diskii/woz/woz.go

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package woz
import (
"encoding/binary"
"fmt"
"hash"
"hash/crc32"
"io"
"strings"
)
const wozHeader = "WOZ1\xFF\n\r\n"
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const TrackLength = 6656
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type Woz struct {
Info Info
Unknowns []UnknownChunk
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TMap [160]uint8
TRKS []TRK
Metadata Metadata
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}
type UnknownChunk struct {
Id string
Data []byte
}
type DiskType uint8
const (
DiskType525 DiskType = 1
DiskType35 DiskType = 2
)
type Info struct {
Version uint8
DiskType DiskType
WriteProtected bool
Synchronized bool
Cleaned bool
Creator string
}
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type TRK struct {
BitStream [6646]uint8
BytesUsed uint16
BitCount uint16
SplicePoint uint16
SpliceNibble uint8
SpliceBitCount uint8
Reserved uint16
}
type Metadata struct {
Keys []string
RawValues map[string]string
}
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type decoder struct {
r io.Reader
woz *Woz
crc hash.Hash32
tmp [3 * 256]byte
crcVal uint32
}
// A FormatError reports that the input is not a valid woz file.
type FormatError string
func (e FormatError) Error() string { return "woz: invalid format: " + string(e) }
type CRCError struct {
Declared uint32
Computed uint32
}
func (e CRCError) Error() string {
return fmt.Sprintf("woz: failed checksum: declared=%d; computed=%d", e.Declared, e.Computed)
}
func (d *decoder) info(format string, args ...interface{}) {
if !strings.HasSuffix(format, "\n") {
format = format + "\n"
}
fmt.Printf("INFO: "+format, args...)
}
func (d *decoder) warn(format string, args ...interface{}) {
if !strings.HasSuffix(format, "\n") {
format = format + "\n"
}
fmt.Printf("WARN: "+format, args...)
}
func (d *decoder) checkHeader() error {
_, err := io.ReadFull(d.r, d.tmp[:len(wozHeader)])
if err != nil {
return err
}
if string(d.tmp[:len(wozHeader)]) != wozHeader {
return FormatError("not a woz file")
}
if err := binary.Read(d.r, binary.LittleEndian, &d.crcVal); err != nil {
return err
}
return nil
}
func (d *decoder) parseChunk() (done bool, err error) {
// Read the chunk type and length
n, err := io.ReadFull(d.r, d.tmp[:8])
if err != nil {
if n == 0 && err == io.EOF {
return true, nil
}
return false, err
}
length := binary.LittleEndian.Uint32(d.tmp[4:8])
d.crc.Write(d.tmp[:8])
switch string(d.tmp[:4]) {
case "INFO":
return false, d.parseINFO(length)
case "TMAP":
return false, d.parseTMAP(length)
case "TRKS":
return false, d.parseTRKS(length)
case "META":
return false, d.parseMETA(length)
default:
return false, d.parseUnknown(string(d.tmp[:4]), length)
}
return false, nil
}
func (d *decoder) parseINFO(length uint32) error {
d.info("INFO chunk!\n")
if length != 60 {
d.warn("expected INFO chunk length of 60; got %d", length)
}
if _, err := io.ReadFull(d.r, d.tmp[:length]); err != nil {
return err
}
d.crc.Write(d.tmp[:length])
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d.woz.Info.Version = d.tmp[0]
d.woz.Info.DiskType = DiskType(d.tmp[1])
d.woz.Info.WriteProtected = d.tmp[2] == 1
d.woz.Info.Synchronized = d.tmp[3] == 1
d.woz.Info.Cleaned = d.tmp[4] == 1
d.woz.Info.Creator = strings.TrimRight(string(d.tmp[5:37]), " ")
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return nil
}
func (d *decoder) parseTMAP(length uint32) error {
d.info("TMAP chunk!\n")
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if length != 160 {
d.warn("expected TMAP chunk length of 160; got %d", length)
}
if _, err := io.ReadFull(d.r, d.woz.TMap[:]); err != nil {
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return err
}
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d.crc.Write(d.woz.TMap[:])
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return nil
}
func (d *decoder) parseTRKS(length uint32) error {
d.info("TRKS chunk!\n")
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if length%TrackLength != 0 {
return FormatError(fmt.Sprintf("expected TRKS chunk length to be a multiple of %d; got %d", TrackLength, length))
}
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buf := make([]byte, length)
if _, err := io.ReadFull(d.r, buf); err != nil {
return err
}
d.crc.Write(buf)
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for offset := 0; offset < int(length); offset += TrackLength {
b := buf[offset : offset+TrackLength]
t := TRK{
BytesUsed: binary.LittleEndian.Uint16(b[6646:6648]),
BitCount: binary.LittleEndian.Uint16(b[6648:6650]),
SplicePoint: binary.LittleEndian.Uint16(b[6650:6652]),
SpliceNibble: b[6652],
SpliceBitCount: b[6653],
Reserved: binary.LittleEndian.Uint16(b[6654:6656]),
}
copy(t.BitStream[:], b)
d.woz.TRKS = append(d.woz.TRKS, t)
}
// type TRK struct {
// Bitstream [6646]uint8
// BytesUsed uint16
// BitCount uint16
// SplicePoint uint16
// SpliceNibble uint8
// SpliceBitCount uint8
// Reserved uint16
// }
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return nil
}
func (d *decoder) parseMETA(length uint32) error {
d.info("META chunk!\n")
buf := make([]byte, length)
if _, err := io.ReadFull(d.r, buf); err != nil {
return err
}
d.crc.Write(buf)
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rows := strings.Split(string(buf), "\n")
m := &d.woz.Metadata
m.RawValues = make(map[string]string, len(rows))
for _, row := range rows {
parts := strings.SplitN(row, "\t", 2)
if len(parts) == 0 {
return FormatError("empty metadata line")
}
if len(parts) == 1 {
return FormatError("strange metadata line with no tab: " + parts[0])
}
m.Keys = append(m.Keys, parts[0])
m.RawValues[parts[0]] = parts[1]
}
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return nil
}
func (d *decoder) parseUnknown(id string, length uint32) error {
d.info("unknown chunk type (%s): ignoring\n", id)
buf := make([]byte, length)
if _, err := io.ReadFull(d.r, buf); err != nil {
return err
}
d.crc.Write(buf)
d.woz.Unknowns = append(d.woz.Unknowns, UnknownChunk{Id: id, Data: buf})
return nil
}
// Decode reads a woz disk image from r and returns it as a *Woz.
func Decode(r io.Reader) (*Woz, error) {
d := &decoder{
r: r,
crc: crc32.NewIEEE(),
woz: &Woz{},
}
if err := d.checkHeader(); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return nil, err
}
// Read all chunks.
for {
done, err := d.parseChunk()
if err != nil {
return nil, err
}
if done {
break
}
}
// Check CRC.
if d.crcVal != d.crc.Sum32() {
return d.woz, CRCError{Declared: d.crcVal, Computed: d.crc.Sum32()}
}
return d.woz, nil
}