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func Copy(src io.Reader, dst io.Writer) error { //... } import gocopy s := file.Open() err := gocopy.Copy(s, d) func Copy(src io.Reader, dst io.Writer) (statusCh, error) { //... go func() { statusCh }() } func Read() { select { case status := <-statusCh: } } type Stat struct { status string err error } func Copy(src io.Reader, dst io.Writer) chan Stat { //... statusCh := make(chan Stat{}) go func() { statusCh{ } } return statusCh } func Read() { select { case status := <-statusCh: } } import gocopy s := file.Open() err := gocopy.Copy(s, d) func Copy(src io.Reader, dst io.Writer) chan Stat { //... statusCh := make(chan Stat{}) buf := make([]byte, 1024) var total int64 go func() { for { n, err := src.Read(buf) if n > 0 { writen, err := dst.Write(buf[:n]) total += int64(writen) if err != nil { statusCh <- Stat{ status: "done with err", err: err, } return } } if err == io.EOF { statusCh <- Stat{ bCopy: total, status: "done", err: nil, } return } if err != nil { statusCh <- Stat{ status: "done with err", err: err, } return } } } return statusCh } func Read() { select { case status := <-statusCh: if status.err != nil { return } } } func Copy(src io.Reader, dst io.Writer) chan Stat { //... statusCh := make(chan Stat{}) buf := make([]byte, 1024) var total int64 go func() { for { select { case : n, err := src.Read(buf) if n > 0 { writen, err := dst.Write(buf[:n]) total += int64(writen) if err != nil { statusCh <- Stat{ status: "done with err", err: err, } return } } if err == io.EOF { statusCh <- Stat{ bCopy: total, status: "done", err: nil, } return } if err != nil { statusCh <- Stat{ status: "done with err", err: err, } return } default: statusCh <- Stat{ bCopy: total, status: "pending", err: nil, } } } } return statusCh } func Read() { select { case status := <-statusCh: if status.err != nil { return } } }

sobes.tech AI

Answer from AI

The provided code demonstrates the idea of asynchronous data copying from io.Reader to io.Writer using a channel to transmit the operation's status.

Main points:

The Copy function launches a goroutine that reads from src and writes to dst in a loop.
During copying, it sends a Stat structure to the statusCh channel, which contains the operation status and any error.
The channel allows the calling code to receive updates on the copying progress or errors.

A simplified implementation example:

package gocopy

import (
    "io"
)

type Stat struct {
    bCopy  int64
    status string
    err    error
}

func Copy(src io.Reader, dst io.Writer) chan Stat {
    statusCh := make(chan Stat)
    buf := make([]byte, 1024)
    var total int64

    go func() {
        defer close(statusCh)
        for {
            n, err := src.Read(buf)
            if n > 0 {
                written, werr := dst.Write(buf[:n])
                total += int64(written)
                if werr != nil {
                    statusCh <- Stat{status: "done with err", err: werr}
                    return
                }
            }
            if err == io.EOF {
                statusCh <- Stat{bCopy: total, status: "done", err: nil}
                return
            }
            if err != nil {
                statusCh <- Stat{status: "done with err", err: err}
                return
            }
            // Intermediate status can be sent if needed
            statusCh <- Stat{bCopy: total, status: "pending", err: nil}
        }
    }()

    return statusCh
}

In the calling code, you can read from the channel to track progress or errors:

func Read(statusCh chan Stat) {
    for status := range statusCh {
        if status.err != nil {
            // handle error
            return
        }
        // handle progress, e.g., display the number of bytes copied
    }
}

Thus, using channels and goroutines allows asynchronous copying and real-time status updates to the caller.

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