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：
type Errors []error
func (m Errors) Error() string {
count := 0
for t := 0; t < len(m); t++ {
if m[t] != nil {
count += 1
}
}
errindex := 0
for t := 0; t < len(m); t++ {
if m[t] != nil {
errindex = t
break
}
}
if count == 0 {
return fmt.Sprintf("(0 errors)")
} else {
if count == 1 {
return fmt.Sprintf("%v", m[errindex])
} else if count == 2 {
return fmt.Sprintf("%v (and 1 other error)", m[errindex])
} else {
return fmt.Sprintf("%v (and %d other errors)", m[errindex], count-1)
}
}
}
你的新代码：
func WriteTo(b []byte, writers ...io.Writer) (n []int, errs errors.Errors) {
if len(writers) == 0 {
return []int{}, nil
}
for i := 0; i < len(writers); i++ {
num, err := writers[i].Write(b) // 将字节写入当前写入器
n = append(n, num) // 添加当前写入器写入的字节数
if err != nil {
switch err {
case io.ErrShortWrite:
errs = append(errs, err)
default:
errs = append(errs, err)
}
}
}
return n, errs
}
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。
[]error{nil, io.ErrShortWrite, nil},
[]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:
type Errors []error
func (m Errors) Error() string {
count := 0
for t := 0; t < len(m); t++ {
if m[t] != nil {
count += 1
}
}
errindex := 0
for t := 0; t < len(m); t++ {
if m[t] != nil {
errindex = t
break
}
}
if count == 0 {
return fmt.Sprintf("(0 errors)")
} else {
if count == 1 {
return fmt.Sprintf("%v", m[errindex])
} else if count == 2 {
return fmt.Sprintf("%v (and 1 other error)", m[errindex])
} else {
return fmt.Sprintf("%v (and %d other errors)", m[errindex], count-1)
}
}
}
My new code:
func WriteTo(b []byte, writers ...io.Writer) (n []int, errs errors.Errors) {
if len(writers) == 0 {
return []int{}, nil
}
for i := 0; i < len(writers); i++ {
num, err := writers[i].Write(b) // write bytes to a current writer
n = append(n, num) // add bytes written by current write
if err!=nil{
switch err{
case io.ErrShortWrite:
errs = append(errs, err)
default:
errs = append(errs, err)
}
}
}
return n, errs
}
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
[]error{nil, io.ErrShortWrite, nil},
[]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：
buf1 := &bytes.Buffer{}
buf2 := &bytes.Buffer{}
w := io.MultiWriter(buf1, buf2)
if _, err := w.Write([]byte("Hello")); err != nil {
panic(err)
}
fmt.Println("Buf1:", buf1.String())
fmt.Println("Buf2:", buf2.String())
这将输出（在Go Playground上尝试）：
Buf1: Hello
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:
buf1 := &bytes.Buffer{}
buf2 := &bytes.Buffer{}
w := io.MultiWriter(buf1, buf2)
if _, err := w.Write([]byte("Hello")); err != nil {
panic(err)
}
fmt.Println("Buf1:", buf1.String())
fmt.Println("Buf2:", buf2.String())
This will output (try it on the Go Playground):
Buf1: Hello
Buf2: Hello
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