// Copyright 2009 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 bufio_test
import (
. "bufio"
"bytes"
"errors"
"fmt"
"io"
"io/ioutil"
"strings"
"testing"
"testing/iotest"
"time"
"unicode/utf8"
)
// Reads from a reader and rot13s the result.
type rot13Reader struct {
r io.Reader
}
func newRot13Reader(r io.Reader) *rot13Reader {
r13 := new(rot13Reader)
r13.r = r
return r13
}
func (r13 *rot13Reader) Read(p []byte) (int, error) {
n, err := r13.r.Read(p)
for i := 0; i < n; i++ {
c := p[i] | 0x20 // lowercase byte
if 'a' <= c && c <= 'm' {
p[i] += 13
} else if 'n' <= c && c <= 'z' {
p[i] -= 13
}
}
return n, err
}
// Call ReadByte to accumulate the text of a file
func readBytes(buf *Reader) string {
var b [1000]byte
nb := 0
for {
c, err := buf.ReadByte()
if err == io.EOF {
break
}
if err == nil {
b[nb] = c
nb++
} else if err != iotest.ErrTimeout {
panic("Data: " + err.Error())
}
}
return string(b[0:nb])
}
func TestReaderSimple(t *testing.T) {
data := "hello world"
b := NewReader(strings.NewReader(data))
if s := readBytes(b); s != "hello world" {
t.Errorf("simple hello world test failed: got %q", s)
}
b = NewReader(newRot13Reader(strings.NewReader(data)))
if s := readBytes(b); s != "uryyb jbeyq" {
t.Errorf("rot13 hello world test failed: got %q", s)
}
}
type readMaker struct {
name string
fn func(io.Reader) io.Reader
}
var readMakers = []readMaker{
{"full", func(r io.Reader) io.Reader { return r }},
{"byte", iotest.OneByteReader},
{"half", iotest.HalfReader},
{"data+err", iotest.DataErrReader},
{"timeout", iotest.TimeoutReader},
}
// Call ReadString (which ends up calling everything else)
// to accumulate the text of a file.
func readLines(b *Reader) string {
s := ""
for {
s1, err := b.ReadString('\n')
if err == io.EOF {
break
}
if err != nil && err != iotest.ErrTimeout {
panic("GetLines: " + err.Error())
}
s += s1
}
return s
}
// Call Read to accumulate the text of a file
func reads(buf *Reader, m int) string {
var b [1000]byte
nb := 0
for {
n, err := buf.Read(b[nb : nb+m])
nb += n
if err == io.EOF {
break
}
}
return string(b[0:nb])
}
type bufReader struct {
name string
fn func(*Reader) string
}
var bufreaders = []bufReader{
{"1", func(b *Reader) string { return reads(b, 1) }},
{"2", func(b *Reader) string { return reads(b, 2) }},
{"3", func(b *Reader) string { return reads(b, 3) }},
{"4", func(b *Reader) string { return reads(b, 4) }},
{"5", func(b *Reader) string { return reads(b, 5) }},
{"7", func(b *Reader) string { return reads(b, 7) }},
{"bytes", readBytes},
{"lines", readLines},
}
const minReadBufferSize = 16
var bufsizes = []int{
0, minReadBufferSize, 23, 32, 46, 64, 93, 128, 1024, 4096,
}
func TestReader(t *testing.T) {
var texts [31]string
str := ""
all := ""
for i := 0; i < len(texts)-1; i++ {
texts[i] = str + "\n"
all += texts[i]
str += string(i%26 + 'a')
}
texts[len(texts)-1] = all
for h := 0; h < len(texts); h++ {
text := texts[h]
for i := 0; i < len(readMakers); i++ {
for j := 0; j < len(bufreaders); j++ {
for k := 0; k < len(bufsizes); k++ {
readmaker := readMakers[i]
bufreader := bufreaders[j]
bufsize := bufsizes[k]
read := readmaker.fn(strings.NewReader(text))
buf := NewReaderSize(read, bufsize)
s := bufreader.fn(buf)
if s != text {
t.Errorf("reader=%s fn=%s bufsize=%d want=%q got=%q",
readmaker.name, bufreader.name, bufsize, text, s)
}
}
}
}
}
}
type zeroReader struct{}
func (zeroReader) Read(p []byte) (int, error) {
return 0, nil
}
func TestZeroReader(t *testing.T) {
var z zeroReader
r := NewReader(z)
c := make(chan error)
go func() {
_, err := r.ReadByte()
c <- err
}()
select {
case err := <-c:
if err == nil {
t.Error("error expected")
} else if err != io.ErrNoProgress {
t.Error("unexpected error:", err)
}
case <-time.After(time.Second):
t.Error("test timed out (endless loop in ReadByte?)")
}
}
// A StringReader delivers its data one string segment at a time via Read.
type StringReader struct {
data []string
step int
}
func (r *StringReader) Read(p []byte) (n int, err error) {
if r.step < len(r.data) {
s := r.data[r.step]
n = copy(p, s)
r.step++
} else {
err = io.EOF
}
return
}
func readRuneSegments(t *testing.T, segments []string) {
got := ""
want := strings.Join(segments, "")
r := NewReader(&StringReader{data: segments})
for {
r, _, err := r.ReadRune()
if err != nil {
if err != io.EOF {
return
}
break
}
got += string(r)
}
if got != want {
t.Errorf("segments=%v got=%s want=%s", segments, got, want)
}
}
var segmentList = [][]string{
{},
{""},
{"日", "本語"},
{"\u65e5", "\u672c", "\u8a9e"},
{"\U000065e5", "\U0000672c", "\U00008a9e"},
{"\xe6", "\x97\xa5\xe6", "\x9c\xac\xe8\xaa\x9e"},
{"Hello", ", ", "World", "!"},
{"Hello", ", ", "", "World", "!"},
}
func TestReadRune(t *testing.T) {
for _, s := range segmentList {
readRuneSegments(t, s)
}
}
func TestUnreadRune(t *testing.T) {
segments := []string{"Hello, world:", "日本語"}
r := NewReader(&StringReader{data: segments})
got := ""
want := strings.Join(segments, "")
// Normal execution.
for {
r1, _, err := r.ReadRune()
if err != nil {
if err != io.EOF {
t.Error("unexpected error on ReadRune:", err)
}
break
}
got += string(r1)
// Put it back and read it again.
if err = r.UnreadRune(); err != nil {
t.Fatal("unexpected error on UnreadRune:", err)
}
r2, _, err := r.ReadRune()
if err != nil {
t.Fatal("unexpected error reading after unreading:", err)
}
if r1 != r2 {
t.Fatalf("incorrect rune after unread: got %c, want %c", r1, r2)
}
}
if got != want {
t.Errorf("got %q, want %q", got, want)
}
}
func TestNoUnreadRuneAfterPeek(t *testing.T) {
br := NewReader(strings.NewReader("example"))
br.ReadRune()
br.Peek(1)
if err := br.UnreadRune(); err == nil {
t.Error("UnreadRune didn't fail after Peek")
}
}
func TestNoUnreadByteAfterPeek(t *testing.T) {
br := NewReader(strings.NewReader("example"))
br.ReadByte()
br.Peek(1)
if err := br.UnreadByte(); err == nil {
t.Error("UnreadByte didn't fail after Peek")
}
}
func TestUnreadByte(t *testing.T) {
segments := []string{"Hello, ", "world"}
r := NewReader(&StringReader{data: segments})
got := ""
want := strings.Join(segments, "")
// Normal execution.
for {
b1, err := r.ReadByte()
if err != nil {
if err != io.EOF {
t.Error("unexpected error on ReadByte:", err)
}
break
}
got += string(b1)
// Put it back and read it again.
if err = r.UnreadByte(); err != nil {
t.Fatal("unexpected error on UnreadByte:", err)
}
b2, err := r.ReadByte()
if err != nil {
t.Fatal("unexpected error reading after unreading:", err)
}
if b1 != b2 {
t.Fatalf("incorrect byte after unread: got %q, want %q", b1, b2)
}
}
if got != want {
t.Errorf("got %q, want %q", got, want)
}
}
func TestUnreadByteMultiple(t *testing.T) {
segments := []string{"Hello, ", "world"}
data := strings.Join(segments, "")
for n := 0; n <= len(data); n++ {
r := NewReader(&StringReader{data: segments})
// Read n bytes.
for i := 0; i < n; i++ {
b, err := r.ReadByte()
if err != nil {
t.Fatalf("n = %d: unexpected error on ReadByte: %v", n, err)
}
if b != data[i] {
t.Fatalf("n = %d: incorrect byte returned from ReadByte: got %q, want %q", n, b, data[i])
}
}
// Unread one byte if there is one.
if n > 0 {
if err := r.UnreadByte(); err != nil {
t.Errorf("n = %d: unexpected error on UnreadByte: %v", n, err)
}
}
// Test that we cannot unread any further.
if err := r.UnreadByte(); err == nil {
t.Errorf("n = %d: expected error on UnreadByte", n)
}
}
}
func TestUnreadByteOthers(t *testing.T) {
// A list of readers to use in conjunction with UnreadByte.
var readers = []func(*Reader, byte) ([]byte, error){
(*Reader).ReadBytes,
(*Reader).ReadSlice,
func(r *Reader, delim byte) ([]byte, error) {
data, err := r.ReadString(delim)
return []byte(data), err
},
// ReadLine doesn't fit the data/pattern easily
// so we leave it out. It should be covered via
// the ReadSlice test since ReadLine simply calls
// ReadSlice, and it's that function that handles
// the last byte.
}
// Try all readers with UnreadByte.
for rno, read := range readers {
// Some input data that is longer than the minimum reader buffer size.
const n = 10
var buf bytes.Buffer
for i := 0; i < n; i++ {
buf.WriteString("abcdefg")
}
r := NewReaderSize(&buf, minReadBufferSize)
readTo := func(delim byte, want string) {
data, err := read(r, delim)
if err != nil {
t.Fatalf("#%d: unexpected error reading to %c: %v", rno, delim, err)
}
if got := string(data); got != want {
t.Fatalf("#%d: got %q, want %q", rno, got, want)
}
}
// Read the data with occasional UnreadByte calls.
for i := 0; i < n; i++ {
readTo('d', "abcd")
for j := 0; j < 3; j++ {
if err := r.UnreadByte(); err != nil {
t.Fatalf("#%d: unexpected error on UnreadByte: %v", rno, err)
}
readTo('d', "d")
}
readTo('g', "efg")
}
// All data should have been read.
_, err := r.ReadByte()
if err != io.EOF {
t.Errorf("#%d: got error %v; want EOF", rno, err)
}
}
}
// Test that UnreadRune fails if the preceding operation was not a ReadRune.
func TestUnreadRuneError(t *testing.T) {
buf := make([]byte, 3) // All runes in this test are 3 bytes long
r := NewReader(&StringReader{data: []string{"日本語日本語日本語"}})
if r.UnreadRune() == nil {
t.Error("expected error on UnreadRune from fresh buffer")
}
_, _, err := r.ReadRune()
if err != nil {
t.Error("unexpected error on ReadRune (1):", err)
}
if err = r.UnreadRune(); err != nil {
t.Error("unexpected error on UnreadRune (1):", err)
}
if r.UnreadRune() == nil {
t.Error("expected error after UnreadRune (1)")
}
// Test error after Read.
_, _, err = r.ReadRune() // reset state
if err != nil {
t.Error("unexpected error on ReadRune (2):", err)
}
_, err = r.Read(buf)
if err != nil {
t.Error("unexpected error on Read (2):", err)
}
if r.UnreadRune() == nil {
t.Error("expected error after Read (2)")
}
// Test error after ReadByte.
_, _, err = r.ReadRune() // reset state
if err != nil {
t.Error("unexpected error on ReadRune (2):", err)
}
for range buf {
_, err = r.ReadByte()
if err != nil {
t.Error("unexpected error on ReadByte (2):", err)
}
}
if r.UnreadRune() == nil {
t.Error("expected error after ReadByte")
}
// Test error after UnreadByte.
_, _, err = r.ReadRune() // reset state
if err != nil {
t.Error("unexpected error on ReadRune (3):", err)
}
_, err = r.ReadByte()
if err != nil {
t.Error("unexpected error on ReadByte (3):", err)
}
err = r.UnreadByte()
if err != nil {
t.Error("unexpected error on UnreadByte (3):", err)
}
if r.UnreadRune() == nil {
t.Error("expected error after UnreadByte (3)")
}
// Test error after ReadSlice.
_, _, err = r.ReadRune() // reset state
if err != nil {
t.Error("unexpected error on ReadRune (4):", err)
}
_, err = r.ReadSlice(0)
if err != io.EOF {
t.Error("unexpected error on ReadSlice (4):", err)
}
if r.UnreadRune() == nil {
t.Error("expected error after ReadSlice (4)")
}
}
func TestUnreadRuneAtEOF(t *testing.T) {
// UnreadRune/ReadRune should error at EOF (was a bug; used to panic)
r := NewReader(strings.NewReader("x"))
r.ReadRune()
r.ReadRune()
r.UnreadRune()
_, _, err := r.ReadRune()
if err == nil {
t.Error("expected error at EOF")
} else if err != io.EOF {
t.Error("expected EOF; got", err)
}
}
func TestReadWriteRune(t *testing.T) {
const NRune = 1000
byteBuf := new(bytes.Buffer)
w := NewWriter(byteBuf)
// Write the runes out using WriteRune
buf := make([]byte, utf8.UTFMax)
for r := rune(0); r < NRune; r++ {
size := utf8.EncodeRune(buf, r)
nbytes, err := w.WriteRune(r)
if err != nil {
t.Fatalf("WriteRune(0x%x) error: %s", r, err)
}
if nbytes != size {
t.Fatalf("WriteRune(0x%x) expected %d, got %d", r, size, nbytes)
}
}
w.Flush()
r := NewReader(byteBuf)
// Read them back with ReadRune
for r1 := rune(0); r1 < NRune; r1++ {
size := utf8.EncodeRune(buf, r1)
nr, nbytes, err := r.ReadRune()
if nr != r1 || nbytes != size || err != nil {
t.Fatalf("ReadRune(0x%x) got 0x%x,%d not 0x%x,%d (err=%s)", r1, nr, nbytes, r1, size, err)
}
}
}
func TestWriter(t *testing.T) {
var data [8192]byte
for i := 0; i < len(data); i++ {
data[i] = byte(' ' + i%('~'-' '))
}
w := new(bytes.Buffer)
for i := 0; i < len(bufsizes); i++ {
for j := 0; j < len(bufsizes); j++ {
nwrite := bufsizes[i]
bs := bufsizes[j]
// Write nwrite bytes using buffer size bs.
// Check that the right amount makes it out
// and that the data is correct.
w.Reset()
buf := NewWriterSize(w, bs)
context := fmt.Sprintf("nwrite=%d bufsize=%d", nwrite, bs)
n, e1 := buf.Write(data[0:nwrite])
if e1 != nil || n != nwrite {
t.Errorf("%s: buf.Write %d = %d, %v", context, nwrite, n, e1)
continue
}
if e := buf.Flush(); e != nil {
t.Errorf("%s: buf.Flush = %v", context, e)
}
written := w.Bytes()
if len(written) != nwrite {
t.Errorf("%s: %d bytes written", context, len(written))
}
for l := 0; l < len(written); l++ {
if written[l] != data[l] {
t.Errorf("wrong bytes written")
t.Errorf("want=%q", data[0:len(written)])
t.Errorf("have=%q", written)
}
}
}
}
}
// Check that write errors are returned properly.
type errorWriterTest struct {
n, m int
err error
expect error
}
func (w errorWriterTest) Write(p []byte) (int, error) {
return len(p) * w.n / w.m, w.err
}
var errorWriterTests = []errorWriterTest{
{0, 1, nil, io.ErrShortWrite},
{1, 2, nil, io.ErrShortWrite},
{1, 1, nil, nil},
{0, 1, io.ErrClosedPipe, io.ErrClosedPipe},
{1, 2, io.ErrClosedPipe, io.ErrClosedPipe},
{1, 1, io.ErrClosedPipe, io.ErrClosedPipe},
}
func TestWriteErrors(t *testing.T) {
for _, w := range errorWriterTests {
buf := NewWriter(w)
_, e := buf.Write([]byte("hello world"))
if e != nil {
t.Errorf("Write hello to %v: %v", w, e)
continue
}
// Two flushes, to verify the error is sticky.
for i := 0; i < 2; i++ {
e = buf.Flush()
if e != w.expect {
t.Errorf("Flush %d/2 %v: got %v, wanted %v", i+1, w, e, w.expect)
}
}
}
}
func TestNewReaderSizeIdempotent(t *testing.T) {
const BufSize = 1000
b := NewReaderSize(strings.NewReader("hello world"), BufSize)
// Does it recognize itself?
b1 := NewReaderSize(b, BufSize)
if b1 != b {
t.Error("NewReaderSize did not detect underlying Reader")
}
// Does it wrap if existing buffer is too small?
b2 := NewReaderSize(b, 2*BufSize)
if b2 == b {
t.Error("NewReaderSize did not enlarge buffer")
}
}
func TestNewWriterSizeIdempotent(t *testing.T) {
const BufSize = 1000
b := NewWriterSize(new(bytes.Buffer), BufSize)
// Does it recognize itself?
b1 := NewWriterSize(b, BufSize)
if b1 != b {
t.Error("NewWriterSize did not detect underlying Writer")
}
// Does it wrap if existing buffer is too small?
b2 := NewWriterSize(b, 2*BufSize)
if b2 == b {
t.Error("NewWriterSize did not enlarge buffer")
}
}
func TestWriteString(t *testing.T) {
const BufSize = 8
buf := new(bytes.Buffer)
b := NewWriterSize(buf, BufSize)
b.WriteString("0") // easy
b.WriteString("123456") // still easy
b.WriteString("7890") // easy after flush
b.WriteString("abcdefghijklmnopqrstuvwxy") // hard
b.WriteString("z")
if err := b.Flush(); err != nil {
t.Error("WriteString", err)
}
s := "01234567890abcdefghijklmnopqrstuvwxyz"
if string(buf.Bytes()) != s {
t.Errorf("WriteString wants %q gets %q", s, string(buf.Bytes()))
}
}
func TestBufferFull(t *testing.T) {
const longString = "And now, hello, world! It is the time for all good men to come to the aid of their party"
buf := NewReaderSize(strings.NewReader(longString), minReadBufferSize)
line, err := buf.ReadSlice('!')
if string(line) != "And now, hello, " || err != ErrBufferFull {
t.Errorf("first ReadSlice(,) = %q, %v", line, err)
}
line, err = buf.ReadSlice('!')
if string(line) != "world!" || err != nil {
t.Errorf("second ReadSlice(,) = %q, %v", line, err)
}
}
func TestPeek(t *testing.T) {
p := make([]byte, 10)
// string is 16 (minReadBufferSize) long.
buf := NewReaderSize(strings.NewReader("abcdefghijklmnop"), minReadBufferSize)
if s, err := buf.Peek(1); string(s) != "a" || err != nil {
t.Fatalf("want %q got %q, err=%v", "a", string(s), err)
}
if s, err := buf.Peek(4); string(s) != "abcd" || err != nil {
t.Fatalf("want %q got %q, err=%v", "abcd", string(s), err)
}
if _, err := buf.Peek(-1); err != ErrNegativeCount {
t.Fatalf("want ErrNegativeCount got %v", err)
}
if s, err := buf.Peek(32); string(s) != "abcdefghijklmnop" || err != ErrBufferFull {
t.Fatalf("want %q, ErrBufFull got %q, err=%v", "abcdefghijklmnop", string(s), err)
}
if _, err := buf.Read(p[0:3]); string(p[0:3]) != "abc" || err != nil {
t.Fatalf("want %q got %q, err=%v", "abc", string(p[0:3]), err)
}
if s, err := buf.Peek(1); string(s) != "d" || err != nil {
t.Fatalf("want %q got %q, err=%v", "d", string(s), err)
}
if s, err := buf.Peek(2); string(s) != "de" || err != nil {
t.Fatalf("want %q got %q, err=%v", "de", string(s), err)
}
if _, err := buf.Read(p[0:3]); string(p[0:3]) != "def" || err != nil {
t.Fatalf("want %q got %q, err=%v", "def", string(p[0:3]), err)
}
if s, err := buf.Peek(4); string(s) != "ghij" || err != nil {
t.Fatalf("want %q got %q, err=%v", "ghij", string(s), err)
}
if _, err := buf.Read(p[0:]); string(p[0:]) != "ghijklmnop" || err != nil {
t.Fatalf("want %q got %q, err=%v", "ghijklmnop", string(p[0:minReadBufferSize]), err)
}
if s, err := buf.Peek(0); string(s) != "" || err != nil {
t.Fatalf("want %q got %q, err=%v", "", string(s), err)
}
if _, err := buf.Peek(1); err != io.EOF {
t.Fatalf("want EOF got %v", err)
}
// Test for issue 3022, not exposing a reader's error on a successful Peek.
buf = NewReaderSize(dataAndEOFReader("abcd"), 32)
if s, err := buf.Peek(2); string(s) != "ab" || err != nil {
t.Errorf(`Peek(2) on "abcd", EOF = %q, %v; want "ab", nil`, string(s), err)
}
if s, err := buf.Peek(4); string(s) != "abcd" || err != nil {
t.Errorf(`Peek(4) on "abcd", EOF = %q, %v; want "abcd", nil`, string(s), err)
}
if n, err := buf.Read(p[0:5]); string(p[0:n]) != "abcd" || err != nil {
t.Fatalf("Read after peek = %q, %v; want abcd, EOF", p[0:n], err)
}
if n, err := buf.Read(p[0:1]); string(p[0:n]) != "" || err != io.EOF {
t.Fatalf(`second Read after peek = %q, %v; want "", EOF`, p[0:n], err)
}
}
type dataAndEOFReader string
func (r dataAndEOFReader) Read(p []byte) (int, error) {
return copy(p, r), io.EOF
}
func TestPeekThenUnreadRune(t *testing.T) {
// This sequence used to cause a crash.
r := NewReader(strings.NewReader("x"))
r.ReadRune()
r.Peek(1)
r.UnreadRune()
r.ReadRune() // Used to panic here
}
var testOutput = []byte("0123456789abcdefghijklmnopqrstuvwxy")
var testInput = []byte("012\n345\n678\n9ab\ncde\nfgh\nijk\nlmn\nopq\nrst\nuvw\nxy")
var testInputrn = []byte("012\r\n345\r\n678\r\n9ab\r\ncde\r\nfgh\r\nijk\r\nlmn\r\nopq\r\nrst\r\nuvw\r\nxy\r\n\n\r\n")
// TestReader wraps a []byte and returns reads of a specific length.
type testReader struct {
data []byte
stride int
}
func (t *testReader) Read(buf []byte) (n int, err error) {
n = t.stride
if n > len(t.data) {
n = len(t.data)
}
if n > len(buf) {
n = len(buf)
}
copy(buf, t.data)
t.data = t.data[n:]
if len(t.data) == 0 {
err = io.EOF
}
return
}
func testReadLine(t *testing.T, input []byte) {
//for stride := 1; stride < len(input); stride++ {
for stride := 1; stride < 2; stride++ {
done := 0
reader := testReader{input, stride}
l := NewReaderSize(&reader, len(input)+1)
for {
line, isPrefix, err := l.ReadLine()
if len(line) > 0 && err != nil {
t.Errorf("ReadLine returned both data and error: %s", err)
}
if isPrefix {
t.Errorf("ReadLine returned prefix")
}
if err != nil {
if err != io.EOF {
t.Fatalf("Got unknown error: %s", err)
}
break
}
if want := testOutput[done : done+len(line)]; !bytes.Equal(want, line) {
t.Errorf("Bad line at stride %d: want: %x got: %x", stride, want, line)
}
done += len(line)
}
if done != len(testOutput) {
t.Errorf("ReadLine didn't return everything: got: %d, want: %d (stride: %d)", done, len(testOutput), stride)
}
}
}
func TestReadLine(t *testing.T) {
testReadLine(t, testInput)
testReadLine(t, testInputrn)
}
func TestLineTooLong(t *testing.T) {
data := make([]byte, 0)
for i := 0; i < minReadBufferSize*5/2; i++ {
data = append(data, '0'+byte(i%10))
}
buf := bytes.NewReader(data)
l := NewReaderSize(buf, minReadBufferSize)
line, isPrefix, err := l.ReadLine()
if !isPrefix || !bytes.Equal(line, data[:minReadBufferSize]) || err != nil {
t.Errorf("bad result for first line: got %q want %q %v", line, data[:minReadBufferSize], err)
}
data = data[len(line):]
line, isPrefix, err = l.ReadLine()
if !isPrefix || !bytes.Equal(line, data[:minReadBufferSize]) || err != nil {
t.Errorf("bad result for second line: got %q want %q %v", line, data[:minReadBufferSize], err)
}
data = data[len(line):]
line, isPrefix, err = l.ReadLine()
if isPrefix || !bytes.Equal(line, data[:minReadBufferSize/2]) || err != nil {
t.Errorf("bad result for third line: got %q want %q %v", line, data[:minReadBufferSize/2], err)
}
line, isPrefix, err = l.ReadLine()
if isPrefix || err == nil {
t.Errorf("expected no more lines: %x %s", line, err)
}
}
func TestReadAfterLines(t *testing.T) {
line1 := "this is line1"
restData := "this is line2\nthis is line 3\n"
inbuf := bytes.NewReader([]byte(line1 + "\n" + restData))
outbuf := new(bytes.Buffer)
maxLineLength := len(line1) + len(restData)/2
l := NewReaderSize(inbuf, maxLineLength)
line, isPrefix, err := l.ReadLine()
if isPrefix || err != nil || string(line) != line1 {
t.Errorf("bad result for first line: isPrefix=%v err=%v line=%q", isPrefix, err, string(line))
}
n, err := io.Copy(outbuf, l)
if int(n) != len(restData) || err != nil {
t.Errorf("bad result for Read: n=%d err=%v", n, err)
}
if outbuf.String() != restData {
t.Errorf("bad result for Read: got %q; expected %q", outbuf.String(), restData)
}
}
func TestReadEmptyBuffer(t *testing.T) {
l := NewReaderSize(new(bytes.Buffer), minReadBufferSize)
line, isPrefix, err := l.ReadLine()
if err != io.EOF {
t.Errorf("expected EOF from ReadLine, got '%s' %t %s", line, isPrefix, err)
}
}
func TestLinesAfterRead(t *testing.T) {
l := NewReaderSize(bytes.NewReader([]byte("foo")), minReadBufferSize)
_, err := ioutil.ReadAll(l)
if err != nil {
t.Error(err)
return
}
line, isPrefix, err := l.ReadLine()
if err != io.EOF {
t.Errorf("expected EOF from ReadLine, got '%s' %t %s", line, isPrefix, err)
}
}
func TestReadLineNonNilLineOrError(t *testing.T) {
r := NewReader(strings.NewReader("line 1\n"))
for i := 0; i < 2; i++ {
l, _, err := r.ReadLine()
if l != nil && err != nil {
t.Fatalf("on line %d/2; ReadLine=%#v, %v; want non-nil line or Error, but not both",
i+1, l, err)
}
}
}
type readLineResult struct {
line []byte
isPrefix bool
err error
}
var readLineNewlinesTests = []struct {
input string
expect []readLineResult
}{
{"012345678901234\r\n012345678901234\r\n", []readLineResult{
{[]byte("012345678901234"), true, nil},
{nil, false, nil},
{[]byte("012345678901234"), true, nil},
{nil, false, nil},
{nil, false, io.EOF},
}},
{"0123456789012345\r012345678901234\r", []readLineResult{
{[]byte("0123456789012345"), true, nil},
{[]byte("\r012345678901234"), true, nil},
{[]byte("\r"), false, nil},
{nil, false, io.EOF},
}},
}
func TestReadLineNewlines(t *testing.T) {
for _, e := range readLineNewlinesTests {
testReadLineNewlines(t, e.input, e.expect)
}
}
func testReadLineNewlines(t *testing.T, input string, expect []readLineResult) {
b := NewReaderSize(strings.NewReader(input), minReadBufferSize)
for i, e := range expect {
line, isPrefix, err := b.ReadLine()
if !bytes.Equal(line, e.line) {
t.Errorf("%q call %d, line == %q, want %q", input, i, line, e.line)
return
}
if isPrefix != e.isPrefix {
t.Errorf("%q call %d, isPrefix == %v, want %v", input, i, isPrefix, e.isPrefix)
return
}
if err != e.err {
t.Errorf("%q call %d, err == %v, want %v", input, i, err, e.err)
return
}
}
}
func createTestInput(n int) []byte {
input := make([]byte, n)
for i := range input {
// 101 and 251 are arbitrary prime numbers.
// The idea is to create an input sequence
// which doesn't repeat too frequently.
input[i] = byte(i % 251)
if i%101 == 0 {
input[i] ^= byte(i / 101)
}
}
return input
}
func TestReaderWriteTo(t *testing.T) {
input := createTestInput(8192)
r := NewReader(onlyReader{bytes.NewReader(input)})
w := new(bytes.Buffer)
if n, err := r.WriteTo(w); err != nil || n != int64(len(input)) {
t.Fatalf("r.WriteTo(w) = %d, %v, want %d, nil", n, err, len(input))
}
for i, val := range w.Bytes() {
if val != input[i] {
t.Errorf("after write: out[%d] = %#x, want %#x", i, val, input[i])
}
}
}
type errorWriterToTest struct {
rn, wn int
rerr, werr error
expected error
}
func (r errorWriterToTest) Read(p []byte) (int, error) {
return len(p) * r.rn, r.rerr
}
func (w errorWriterToTest) Write(p []byte) (int, error) {
return len(p) * w.wn, w.werr
}
var errorWriterToTests = []errorWriterToTest{
{1, 0, nil, io.ErrClosedPipe, io.ErrClosedPipe},
{0, 1, io.ErrClosedPipe, nil, io.ErrClosedPipe},
{0, 0, io.ErrUnexpectedEOF, io.ErrClosedPipe, io.ErrClosedPipe},
{0, 1, io.EOF, nil, nil},
}
func TestReaderWriteToErrors(t *testing.T) {
for i, rw := range errorWriterToTests {
r := NewReader(rw)
if _, err := r.WriteTo(rw); err != rw.expected {
t.Errorf("r.WriteTo(errorWriterToTests[%d]) = _, %v, want _,%v", i, err, rw.expected)
}
}
}
func TestWriterReadFrom(t *testing.T) {
ws := []func(io.Writer) io.Writer{
func(w io.Writer) io.Writer { return onlyWriter{w} },
func(w io.Writer) io.Writer { return w },
}
rs := []func(io.Reader) io.Reader{
iotest.DataErrReader,
func(r io.Reader) io.Reader { return r },
}
for ri, rfunc := range rs {
for wi, wfunc := range ws {
input := createTestInput(8192)
b := new(bytes.Buffer)
w := NewWriter(wfunc(b))
r := rfunc(bytes.NewReader(input))
if n, err := w.ReadFrom(r); err != nil || n != int64(len(input)) {
t.Errorf("ws[%d],rs[%d]: w.ReadFrom(r) = %d, %v, want %d, nil", wi, ri, n, err, len(input))
continue
}
if err := w.Flush(); err != nil {
t.Errorf("Flush returned %v", err)
continue
}
if got, want := b.String(), string(input); got != want {
t.Errorf("ws[%d], rs[%d]:\ngot %q\nwant %q\n", wi, ri, got, want)
}
}
}
}
type errorReaderFromTest struct {
rn, wn int
rerr, werr error
expected error
}
func (r errorReaderFromTest) Read(p []byte) (int, error) {
return len(p) * r.rn, r.rerr
}
func (w errorReaderFromTest) Write(p []byte) (int, error) {
return len(p) * w.wn, w.werr
}
var errorReaderFromTests = []errorReaderFromTest{
{0, 1, io.EOF, nil, nil},
{1, 1, io.EOF, nil, nil},
{0, 1, io.ErrClosedPipe, nil, io.ErrClosedPipe},
{0, 0, io.ErrClosedPipe, io.ErrShortWrite, io.ErrClosedPipe},
{1, 0, nil, io.ErrShortWrite, io.ErrShortWrite},
}
func TestWriterReadFromErrors(t *testing.T) {
for i, rw := range errorReaderFromTests {
w := NewWriter(rw)
if _, err := w.ReadFrom(rw); err != rw.expected {
t.Errorf("w.ReadFrom(errorReaderFromTests[%d]) = _, %v, want _,%v", i, err, rw.expected)
}
}
}
// TestWriterReadFromCounts tests that using io.Copy to copy into a
// bufio.Writer does not prematurely flush the buffer. For example, when
// buffering writes to a network socket, excessive network writes should be
// avoided.
func TestWriterReadFromCounts(t *testing.T) {
var w0 writeCountingDiscard
b0 := NewWriterSize(&w0, 1234)
b0.WriteString(strings.Repeat("x", 1000))
if w0 != 0 {
t.Fatalf("write 1000 'x's: got %d writes, want 0", w0)
}
b0.WriteString(strings.Repeat("x", 200))
if w0 != 0 {
t.Fatalf("write 1200 'x's: got %d writes, want 0", w0)
}
io.Copy(b0, onlyReader{strings.NewReader(strings.Repeat("x", 30))})
if w0 != 0 {
t.Fatalf("write 1230 'x's: got %d writes, want 0", w0)
}
io.Copy(b0, onlyReader{strings.NewReader(strings.Repeat("x", 9))})
if w0 != 1 {
t.Fatalf("write 1239 'x's: got %d writes, want 1", w0)
}
var w1 writeCountingDiscard
b1 := NewWriterSize(&w1, 1234)
b1.WriteString(strings.Repeat("x", 1200))
b1.Flush()
if w1 != 1 {
t.Fatalf("flush 1200 'x's: got %d writes, want 1", w1)
}
b1.WriteString(strings.Repeat("x", 89))
if w1 != 1 {
t.Fatalf("write 1200 + 89 'x's: got %d writes, want 1", w1)
}
io.Copy(b1, onlyReader{strings.NewReader(strings.Repeat("x", 700))})
if w1 != 1 {
t.Fatalf("write 1200 + 789 'x's: got %d writes, want 1", w1)
}
io.Copy(b1, onlyReader{strings.NewReader(strings.Repeat("x", 600))})
if w1 != 2 {
t.Fatalf("write 1200 + 1389 'x's: got %d writes, want 2", w1)
}
b1.Flush()
if w1 != 3 {
t.Fatalf("flush 1200 + 1389 'x's: got %d writes, want 3", w1)
}
}
// A writeCountingDiscard is like ioutil.Discard and counts the number of times
// Write is called on it.
type writeCountingDiscard int
func (w *writeCountingDiscard) Write(p []byte) (int, error) {
*w++
return len(p), nil
}
type negativeReader int
func (r *negativeReader) Read([]byte) (int, error) { return -1, nil }
func TestNegativeRead(t *testing.T) {
// should panic with a description pointing at the reader, not at itself.
// (should NOT panic with slice index error, for example.)
b := NewReader(new(negativeReader))
defer func() {
switch err := recover().(type) {
case nil:
t.Fatal("read did not panic")
case error:
if !strings.Contains(err.Error(), "reader returned negative count from Read") {
t.Fatalf("wrong panic: %v", err)
}
default:
t.Fatalf("unexpected panic value: %T(%v)", err, err)
}
}()
b.Read(make([]byte, 100))
}
var errFake = errors.New("fake error")
type errorThenGoodReader struct {
didErr bool
nread int
}
func (r *errorThenGoodReader) Read(p []byte) (int, error) {
r.nread++
if !r.didErr {
r.didErr = true
return 0, errFake
}
return len(p), nil
}
func TestReaderClearError(t *testing.T) {
r := &errorThenGoodReader{}
b := NewReader(r)
buf := make([]byte, 1)
if _, err := b.Read(nil); err != nil {
t.Fatalf("1st nil Read = %v; want nil", err)
}
if _, err := b.Read(buf); err != errFake {
t.Fatalf("1st Read = %v; want errFake", err)
}
if _, err := b.Read(nil); err != nil {
t.Fatalf("2nd nil Read = %v; want nil", err)
}
if _, err := b.Read(buf); err != nil {
t.Fatalf("3rd Read with buffer = %v; want nil", err)
}
if r.nread != 2 {
t.Errorf("num reads = %d; want 2", r.nread)
}
}
// Test for golang.org/issue/5947
func TestWriterReadFromWhileFull(t *testing.T) {
buf := new(bytes.Buffer)
w := NewWriterSize(buf, 10)
// Fill buffer exactly.
n, err := w.Write([]byte("0123456789"))
if n != 10 || err != nil {
t.Fatalf("Write returned (%v, %v), want (10, nil)", n, err)
}
// Use ReadFrom to read in some data.
n2, err := w.ReadFrom(strings.NewReader("abcdef"))
if n2 != 6 || err != nil {
t.Fatalf("ReadFrom returned (%v, %v), want (6, nil)", n2, err)
}
}
type emptyThenNonEmptyReader struct {
r io.Reader
n int
}
func (r *emptyThenNonEmptyReader) Read(p []byte) (int, error) {
if r.n <= 0 {
return r.r.Read(p)
}
r.n--
return 0, nil
}
// Test for golang.org/issue/7611
func TestWriterReadFromUntilEOF(t *testing.T) {
buf := new(bytes.Buffer)
w := NewWriterSize(buf, 5)
// Partially fill buffer
n, err := w.Write([]byte("0123"))
if n != 4 || err != nil {
t.Fatalf("Write returned (%v, %v), want (4, nil)", n, err)
}
// Use ReadFrom to read in some data.
r := &emptyThenNonEmptyReader{r: strings.NewReader("abcd"), n: 3}
n2, err := w.ReadFrom(r)
if n2 != 4 || err != nil {
t.Fatalf("ReadFrom returned (%v, %v), want (4, nil)", n2, err)
}
w.Flush()
if got, want := string(buf.Bytes()), "0123abcd"; got != want {
t.Fatalf("buf.Bytes() returned %q, want %q", got, want)
}
}
func TestWriterReadFromErrNoProgress(t *testing.T) {
buf := new(bytes.Buffer)
w := NewWriterSize(buf, 5)
// Partially fill buffer
n, err := w.Write([]byte("0123"))
if n != 4 || err != nil {
t.Fatalf("Write returned (%v, %v), want (4, nil)", n, err)
}
// Use ReadFrom to read in some data.
r := &emptyThenNonEmptyReader{r: strings.NewReader("abcd"), n: 100}
n2, err := w.ReadFrom(r)
if n2 != 0 || err != io.ErrNoProgress {
t.Fatalf("buf.Bytes() returned (%v, %v), want (0, io.ErrNoProgress)", n2, err)
}
}
func TestReadZero(t *testing.T) {
for _, size := range []int{100, 2} {
t.Run(fmt.Sprintf("bufsize=%d", size), func(t *testing.T) {
r := io.MultiReader(strings.NewReader("abc"), &emptyThenNonEmptyReader{r: strings.NewReader("def"), n: 1})
br := NewReaderSize(r, size)
want := func(s string, wantErr error) {
p := make([]byte, 50)
n, err := br.Read(p)
if err != wantErr || n != len(s) || string(p[:n]) != s {
t.Fatalf("read(%d) = %q, %v, want %q, %v", len(p), string(p[:n]), err, s, wantErr)
}
t.Logf("read(%d) = %q, %v", len(p), string(p[:n]), err)
}
want("abc", nil)
want("", nil)
want("def", nil)
want("", io.EOF)
})
}
}
func TestReaderReset(t *testing.T) {
r := NewReader(strings.NewReader("foo foo"))
buf := make([]byte, 3)
r.Read(buf)
if string(buf) != "foo" {
t.Errorf("buf = %q; want foo", buf)
}
r.Reset(strings.NewReader("bar bar"))
all, err := ioutil.ReadAll(r)
if err != nil {
t.Fatal(err)
}
if string(all) != "bar bar" {
t.Errorf("ReadAll = %q; want bar bar", all)
}
}
func TestWriterReset(t *testing.T) {
var buf1, buf2 bytes.Buffer
w := NewWriter(&buf1)
w.WriteString("foo")
w.Reset(&buf2) // and not flushed
w.WriteString("bar")
w.Flush()
if buf1.String() != "" {
t.Errorf("buf1 = %q; want empty", buf1.String())
}
if buf2.String() != "bar" {
t.Errorf("buf2 = %q; want bar", buf2.String())
}
}
func TestReaderDiscard(t *testing.T) {
tests := []struct {
name string
r io.Reader
bufSize int // 0 means 16
peekSize int
n int // input to Discard
want int // from Discard
wantErr error // from Discard
wantBuffered int
}{
{
name: "normal case",
r: strings.NewReader("abcdefghijklmnopqrstuvwxyz"),
peekSize: 16,
n: 6,
want: 6,
wantBuffered: 10,
},
{
name: "discard causing read",
r: strings.NewReader("abcdefghijklmnopqrstuvwxyz"),
n: 6,
want: 6,
wantBuffered: 10,
},
{
name: "discard all without peek",
r: strings.NewReader("abcdefghijklmnopqrstuvwxyz"),
n: 26,
want: 26,
wantBuffered: 0,
},
{
name: "discard more than end",
r: strings.NewReader("abcdefghijklmnopqrstuvwxyz"),
n: 27,
want: 26,
wantErr: io.EOF,
wantBuffered: 0,
},
// Any error from filling shouldn't show up until we
// get past the valid bytes. Here we return we return 5 valid bytes at the same time
// as an error, but test that we don't see the error from Discard.
{
name: "fill error, discard less",
r: newScriptedReader(func(p []byte) (n int, err error) {
if len(p) < 5 {
panic("unexpected small read")
}
return 5, errors.New("5-then-error")
}),
n: 4,
want: 4,
wantErr: nil,
wantBuffered: 1,
},
{
name: "fill error, discard equal",
r: newScriptedReader(func(p []byte) (n int, err error) {
if len(p) < 5 {
panic("unexpected small read")
}
return 5, errors.New("5-then-error")
}),
n: 5,
want: 5,
wantErr: nil,
wantBuffered: 0,
},
{
name: "fill error, discard more",
r: newScriptedReader(func(p []byte) (n int, err error) {
if len(p) < 5 {
panic("unexpected small read")
}
return 5, errors.New("5-then-error")
}),
n: 6,
want: 5,
wantErr: errors.New("5-then-error"),
wantBuffered: 0,
},
// Discard of 0 shouldn't cause a read:
{
name: "discard zero",
r: newScriptedReader(), // will panic on Read
n: 0,
want: 0,
wantErr: nil,
wantBuffered: 0,
},
{
name: "discard negative",
r: newScriptedReader(), // will panic on Read
n: -1,
want: 0,
wantErr: ErrNegativeCount,
wantBuffered: 0,
},
}
for _, tt := range tests {
br := NewReaderSize(tt.r, tt.bufSize)
if tt.peekSize > 0 {
peekBuf, err := br.Peek(tt.peekSize)
if err != nil {
t.Errorf("%s: Peek(%d): %v", tt.name, tt.peekSize, err)
continue
}
if len(peekBuf) != tt.peekSize {
t.Errorf("%s: len(Peek(%d)) = %v; want %v", tt.name, tt.peekSize, len(peekBuf), tt.peekSize)
continue
}
}
discarded, err := br.Discard(tt.n)
if ge, we := fmt.Sprint(err), fmt.Sprint(tt.wantErr); discarded != tt.want || ge != we {
t.Errorf("%s: Discard(%d) = (%v, %v); want (%v, %v)", tt.name, tt.n, discarded, ge, tt.want, we)
continue
}
if bn := br.Buffered(); bn != tt.wantBuffered {
t.Errorf("%s: after Discard, Buffered = %d; want %d", tt.name, bn, tt.wantBuffered)
}
}
}
func TestReaderSize(t *testing.T) {
if got, want := NewReader(nil).Size(), DefaultBufSize; got != want {
t.Errorf("NewReader's Reader.Size = %d; want %d", got, want)
}
if got, want := NewReaderSize(nil, 1234).Size(), 1234; got != want {
t.Errorf("NewReaderSize's Reader.Size = %d; want %d", got, want)
}
}
func TestWriterSize(t *testing.T) {
if got, want := NewWriter(nil).Size(), DefaultBufSize; got != want {
t.Errorf("NewWriter's Writer.Size = %d; want %d", got, want)
}
if got, want := NewWriterSize(nil, 1234).Size(), 1234; got != want {
t.Errorf("NewWriterSize's Writer.Size = %d; want %d", got, want)
}
}
// An onlyReader only implements io.Reader, no matter what other methods the underlying implementation may have.
type onlyReader struct {
io.Reader
}
// An onlyWriter only implements io.Writer, no matter what other methods the underlying implementation may have.
type onlyWriter struct {
io.Writer
}
// A scriptedReader is an io.Reader that executes its steps sequentially.
type scriptedReader []func(p []byte) (n int, err error)
func (sr *scriptedReader) Read(p []byte) (n int, err error) {
if len(*sr) == 0 {
panic("too many Read calls on scripted Reader. No steps remain.")
}
step := (*sr)[0]
*sr = (*sr)[1:]
return step(p)
}
func newScriptedReader(steps ...func(p []byte) (n int, err error)) io.Reader {
sr := scriptedReader(steps)
return &sr
}
func BenchmarkReaderCopyOptimal(b *testing.B) {
// Optimal case is where the underlying reader implements io.WriterTo
srcBuf := bytes.NewBuffer(make([]byte, 8192))
src := NewReader(srcBuf)
dstBuf := new(bytes.Buffer)
dst := onlyWriter{dstBuf}
for i := 0; i < b.N; i++ {
srcBuf.Reset()
src.Reset(srcBuf)
dstBuf.Reset()
io.Copy(dst, src)
}
}
func BenchmarkReaderCopyUnoptimal(b *testing.B) {
// Unoptimal case is where the underlying reader doesn't implement io.WriterTo
srcBuf := bytes.NewBuffer(make([]byte, 8192))
src := NewReader(onlyReader{srcBuf})
dstBuf := new(bytes.Buffer)
dst := onlyWriter{dstBuf}
for i := 0; i < b.N; i++ {
srcBuf.Reset()
src.Reset(onlyReader{srcBuf})
dstBuf.Reset()
io.Copy(dst, src)
}
}
func BenchmarkReaderCopyNoWriteTo(b *testing.B) {
srcBuf := bytes.NewBuffer(make([]byte, 8192))
srcReader := NewReader(srcBuf)
src := onlyReader{srcReader}
dstBuf := new(bytes.Buffer)
dst := onlyWriter{dstBuf}
for i := 0; i < b.N; i++ {
srcBuf.Reset()
srcReader.Reset(srcBuf)
dstBuf.Reset()
io.Copy(dst, src)
}
}
func BenchmarkReaderWriteToOptimal(b *testing.B) {
const bufSize = 16 << 10
buf := make([]byte, bufSize)
r := bytes.NewReader(buf)
srcReader := NewReaderSize(onlyReader{r}, 1<<10)
if _, ok := ioutil.Discard.(io.ReaderFrom); !ok {
b.Fatal("ioutil.Discard doesn't support ReaderFrom")
}
for i := 0; i < b.N; i++ {
r.Seek(0, io.SeekStart)
srcReader.Reset(onlyReader{r})
n, err := srcReader.WriteTo(ioutil.Discard)
if err != nil {
b.Fatal(err)
}
if n != bufSize {
b.Fatalf("n = %d; want %d", n, bufSize)
}
}
}
func BenchmarkWriterCopyOptimal(b *testing.B) {
// Optimal case is where the underlying writer implements io.ReaderFrom
srcBuf := bytes.NewBuffer(make([]byte, 8192))
src := onlyReader{srcBuf}
dstBuf := new(bytes.Buffer)
dst := NewWriter(dstBuf)
for i := 0; i < b.N; i++ {
srcBuf.Reset()
dstBuf.Reset()
dst.Reset(dstBuf)
io.Copy(dst, src)
}
}
func BenchmarkWriterCopyUnoptimal(b *testing.B) {
srcBuf := bytes.NewBuffer(make([]byte, 8192))
src := onlyReader{srcBuf}
dstBuf := new(bytes.Buffer)
dst := NewWriter(onlyWriter{dstBuf})
for i := 0; i < b.N; i++ {
srcBuf.Reset()
dstBuf.Reset()
dst.Reset(onlyWriter{dstBuf})
io.Copy(dst, src)
}
}
func BenchmarkWriterCopyNoReadFrom(b *testing.B) {
srcBuf := bytes.NewBuffer(make([]byte, 8192))
src := onlyReader{srcBuf}
dstBuf := new(bytes.Buffer)
dstWriter := NewWriter(dstBuf)
dst := onlyWriter{dstWriter}
for i := 0; i < b.N; i++ {
srcBuf.Reset()
dstBuf.Reset()
dstWriter.Reset(dstBuf)
io.Copy(dst, src)
}
}
func BenchmarkReaderEmpty(b *testing.B) {
b.ReportAllocs()
str := strings.Repeat("x", 16<<10)
for i := 0; i < b.N; i++ {
br := NewReader(strings.NewReader(str))
n, err := io.Copy(ioutil.Discard, br)
if err != nil {
b.Fatal(err)
}
if n != int64(len(str)) {
b.Fatal("wrong length")
}
}
}
func BenchmarkWriterEmpty(b *testing.B) {
b.ReportAllocs()
str := strings.Repeat("x", 1<<10)
bs := []byte(str)
for i := 0; i < b.N; i++ {
bw := NewWriter(ioutil.Discard)
bw.Flush()
bw.WriteByte('a')
bw.Flush()
bw.WriteRune('B')
bw.Flush()
bw.Write(bs)
bw.Flush()
bw.WriteString(str)
bw.Flush()
}
}
func BenchmarkWriterFlush(b *testing.B) {
b.ReportAllocs()
bw := NewWriter(ioutil.Discard)
str := strings.Repeat("x", 50)
for i := 0; i < b.N; i++ {
bw.WriteString(str)
bw.Flush()
}
}