izapple2/file2mg.go

85 lines
1.6 KiB
Go

package apple2
import (
"encoding/binary"
"errors"
"io"
)
/*
Valid for ProDos disks in 2MG format.
See:
https://apple2.org.za/gswv/a2zine/Docs/DiskImage_2MG_Info.txt
*/
const (
file2mgPreamble = uint32(1196247346) // "2IMG"
file2mgFormatProdos = 1
file2mgVersion = 1
)
type file2mgHeader struct {
Preamble uint32
Creator uint32
HeaderSize uint16
Version uint16
Format uint32
Flags uint32
Blocks uint32
OffsetData uint32
LengthData uint32
OffsetComment uint32
LengthComment uint32
OffsetCreator uint32
LengthCreator uint32
}
func parse2mg(bd *blockDisk) error {
fileInfo, err := bd.file.Stat()
if err != nil {
return err
}
var header file2mgHeader
minHeaderSize := binary.Size(&header)
if fileInfo.Size() < int64(minHeaderSize) {
return errors.New("Invalid 2MG file")
}
err = readHeader(bd.file, &header)
if err != nil {
return err
}
bd.blocks = header.Blocks
bd.dataOffset = header.OffsetData
if fileInfo.Size() < int64(bd.dataOffset+bd.blocks*proDosBlockSize) {
return errors.New("The 2MG file is too small")
}
return nil
}
func readHeader(buf io.Reader, header *file2mgHeader) error {
err := binary.Read(buf, binary.LittleEndian, header)
if err != nil {
return err
}
if header.Preamble != file2mgPreamble {
return errors.New("The 2mg file must start with '2IMG'")
}
if header.Format != file2mgFormatProdos {
return errors.New("Only prodos disks are supported")
}
if header.Version != file2mgVersion {
return errors.New("Version of 2MG image not supported")
}
return nil
}