QEMU Image Format detection (golang)

qemu-img-format.go

package qemu

import (
	"bytes"
	"io"
)

type Format string

const (
	UNKNOWN Format = "UNKNOWN"
	QCOW2          = "QCOW2"
	RAW            = "RAW"
)

var qcow2Header = []byte{0x51, 0x46, 0x49, 0xFB}
var rawHeader = []byte{0xeb, 0x00, 0x90}

func GetFormat(r io.Reader) (Format, error) {
	header := make([]byte, 4)
	_, err := r.Read(header)
	if err != nil {
		return UNKNOWN, err
	}

	var f Format

	f = UNKNOWN
	if bytes.Equal(header, qcow2Header) {
		f = QCOW2
	} else if header[0] == rawHeader[0] && header[2] == rawHeader[2] {
		f = RAW
	}

	return f, nil
}