英文:
Get the amount of bytes streamed from an io.Reader Read
问题
这是我的代码片段，它执行一个GET请求，并将响应流式传输到cmd.Stdin。
resp, err := httpClient.Get(url)
if err != nil {
err = errors.Wrap(err, "HTTP请求失败")
return
}
reader := bufio.NewReader(resp.Body)
args = append(args, "-") // 在stdin上继续监听文件数据
cmd := exec.Command("exiftool", args...)
stdout, err := cmd.StdoutPipe()
if err != nil {
return
}
cmd.Stdin = reader
err = cmd.Start()
if err != nil {
return
}
我想知道在执行完成时流式传输了多少数据。
所以我需要捕获在流式传输时正在读取的内容，或者至少捕获正在读取的内容的大小。
英文:
Here is a snippet of my code that does a GET request, and streams the response into cmd.Stdin.
resp, err = httpClient.Get(url)
if err != nil {
err = errors.Wrap(err, "HTTP request failed")
return
}
reader = bufio.NewReader(resp.Body)
args = append(args, "-") // Keep listening on stdin for file data
cmd := exec.Command("exiftool", args...)
stdout, err := cmd.StdoutPipe()
if err != nil {
return
}
cmd.Stdin = reader
err = cmd.Start()
if err != nil {
return
}
I want to know how much data is streamed by the time it finishes executing.
So what I need is to capture what is being read while it's streaming, or at least capture the size of what is being read.
答案1
得分: 4
包装读取器。在包装器中计数。
type wrapper struct {
io.Reader
n int
}
func (w *wrapper) Read(p []byte) (int, error) {
n, err := w.Reader.Read(p)
w.n += n
return n, err
}
将其插入到应用程序中，如下所示：
args = append(args, "-")
cmd := exec.Command("exiftool", args...)
stdout, err := cmd.StdoutPipe()
if err != nil {
return
}
reader := &wrapper{Reader: resp.Body}
cmd.Stdin = reader
err = cmd.Run()
if err != nil {
return
}
fmt.Println(reader.n) // 打印读取的字节数。
因为 exec 包在从响应复制到 stdin 时使用缓冲区，所以 bufio.Reader 不太可能提供好处。如果确实有一些好处，可以使用以下**其中一种**选项：
```go
reader := &wrapper{Reader: bufio.NewReader(resp.Body)} // 选项 1
cmd.Stdin = bufio.NewReader(reader) // 选项 2
英文:
Wrap the reader. Count in the wrapper.
type wrapper struct {
io.Reader
n int
}
func (w *wrapper) Read(p []byte) (int, error) {
n, err := w.Reader.Read(p)
w.n += n
return n, err
}
Plug it into your application like this:
args = append(args, "-")
cmd := exec.Command("exiftool", args...)
stdout, err := cmd.StdoutPipe()
if err != nil {
return
}
reader := &wrapper{Reader: resp.Body}
cmd.Stdin = reader
err = cmd.Run()
if err != nil {
return
}
fmt.Println(reader.n) // prints number of bytes read.
Because the exec package uses a buffer when copying from the response to the stdin, a bufio.Reader is unlikely to provide a benefit. In case there is some benefit, use one of these options;
reader := &wrapper{Reader: bufio.NewReader(resp.Body)} // Option 1
cmd.Stdin = bufio.NewReader(reader) // Option 2
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