ctxcopy

ctxcopy

Update: this repo is no longer maintained. Use iocopy instead.

ctxcopy is a Golang package which provides helper functions for performing context-aware copy task.

Google's Context

• Context type, which carries deadlines, cancelation signals, and other request-scoped values across API boundaries and between processes.
• References:
• https://godoc.org/golang.org/x/net/context
• http://blog.golang.org/context

Context-aware

• ctxcopy.Copy()'s first parameter is Context type.
• Copy() will stop if context's cancel() function is called in other goroutines.
• Copy() will stop if context's deadline exceeded.

Example

// 1. Run "go get github.com/northbright/pathhelper" to install pathhelper.
// 2. Run "go test -c && ./ctxcopy.test"
func ExampleCopy() {
    // Download a zip from web server to local storage to test Copy().
    url := "https://github.com/northbright/plants/archive/master.zip"
    totalTimeoutSeconds := 10 // to make download successful, set it to 300 or more.
    totalTimeout := time.Duration(time.Duration(totalTimeoutSeconds) * time.Second)

    // Make context to carry a deadline(timeout).
    // See http://blog.golang.org/context for more information.
    ctx, cancel := context.WithTimeout(context.Background(), totalTimeout)
    defer cancel()

    // Get response body for source.
    resp, err := http.Get(url)
    if err != nil {
        fmt.Fprintf(os.Stderr, "http.Get(%v) err: %v\n", url, err)
        return
    }
    defer resp.Body.Close()

    // Create a file for destination.
    fileName, _ := pathhelper.GetAbsPath("./1.zip")
    f, err := os.Create(fileName)
    if err != nil {
        fmt.Fprintf(os.Stderr, "os.Create(%v) err: %v\n", fileName, err)
        return
    }
    defer f.Sync()
    defer f.Close()

    buf := make([]byte, 2*1024*1024)

    // Copy starts.
    // Copy operation will be canceled if cancel() is called in other goroutine.
    // Copy operation will be stoped if deadline is exceeded(timeout).
    err = ctxcopy.Copy(ctx, f, resp.Body, buf)
    if err != nil {
        fmt.Fprintf(os.Stderr, "ctxcopy.Copy() err: %v\n", err)
    } else {
        fmt.Fprintf(os.Stderr, "ctxcopy.Copy() succeeded.\n")
    }

    // Output:
}

Go Version Requirement

• Go 1.5 and later
• See Fix the *http.Request has no field or method Cancel Issue

Documentation

• API References

License

• MIT License

References

• https://godoc.org/golang.org/x/net/context
• http://blog.golang.org/context
• https://github.com/golang/net/tree/master/context