英文:
How can I get os.Errno from os.Error? Other ways to use os.Timeout?
问题
The net.Conn interface provides the SetTimeout methods and I am supposed to check the returned error with os.Timeout. However I see no way of calling os.Timeout on the returned os.Error.
(The os.Error I've got is read unix @: Resource temporarily unavailable which seem to consists of two parts: description of the function which timed out and the strerror description of the EAGAIN. I've tried err == os.EAGAIN and it doesn't work, probably because of the extra information in os.Error).
英文:
The net.Conn interface provides the SetTimeout methods and I am supposed to check the returned error with os.Timeout. However I see no way of calling os.Timeout on the returned os.Error.
(The os.Error I've got is read unix @: Resource temporarily unavailable which seem to consists of two parts: description of the function which timed out and the strerror description of the EAGAIN. I've tried err == os.EAGAIN and it doesn't work, probably because of the extra information in os.Error).
答案1
得分: 1
"An I/O Package"部分的Go教程中有以下代码片段：
func OpenFile(name string, mode int, perm uint32) (file *File, err os.Error) {
r, e := syscall.Open(name, mode, perm)
if e != 0 {
err = os.Errno(e)
}
return newFile(r, name), err
}
syscall.Open()的签名如下：
func Open(path string, mode int, perm uint32) (fd int, errno int)
所以我认为可以安全地假设os.Error仍然只是整数错误代码，只是添加了一些额外的内容，你检查它的方法是正确的。
为了调查为什么err == os.EAGAIN对你不起作用，我会将错误打印为int类型的值，然后在你的平台的errno.h文件中搜索打印的值。
英文:
The "An I/O Package" section of the Go tutorial has this snippet:
func OpenFile(name string, mode int, perm uint32) (file *File, err os.Error) {
r, e := syscall.Open(name, mode, perm)
if e != 0 {
err = os.Errno(e)
}
return newFile(r, name), err
}
syscall.Open() has this signature:
func Open(path string, mode int, perm uint32) (fd int, errno int)
So I think it's safe to assume os.Error is still just that integer error code, just with the added fluff and your approach to check it is correct.
To investigate why err == os.EAGAIN did not work for you, I'd print the error as a value of type int and then grepped your platform's errno.h file for the value printed.
答案2
得分: 0
你需要进行类型断言。假设kon是net.Conn类型，你将读取到缓冲区buf。然后：
if numread, err := kon.Read(buf); err != nil {
if val, ok := err.(os.Errno); ok {
if val.Timeout() {
println("连接到:", kon.RemoteAddr().String(), "超时。")
}
}
}
当然，这只是一个简要的想法。在实践中，你可能希望做一些更优雅（更复杂）的事情，并使用类型切换同时考虑更多情况。
英文:
You need to do a type assertion. Let's say kon is type net.Conn and you read into buffer buf. Then:
if numread, err := kon.Read(buf); err != nil {
if val, ok := err.(os.Errno); ok {
if val.Timeout() {
println("Connection to:", kon.RemoteAddr().String(), "timed out.")
}
}
}
That's of course only a gist of the idea. In practice you probably want to do something more elegant (aka more RL complexleete) and consider more cases at once with Type switches.
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