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
5package strings_test
6
7import (
8	"bytes"
9	"fmt"
10	"io"
11	"strings"
12	"sync"
13	"testing"
14)
15
16func 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
64func 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
74func 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
102func 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
118func 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
139func 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.
162func 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
173func 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
193func 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