand.NewSource(1))
for i := 0; i < 10; i++ {
if i%2 == 0 {
for j := 0; j < 1e5; j++ {
src[1e5*i+j] = uint8(rng.Intn(256))
}
} else {
for j := 0; j < 1e5; j++ {
src[1e5*i+j] = uint8(i)
}
}
}
buf := new(bytes.Buffer)
if _, err := NewWriter(buf).Write(src); err != nil {
t.Fatalf("Write: encoding: %v", err)
}
dst, err := ioutil.ReadAll(NewReader(buf))
if err != nil {
t.Fatalf("ReadAll: decoding: %v", err)
}
if err := cmp(dst, src); err != nil {
t.Fatal(err)
}
}
func TestWriterGoldenOutput(t *testing.T) {
buf := new(bytes.Buffer)
w := NewBufferedWriter(buf)
defer w.Close()
w.Write([]byte("abcd")) // Not compressible.
w.Flush()
w.Write(bytes.Repeat([]byte{'A'}, 150)) // Compressible.
w.Flush()
// The next chunk is also compressible, but a naive, greedy encoding of the
// overall length 67 copy as a length 64 copy (the longest expressible as a
// tagCopy1 or tagCopy2) plus a length 3 remainder would be two 3-byte
// tagCopy2 tags (6 bytes), since the minimum length for a tagCopy1 is 4
// bytes. Instead, we could do it shorter, in 5 bytes: a 3-byte tagCopy2
// (of length 60) and a 2-byte tagCopy1 (of length 7).
w.Write(bytes.Repeat([]byte{'B'}, 68))
w.Write([]byte("efC")) // Not compressible.
w.Write(bytes.Repeat([]byte{'C'}, 20)) // Compressible.
w.Write(bytes.Repeat([]byte{'B'}, 20)) // Compressible.
w.Write([]byte("g")) // Not compressible.
w.Flush()
got := buf.String()
want := strings.Join([]string{
magicChunk,
"\x01\x08\x00\x00", // Uncompressed chunk, 8 bytes long (including 4 byte checksum).
"\x68\x10\xe6\xb6", // Checksum.
"\x61\x62\x63\x64", // Uncompressed payload: "abcd".
"\x00\x11\x00\x00", // Compressed chunk, 17 bytes long (including 4 byte checksum).
"\x5f\xeb\xf2\x10", // Checksum.
"\x96\x01", // Compressed payload: Uncompressed length (varint encoded): 150.
"\x00\x41", // Compressed payload: tagLiteral, length=1, "A".
"\xfe\x01\x00", // Compressed payload: tagCopy2, length=64, offset=1.
"\xfe\x01\x00", // Compressed payload: tagCopy2, length=64, offset=1.
"\x52\x01\x00", // Compressed payload: tagCopy2, length=21, offset=1.
"\x00\x18\x00\x00", // Compressed chunk, 24 bytes long (including 4 byte checksum).
"\x30\x85\x69\xeb", // Checksum.
"\x70", // Compressed payload: Uncompressed length (varint encoded): 112.
"\x00\x42", // Compressed payload: tagLiteral, length=1, "B".
"\xee\x01\x00", // Compressed payload: tagCopy2, length=60, offset=1.
"\x0d\x01", // Compressed payload: tagCopy1, length=7, offset=1.
"\x08\x65\x66\x43", // Compressed payload: tagLiteral, length=3, "efC".
"\x4e\x01\x00", // Compressed payload: tagCopy2, length=20, offset=1.
"\x4e\x5a\x00", // Compressed payload: tagCopy2, length=20, offset=90.
"\x00\x67", // Compressed payload: tagLiteral, length=1, "g".
}, "")
if got != want {
t.Fatalf("\ngot: % x\nwant: % x", got, want)
}
}
func TestEmitLiteral(t *testing.T) {
testCases := []struct {
length int
want string
}{
{1, "\x00"},
{2, "\x04"},
{59, "\xe8"},
{60, "\xec"},
{61, "\xf0\x3c"},
{62, "\xf0\x3d"},
{254, "\xf0\xfd"},
{255, "\xf0\xfe"},
{256, "\xf0\xff"},
{257, "\xf4\x00\x01"},
{65534, "\xf4\xfd\xff"},
{65535, "\xf4\xfe\xff"},
{65536, "\xf4\xff\xff"},
}
dst := make([]byte, 70000)
nines := bytes.Repeat([]byte{0x99}, 65536)
for _, tc := range testCases {
lit := nines[:tc.length]
n := emitLiteral(dst, lit)
if !bytes.HasSuffix(dst[:n], lit) {
t.Errorf("length=%d: did not end with that many literal bytes", tc.length)
continue
}
got := string(dst[:n-tc.length])
if got != tc.want {
t.Errorf("length=%d:\ngot % x\nwant % x", tc.length, got, tc.want)
continue
}
}
}
func TestEmitCopy(t *testing.T) {
testCases := []struct {
offset int
length int
want string
}{
{8, 04, "\x01\x08"},
{8, 11, "\x1d\x08"},
{8, 12, "\x2e\x08\x00"},
{8, 13, "\x32\x08\x00"},
{8, 59, "\xea\x08\x00"},
{8, 60, "\xee\x08\x00"},
{8, 61, "\xf2\x08\x00"},
{8, 62, "\xf6\x08\x00"},
{8, 63, "\xfa\x08\x00"},
{8, 64, "\xfe\x08\x00"},
{8, 65, "\xee\x08\x00\x05\x08"},
{8, 66, "\xee\x08\x00\x09\x08"},
{8, 67, "\xee\x08\x00\x0d\x08"},
{8, 68, "\xfe\x08\x00\x01\x08"},
{8, 69, "\xfe\x08\x00\x05\x08"},
{8, 80, "\xfe\x08\x00\x3e\x08\x00"},
{256, 04, "\x21\x00"},
{256, 11, "\x3d\x00"},
{256, 12, "\x2e\x00\x01"},
{256, 13, "\x32\x00\x01"},
{256, 59, "\xea\x00\x01"},
{256, 60, "\xee\x00\x01"},
{256, 61, "\xf2\x00\x01"},
{256, 62, "\xf6\x00\x01"},
{256, 63, "\xfa\x00\x01"},
{256, 64, "\xfe\x00\x01"},
{256, 65, "\xee\x00\x01\x25\x00"},
{256, 66, "\xee\x00\x01\x29\x00"},
{256, 67, "\xee\x00\x01\x2d\x00"},
{256, 68, "\xfe\x00\x01\x21\x00"},
{256, 69, "\xfe\x00\x01\x25\x00"},
{256, 80, "\xfe\x00\x01\x3e\x00\x01"},
{2048, 04, "\x0e\x00\x08"},
{2048, 11, "\x2a\x00\x08"},
{2048, 12, "\x2e\x00\x08"},
{2048, 13, "\x32\x00\x08"},
{2048, 59, "\xea\x00\x08"},
{2048, 60, "\xee\x00\x08"},
{2048, 61, "\xf2\x00\x08"},
{2048, 62, "\xf6\x00\x08"},
{2048, 63, "\xfa\x00\x08"},
{2048, 64, "\xfe\x00\x08"},
{2048, 65, "\xee\x00\x08\x12\x00\x08"},
{2048, 66, "\xee\x00\x08\x16\x00\x08"},
{2048, 67, "\xee\x00\x08\x1a\x00\x08"},
{2048, 68, "\xfe\x00\x08\x0e\x00\x08"},
{2048, 69, "\xfe\x00\x08\x12\x00\x08"},
{2048, 80, "\xfe\x00\x08\x3e\x00\x08"},
}
dst := make([]byte, 1024)
for _, tc := range testCases {
n := emitCopy(dst, tc.offset, tc.length)
got := string(dst[:n])
if got != tc.want {
t.Errorf("offset=%d, length=%d:\ngot % x\nwant % x", tc.offset, tc.length, got, tc.want)
}
}
}
func TestNewBufferedWriter(t *testing.T) {
// Test all 32 possible sub-sequences of these 5 input slices.
//
// Their lengths sum to 400,000, which is over 6 times the Writer ibuf
// capacity: 6 * maxBlockSize is 393,216.
inputs := [][]byte{
bytes.Repeat([]byte{'a'}, 40000),
bytes.Repeat([]byte{'b'}, 150000),
bytes.Repeat([]byte{'c'}, 60000),
bytes.Repeat([]byte{'d'}, 120000),
bytes.Repeat([]byte{'e'}, 30000),
}
loop:
for i := 0; i < 1<<uint(len(inputs)); i++ {
var want []byte
buf := new(bytes.Buffer)
w := NewBufferedWriter(buf)
for j, input := range inputs {
if i&(1<<uint(j)) == 0 {
continue
}
if _, err := w.Write(input); err != nil {
t.Errorf("i=%#02x: j=%d: Write: %v", i, j, err)
continue loop
}
want = append(want, input...)
}
if err := w.Close(); err != nil {
t.Errorf("i=%#02x: Close: %v", i, err)
continue
}
got, err := ioutil.ReadAll(NewReader(buf))
if err != nil {
t.Errorf("i=%#02x: ReadAll: %v", i, err)
continue
}
if err := cmp(got, want); err != nil {
t.Errorf("i=%#02x: %v", i, err)
continue
}
}
}
func TestFlush(t *testing.T) {
buf := new(bytes.Buffer)
w := NewBufferedWriter(buf)
defer w.Close()
if _, err := w.Write(bytes.Repeat([]byte{'x'}, 20)); err != nil {
t.Fatalf("Write: %v", err)
}
if n := buf.Len(); n != 0 {
t.Fatalf("before Flush: %d bytes were written to the underlying io.Writer, want 0", n)
}
if err := w.Flush(); err != nil {
t.Fatalf("Flush: %v", err)
}
if n := buf.Len(); n == 0 {
t.Fatalf("after Flush: %d bytes were written to the underlying io.Writer, want non-0", n)
}
}
func TestReaderUncompressedDataOK(t *testing.T) {
r := NewReader(strings.NewReader(magicChunk +
"\x01\x08\x00\x00" + // Uncompressed chunk, 8 bytes long (including 4 byte checksum).
"\x68\x10\xe6\xb6" + // Checksum.
"\x61\x62\x63\x64", // Uncompressed payload: "abcd".
))
g, err := ioutil.ReadAll(r)
if err != nil {
t.Fatal(err)
}
if got, want := string(g), "abcd"; got != want {
t.Fatalf("got %q, want %q", got, want)
}
}
func TestReaderUncompressedDataNoPayload(t *testing.T) {
r := NewReader(strings.NewReader(magicChunk +
"\x01\x04\x00\x00" + // Uncompressed chunk, 4 bytes long.
"", // No payload; corrupt input.
))
if _, err := ioutil.ReadAll(r); err != ErrCorrupt {
t.Fatalf("got %v, want %v", err, ErrCorrupt)
}
}
func TestReaderUncompressedDataTooLong(t *testing.T) {
// https://github.com/google/snappy/blob/master/framing_format.txt section
// 4.3 says that "the maximum legal chunk length... is 65540", or 0x10004.
const n = 0x10005
r := NewReader(strings.NewReader(magicChunk +
"\x01\x05\x00\x01" + // Uncompressed chunk, n bytes long.
strings.Repeat("\x00", n),
))
if _, err := ioutil.ReadAll(r); err != ErrCorrupt {
t.Fatalf("got %v, want %v", err, ErrCorrupt)
}
}
func TestReaderReset(t *testing.T) {
gold := bytes.Repeat([]byte("All that is gold does not glitter,\n"), 10000)
buf := new(bytes.Buffer)
if _, err := NewWriter(buf).Write(gold); err != nil {