yvesdecoder.go

package main

import (
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"os"
)

type yvesDecoder struct {
	inner io.Reader
}

func NewYvesDecoder(r io.Reader) io.Reader {
	return &yvesDecoder{
		inner: r,
	}
}

func (d *yvesDecoder) decodeByte(b byte) byte {
	return b>>5 | b<<3
}

func (d *yvesDecoder) Read(buffer []byte) (int, error) {
	pc := len(buffer) / 2
	buffer = buffer[:pc*2]

	read, err := d.inner.Read(buffer)
	for n := 0; n <= read && n <= (pc-1)*2; n += 2 {
		buffer[n], buffer[n+1] = d.decodeByte(buffer[n]), d.decodeByte(buffer[n+1])
		if n+1 < read {
			buffer[n], buffer[n+1] = buffer[n+1], buffer[n]
		}
	}

	return read, err
}

func handle(err error) {
	if err != nil {
		log.Fatal(err)
	}
}

func ReadFile(name string) ([]byte, error) {
	f, err := os.Open(name)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	decr := NewYvesDecoder(f)
	return ioutil.ReadAll(decr)
}

func main() {
	data, err := ReadFile("1.yves")
	handle(err)
	fmt.Println(string(data))
}