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Source file src/strings/reader_test.go

Documentation: strings

     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 strings_test
     6  
     7  import (
     8  	"bytes"
     9  	"fmt"
    10  	"io"
    11  	"strings"
    12  	"sync"
    13  	"testing"
    14  )
    15  
    16  func TestReader(t *testing.T) {
    17  	r := strings.NewReader("0123456789")
    18  	tests := []struct {
    19  		off     int64
    20  		seek    int
    21  		n       int
    22  		want    string
    23  		wantpos int64
    24  		readerr error
    25  		seekerr string
    26  	}{
    27  		{seek: io.SeekStart, off: 0, n: 20, want: "0123456789"},
    28  		{seek: io.SeekStart, off: 1, n: 1, want: "1"},
    29  		{seek: io.SeekCurrent, off: 1, wantpos: 3, n: 2, want: "34"},
    30  		{seek: io.SeekStart, off: -1, seekerr: "strings.Reader.Seek: negative position"},
    31  		{seek: io.SeekStart, off: 1 << 33, wantpos: 1 << 33, readerr: io.EOF},
    32  		{seek: io.SeekCurrent, off: 1, wantpos: 1<<33 + 1, readerr: io.EOF},
    33  		{seek: io.SeekStart, n: 5, want: "01234"},
    34  		{seek: io.SeekCurrent, n: 5, want: "56789"},
    35  		{seek: io.SeekEnd, off: -1, n: 1, wantpos: 9, want: "9"},
    36  	}
    37  
    38  	for i, tt := range tests {
    39  		pos, err := r.Seek(tt.off, tt.seek)
    40  		if err == nil && tt.seekerr != "" {
    41  			t.Errorf("%d. want seek error %q", i, tt.seekerr)
    42  			continue
    43  		}
    44  		if err != nil && err.Error() != tt.seekerr {
    45  			t.Errorf("%d. seek error = %q; want %q", i, err.Error(), tt.seekerr)
    46  			continue
    47  		}
    48  		if tt.wantpos != 0 && tt.wantpos != pos {
    49  			t.Errorf("%d. pos = %d, want %d", i, pos, tt.wantpos)
    50  		}
    51  		buf := make([]byte, tt.n)
    52  		n, err := r.Read(buf)
    53  		if err != tt.readerr {
    54  			t.Errorf("%d. read = %v; want %v", i, err, tt.readerr)
    55  			continue
    56  		}
    57  		got := string(buf[:n])
    58  		if got != tt.want {
    59  			t.Errorf("%d. got %q; want %q", i, got, tt.want)
    60  		}
    61  	}
    62  }
    63  
    64  func TestReadAfterBigSeek(t *testing.T) {
    65  	r := strings.NewReader("0123456789")
    66  	if _, err := r.Seek(1<<31+5, io.SeekStart); err != nil {
    67  		t.Fatal(err)
    68  	}
    69  	if n, err := r.Read(make([]byte, 10)); n != 0 || err != io.EOF {
    70  		t.Errorf("Read = %d, %v; want 0, EOF", n, err)
    71  	}
    72  }
    73  
    74  func TestReaderAt(t *testing.T) {
    75  	r := strings.NewReader("0123456789")
    76  	tests := []struct {
    77  		off     int64
    78  		n       int
    79  		want    string
    80  		wanterr any
    81  	}{
    82  		{0, 10, "0123456789", nil},
    83  		{1, 10, "123456789", io.EOF},
    84  		{1, 9, "123456789", nil},
    85  		{11, 10, "", io.EOF},
    86  		{0, 0, "", nil},
    87  		{-1, 0, "", "strings.Reader.ReadAt: negative offset"},
    88  	}
    89  	for i, tt := range tests {
    90  		b := make([]byte, tt.n)
    91  		rn, err := r.ReadAt(b, tt.off)
    92  		got := string(b[:rn])
    93  		if got != tt.want {
    94  			t.Errorf("%d. got %q; want %q", i, got, tt.want)
    95  		}
    96  		if fmt.Sprintf("%v", err) != fmt.Sprintf("%v", tt.wanterr) {
    97  			t.Errorf("%d. got error = %v; want %v", i, err, tt.wanterr)
    98  		}
    99  	}
   100  }
   101  
   102  func TestReaderAtConcurrent(t *testing.T) {
   103  	// Test for the race detector, to verify ReadAt doesn't mutate
   104  	// any state.
   105  	r := strings.NewReader("0123456789")
   106  	var wg sync.WaitGroup
   107  	for i := 0; i < 5; i++ {
   108  		wg.Add(1)
   109  		go func(i int) {
   110  			defer wg.Done()
   111  			var buf [1]byte
   112  			r.ReadAt(buf[:], int64(i))
   113  		}(i)
   114  	}
   115  	wg.Wait()
   116  }
   117  
   118  func TestEmptyReaderConcurrent(t *testing.T) {
   119  	// Test for the race detector, to verify a Read that doesn't yield any bytes
   120  	// is okay to use from multiple goroutines. This was our historic behavior.
   121  	// See golang.org/issue/7856
   122  	r := strings.NewReader("")
   123  	var wg sync.WaitGroup
   124  	for i := 0; i < 5; i++ {
   125  		wg.Add(2)
   126  		go func() {
   127  			defer wg.Done()
   128  			var buf [1]byte
   129  			r.Read(buf[:])
   130  		}()
   131  		go func() {
   132  			defer wg.Done()
   133  			r.Read(nil)
   134  		}()
   135  	}
   136  	wg.Wait()
   137  }
   138  
   139  func TestWriteTo(t *testing.T) {
   140  	const str = "0123456789"
   141  	for i := 0; i <= len(str); i++ {
   142  		s := str[i:]
   143  		r := strings.NewReader(s)
   144  		var b bytes.Buffer
   145  		n, err := r.WriteTo(&b)
   146  		if expect := int64(len(s)); n != expect {
   147  			t.Errorf("got %v; want %v", n, expect)
   148  		}
   149  		if err != nil {
   150  			t.Errorf("for length %d: got error = %v; want nil", len(s), err)
   151  		}
   152  		if b.String() != s {
   153  			t.Errorf("got string %q; want %q", b.String(), s)
   154  		}
   155  		if r.Len() != 0 {
   156  			t.Errorf("reader contains %v bytes; want 0", r.Len())
   157  		}
   158  	}
   159  }
   160  
   161  // tests that Len is affected by reads, but Size is not.
   162  func TestReaderLenSize(t *testing.T) {
   163  	r := strings.NewReader("abc")
   164  	io.CopyN(io.Discard, r, 1)
   165  	if r.Len() != 2 {
   166  		t.Errorf("Len = %d; want 2", r.Len())
   167  	}
   168  	if r.Size() != 3 {
   169  		t.Errorf("Size = %d; want 3", r.Size())
   170  	}
   171  }
   172  
   173  func TestReaderReset(t *testing.T) {
   174  	r := strings.NewReader("世界")
   175  	if _, _, err := r.ReadRune(); err != nil {
   176  		t.Errorf("ReadRune: unexpected error: %v", err)
   177  	}
   178  
   179  	const want = "abcdef"
   180  	r.Reset(want)
   181  	if err := r.UnreadRune(); err == nil {
   182  		t.Errorf("UnreadRune: expected error, got nil")
   183  	}
   184  	buf, err := io.ReadAll(r)
   185  	if err != nil {
   186  		t.Errorf("ReadAll: unexpected error: %v", err)
   187  	}
   188  	if got := string(buf); got != want {
   189  		t.Errorf("ReadAll: got %q, want %q", got, want)
   190  	}
   191  }
   192  
   193  func TestReaderZero(t *testing.T) {
   194  	if l := (&strings.Reader{}).Len(); l != 0 {
   195  		t.Errorf("Len: got %d, want 0", l)
   196  	}
   197  
   198  	if n, err := (&strings.Reader{}).Read(nil); n != 0 || err != io.EOF {
   199  		t.Errorf("Read: got %d, %v; want 0, io.EOF", n, err)
   200  	}
   201  
   202  	if n, err := (&strings.Reader{}).ReadAt(nil, 11); n != 0 || err != io.EOF {
   203  		t.Errorf("ReadAt: got %d, %v; want 0, io.EOF", n, err)
   204  	}
   205  
   206  	if b, err := (&strings.Reader{}).ReadByte(); b != 0 || err != io.EOF {
   207  		t.Errorf("ReadByte: got %d, %v; want 0, io.EOF", b, err)
   208  	}
   209  
   210  	if ch, size, err := (&strings.Reader{}).ReadRune(); ch != 0 || size != 0 || err != io.EOF {
   211  		t.Errorf("ReadRune: got %d, %d, %v; want 0, 0, io.EOF", ch, size, err)
   212  	}
   213  
   214  	if offset, err := (&strings.Reader{}).Seek(11, io.SeekStart); offset != 11 || err != nil {
   215  		t.Errorf("Seek: got %d, %v; want 11, nil", offset, err)
   216  	}
   217  
   218  	if s := (&strings.Reader{}).Size(); s != 0 {
   219  		t.Errorf("Size: got %d, want 0", s)
   220  	}
   221  
   222  	if (&strings.Reader{}).UnreadByte() == nil {
   223  		t.Errorf("UnreadByte: got nil, want error")
   224  	}
   225  
   226  	if (&strings.Reader{}).UnreadRune() == nil {
   227  		t.Errorf("UnreadRune: got nil, want error")
   228  	}
   229  
   230  	if n, err := (&strings.Reader{}).WriteTo(io.Discard); n != 0 || err != nil {
   231  		t.Errorf("WriteTo: got %d, %v; want 0, nil", n, err)
   232  	}
   233  }
   234  

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