How can I write from multiple writers in golang?

huangapple
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英文:

How can I write from multiple writers in golang?

问题

创建一个函数，该函数将数据写入多个写入器，并返回每个写入器写入的字节数，返回的字节数的索引位置对应于写入器的索引位置。如果切片为空，则返回空切片([]int{})。

错误函数：

  1. type Errors []error
  3. func (m Errors) Error() string {
  4.     count := 0
  5.     for t := 0; t < len(m); t++ {
  6.         if m[t] != nil {
  7.             count += 1
  8.         }
  9.     }
  10.     errindex := 0
  11.     for t := 0; t < len(m); t++ {
  12.         if m[t] != nil {
  13.             errindex = t
  14.             break
  15.         }
  16.     }
  18.     if count == 0 {
  19.         return fmt.Sprintf("(0 errors)")
  20.     } else {
  21.         if count == 1 {
  22.             return fmt.Sprintf("%v", m[errindex])
  23.         } else if count == 2 {
  24.             return fmt.Sprintf("%v (and 1 other error)", m[errindex])
  25.         } else {
  26.             return fmt.Sprintf("%v (and %d other errors)", m[errindex], count-1)
  27.         }
  28.     }
  29. }

你的新代码：

  1. func WriteTo(b []byte, writers ...io.Writer) (n []int, errs errors.Errors) {
  2.     if len(writers) == 0 {
  3.         return []int{}, nil
  4.     }
  5.     for i := 0; i < len(writers); i++ {
  6.         num, err := writers[i].Write(b) // 将字节写入当前写入器
  7.         n = append(n, num)              // 添加当前写入器写入的字节数
  8.         if err != nil {
  9.             switch err {
  10.             case io.ErrShortWrite:
  11.                 errs = append(errs, err)
  12.             default:
  13.                 errs = append(errs, err)
  14.             }
  15.         }
  16.     }
  17.     return n, errs
  18. }

你尝试修复代码，但有些测试未通过。你无法看出问题所在。当count == 1时，返回的是count == 0的情况，当count == 2时，返回的是count == 0的情况。

  1. []error{nil, io.ErrShortWrite, nil},
  3. []error{nil, io.ErrShortWrite, io.ErrShortWrite},

以上是测试用例。

英文:

The idea is to create a function that will write to several writers and do a return so that:

  • write the []byte slice to all writers
  • return n bytes written by each writer with index position corresponding to the index position of the writer.
    -if slice is empty return ([]int{})
    ... etc

Error function:

  1. type Errors []error
  4. func (m Errors) Error() string {
  5. 	count := 0
  6. 	for t := 0; t &lt; len(m); t++ {
  7. 		if m[t] != nil {
  8. 			count += 1
  10. 		}
  11. 	}
  12. 	errindex := 0
  13. 	for t := 0; t &lt; len(m); t++ {
  14. 		if m[t] != nil {
  15. 			errindex = t
  16. 			break
  17. 		}
  18. 	}
  20. 	if count == 0 {
  21. 		return fmt.Sprintf(&quot;(0 errors)&quot;)
  22. 	} else {
  23. 		if count == 1 {
  24. 			return fmt.Sprintf(&quot;%v&quot;, m[errindex])
  25. 		} else if count == 2 {
  26. 			return fmt.Sprintf(&quot;%v (and 1 other error)&quot;, m[errindex])
  27. 		} else {
  28. 			return fmt.Sprintf(&quot;%v (and %d other errors)&quot;, m[errindex], count-1)
  30. 		}
  32. 	}
  33. }

My new code:

  1. func WriteTo(b []byte, writers ...io.Writer) (n []int, errs errors.Errors) {
  2. 	if len(writers) == 0 {
  3. 		return []int{}, nil
  4. 	}
  5. 	for i := 0; i &lt; len(writers); i++ {
  6. 		num, err := writers[i].Write(b) // write bytes to a current writer
  7. 		n = append(n, num)              // add bytes written by current write
  8. 		if err!=nil{
  9. 			switch err{
  10. 			case io.ErrShortWrite:
  11. 				errs = append(errs, err)
  12. 			default:
  13. 				errs = append(errs, err)
  14. 			}
  15. 		}
  16. 	}
  17. 	return n, errs
  18. }

I try to fix it but some tests don't pass. Can't really see the problem. Instead of returning when count == 1, returns when count == 0 and when count == 2, return as for count == 0

  1. 	[]error{nil, io.ErrShortWrite, nil},
  3. 	[]error{nil, io.ErrShortWrite, io.ErrShortWrite},

答案1

得分: 4

你可以使用io.MultiWriter()函数，它接受任意数量的io.Writer并返回一个单一的io.Writer，该写入器将数据复制到所有提供的写入器中。

例如：

  1. buf1 := &bytes.Buffer{}
  2. buf2 := &bytes.Buffer{}
  4. w := io.MultiWriter(buf1, buf2)
  6. if _, err := w.Write([]byte("Hello")); err != nil {
  7. 	panic(err)
  8. }
  10. fmt.Println("Buf1:", buf1.String())
  11. fmt.Println("Buf2:", buf2.String())

这将输出（在Go Playground上尝试）：

  1. Buf1: Hello
  2. Buf2: Hello
英文:

You may use io.MultiWriter() which takes arbitrary number of io.Writers and returns a single io.Writer, which duplicates writes to all provided writers.

For example:

  1. buf1 := &amp;bytes.Buffer{}
  2. buf2 := &amp;bytes.Buffer{}
  4. w := io.MultiWriter(buf1, buf2)
  6. if _, err := w.Write([]byte(&quot;Hello&quot;)); err != nil {
  7. 	panic(err)
  8. }
  10. fmt.Println(&quot;Buf1:&quot;, buf1.String())
  11. fmt.Println(&quot;Buf2:&quot;, buf2.String())

This will output (try it on the Go Playground):

  1. Buf1: Hello
  2. Buf2: Hello

huangapple
  • 本文由 发表于 2021年9月18日 17:13:53
  • 转载请务必保留本文链接：https://go.coder-hub.com/69233257.html
  • go
  • io
  • writer
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