File src/0dev.org/commands/mtf/main.go artifact a9b931eec8 part of check-in 470d7e947b

package main

import (
	mtf "0dev.org/encoding/mtf"
	iou "0dev.org/ioutil"
	"flag"
	"fmt"
	"io"
	"os"
)

func main() {
	d := flag.Bool("d", false, "Use to toggle decode mode")
	flag.Parse()

	var code int
	if *d {
		code = decode(os.Stdout, os.Stdin)
	} else {
		code = encode(os.Stdout, os.Stdin)
	}

	os.Exit(code)
}

// Transforms the data according to the move-to-front algorithm
// I/O is buffered for better performance
func encode(output io.Writer, input io.Reader) int {
	var (
		err     error
		encoder io.Reader = mtf.Encoder(iou.SizedReader(input, 4096))
	)

	_, err = io.Copy(output, encoder)
	if err != nil {
		fmt.Fprintln(os.Stderr, "Error while encoding.\n", err)
		return 1
	}

	return 0
}

// Reverses MTF`ed data and writes back the original bytes
// I/O is buffered for better performance
func decode(output io.Writer, input io.Reader) int {
	var (
		err     error
		decoder io.Reader = mtf.Decoder(iou.SizedReader(input, 4096))
	)

	_, err = io.Copy(output, decoder)
	if err != nil {
		fmt.Fprintln(os.Stderr, "Error while decoding.\n", err)
		return 1
	}

	return 0
}