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Source file src/bytes/buffer_test.go

Documentation: bytes

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package bytes_test
     6  
     7  import (
     8  	. "bytes"
     9  	"io"
    10  	"math/rand"
    11  	"runtime"
    12  	"testing"
    13  	"unicode/utf8"
    14  )
    15  
    16  const N = 10000       // make this bigger for a larger (and slower) test
    17  var testString string // test data for write tests
    18  var testBytes []byte  // test data; same as testString but as a slice.
    19  
    20  type negativeReader struct{}
    21  
    22  func (r *negativeReader) Read([]byte) (int, error) { return -1, nil }
    23  
    24  func init() {
    25  	testBytes = make([]byte, N)
    26  	for i := 0; i < N; i++ {
    27  		testBytes[i] = 'a' + byte(i%26)
    28  	}
    29  	testString = string(testBytes)
    30  }
    31  
    32  // Verify that contents of buf match the string s.
    33  func check(t *testing.T, testname string, buf *Buffer, s string) {
    34  	bytes := buf.Bytes()
    35  	str := buf.String()
    36  	if buf.Len() != len(bytes) {
    37  		t.Errorf("%s: buf.Len() == %d, len(buf.Bytes()) == %d", testname, buf.Len(), len(bytes))
    38  	}
    39  
    40  	if buf.Len() != len(str) {
    41  		t.Errorf("%s: buf.Len() == %d, len(buf.String()) == %d", testname, buf.Len(), len(str))
    42  	}
    43  
    44  	if buf.Len() != len(s) {
    45  		t.Errorf("%s: buf.Len() == %d, len(s) == %d", testname, buf.Len(), len(s))
    46  	}
    47  
    48  	if string(bytes) != s {
    49  		t.Errorf("%s: string(buf.Bytes()) == %q, s == %q", testname, string(bytes), s)
    50  	}
    51  }
    52  
    53  // Fill buf through n writes of string fus.
    54  // The initial contents of buf corresponds to the string s;
    55  // the result is the final contents of buf returned as a string.
    56  func fillString(t *testing.T, testname string, buf *Buffer, s string, n int, fus string) string {
    57  	check(t, testname+" (fill 1)", buf, s)
    58  	for ; n > 0; n-- {
    59  		m, err := buf.WriteString(fus)
    60  		if m != len(fus) {
    61  			t.Errorf(testname+" (fill 2): m == %d, expected %d", m, len(fus))
    62  		}
    63  		if err != nil {
    64  			t.Errorf(testname+" (fill 3): err should always be nil, found err == %s", err)
    65  		}
    66  		s += fus
    67  		check(t, testname+" (fill 4)", buf, s)
    68  	}
    69  	return s
    70  }
    71  
    72  // Fill buf through n writes of byte slice fub.
    73  // The initial contents of buf corresponds to the string s;
    74  // the result is the final contents of buf returned as a string.
    75  func fillBytes(t *testing.T, testname string, buf *Buffer, s string, n int, fub []byte) string {
    76  	check(t, testname+" (fill 1)", buf, s)
    77  	for ; n > 0; n-- {
    78  		m, err := buf.Write(fub)
    79  		if m != len(fub) {
    80  			t.Errorf(testname+" (fill 2): m == %d, expected %d", m, len(fub))
    81  		}
    82  		if err != nil {
    83  			t.Errorf(testname+" (fill 3): err should always be nil, found err == %s", err)
    84  		}
    85  		s += string(fub)
    86  		check(t, testname+" (fill 4)", buf, s)
    87  	}
    88  	return s
    89  }
    90  
    91  func TestNewBuffer(t *testing.T) {
    92  	buf := NewBuffer(testBytes)
    93  	check(t, "NewBuffer", buf, testString)
    94  }
    95  
    96  func TestNewBufferString(t *testing.T) {
    97  	buf := NewBufferString(testString)
    98  	check(t, "NewBufferString", buf, testString)
    99  }
   100  
   101  // Empty buf through repeated reads into fub.
   102  // The initial contents of buf corresponds to the string s.
   103  func empty(t *testing.T, testname string, buf *Buffer, s string, fub []byte) {
   104  	check(t, testname+" (empty 1)", buf, s)
   105  
   106  	for {
   107  		n, err := buf.Read(fub)
   108  		if n == 0 {
   109  			break
   110  		}
   111  		if err != nil {
   112  			t.Errorf(testname+" (empty 2): err should always be nil, found err == %s", err)
   113  		}
   114  		s = s[n:]
   115  		check(t, testname+" (empty 3)", buf, s)
   116  	}
   117  
   118  	check(t, testname+" (empty 4)", buf, "")
   119  }
   120  
   121  func TestBasicOperations(t *testing.T) {
   122  	var buf Buffer
   123  
   124  	for i := 0; i < 5; i++ {
   125  		check(t, "TestBasicOperations (1)", &buf, "")
   126  
   127  		buf.Reset()
   128  		check(t, "TestBasicOperations (2)", &buf, "")
   129  
   130  		buf.Truncate(0)
   131  		check(t, "TestBasicOperations (3)", &buf, "")
   132  
   133  		n, err := buf.Write(testBytes[0:1])
   134  		if n != 1 {
   135  			t.Errorf("wrote 1 byte, but n == %d", n)
   136  		}
   137  		if err != nil {
   138  			t.Errorf("err should always be nil, but err == %s", err)
   139  		}
   140  		check(t, "TestBasicOperations (4)", &buf, "a")
   141  
   142  		buf.WriteByte(testString[1])
   143  		check(t, "TestBasicOperations (5)", &buf, "ab")
   144  
   145  		n, err = buf.Write(testBytes[2:26])
   146  		if n != 24 {
   147  			t.Errorf("wrote 24 bytes, but n == %d", n)
   148  		}
   149  		check(t, "TestBasicOperations (6)", &buf, testString[0:26])
   150  
   151  		buf.Truncate(26)
   152  		check(t, "TestBasicOperations (7)", &buf, testString[0:26])
   153  
   154  		buf.Truncate(20)
   155  		check(t, "TestBasicOperations (8)", &buf, testString[0:20])
   156  
   157  		empty(t, "TestBasicOperations (9)", &buf, testString[0:20], make([]byte, 5))
   158  		empty(t, "TestBasicOperations (10)", &buf, "", make([]byte, 100))
   159  
   160  		buf.WriteByte(testString[1])
   161  		c, err := buf.ReadByte()
   162  		if err != nil {
   163  			t.Error("ReadByte unexpected eof")
   164  		}
   165  		if c != testString[1] {
   166  			t.Errorf("ReadByte wrong value c=%v", c)
   167  		}
   168  		c, err = buf.ReadByte()
   169  		if err == nil {
   170  			t.Error("ReadByte unexpected not eof")
   171  		}
   172  	}
   173  }
   174  
   175  func TestLargeStringWrites(t *testing.T) {
   176  	var buf Buffer
   177  	limit := 30
   178  	if testing.Short() {
   179  		limit = 9
   180  	}
   181  	for i := 3; i < limit; i += 3 {
   182  		s := fillString(t, "TestLargeWrites (1)", &buf, "", 5, testString)
   183  		empty(t, "TestLargeStringWrites (2)", &buf, s, make([]byte, len(testString)/i))
   184  	}
   185  	check(t, "TestLargeStringWrites (3)", &buf, "")
   186  }
   187  
   188  func TestLargeByteWrites(t *testing.T) {
   189  	var buf Buffer
   190  	limit := 30
   191  	if testing.Short() {
   192  		limit = 9
   193  	}
   194  	for i := 3; i < limit; i += 3 {
   195  		s := fillBytes(t, "TestLargeWrites (1)", &buf, "", 5, testBytes)
   196  		empty(t, "TestLargeByteWrites (2)", &buf, s, make([]byte, len(testString)/i))
   197  	}
   198  	check(t, "TestLargeByteWrites (3)", &buf, "")
   199  }
   200  
   201  func TestLargeStringReads(t *testing.T) {
   202  	var buf Buffer
   203  	for i := 3; i < 30; i += 3 {
   204  		s := fillString(t, "TestLargeReads (1)", &buf, "", 5, testString[0:len(testString)/i])
   205  		empty(t, "TestLargeReads (2)", &buf, s, make([]byte, len(testString)))
   206  	}
   207  	check(t, "TestLargeStringReads (3)", &buf, "")
   208  }
   209  
   210  func TestLargeByteReads(t *testing.T) {
   211  	var buf Buffer
   212  	for i := 3; i < 30; i += 3 {
   213  		s := fillBytes(t, "TestLargeReads (1)", &buf, "", 5, testBytes[0:len(testBytes)/i])
   214  		empty(t, "TestLargeReads (2)", &buf, s, make([]byte, len(testString)))
   215  	}
   216  	check(t, "TestLargeByteReads (3)", &buf, "")
   217  }
   218  
   219  func TestMixedReadsAndWrites(t *testing.T) {
   220  	var buf Buffer
   221  	s := ""
   222  	for i := 0; i < 50; i++ {
   223  		wlen := rand.Intn(len(testString))
   224  		if i%2 == 0 {
   225  			s = fillString(t, "TestMixedReadsAndWrites (1)", &buf, s, 1, testString[0:wlen])
   226  		} else {
   227  			s = fillBytes(t, "TestMixedReadsAndWrites (1)", &buf, s, 1, testBytes[0:wlen])
   228  		}
   229  
   230  		rlen := rand.Intn(len(testString))
   231  		fub := make([]byte, rlen)
   232  		n, _ := buf.Read(fub)
   233  		s = s[n:]
   234  	}
   235  	empty(t, "TestMixedReadsAndWrites (2)", &buf, s, make([]byte, buf.Len()))
   236  }
   237  
   238  func TestCapWithPreallocatedSlice(t *testing.T) {
   239  	buf := NewBuffer(make([]byte, 10))
   240  	n := buf.Cap()
   241  	if n != 10 {
   242  		t.Errorf("expected 10, got %d", n)
   243  	}
   244  }
   245  
   246  func TestCapWithSliceAndWrittenData(t *testing.T) {
   247  	buf := NewBuffer(make([]byte, 0, 10))
   248  	buf.Write([]byte("test"))
   249  	n := buf.Cap()
   250  	if n != 10 {
   251  		t.Errorf("expected 10, got %d", n)
   252  	}
   253  }
   254  
   255  func TestNil(t *testing.T) {
   256  	var b *Buffer
   257  	if b.String() != "<nil>" {
   258  		t.Errorf("expected <nil>; got %q", b.String())
   259  	}
   260  }
   261  
   262  func TestReadFrom(t *testing.T) {
   263  	var buf Buffer
   264  	for i := 3; i < 30; i += 3 {
   265  		s := fillBytes(t, "TestReadFrom (1)", &buf, "", 5, testBytes[0:len(testBytes)/i])
   266  		var b Buffer
   267  		b.ReadFrom(&buf)
   268  		empty(t, "TestReadFrom (2)", &b, s, make([]byte, len(testString)))
   269  	}
   270  }
   271  
   272  type panicReader struct{ panic bool }
   273  
   274  func (r panicReader) Read(p []byte) (int, error) {
   275  	if r.panic {
   276  		panic(nil)
   277  	}
   278  	return 0, io.EOF
   279  }
   280  
   281  // Make sure that an empty Buffer remains empty when
   282  // it is "grown" before a Read that panics
   283  func TestReadFromPanicReader(t *testing.T) {
   284  
   285  	// First verify non-panic behaviour
   286  	var buf Buffer
   287  	i, err := buf.ReadFrom(panicReader{})
   288  	if err != nil {
   289  		t.Fatal(err)
   290  	}
   291  	if i != 0 {
   292  		t.Fatalf("unexpected return from bytes.ReadFrom (1): got: %d, want %d", i, 0)
   293  	}
   294  	check(t, "TestReadFromPanicReader (1)", &buf, "")
   295  
   296  	// Confirm that when Reader panics, the emtpy buffer remains empty
   297  	var buf2 Buffer
   298  	defer func() {
   299  		recover()
   300  		check(t, "TestReadFromPanicReader (2)", &buf2, "")
   301  	}()
   302  	buf2.ReadFrom(panicReader{panic: true})
   303  }
   304  
   305  func TestReadFromNegativeReader(t *testing.T) {
   306  	var b Buffer
   307  	defer func() {
   308  		switch err := recover().(type) {
   309  		case nil:
   310  			t.Fatal("bytes.Buffer.ReadFrom didn't panic")
   311  		case error:
   312  			// this is the error string of errNegativeRead
   313  			wantError := "bytes.Buffer: reader returned negative count from Read"
   314  			if err.Error() != wantError {
   315  				t.Fatalf("recovered panic: got %v, want %v", err.Error(), wantError)
   316  			}
   317  		default:
   318  			t.Fatalf("unexpected panic value: %#v", err)
   319  		}
   320  	}()
   321  
   322  	b.ReadFrom(new(negativeReader))
   323  }
   324  
   325  func TestWriteTo(t *testing.T) {
   326  	var buf Buffer
   327  	for i := 3; i < 30; i += 3 {
   328  		s := fillBytes(t, "TestWriteTo (1)", &buf, "", 5, testBytes[0:len(testBytes)/i])
   329  		var b Buffer
   330  		buf.WriteTo(&b)
   331  		empty(t, "TestWriteTo (2)", &b, s, make([]byte, len(testString)))
   332  	}
   333  }
   334  
   335  func TestRuneIO(t *testing.T) {
   336  	const NRune = 1000
   337  	// Built a test slice while we write the data
   338  	b := make([]byte, utf8.UTFMax*NRune)
   339  	var buf Buffer
   340  	n := 0
   341  	for r := rune(0); r < NRune; r++ {
   342  		size := utf8.EncodeRune(b[n:], r)
   343  		nbytes, err := buf.WriteRune(r)
   344  		if err != nil {
   345  			t.Fatalf("WriteRune(%U) error: %s", r, err)
   346  		}
   347  		if nbytes != size {
   348  			t.Fatalf("WriteRune(%U) expected %d, got %d", r, size, nbytes)
   349  		}
   350  		n += size
   351  	}
   352  	b = b[0:n]
   353  
   354  	// Check the resulting bytes
   355  	if !Equal(buf.Bytes(), b) {
   356  		t.Fatalf("incorrect result from WriteRune: %q not %q", buf.Bytes(), b)
   357  	}
   358  
   359  	p := make([]byte, utf8.UTFMax)
   360  	// Read it back with ReadRune
   361  	for r := rune(0); r < NRune; r++ {
   362  		size := utf8.EncodeRune(p, r)
   363  		nr, nbytes, err := buf.ReadRune()
   364  		if nr != r || nbytes != size || err != nil {
   365  			t.Fatalf("ReadRune(%U) got %U,%d not %U,%d (err=%s)", r, nr, nbytes, r, size, err)
   366  		}
   367  	}
   368  
   369  	// Check that UnreadRune works
   370  	buf.Reset()
   371  
   372  	// check at EOF
   373  	if err := buf.UnreadRune(); err == nil {
   374  		t.Fatal("UnreadRune at EOF: got no error")
   375  	}
   376  	if _, _, err := buf.ReadRune(); err == nil {
   377  		t.Fatal("ReadRune at EOF: got no error")
   378  	}
   379  	if err := buf.UnreadRune(); err == nil {
   380  		t.Fatal("UnreadRune after ReadRune at EOF: got no error")
   381  	}
   382  
   383  	// check not at EOF
   384  	buf.Write(b)
   385  	for r := rune(0); r < NRune; r++ {
   386  		r1, size, _ := buf.ReadRune()
   387  		if err := buf.UnreadRune(); err != nil {
   388  			t.Fatalf("UnreadRune(%U) got error %q", r, err)
   389  		}
   390  		r2, nbytes, err := buf.ReadRune()
   391  		if r1 != r2 || r1 != r || nbytes != size || err != nil {
   392  			t.Fatalf("ReadRune(%U) after UnreadRune got %U,%d not %U,%d (err=%s)", r, r2, nbytes, r, size, err)
   393  		}
   394  	}
   395  }
   396  
   397  func TestNext(t *testing.T) {
   398  	b := []byte{0, 1, 2, 3, 4}
   399  	tmp := make([]byte, 5)
   400  	for i := 0; i <= 5; i++ {
   401  		for j := i; j <= 5; j++ {
   402  			for k := 0; k <= 6; k++ {
   403  				// 0 <= i <= j <= 5; 0 <= k <= 6
   404  				// Check that if we start with a buffer
   405  				// of length j at offset i and ask for
   406  				// Next(k), we get the right bytes.
   407  				buf := NewBuffer(b[0:j])
   408  				n, _ := buf.Read(tmp[0:i])
   409  				if n != i {
   410  					t.Fatalf("Read %d returned %d", i, n)
   411  				}
   412  				bb := buf.Next(k)
   413  				want := k
   414  				if want > j-i {
   415  					want = j - i
   416  				}
   417  				if len(bb) != want {
   418  					t.Fatalf("in %d,%d: len(Next(%d)) == %d", i, j, k, len(bb))
   419  				}
   420  				for l, v := range bb {
   421  					if v != byte(l+i) {
   422  						t.Fatalf("in %d,%d: Next(%d)[%d] = %d, want %d", i, j, k, l, v, l+i)
   423  					}
   424  				}
   425  			}
   426  		}
   427  	}
   428  }
   429  
   430  var readBytesTests = []struct {
   431  	buffer   string
   432  	delim    byte
   433  	expected []string
   434  	err      error
   435  }{
   436  	{"", 0, []string{""}, io.EOF},
   437  	{"a\x00", 0, []string{"a\x00"}, nil},
   438  	{"abbbaaaba", 'b', []string{"ab", "b", "b", "aaab"}, nil},
   439  	{"hello\x01world", 1, []string{"hello\x01"}, nil},
   440  	{"foo\nbar", 0, []string{"foo\nbar"}, io.EOF},
   441  	{"alpha\nbeta\ngamma\n", '\n', []string{"alpha\n", "beta\n", "gamma\n"}, nil},
   442  	{"alpha\nbeta\ngamma", '\n', []string{"alpha\n", "beta\n", "gamma"}, io.EOF},
   443  }
   444  
   445  func TestReadBytes(t *testing.T) {
   446  	for _, test := range readBytesTests {
   447  		buf := NewBufferString(test.buffer)
   448  		var err error
   449  		for _, expected := range test.expected {
   450  			var bytes []byte
   451  			bytes, err = buf.ReadBytes(test.delim)
   452  			if string(bytes) != expected {
   453  				t.Errorf("expected %q, got %q", expected, bytes)
   454  			}
   455  			if err != nil {
   456  				break
   457  			}
   458  		}
   459  		if err != test.err {
   460  			t.Errorf("expected error %v, got %v", test.err, err)
   461  		}
   462  	}
   463  }
   464  
   465  func TestReadString(t *testing.T) {
   466  	for _, test := range readBytesTests {
   467  		buf := NewBufferString(test.buffer)
   468  		var err error
   469  		for _, expected := range test.expected {
   470  			var s string
   471  			s, err = buf.ReadString(test.delim)
   472  			if s != expected {
   473  				t.Errorf("expected %q, got %q", expected, s)
   474  			}
   475  			if err != nil {
   476  				break
   477  			}
   478  		}
   479  		if err != test.err {
   480  			t.Errorf("expected error %v, got %v", test.err, err)
   481  		}
   482  	}
   483  }
   484  
   485  func BenchmarkReadString(b *testing.B) {
   486  	const n = 32 << 10
   487  
   488  	data := make([]byte, n)
   489  	data[n-1] = 'x'
   490  	b.SetBytes(int64(n))
   491  	for i := 0; i < b.N; i++ {
   492  		buf := NewBuffer(data)
   493  		_, err := buf.ReadString('x')
   494  		if err != nil {
   495  			b.Fatal(err)
   496  		}
   497  	}
   498  }
   499  
   500  func TestGrow(t *testing.T) {
   501  	x := []byte{'x'}
   502  	y := []byte{'y'}
   503  	tmp := make([]byte, 72)
   504  	for _, startLen := range []int{0, 100, 1000, 10000, 100000} {
   505  		xBytes := Repeat(x, startLen)
   506  		for _, growLen := range []int{0, 100, 1000, 10000, 100000} {
   507  			buf := NewBuffer(xBytes)
   508  			// If we read, this affects buf.off, which is good to test.
   509  			readBytes, _ := buf.Read(tmp)
   510  			buf.Grow(growLen)
   511  			yBytes := Repeat(y, growLen)
   512  			// Check no allocation occurs in write, as long as we're single-threaded.
   513  			var m1, m2 runtime.MemStats
   514  			runtime.ReadMemStats(&m1)
   515  			buf.Write(yBytes)
   516  			runtime.ReadMemStats(&m2)
   517  			if runtime.GOMAXPROCS(-1) == 1 && m1.Mallocs != m2.Mallocs {
   518  				t.Errorf("allocation occurred during write")
   519  			}
   520  			// Check that buffer has correct data.
   521  			if !Equal(buf.Bytes()[0:startLen-readBytes], xBytes[readBytes:]) {
   522  				t.Errorf("bad initial data at %d %d", startLen, growLen)
   523  			}
   524  			if !Equal(buf.Bytes()[startLen-readBytes:startLen-readBytes+growLen], yBytes) {
   525  				t.Errorf("bad written data at %d %d", startLen, growLen)
   526  			}
   527  		}
   528  	}
   529  }
   530  
   531  func TestGrowOverflow(t *testing.T) {
   532  	defer func() {
   533  		if err := recover(); err != ErrTooLarge {
   534  			t.Errorf("after too-large Grow, recover() = %v; want %v", err, ErrTooLarge)
   535  		}
   536  	}()
   537  
   538  	buf := NewBuffer(make([]byte, 1))
   539  	const maxInt = int(^uint(0) >> 1)
   540  	buf.Grow(maxInt)
   541  }
   542  
   543  // Was a bug: used to give EOF reading empty slice at EOF.
   544  func TestReadEmptyAtEOF(t *testing.T) {
   545  	b := new(Buffer)
   546  	slice := make([]byte, 0)
   547  	n, err := b.Read(slice)
   548  	if err != nil {
   549  		t.Errorf("read error: %v", err)
   550  	}
   551  	if n != 0 {
   552  		t.Errorf("wrong count; got %d want 0", n)
   553  	}
   554  }
   555  
   556  func TestUnreadByte(t *testing.T) {
   557  	b := new(Buffer)
   558  
   559  	// check at EOF
   560  	if err := b.UnreadByte(); err == nil {
   561  		t.Fatal("UnreadByte at EOF: got no error")
   562  	}
   563  	if _, err := b.ReadByte(); err == nil {
   564  		t.Fatal("ReadByte at EOF: got no error")
   565  	}
   566  	if err := b.UnreadByte(); err == nil {
   567  		t.Fatal("UnreadByte after ReadByte at EOF: got no error")
   568  	}
   569  
   570  	// check not at EOF
   571  	b.WriteString("abcdefghijklmnopqrstuvwxyz")
   572  
   573  	// after unsuccessful read
   574  	if n, err := b.Read(nil); n != 0 || err != nil {
   575  		t.Fatalf("Read(nil) = %d,%v; want 0,nil", n, err)
   576  	}
   577  	if err := b.UnreadByte(); err == nil {
   578  		t.Fatal("UnreadByte after Read(nil): got no error")
   579  	}
   580  
   581  	// after successful read
   582  	if _, err := b.ReadBytes('m'); err != nil {
   583  		t.Fatalf("ReadBytes: %v", err)
   584  	}
   585  	if err := b.UnreadByte(); err != nil {
   586  		t.Fatalf("UnreadByte: %v", err)
   587  	}
   588  	c, err := b.ReadByte()
   589  	if err != nil {
   590  		t.Fatalf("ReadByte: %v", err)
   591  	}
   592  	if c != 'm' {
   593  		t.Errorf("ReadByte = %q; want %q", c, 'm')
   594  	}
   595  }
   596  
   597  // Tests that we occasionally compact. Issue 5154.
   598  func TestBufferGrowth(t *testing.T) {
   599  	var b Buffer
   600  	buf := make([]byte, 1024)
   601  	b.Write(buf[0:1])
   602  	var cap0 int
   603  	for i := 0; i < 5<<10; i++ {
   604  		b.Write(buf)
   605  		b.Read(buf)
   606  		if i == 0 {
   607  			cap0 = b.Cap()
   608  		}
   609  	}
   610  	cap1 := b.Cap()
   611  	// (*Buffer).grow allows for 2x capacity slop before sliding,
   612  	// so set our error threshold at 3x.
   613  	if cap1 > cap0*3 {
   614  		t.Errorf("buffer cap = %d; too big (grew from %d)", cap1, cap0)
   615  	}
   616  }
   617  
   618  func BenchmarkWriteByte(b *testing.B) {
   619  	const n = 4 << 10
   620  	b.SetBytes(n)
   621  	buf := NewBuffer(make([]byte, n))
   622  	for i := 0; i < b.N; i++ {
   623  		buf.Reset()
   624  		for i := 0; i < n; i++ {
   625  			buf.WriteByte('x')
   626  		}
   627  	}
   628  }
   629  
   630  func BenchmarkWriteRune(b *testing.B) {
   631  	const n = 4 << 10
   632  	const r = '☺'
   633  	b.SetBytes(int64(n * utf8.RuneLen(r)))
   634  	buf := NewBuffer(make([]byte, n*utf8.UTFMax))
   635  	for i := 0; i < b.N; i++ {
   636  		buf.Reset()
   637  		for i := 0; i < n; i++ {
   638  			buf.WriteRune(r)
   639  		}
   640  	}
   641  }
   642  
   643  // From Issue 5154.
   644  func BenchmarkBufferNotEmptyWriteRead(b *testing.B) {
   645  	buf := make([]byte, 1024)
   646  	for i := 0; i < b.N; i++ {
   647  		var b Buffer
   648  		b.Write(buf[0:1])
   649  		for i := 0; i < 5<<10; i++ {
   650  			b.Write(buf)
   651  			b.Read(buf)
   652  		}
   653  	}
   654  }
   655  
   656  // Check that we don't compact too often. From Issue 5154.
   657  func BenchmarkBufferFullSmallReads(b *testing.B) {
   658  	buf := make([]byte, 1024)
   659  	for i := 0; i < b.N; i++ {
   660  		var b Buffer
   661  		b.Write(buf)
   662  		for b.Len()+20 < b.Cap() {
   663  			b.Write(buf[:10])
   664  		}
   665  		for i := 0; i < 5<<10; i++ {
   666  			b.Read(buf[:1])
   667  			b.Write(buf[:1])
   668  		}
   669  	}
   670  }
   671  

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