Adding upstream version 1.22.1.upstream/1.22.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1996 insertions, 0 deletions

diff --git a/src/bufio/bufio_test.go b/src/bufio/bufio_test.go
new file mode 100644
index 0000000..a8c1e50
--- /dev/null
+++ b/src/bufio/bufio_test.go
@@ -0,0 +1,1996 @@
+// 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"
+	"math/rand"
+	"strconv"
+	"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(rune(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 TestNoUnreadRuneAfterDiscard(t *testing.T) {
+	br := NewReader(strings.NewReader("example"))
+	br.ReadRune()
+	br.Discard(1)
+	if err := br.UnreadRune(); err == nil {
+		t.Error("UnreadRune didn't fail after Discard")
+	}
+}
+
+func TestNoUnreadByteAfterDiscard(t *testing.T) {
+	br := NewReader(strings.NewReader("example"))
+	br.ReadByte()
+	br.Discard(1)
+	if err := br.UnreadByte(); err == nil {
+		t.Error("UnreadByte didn't fail after Discard")
+	}
+}
+
+func TestNoUnreadRuneAfterWriteTo(t *testing.T) {
+	br := NewReader(strings.NewReader("example"))
+	br.WriteTo(io.Discard)
+	if err := br.UnreadRune(); err == nil {
+		t.Error("UnreadRune didn't fail after WriteTo")
+	}
+}
+
+func TestNoUnreadByteAfterWriteTo(t *testing.T) {
+	br := NewReader(strings.NewReader("example"))
+	br.WriteTo(io.Discard)
+	if err := br.UnreadByte(); err == nil {
+		t.Error("UnreadByte didn't fail after WriteTo")
+	}
+}
+
+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 TestWriteInvalidRune(t *testing.T) {
+	// Invalid runes, including negative ones, should be written as the
+	// replacement character.
+	for _, r := range []rune{-1, utf8.MaxRune + 1} {
+		var buf strings.Builder
+		w := NewWriter(&buf)
+		w.WriteRune(r)
+		w.Flush()
+		if s := buf.String(); s != "\uFFFD" {
+			t.Errorf("WriteRune(%d) wrote %q, not replacement character", r, s)
+		}
+	}
+}
+
+func TestReadStringAllocs(t *testing.T) {
+	r := strings.NewReader("       foo       foo        42        42        42        42        42        42        42        42       4.2       4.2       4.2       4.2\n")
+	buf := NewReader(r)
+	allocs := testing.AllocsPerRun(100, func() {
+		r.Seek(0, io.SeekStart)
+		buf.Reset(r)
+
+		_, err := buf.ReadString('\n')
+		if err != nil {
+			t.Fatal(err)
+		}
+	})
+	if allocs != 1 {
+		t.Errorf("Unexpected number of allocations, got %f, want 1", allocs)
+	}
+}
+
+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)
+				}
+			}
+		}
+	}
+}
+
+func TestWriterAppend(t *testing.T) {
+	got := new(bytes.Buffer)
+	var want []byte
+	rn := rand.New(rand.NewSource(0))
+	w := NewWriterSize(got, 64)
+	for i := 0; i < 100; i++ {
+		// Obtain a buffer to append to.
+		b := w.AvailableBuffer()
+		if w.Available() != cap(b) {
+			t.Fatalf("Available() = %v, want %v", w.Available(), cap(b))
+		}
+
+		// While not recommended, it is valid to append to a shifted buffer.
+		// This forces Write to copy the input.
+		if rn.Intn(8) == 0 && cap(b) > 0 {
+			b = b[1:1:cap(b)]
+		}
+
+		// Append a random integer of varying width.
+		n := int64(rn.Intn(1 << rn.Intn(30)))
+		want = append(strconv.AppendInt(want, n, 10), ' ')
+		b = append(strconv.AppendInt(b, n, 10), ' ')
+		w.Write(b)
+	}
+	w.Flush()
+
+	if !bytes.Equal(got.Bytes(), want) {
+		t.Errorf("output mismatch:\ngot  %s\nwant %s", got.Bytes(), want)
+	}
+}
+
+// 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(strings.Builder)
+	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 buf.String() != s {
+		t.Errorf("WriteString wants %q gets %q", s, buf.String())
+	}
+}
+
+func TestWriteStringStringWriter(t *testing.T) {
+	const BufSize = 8
+	{
+		tw := &teststringwriter{}
+		b := NewWriterSize(tw, BufSize)
+		b.WriteString("1234")
+		tw.check(t, "", "")
+		b.WriteString("56789012")   // longer than BufSize
+		tw.check(t, "12345678", "") // but not enough (after filling the partially-filled buffer)
+		b.Flush()
+		tw.check(t, "123456789012", "")
+	}
+	{
+		tw := &teststringwriter{}
+		b := NewWriterSize(tw, BufSize)
+		b.WriteString("123456789")   // long string, empty buffer:
+		tw.check(t, "", "123456789") // use WriteString
+	}
+	{
+		tw := &teststringwriter{}
+		b := NewWriterSize(tw, BufSize)
+		b.WriteString("abc")
+		tw.check(t, "", "")
+		b.WriteString("123456789012345")      // long string, non-empty buffer
+		tw.check(t, "abc12345", "6789012345") // use Write and then WriteString since the remaining part is still longer than BufSize
+	}
+	{
+		tw := &teststringwriter{}
+		b := NewWriterSize(tw, BufSize)
+		b.Write([]byte("abc")) // same as above, but use Write instead of WriteString
+		tw.check(t, "", "")
+		b.WriteString("123456789012345")
+		tw.check(t, "abc12345", "6789012345") // same as above
+	}
+}
+
+type teststringwriter struct {
+	write       string
+	writeString string
+}
+
+func (w *teststringwriter) Write(b []byte) (int, error) {
+	w.write += string(b)
+	return len(b), nil
+}
+
+func (w *teststringwriter) WriteString(s string) (int, error) {
+	w.writeString += s
+	return len(s), nil
+}
+
+func (w *teststringwriter) check(t *testing.T, write, writeString string) {
+	t.Helper()
+	if w.write != write {
+		t.Errorf("write: expected %q, got %q", write, w.write)
+	}
+	if w.writeString != writeString {
+		t.Errorf("writeString: expected %q, got %q", writeString, w.writeString)
+	}
+}
+
+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(strings.Builder)
+	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 := io.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(strings.Builder)
+			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 io.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 := buf.String(), "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)
+	}
+}
+
+type readFromWriter struct {
+	buf           []byte
+	writeBytes    int
+	readFromBytes int
+}
+
+func (w *readFromWriter) Write(p []byte) (int, error) {
+	w.buf = append(w.buf, p...)
+	w.writeBytes += len(p)
+	return len(p), nil
+}
+
+func (w *readFromWriter) ReadFrom(r io.Reader) (int64, error) {
+	b, err := io.ReadAll(r)
+	w.buf = append(w.buf, b...)
+	w.readFromBytes += len(b)
+	return int64(len(b)), err
+}
+
+// Test that calling (*Writer).ReadFrom with a partially-filled buffer
+// fills the buffer before switching over to ReadFrom.
+func TestWriterReadFromWithBufferedData(t *testing.T) {
+	const bufsize = 16
+
+	input := createTestInput(64)
+	rfw := &readFromWriter{}
+	w := NewWriterSize(rfw, bufsize)
+
+	const writeSize = 8
+	if n, err := w.Write(input[:writeSize]); n != writeSize || err != nil {
+		t.Errorf("w.Write(%v bytes) = %v, %v; want %v, nil", writeSize, n, err, writeSize)
+	}
+	n, err := w.ReadFrom(bytes.NewReader(input[writeSize:]))
+	if wantn := len(input[writeSize:]); int(n) != wantn || err != nil {
+		t.Errorf("io.Copy(w, %v bytes) = %v, %v; want %v, nil", wantn, n, err, wantn)
+	}
+	if err := w.Flush(); err != nil {
+		t.Errorf("w.Flush() = %v, want nil", err)
+	}
+
+	if got, want := rfw.writeBytes, bufsize; got != want {
+		t.Errorf("wrote %v bytes with Write, want %v", got, want)
+	}
+	if got, want := rfw.readFromBytes, len(input)-bufsize; got != want {
+		t.Errorf("wrote %v bytes with ReadFrom, want %v", got, want)
+	}
+}
+
+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) {
+	checkAll := func(r *Reader, want string) {
+		t.Helper()
+		all, err := io.ReadAll(r)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if string(all) != want {
+			t.Errorf("ReadAll returned %q, want %q", all, want)
+		}
+	}
+
+	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"))
+	checkAll(r, "bar bar")
+
+	*r = Reader{} // zero out the Reader
+	r.Reset(strings.NewReader("bar bar"))
+	checkAll(r, "bar bar")
+
+	// Wrap a reader and then Reset to that reader.
+	r.Reset(strings.NewReader("recur"))
+	r2 := NewReader(r)
+	checkAll(r2, "recur")
+	r.Reset(strings.NewReader("recur2"))
+	r2.Reset(r)
+	checkAll(r2, "recur2")
+}
+
+func TestWriterReset(t *testing.T) {
+	var buf1, buf2, buf3, buf4, buf5 strings.Builder
+	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())
+	}
+
+	*w = Writer{}  // zero out the Writer
+	w.Reset(&buf3) // and not flushed
+	w.WriteString("bar")
+	w.Flush()
+	if buf1.String() != "" {
+		t.Errorf("buf1 = %q; want empty", buf1.String())
+	}
+	if buf3.String() != "bar" {
+		t.Errorf("buf3 = %q; want bar", buf3.String())
+	}
+
+	// Wrap a writer and then Reset to that writer.
+	w.Reset(&buf4)
+	w2 := NewWriter(w)
+	w2.WriteString("recur")
+	w2.Flush()
+	if buf4.String() != "recur" {
+		t.Errorf("buf4 = %q, want %q", buf4.String(), "recur")
+	}
+	w.Reset(&buf5)
+	w2.Reset(w)
+	w2.WriteString("recur2")
+	w2.Flush()
+	if buf5.String() != "recur2" {
+		t.Errorf("buf5 = %q, want %q", buf5.String(), "recur2")
+	}
+}
+
+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 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
+}
+
+// eofReader returns the number of bytes read and io.EOF for the read that consumes the last of the content.
+type eofReader struct {
+	buf []byte
+}
+
+func (r *eofReader) Read(p []byte) (int, error) {
+	read := copy(p, r.buf)
+	r.buf = r.buf[read:]
+
+	switch read {
+	case 0, len(r.buf):
+		// As allowed in the documentation, this will return io.EOF
+		// in the same call that consumes the last of the data.
+		// https://godoc.org/io#Reader
+		return read, io.EOF
+	}
+
+	return read, nil
+}
+
+func TestPartialReadEOF(t *testing.T) {
+	src := make([]byte, 10)
+	eofR := &eofReader{buf: src}
+	r := NewReader(eofR)
+
+	// Start by reading 5 of the 10 available bytes.
+	dest := make([]byte, 5)
+	read, err := r.Read(dest)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if n := len(dest); read != n {
+		t.Fatalf("read %d bytes; wanted %d bytes", read, n)
+	}
+
+	// The Reader should have buffered all the content from the io.Reader.
+	if n := len(eofR.buf); n != 0 {
+		t.Fatalf("got %d bytes left in bufio.Reader source; want 0 bytes", n)
+	}
+	// To prove the point, check that there are still 5 bytes available to read.
+	if n := r.Buffered(); n != 5 {
+		t.Fatalf("got %d bytes buffered in bufio.Reader; want 5 bytes", n)
+	}
+
+	// This is the second read of 0 bytes.
+	read, err = r.Read([]byte{})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if read != 0 {
+		t.Fatalf("read %d bytes; want 0 bytes", read)
+	}
+}
+
+type writerWithReadFromError struct{}
+
+func (w writerWithReadFromError) ReadFrom(r io.Reader) (int64, error) {
+	return 0, errors.New("writerWithReadFromError error")
+}
+
+func (w writerWithReadFromError) Write(b []byte) (n int, err error) {
+	return 10, nil
+}
+
+func TestWriterReadFromMustSetUnderlyingError(t *testing.T) {
+	var wr = NewWriter(writerWithReadFromError{})
+	if _, err := wr.ReadFrom(strings.NewReader("test2")); err == nil {
+		t.Fatal("expected ReadFrom returns error, got nil")
+	}
+	if _, err := wr.Write([]byte("123")); err == nil {
+		t.Fatal("expected Write returns error, got nil")
+	}
+}
+
+type writeErrorOnlyWriter struct{}
+
+func (w writeErrorOnlyWriter) Write(p []byte) (n int, err error) {
+	return 0, errors.New("writeErrorOnlyWriter error")
+}
+
+// Ensure that previous Write errors are immediately returned
+// on any ReadFrom. See golang.org/issue/35194.
+func TestWriterReadFromMustReturnUnderlyingError(t *testing.T) {
+	var wr = NewWriter(writeErrorOnlyWriter{})
+	s := "test1"
+	wantBuffered := len(s)
+	if _, err := wr.WriteString(s); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if err := wr.Flush(); err == nil {
+		t.Error("expected flush error, got nil")
+	}
+	if _, err := wr.ReadFrom(strings.NewReader("test2")); err == nil {
+		t.Fatal("expected error, got nil")
+	}
+	if buffered := wr.Buffered(); buffered != wantBuffered {
+		t.Fatalf("Buffered = %v; want %v", buffered, wantBuffered)
+	}
+}
+
+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 := io.Discard.(io.ReaderFrom); !ok {
+		b.Fatal("io.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(io.Discard)
+		if err != nil {
+			b.Fatal(err)
+		}
+		if n != bufSize {
+			b.Fatalf("n = %d; want %d", n, bufSize)
+		}
+	}
+}
+
+func BenchmarkReaderReadString(b *testing.B) {
+	r := strings.NewReader("       foo       foo        42        42        42        42        42        42        42        42       4.2       4.2       4.2       4.2\n")
+	buf := NewReader(r)
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		r.Seek(0, io.SeekStart)
+		buf.Reset(r)
+
+		_, err := buf.ReadString('\n')
+		if err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+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(io.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(io.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(io.Discard)
+	str := strings.Repeat("x", 50)
+	for i := 0; i < b.N; i++ {
+		bw.WriteString(str)
+		bw.Flush()
+	}
+}