buffer_test.go

// 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 bytes

import (
	"io"
	"math/rand"
	"testing"
)

const N = 10000      // make this bigger for a larger (and slower) test
var data string      // test data for write tests
var testBytes []byte // test data; same as data but as a slice.

func init() {
	testBytes = make([]byte, N)
	for i := 0; i < N; i++ {
		testBytes[i] = 'a' + byte(i%26)
	}
	data = string(testBytes)
}

func (b *Buffer) Bytes() []byte {
	x := *b
	return []byte(x)
}

func (b *Buffer) Reset() {
	b.Truncate(0)
}

func (b *Buffer) Truncate(n int) {
	*b = (*b)[:n]
}

func (b *Buffer) String() string { 
	if b == nil {
		return "<nil>"
	}
	return string(*b) 
}

func (b *Buffer) Len() int { return len(*b) }

func (b *Buffer) Cap() int { return cap(*b) }

func (b *Buffer) WriteString(s string) (int, error) {
	return b.Write([]byte(s))
}

func (b *Buffer) WriteByte(c byte) error {
	*b = append(*b, c)
	return nil
}

func (b *Buffer) ReadByte() (byte, error) {
	if b.Len() == 0 {
		return 0, io.EOF
	}
	c := (*b)[0]
	*b = (*b)[1:]
	return c, nil
}

func NewBuffer(b []byte) *Buffer {
	x := Buffer(b)
	return &x
}

func NewBufferString(s string) *Buffer {
	return NewBuffer([]byte(s))
}

// Verify that contents of buf match the string s.
func check(t *testing.T, testname string, buf *Buffer, s string) {
	bytes := buf.Bytes()
	str := buf.String()
	if buf.Len() != len(bytes) {
		t.Errorf("%s: buf.Len() == %d, len(buf.Bytes()) == %d", testname, buf.Len(), len(bytes))
	}

	if buf.Len() != len(str) {
		t.Errorf("%s: buf.Len() == %d, len(buf.String()) == %d", testname, buf.Len(), len(str))
	}

	if buf.Len() != len(s) {
		t.Errorf("%s: buf.Len() == %d, len(s) == %d", testname, buf.Len(), len(s))
	}

	if string(bytes) != s {
		t.Errorf("%s: string(buf.Bytes()) == %q, s == %q", testname, string(bytes), s)
	}
}

// Fill buf through n writes of string fus.
// The initial contents of buf corresponds to the string s;
// the result is the final contents of buf returned as a string.
func fillString(t *testing.T, testname string, buf *Buffer, s string, n int, fus string) string {
	check(t, testname+" (fill 1)", buf, s)
	for ; n > 0; n-- {
		m, err := buf.WriteString(fus)
		if m != len(fus) {
			t.Errorf(testname+" (fill 2): m == %d, expected %d", m, len(fus))
		}
		if err != nil {
			t.Errorf(testname+" (fill 3): err should always be nil, found err == %s", err)
		}
		s += fus
		check(t, testname+" (fill 4)", buf, s)
	}
	return s
}

// Fill buf through n writes of byte slice fub.
// The initial contents of buf corresponds to the string s;
// the result is the final contents of buf returned as a string.
func fillBytes(t *testing.T, testname string, buf *Buffer, s string, n int, fub []byte) string {
	check(t, testname+" (fill 1)", buf, s)
	for ; n > 0; n-- {
		m, err := buf.Write(fub)
		if m != len(fub) {
			t.Errorf(testname+" (fill 2): m == %d, expected %d", m, len(fub))
		}
		if err != nil {
			t.Errorf(testname+" (fill 3): err should always be nil, found err == %s", err)
		}
		s += string(fub)
		check(t, testname+" (fill 4)", buf, s)
	}
	return s
}

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

func TestNewBufferString(t *testing.T) {
	buf := NewBufferString(data)
	check(t, "NewBufferString", buf, data)
}

// Empty buf through repeated reads into fub.
// The initial contents of buf corresponds to the string s.
func empty(t *testing.T, testname string, buf *Buffer, s string, fub []byte) {
	check(t, testname+" (empty 1)", buf, s)

	for {
		n, err := buf.Read(fub)
		if n == 0 {
			break
		}
		if err != nil {
			t.Errorf(testname+" (empty 2): err should always be nil, found err == %s", err)
		}
		s = s[n:]
		check(t, testname+" (empty 3)", buf, s)
	}

	check(t, testname+" (empty 4)", buf, "")
}

func TestBasicOperations(t *testing.T) {
	var buf Buffer

	for i := 0; i < 5; i++ {
		check(t, "TestBasicOperations (1)", &buf, "")

		buf.Reset()
		check(t, "TestBasicOperations (2)", &buf, "")

		buf.Truncate(0)
		check(t, "TestBasicOperations (3)", &buf, "")

		n, err := buf.Write([]byte(data[0:1]))
		if n != 1 {
			t.Errorf("wrote 1 byte, but n == %d", n)
		}
		if err != nil {
			t.Errorf("err should always be nil, but err == %s", err)
		}
		check(t, "TestBasicOperations (4)", &buf, "a")

		buf.WriteByte(data[1])
		check(t, "TestBasicOperations (5)", &buf, "ab")

		n, err = buf.Write([]byte(data[2:26]))
		if n != 24 {
			t.Errorf("wrote 25 bytes, but n == %d", n)
		}
		check(t, "TestBasicOperations (6)", &buf, string(data[0:26]))

		buf.Truncate(26)
		check(t, "TestBasicOperations (7)", &buf, string(data[0:26]))

		buf.Truncate(20)
		check(t, "TestBasicOperations (8)", &buf, string(data[0:20]))

		empty(t, "TestBasicOperations (9)", &buf, string(data[0:20]), make([]byte, 5))
		empty(t, "TestBasicOperations (10)", &buf, "", make([]byte, 100))

		buf.WriteByte(data[1])
		c, err := buf.ReadByte()
		if err != nil {
			t.Error("ReadByte unexpected eof")
		}
		if c != data[1] {
			t.Errorf("ReadByte wrong value c=%v", c)
		}
		c, err = buf.ReadByte()
		if err == nil {
			t.Error("ReadByte unexpected not eof")
		}
	}
}

func TestLargeStringWrites(t *testing.T) {
	var buf Buffer
	limit := 30
	if testing.Short() {
		limit = 9
	}
	for i := 3; i < limit; i += 3 {
		s := fillString(t, "TestLargeWrites (1)", &buf, "", 5, data)
		empty(t, "TestLargeStringWrites (2)", &buf, s, make([]byte, len(data)/i))
	}
	check(t, "TestLargeStringWrites (3)", &buf, "")
}

func TestLargeByteWrites(t *testing.T) {
	var buf Buffer
	limit := 30
	if testing.Short() {
		limit = 9
	}
	for i := 3; i < limit; i += 3 {
		s := fillBytes(t, "TestLargeWrites (1)", &buf, "", 5, testBytes)
		empty(t, "TestLargeByteWrites (2)", &buf, s, make([]byte, len(data)/i))
	}
	check(t, "TestLargeByteWrites (3)", &buf, "")
}

func TestLargeStringReads(t *testing.T) {
	var buf Buffer
	for i := 3; i < 30; i += 3 {
		s := fillString(t, "TestLargeReads (1)", &buf, "", 5, data[0:len(data)/i])
		empty(t, "TestLargeReads (2)", &buf, s, make([]byte, len(data)))
	}
	check(t, "TestLargeStringReads (3)", &buf, "")
}

func TestLargeByteReads(t *testing.T) {
	var buf Buffer
	for i := 3; i < 30; i += 3 {
		s := fillBytes(t, "TestLargeReads (1)", &buf, "", 5, testBytes[0:len(testBytes)/i])
		empty(t, "TestLargeReads (2)", &buf, s, make([]byte, len(data)))
	}
	check(t, "TestLargeByteReads (3)", &buf, "")
}

func TestMixedReadsAndWrites(t *testing.T) {
	var buf Buffer
	s := ""
	for i := 0; i < 50; i++ {
		wlen := rand.Intn(len(data))
		if i%2 == 0 {
			s = fillString(t, "TestMixedReadsAndWrites (1)", &buf, s, 1, data[0:wlen])
		} else {
			s = fillBytes(t, "TestMixedReadsAndWrites (1)", &buf, s, 1, testBytes[0:wlen])
		}

		rlen := rand.Intn(len(data))
		fub := make([]byte, rlen)
		n, _ := buf.Read(fub)
		s = s[n:]
	}
	empty(t, "TestMixedReadsAndWrites (2)", &buf, s, make([]byte, buf.Len()))
}

func TestCapWithPreallocatedSlice(t *testing.T) {
	buf := NewBuffer(make([]byte, 10))
	n := buf.Cap()
	if n != 10 {
		t.Errorf("expected 10, got %d", n)
	}
}

func TestCapWithSliceAndWrittenData(t *testing.T) {
	buf := NewBuffer(make([]byte, 0, 10))
	buf.Write([]byte("test"))
	n := buf.Cap()
	if n != 10 {
		t.Errorf("expected 10, got %d", n)
	}
}

func TestNil(t *testing.T) {
	var b *Buffer
	if b.String() != "<nil>" {
		t.Errorf("expected <nil>; got %q", b.String())
	}
}

// Was a bug: used to give EOF reading empty slice at EOF.
func TestReadEmptyAtEOF(t *testing.T) {
	b := new(Buffer)
	slice := make([]byte, 0)
	n, err := b.Read(slice)
	if err != nil {
		t.Errorf("read error: %v", err)
	}
	if n != 0 {
		t.Errorf("wrong count; got %d want 0", n)
	}
}

// From Issue 5154.
func BenchmarkBufferNotEmptyWriteRead(b *testing.B) {
	buf := make([]byte, 1024)
	for i := 0; i < b.N; i++ {
		var b Buffer
		b.Write(buf[0:1])
		for i := 0; i < 5<<10; i++ {
			b.Write(buf)
			b.Read(buf)
		}
	}
}

// Check that we don't compact too often. From Issue 5154.
func BenchmarkBufferFullSmallReads(b *testing.B) {
	buf := make([]byte, 1024)
	for i := 0; i < b.N; i++ {
		var b Buffer
		b.Write(buf)
		for b.Len()+20 < b.Cap() {
			b.Write(buf[:10])
		}
		for i := 0; i < 5<<10; i++ {
			b.Read(buf[:1])
			b.Write(buf[:1])
		}
	}
}