}
		s += string(fub)
		check(t, testname+" (fill 4)", buf, s)
	}
	return s
}

func TestNewBuffer(t *testing.T) {
	buf := NewBuffer(testBytes)
	check(t, "NewBuffer", buf, testString)
}

var buf Buffer

// Calling NewBuffer and immediately shallow copying the Buffer struct
// should not result in any allocations.
// This can be used to reset the underlying []byte of an existing Buffer.

			if err != nil {
				return
			}
			buf := bytes.NewBuffer(nil)
			if _, err := io.Copy(buf, r); err != nil {
				continue
			}
			files = append(files, file{header: hdr, content: buf.Bytes()})
		}

		// If we were unable to read anything out of the archive don't
		// bother trying to roundtrip it.
		if len(files) == 0 {
			return
		}

		out := bytes.NewBuffer(nil)
		w := NewWriter(out)
		for _, f := range files {

		b = strconv.AppendInt(b, int64(i), 10)
		b = append(b, ' ')
		buf.Write(b)
	}
	os.Stdout.Write(buf.Bytes())
	// Output: 0 1 2 3
}

func ExampleBuffer_Cap() {
	buf1 := bytes.NewBuffer(make([]byte, 10))
	buf2 := bytes.NewBuffer(make([]byte, 0, 10))
	fmt.Println(buf1.Cap())
	fmt.Println(buf2.Cap())
	// Output:
	// 10
	// 10
}

func ExampleBuffer_Grow() {
	var b bytes.Buffer
	b.Grow(64)
	bb := b.Bytes()

	args := append(append([]string(nil), os.Args[1:]...), "-test.run=^Test18146$")
	for n := attempts; n > 0; n-- {
		cmd := exec.Command(os.Args[0], args...)
		cmd.Env = append(os.Environ(), "test18146=exec")
		buf := bytes.NewBuffer(nil)
		cmd.Stdout = buf
		cmd.Stderr = buf
		if err := cmd.Start(); err != nil {
			// We are starting so many processes that on
			// some systems (problem seen on Darwin,

		}
		tt.f(reader)
		err := reader.UnreadRune()
		if err == nil {
			t.Errorf("Unreading after %s: expected error", tt.name)
		}
	}
}

func TestReaderDoubleUnreadRune(t *testing.T) {
	buf := NewBuffer([]byte("groucho"))
	if _, _, err := buf.ReadRune(); err != nil {
		// should not happen
		t.Fatal(err)
	}
	if err := buf.UnreadByte(); err != nil {
		// should not happen
		t.Fatal(err)
	}

	slice, err := b.readSlice(delim)
	return string(slice), err
}

// NewBuffer creates and initializes a new [Buffer] using buf as its
// initial contents. The new [Buffer] takes ownership of buf, and the
// caller should not use buf after this call. NewBuffer is intended to
// prepare a [Buffer] to read existing data. It can also be used to set

	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))

	if err != ErrFormat {
		t.Fatalf("unexpected error, got: %v, want: %v", err, ErrFormat)
	}

	// Also check that an archive containing a handful of empty
	// files doesn't cause an issue
	b := bytes.NewBuffer(nil)
	w := NewWriter(b)
	for i := 0; i < 5; i++ {
		_, err := w.Create("")
		if err != nil {
			t.Fatalf("Writer.Create failed: %s", err)
		}
	}
	if err := w.Close(); err != nil {