替换* os.Go默认日志文件

Question

I'm trying to write a wrapper for Go's built-in logger. This is to have compatibility.

package main

import (
    "log"
    "os"
)

var(
    mylog *log.Logger
)

func main() {
    mylog = log.New(os.Stdout, "", 0)
    mylog.Printf("test")
}

Instead of using os.Stdout, I want to create one something. Similar to os.Stdout but prints with prefix like below.

package main

import( 
    "log"
    "mylibrary"
)

var(
    mylog *log.Logger
)

func main() {
    mylog = log.New(mylibrary.Prefix, "", 0)
    mylog.Printf("test")
}

Basically, I still want to have *log.Logger while having custom log. Can someone give me a hint how I can make this works?

Currently, I'm using following to do that. But I bet there's a better way.

func NewIoWriter(f func(string)) *io.PipeWriter {
    r, w := io.Pipe()
    go func() {
        scanner := bufio.NewScanner(r)
        for scanner.Scan() {
            f(scanner.Text())
        }
        if err := scanner.Err(); err != nil {
            f(err.Error())
        }
        r.Close()
    }()
    runtime.SetFinalizer(w, (*io.PipeWriter).Close)
    return w
}

What would be the better way to make it work?

Thank you

Answer 1

How about something like this:

type myLogWriter struct {
    logFunc func(string)
    line    string
}

func (w *myLogWriter) Write(b []byte) (int, error) {
    l := len(b)
    for len(b) != 0 {
        i := bytes.Index(b, []byte{'
'})
        if i == -1 {
            w.line += string(b)
            break
        } else {
            w.logFunc(w.line + string(b[:i]))
            b = b[i+1:]
            w.line = ""
        }
    }

    return l, nil
}

func NewLogWriter(f func(string)) *myLogWriter {
    return &myLogWriter{
        logFunc: f,
    }
}

See https://play.golang.org/p/L6PG1gCK1er.