muesli/console.go

package muesli

import "io"
import "fmt"
import "os"

// Consoler is an interface to a virtual console that the VM 's frames use for
// stdin, stdout, stderr, and logging output.
// This allows you to redirect the output of the VM and any built-in functions 
// to whatever you like.
type Consoler interface {
    LogTo() io.Writer // logs should be written to this writer of not nil
    Out() io.Writer // standard output goes to this writer of not nil.
    Err() io.Writer // standard error go to this writer if not nil
    In() io.Reader // can read standard input from this reader if not nil
}


// BasicConsole is a reusable virtual console struct. 
// It implements the BasicConsoler interface
type BasicConsole struct {
    log io.Writer
    out io.Writer
    err io.Writer
    in io.Reader
} 


func (c BasicConsole) LogTo() io.Writer {
    return c.log
}


func (c BasicConsole) Out() io.Writer {
    return c.out
}


func (c BasicConsole) Err() io.Writer {
    return c.err
}


func (c BasicConsole) In() io.Reader {
    return c.in
}


func NewBasicConsole(log, out, err io.Writer, in io.Reader) BasicConsole {
    return BasicConsole { log, out, err, in }
}

var _ Consoler = BasicConsole{}


// Console is a fully features wrapper BasicConsole, easier to use with Printf 
// and Log, etc, and implements the Logger and Consoler interface.
type Console struct {
    LoggerWrapper
    Consoler
}

func (c *Console) Fprintf(out io.Writer, format string, args ... interface{}) (int, error) {
    if out != nil {
        return fmt.Fprintf(out, format, args...)
    }
    return 0, nil
}

func (c *Console) Fprintln(out io.Writer, args ... interface{}) (int, error) {
    if out != nil {
        return fmt.Fprintln(out, args...)
    }
    return 0, nil
}


func (c *Console) Log(level string, file string, line int, format string, args ...interface{}) {
    log := c.Consoler.LogTo()
    c.Fprintf(log, "%s:%s:%d: ", level, file, line)
    c.Fprintf(log, format, args...)
}

func (c *Console) Printf(format string, args ...interface{}) {
    out := c.Out()
    c.Fprintf(out, format, args...)
}

func (c *Console) Println(args ...interface{}) {
    out := c.Out()
    c.Fprintln(out, args...)
}


func (c *Console) Errf(format string, args ...interface{}) {
    err := c.Err()
    c.Fprintf(err, format, args...)
}

func NewConsole(log, out, err io.Writer, in io.Reader) *Console {
    console := &Console{}
    console.Consoler = NewBasicConsole(log, out, err, in)
    return console
}


// also implement the tracer interface 
func (c *Console) Trace(vm VM, format string, args ... interface{}) bool {
	args = append([]interface{}{vm.BackTrace()}, args...)	
    c.LogTrace("%s: " + format, args...)
    return false
}

func NewStdConsole() *Console {
    return NewConsole(os.Stdout, os.Stdout, os.Stderr, os.Stdin)
}