libgo/go/io/example_test.go

   1 // Copyright 2015 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 io_test
   6
   7 import (
   8         "bytes"
   9         "fmt"
  10         "io"
  11         "io/ioutil"
  12         "log"
  13         "os"
  14         "strings"
  15 )
  16
  17 func ExampleCopy() {
  18         r := strings.NewReader("some io.Reader stream to be read\n")
  19
  20         if _, err := io.Copy(os.Stdout, r); err != nil {
  21                 log.Fatal(err)
  22         }
  23
  24         // Output:
  25         // some io.Reader stream to be read
  26 }
  27
  28 func ExampleCopyBuffer() {
  29         r1 := strings.NewReader("first reader\n")
  30         r2 := strings.NewReader("second reader\n")
  31         buf := make([]byte, 8)
  32
  33         // buf is used here...
  34         if _, err := io.CopyBuffer(os.Stdout, r1, buf); err != nil {
  35                 log.Fatal(err)
  36         }
  37
  38         // ... reused here also. No need to allocate an extra buffer.
  39         if _, err := io.CopyBuffer(os.Stdout, r2, buf); err != nil {
  40                 log.Fatal(err)
  41         }
  42
  43         // Output:
  44         // first reader
  45         // second reader
  46 }
  47
  48 func ExampleCopyN() {
  49         r := strings.NewReader("some io.Reader stream to be read")
  50
  51         if _, err := io.CopyN(os.Stdout, r, 5); err != nil {
  52                 log.Fatal(err)
  53         }
  54
  55         // Output:
  56         // some
  57 }
  58
  59 func ExampleReadAtLeast() {
  60         r := strings.NewReader("some io.Reader stream to be read\n")
  61
  62         buf := make([]byte, 33)
  63         if _, err := io.ReadAtLeast(r, buf, 4); err != nil {
  64                 log.Fatal(err)
  65         }
  66         fmt.Printf("%s\n", buf)
  67
  68         // buffer smaller than minimal read size.
  69         shortBuf := make([]byte, 3)
  70         if _, err := io.ReadAtLeast(r, shortBuf, 4); err != nil {
  71                 fmt.Println("error:", err)
  72         }
  73
  74         // minimal read size bigger than io.Reader stream
  75         longBuf := make([]byte, 64)
  76         if _, err := io.ReadAtLeast(r, longBuf, 64); err != nil {
  77                 fmt.Println("error:", err)
  78         }
  79
  80         // Output:
  81         // some io.Reader stream to be read
  82         //
  83         // error: short buffer
  84         // error: EOF
  85 }
  86
  87 func ExampleReadFull() {
  88         r := strings.NewReader("some io.Reader stream to be read\n")
  89
  90         buf := make([]byte, 4)
  91         if _, err := io.ReadFull(r, buf); err != nil {
  92                 log.Fatal(err)
  93         }
  94         fmt.Printf("%s\n", buf)
  95
  96         // minimal read size bigger than io.Reader stream
  97         longBuf := make([]byte, 64)
  98         if _, err := io.ReadFull(r, longBuf); err != nil {
  99                 fmt.Println("error:", err)
 100         }
 101
 102         // Output:
 103         // some
 104         // error: unexpected EOF
 105 }
 106
 107 func ExampleWriteString() {
 108         io.WriteString(os.Stdout, "Hello World")
 109
 110         // Output: Hello World
 111 }
 112
 113 func ExampleLimitReader() {
 114         r := strings.NewReader("some io.Reader stream to be read\n")
 115         lr := io.LimitReader(r, 4)
 116
 117         if _, err := io.Copy(os.Stdout, lr); err != nil {
 118                 log.Fatal(err)
 119         }
 120
 121         // Output:
 122         // some
 123 }
 124
 125 func ExampleMultiReader() {
 126         r1 := strings.NewReader("first reader ")
 127         r2 := strings.NewReader("second reader ")
 128         r3 := strings.NewReader("third reader\n")
 129         r := io.MultiReader(r1, r2, r3)
 130
 131         if _, err := io.Copy(os.Stdout, r); err != nil {
 132                 log.Fatal(err)
 133         }
 134
 135         // Output:
 136         // first reader second reader third reader
 137 }
 138
 139 func ExampleTeeReader() {
 140         r := strings.NewReader("some io.Reader stream to be read\n")
 141         var buf bytes.Buffer
 142         tee := io.TeeReader(r, &buf)
 143
 144         printall := func(r io.Reader) {
 145                 b, err := ioutil.ReadAll(r)
 146                 if err != nil {
 147                         log.Fatal(err)
 148                 }
 149
 150                 fmt.Printf("%s", b)
 151         }
 152
 153         printall(tee)
 154         printall(&buf)
 155
 156         // Output:
 157         // some io.Reader stream to be read
 158         // some io.Reader stream to be read
 159 }
 160
 161 func ExampleSectionReader() {
 162         r := strings.NewReader("some io.Reader stream to be read\n")
 163         s := io.NewSectionReader(r, 5, 17)
 164
 165         if _, err := io.Copy(os.Stdout, s); err != nil {
 166                 log.Fatal(err)
 167         }
 168
 169         // Output:
 170         // io.Reader stream
 171 }
 172
 173 func ExampleSectionReader_ReadAt() {
 174         r := strings.NewReader("some io.Reader stream to be read\n")
 175         s := io.NewSectionReader(r, 5, 16)
 176
 177         buf := make([]byte, 6)
 178         if _, err := s.ReadAt(buf, 10); err != nil {
 179                 log.Fatal(err)
 180         }
 181
 182         fmt.Printf("%s\n", buf)
 183
 184         // Output:
 185         // stream
 186 }
 187
 188 func ExampleSectionReader_Seek() {
 189         r := strings.NewReader("some io.Reader stream to be read\n")
 190         s := io.NewSectionReader(r, 5, 16)
 191
 192         if _, err := s.Seek(10, io.SeekStart); err != nil {
 193                 log.Fatal(err)
 194         }
 195
 196         buf := make([]byte, 6)
 197         if _, err := s.Read(buf); err != nil {
 198                 log.Fatal(err)
 199         }
 200
 201         fmt.Printf("%s\n", buf)
 202
 203         // Output:
 204         // stream
 205 }
 206
 207 func ExampleSeeker_Seek() {
 208         r := strings.NewReader("some io.Reader stream to be read\n")
 209         if _, err := io.Copy(os.Stdout, r); err != nil {
 210                 log.Fatal(err)
 211         }
 212
 213         r.Seek(15, io.SeekStart)
 214         if _, err := io.Copy(os.Stdout, r); err != nil {
 215                 log.Fatal(err)
 216         }
 217
 218         r.Seek(-5, io.SeekEnd)
 219         if _, err := io.Copy(os.Stdout, r); err != nil {
 220                 log.Fatal(err)
 221         }
 222
 223         // Output:
 224         // some io.Reader stream to be read
 225         // stream to be read
 226         // read
 227 }
 228
 229 func ExampleMultiWriter() {
 230         r := strings.NewReader("some io.Reader stream to be read\n")
 231
 232         var buf1, buf2 bytes.Buffer
 233         w := io.MultiWriter(&buf1, &buf2)
 234
 235         if _, err := io.Copy(w, r); err != nil {
 236                 log.Fatal(err)
 237         }
 238
 239         fmt.Print(buf1.String())
 240         fmt.Print(buf2.String())
 241
 242         // Output:
 243         // some io.Reader stream to be read
 244         // some io.Reader stream to be read
 245 }