Source file src/bytes/reader_test.go

     1  // Copyright 2012 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  	"fmt"
    10  	"io"
    11  	"sync"
    12  	"testing"
    13  )
    14  
    15  func TestReader(t *testing.T) {
    16  	r := NewReader([]byte("0123456789"))
    17  	tests := []struct {
    18  		off     int64
    19  		seek    int
    20  		n       int
    21  		want    string
    22  		wantpos int64
    23  		readerr error
    24  		seekerr string
    25  	}{
    26  		{seek: io.SeekStart, off: 0, n: 20, want: "0123456789"},
    27  		{seek: io.SeekStart, off: 1, n: 1, want: "1"},
    28  		{seek: io.SeekCurrent, off: 1, wantpos: 3, n: 2, want: "34"},
    29  		{seek: io.SeekStart, off: -1, seekerr: "bytes.Reader.Seek: negative position"},
    30  		{seek: io.SeekStart, off: 1 << 33, wantpos: 1 << 33, readerr: io.EOF},
    31  		{seek: io.SeekCurrent, off: 1, wantpos: 1<<33 + 1, readerr: io.EOF},
    32  		{seek: io.SeekStart, n: 5, want: "01234"},
    33  		{seek: io.SeekCurrent, n: 5, want: "56789"},
    34  		{seek: io.SeekEnd, off: -1, n: 1, wantpos: 9, want: "9"},
    35  	}
    36  
    37  	for i, tt := range tests {
    38  		pos, err := r.Seek(tt.off, tt.seek)
    39  		if err == nil && tt.seekerr != "" {
    40  			t.Errorf("%d. want seek error %q", i, tt.seekerr)
    41  			continue
    42  		}
    43  		if err != nil && err.Error() != tt.seekerr {
    44  			t.Errorf("%d. seek error = %q; want %q", i, err.Error(), tt.seekerr)
    45  			continue
    46  		}
    47  		if tt.wantpos != 0 && tt.wantpos != pos {
    48  			t.Errorf("%d. pos = %d, want %d", i, pos, tt.wantpos)
    49  		}
    50  		buf := make([]byte, tt.n)
    51  		n, err := r.Read(buf)
    52  		if err != tt.readerr {
    53  			t.Errorf("%d. read = %v; want %v", i, err, tt.readerr)
    54  			continue
    55  		}
    56  		got := string(buf[:n])
    57  		if got != tt.want {
    58  			t.Errorf("%d. got %q; want %q", i, got, tt.want)
    59  		}
    60  	}
    61  }
    62  
    63  func TestReadAfterBigSeek(t *testing.T) {
    64  	r := NewReader([]byte("0123456789"))
    65  	if _, err := r.Seek(1<<31+5, io.SeekStart); err != nil {
    66  		t.Fatal(err)
    67  	}
    68  	if n, err := r.Read(make([]byte, 10)); n != 0 || err != io.EOF {
    69  		t.Errorf("Read = %d, %v; want 0, EOF", n, err)
    70  	}
    71  }
    72  
    73  func TestReaderAt(t *testing.T) {
    74  	r := NewReader([]byte("0123456789"))
    75  	tests := []struct {
    76  		off     int64
    77  		n       int
    78  		want    string
    79  		wanterr any
    80  	}{
    81  		{0, 10, "0123456789", nil},
    82  		{1, 10, "123456789", io.EOF},
    83  		{1, 9, "123456789", nil},
    84  		{11, 10, "", io.EOF},
    85  		{0, 0, "", nil},
    86  		{-1, 0, "", "bytes.Reader.ReadAt: negative offset"},
    87  	}
    88  	for i, tt := range tests {
    89  		b := make([]byte, tt.n)
    90  		rn, err := r.ReadAt(b, tt.off)
    91  		got := string(b[:rn])
    92  		if got != tt.want {
    93  			t.Errorf("%d. got %q; want %q", i, got, tt.want)
    94  		}
    95  		if fmt.Sprintf("%v", err) != fmt.Sprintf("%v", tt.wanterr) {
    96  			t.Errorf("%d. got error = %v; want %v", i, err, tt.wanterr)
    97  		}
    98  	}
    99  }
   100  
   101  func TestReaderAtConcurrent(t *testing.T) {
   102  	// Test for the race detector, to verify ReadAt doesn't mutate
   103  	// any state.
   104  	r := NewReader([]byte("0123456789"))
   105  	var wg sync.WaitGroup
   106  	for i := 0; i < 5; i++ {
   107  		wg.Add(1)
   108  		go func(i int) {
   109  			defer wg.Done()
   110  			var buf [1]byte
   111  			r.ReadAt(buf[:], int64(i))
   112  		}(i)
   113  	}
   114  	wg.Wait()
   115  }
   116  
   117  func TestEmptyReaderConcurrent(t *testing.T) {
   118  	// Test for the race detector, to verify a Read that doesn't yield any bytes
   119  	// is okay to use from multiple goroutines. This was our historic behavior.
   120  	// See golang.org/issue/7856
   121  	r := NewReader([]byte{})
   122  	var wg sync.WaitGroup
   123  	for i := 0; i < 5; i++ {
   124  		wg.Add(2)
   125  		go func() {
   126  			defer wg.Done()
   127  			var buf [1]byte
   128  			r.Read(buf[:])
   129  		}()
   130  		go func() {
   131  			defer wg.Done()
   132  			r.Read(nil)
   133  		}()
   134  	}
   135  	wg.Wait()
   136  }
   137  
   138  func TestReaderWriteTo(t *testing.T) {
   139  	for i := 0; i < 30; i += 3 {
   140  		var l int
   141  		if i > 0 {
   142  			l = len(testString) / i
   143  		}
   144  		s := testString[:l]
   145  		r := NewReader(testBytes[:l])
   146  		var b Buffer
   147  		n, err := r.WriteTo(&b)
   148  		if expect := int64(len(s)); n != expect {
   149  			t.Errorf("got %v; want %v", n, expect)
   150  		}
   151  		if err != nil {
   152  			t.Errorf("for length %d: got error = %v; want nil", l, err)
   153  		}
   154  		if b.String() != s {
   155  			t.Errorf("got string %q; want %q", b.String(), s)
   156  		}
   157  		if r.Len() != 0 {
   158  			t.Errorf("reader contains %v bytes; want 0", r.Len())
   159  		}
   160  	}
   161  }
   162  
   163  func TestReaderLen(t *testing.T) {
   164  	const data = "hello world"
   165  	r := NewReader([]byte(data))
   166  	if got, want := r.Len(), 11; got != want {
   167  		t.Errorf("r.Len(): got %d, want %d", got, want)
   168  	}
   169  	if n, err := r.Read(make([]byte, 10)); err != nil || n != 10 {
   170  		t.Errorf("Read failed: read %d %v", n, err)
   171  	}
   172  	if got, want := r.Len(), 1; got != want {
   173  		t.Errorf("r.Len(): got %d, want %d", got, want)
   174  	}
   175  	if n, err := r.Read(make([]byte, 1)); err != nil || n != 1 {
   176  		t.Errorf("Read failed: read %d %v; want 1, nil", n, err)
   177  	}
   178  	if got, want := r.Len(), 0; got != want {
   179  		t.Errorf("r.Len(): got %d, want %d", got, want)
   180  	}
   181  }
   182  
   183  var UnreadRuneErrorTests = []struct {
   184  	name string
   185  	f    func(*Reader)
   186  }{
   187  	{"Read", func(r *Reader) { r.Read([]byte{0}) }},
   188  	{"ReadByte", func(r *Reader) { r.ReadByte() }},
   189  	{"UnreadRune", func(r *Reader) { r.UnreadRune() }},
   190  	{"Seek", func(r *Reader) { r.Seek(0, io.SeekCurrent) }},
   191  	{"WriteTo", func(r *Reader) { r.WriteTo(&Buffer{}) }},
   192  }
   193  
   194  func TestUnreadRuneError(t *testing.T) {
   195  	for _, tt := range UnreadRuneErrorTests {
   196  		reader := NewReader([]byte("0123456789"))
   197  		if _, _, err := reader.ReadRune(); err != nil {
   198  			// should not happen
   199  			t.Fatal(err)
   200  		}
   201  		tt.f(reader)
   202  		err := reader.UnreadRune()
   203  		if err == nil {
   204  			t.Errorf("Unreading after %s: expected error", tt.name)
   205  		}
   206  	}
   207  }
   208  
   209  func TestReaderDoubleUnreadRune(t *testing.T) {
   210  	buf := NewBuffer([]byte("groucho"))
   211  	if _, _, err := buf.ReadRune(); err != nil {
   212  		// should not happen
   213  		t.Fatal(err)
   214  	}
   215  	if err := buf.UnreadByte(); err != nil {
   216  		// should not happen
   217  		t.Fatal(err)
   218  	}
   219  	if err := buf.UnreadByte(); err == nil {
   220  		t.Fatal("UnreadByte: expected error, got nil")
   221  	}
   222  }
   223  
   224  // verify that copying from an empty reader always has the same results,
   225  // regardless of the presence of a WriteTo method.
   226  func TestReaderCopyNothing(t *testing.T) {
   227  	type nErr struct {
   228  		n   int64
   229  		err error
   230  	}
   231  	type justReader struct {
   232  		io.Reader
   233  	}
   234  	type justWriter struct {
   235  		io.Writer
   236  	}
   237  	discard := justWriter{io.Discard} // hide ReadFrom
   238  
   239  	var with, withOut nErr
   240  	with.n, with.err = io.Copy(discard, NewReader(nil))
   241  	withOut.n, withOut.err = io.Copy(discard, justReader{NewReader(nil)})
   242  	if with != withOut {
   243  		t.Errorf("behavior differs: with = %#v; without: %#v", with, withOut)
   244  	}
   245  }
   246  
   247  // tests that Len is affected by reads, but Size is not.
   248  func TestReaderLenSize(t *testing.T) {
   249  	r := NewReader([]byte("abc"))
   250  	io.CopyN(io.Discard, r, 1)
   251  	if r.Len() != 2 {
   252  		t.Errorf("Len = %d; want 2", r.Len())
   253  	}
   254  	if r.Size() != 3 {
   255  		t.Errorf("Size = %d; want 3", r.Size())
   256  	}
   257  }
   258  
   259  func TestReaderReset(t *testing.T) {
   260  	r := NewReader([]byte("世界"))
   261  	if _, _, err := r.ReadRune(); err != nil {
   262  		t.Errorf("ReadRune: unexpected error: %v", err)
   263  	}
   264  
   265  	const want = "abcdef"
   266  	r.Reset([]byte(want))
   267  	if err := r.UnreadRune(); err == nil {
   268  		t.Errorf("UnreadRune: expected error, got nil")
   269  	}
   270  	buf, err := io.ReadAll(r)
   271  	if err != nil {
   272  		t.Errorf("ReadAll: unexpected error: %v", err)
   273  	}
   274  	if got := string(buf); got != want {
   275  		t.Errorf("ReadAll: got %q, want %q", got, want)
   276  	}
   277  }
   278  
   279  func TestReaderZero(t *testing.T) {
   280  	if l := (&Reader{}).Len(); l != 0 {
   281  		t.Errorf("Len: got %d, want 0", l)
   282  	}
   283  
   284  	if n, err := (&Reader{}).Read(nil); n != 0 || err != io.EOF {
   285  		t.Errorf("Read: got %d, %v; want 0, io.EOF", n, err)
   286  	}
   287  
   288  	if n, err := (&Reader{}).ReadAt(nil, 11); n != 0 || err != io.EOF {
   289  		t.Errorf("ReadAt: got %d, %v; want 0, io.EOF", n, err)
   290  	}
   291  
   292  	if b, err := (&Reader{}).ReadByte(); b != 0 || err != io.EOF {
   293  		t.Errorf("ReadByte: got %d, %v; want 0, io.EOF", b, err)
   294  	}
   295  
   296  	if ch, size, err := (&Reader{}).ReadRune(); ch != 0 || size != 0 || err != io.EOF {
   297  		t.Errorf("ReadRune: got %d, %d, %v; want 0, 0, io.EOF", ch, size, err)
   298  	}
   299  
   300  	if offset, err := (&Reader{}).Seek(11, io.SeekStart); offset != 11 || err != nil {
   301  		t.Errorf("Seek: got %d, %v; want 11, nil", offset, err)
   302  	}
   303  
   304  	if s := (&Reader{}).Size(); s != 0 {
   305  		t.Errorf("Size: got %d, want 0", s)
   306  	}
   307  
   308  	if (&Reader{}).UnreadByte() == nil {
   309  		t.Errorf("UnreadByte: got nil, want error")
   310  	}
   311  
   312  	if (&Reader{}).UnreadRune() == nil {
   313  		t.Errorf("UnreadRune: got nil, want error")
   314  	}
   315  
   316  	if n, err := (&Reader{}).WriteTo(io.Discard); n != 0 || err != nil {
   317  		t.Errorf("WriteTo: got %d, %v; want 0, nil", n, err)
   318  	}
   319  }
   320  

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