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https://github.com/zellyn/diskii.git
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Add (untested) ProDOS marshaling and unmarshaling
This commit is contained in:
Zellyn Hunter
parent
209d326cb8
commit
4b4612c31f
@ -2,9 +2,13 @@
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// Package prodos contains routines for working with the on-disk
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// structures of Apple ProDOS.
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//
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// TODO(zellyn): remove errors from FromBlock(), and move validation
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// into separate Validate() functions.
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package prodos
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import (
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"encoding/binary"
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"fmt"
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"io"
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)
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@ -57,7 +61,9 @@ func (vbm VolumeBitMap) mark(block uint16, set bool) {
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}
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}
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func (vbm VolumeBitMap) Free(block uint16) bool {
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// IsFree returns true if the given block on the device is free,
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// according to the VolumeBitMap.
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func (vbm VolumeBitMap) IsFree(block uint16) bool {
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byteIndex := block >> 3
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blockIndex := byteIndex / 512
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blockByteIndex := byteIndex % 512
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@ -90,11 +96,35 @@ func (vbm VolumeBitMap) Write(bd BlockDevice, startBlock uint16) error {
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return nil
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}
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// DateTime represents the 4-byte ProDOS y/m/d h/m timestamp.
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type DateTime struct {
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YMD [2]byte
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HM [2]byte
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}
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// toBytes returns a four-byte slice representing a DateTime.
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func (dt DateTime) toBytes() []byte {
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return []byte{dt.YMD[0], dt.YMD[1], dt.HM[0], dt.HM[1]}
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}
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// fromBytes turns a slice of four bytes back into a DateTime.
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func (dt *DateTime) fromBytes(b []byte) error {
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if len(b) != 4 {
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return fmt.Errorf("DateTime expects 4 bytes; got %d", len(b))
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}
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if b[2] >= 0x20 {
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return fmt.Errorf("DateTime expects hour<0x20; got 0x%02x", b[2])
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}
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if b[3] >= 0x40 {
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return fmt.Errorf("DateTime expects minute<0x40; got 0x%02x", b[3])
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}
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dt.YMD[0] = b[0]
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dt.YMD[1] = b[1]
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dt.HM[0] = b[2]
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dt.HM[1] = b[3]
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return nil
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}
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// VolumeDirectoryKeyBlock is the struct used to hold the ProDOS Volume Directory Key
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// Block structure. See page 4-4 of Beneath Apple ProDOS.
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type VolumeDirectoryKeyBlock struct {
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@ -104,6 +134,36 @@ type VolumeDirectoryKeyBlock struct {
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Descriptors [12]FileDescriptor
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}
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// ToBlock marshals the VolumeDirectoryKeyBlock to a Block of bytes.
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func (vdkb VolumeDirectoryKeyBlock) ToBlock() Block {
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var block Block
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binary.LittleEndian.PutUint16(block[0x0:0x2], vdkb.Prev)
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binary.LittleEndian.PutUint16(block[0x2:0x4], vdkb.Next)
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copyBytes(block[0x04:0x02b], vdkb.Header.toBytes())
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for i, desc := range vdkb.Descriptors {
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copyBytes(block[0x2b+i*0x27:0x2b+(i+1)*0x27], desc.toBytes())
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}
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return block
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}
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// FromBlock unmarshals a Block of bytes into a VolumeDirectoryKeyBlock.
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func (vdkb *VolumeDirectoryKeyBlock) FromBlock(block Block) error {
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vdkb.Prev = binary.LittleEndian.Uint16(block[0x0:0x2])
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if vdkb.Prev != 0 {
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return fmt.Errorf("Volume Directory Key Block should have a `Previous` block of 0, got $%04x", vdkb.Prev)
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}
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vdkb.Next = binary.LittleEndian.Uint16(block[0x2:0x4])
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if err := vdkb.Header.fromBytes(block[0x04:0x2b]); err != nil {
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return err
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}
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for i := range vdkb.Descriptors {
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if err := vdkb.Descriptors[i].fromBytes(block[0x2b+i*0x27 : 0x2b+(i+1)*0x27]); err != nil {
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return fmt.Errorf("cannot deserialize file descriptor %d of Volume Directory Key Block: %v", err)
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}
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}
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return nil
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}
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// VolumeDirectoryBlock is a normal (non-key) segment in the Volume Directory Header.
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type VolumeDirectoryBlock struct {
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Prev uint16 // Pointer to previous block in the Volume Directory.
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@ -111,6 +171,29 @@ type VolumeDirectoryBlock struct {
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Descriptors [13]FileDescriptor
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}
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// ToBlock marshals a VolumeDirectoryBlock to a Block of bytes.
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func (vdb VolumeDirectoryBlock) ToBlock() Block {
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var block Block
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binary.LittleEndian.PutUint16(block[0x0:0x2], vdb.Prev)
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binary.LittleEndian.PutUint16(block[0x2:0x4], vdb.Next)
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for i, desc := range vdb.Descriptors {
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copyBytes(block[0x04+i*0x27:0x04+(i+1)*0x27], desc.toBytes())
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}
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return block
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}
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// FromBlock unmarshals a Block of bytes into a VolumeDirectoryBlock.
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func (vdb *VolumeDirectoryBlock) FromBlock(block Block) error {
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vdb.Prev = binary.LittleEndian.Uint16(block[0x0:0x2])
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vdb.Next = binary.LittleEndian.Uint16(block[0x2:0x4])
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for i := range vdb.Descriptors {
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if err := vdb.Descriptors[i].fromBytes(block[0x4+i*0x27 : 0x4+(i+1)*0x27]); err != nil {
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return fmt.Errorf("cannot deserialize file descriptor %d of Volume Directory Block: %v", err)
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}
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}
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return nil
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}
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type VolumeDirectoryHeader struct {
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TypeAndNameLength byte // Storage type (top four bits) and volume name length (lower four).
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VolumeName [15]byte // Volume name (actual length defined in TypeAndNameLength)
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@ -118,7 +201,7 @@ type VolumeDirectoryHeader struct {
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Creation DateTime // Date and time volume was formatted
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Version byte
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MinVersion byte
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Access byte
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Access Access
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EntryLength byte // Length of each entry in the Volume Directory: usually $27
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EntriesPerBlock byte // Usually $0D
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FileCount uint16 // Number of active entries in the Volume Directory, not counting the Volume Directory Header
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@ -126,6 +209,46 @@ type VolumeDirectoryHeader struct {
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TotalBlocks uint16 // Total number of blocks on the device. $118 (280) for a 35-track diskette.
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}
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// toBytes converts a VolumeDirectoryHeader to a slice of bytes.
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func (vdh VolumeDirectoryHeader) toBytes() []byte {
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buf := make([]byte, 0x27)
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buf[0] = vdh.TypeAndNameLength
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copyBytes(buf[1:0x10], vdh.VolumeName[:])
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copyBytes(buf[0x10:0x18], vdh.Unused1[:])
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copyBytes(buf[0x18:0x1c], vdh.Creation.toBytes())
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buf[0x1c] = vdh.Version
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buf[0x1d] = vdh.MinVersion
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buf[0x1e] = byte(vdh.Access)
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buf[0x1f] = vdh.EntryLength
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buf[0x20] = vdh.EntriesPerBlock
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binary.LittleEndian.PutUint16(buf[0x20:0x22], vdh.FileCount)
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binary.LittleEndian.PutUint16(buf[0x22:0x24], vdh.BitMapPointer)
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binary.LittleEndian.PutUint16(buf[0x24:0x26], vdh.TotalBlocks)
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return buf
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}
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// fromBytes unmarshals a slice of bytes into a VolumeDirectoryHeader.
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func (vdh *VolumeDirectoryHeader) fromBytes(buf []byte) error {
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if len(buf) != 0x27 {
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return fmt.Errorf("VolumeDirectoryHeader should be 0x27 bytes long; got 0x%02x", len(buf))
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}
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vdh.TypeAndNameLength = buf[0]
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copyBytes(vdh.VolumeName[:], buf[1:0x10])
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copyBytes(vdh.Unused1[:], buf[0x10:0x18])
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if err := vdh.Creation.fromBytes(buf[0x18:0x1c]); err != nil {
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return fmt.Errorf("unable to deserialize Volume Directory Header Creation date/time: %v", err)
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}
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vdh.Version = buf[0x1c]
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vdh.MinVersion = buf[0x1d]
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vdh.Access = Access(buf[0x1e])
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vdh.EntryLength = buf[0x1f]
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vdh.EntriesPerBlock = buf[0x20]
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vdh.FileCount = binary.LittleEndian.Uint16(buf[0x20:0x22])
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vdh.BitMapPointer = binary.LittleEndian.Uint16(buf[0x22:0x24])
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vdh.TotalBlocks = binary.LittleEndian.Uint16(buf[0x24:0x26])
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return nil
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}
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type Access byte
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const (
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@ -159,6 +282,57 @@ type FileDescriptor struct {
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HeaderPointer uint16 // Block number of the key block for the directory which describes this file.
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}
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// Filename returns the string filename of a file descriptor.
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func (fd FileDescriptor) Filename() string {
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return string(fd.FileName[0 : fd.TypeAndNameLength&0xf])
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}
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// toBytes converts a FileDescriptor to a slice of bytes.
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func (fd FileDescriptor) toBytes() []byte {
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buf := make([]byte, 0x27)
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buf[0] = fd.TypeAndNameLength
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copyBytes(buf[1:0x10], fd.FileName[:])
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buf[0x10] = fd.FileType
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binary.LittleEndian.PutUint16(buf[0x11:0x13], fd.KeyPointer)
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binary.LittleEndian.PutUint16(buf[0x13:0x15], fd.BlocksUsed)
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copyBytes(buf[0x15:0x18], fd.Eof[:])
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copyBytes(buf[0x18:0x1c], fd.Creation.toBytes())
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buf[0x1c] = fd.Version
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buf[0x1d] = fd.MinVersion
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buf[0x1e] = byte(fd.Access)
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binary.LittleEndian.PutUint16(buf[0x1f:0x21], fd.AuxType)
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copyBytes(buf[0x21:0x25], fd.LastMod.toBytes())
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binary.LittleEndian.PutUint16(buf[0x25:0x27], fd.HeaderPointer)
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return buf
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}
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// fromBytes unmarshals a slice of bytes into a FileDescriptor.
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func (fd *FileDescriptor) fromBytes(buf []byte) error {
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if len(buf) != 0x27 {
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return fmt.Errorf("FileDescriptor should be 0x27 bytes long; got 0x%02x", len(buf))
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}
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fd.TypeAndNameLength = buf[0]
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copyBytes(fd.FileName[:], buf[1:0x10])
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fd.FileType = buf[0x10]
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fd.KeyPointer = binary.LittleEndian.Uint16(buf[0x11:0x13])
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fd.BlocksUsed = binary.LittleEndian.Uint16(buf[0x13:0x15])
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copyBytes(fd.Eof[:], buf[0x15:0x18])
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if err := fd.Creation.fromBytes(buf[0x18:0x1c]); err != nil {
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return fmt.Errorf("unable to unmarshal Creation date/time of FileDescriptor %q: %v", fd.Filename(), err)
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}
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fd.Version = buf[0x1c]
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fd.MinVersion = buf[0x1d]
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fd.Access = Access(buf[0x1e])
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fd.AuxType = binary.LittleEndian.Uint16(buf[0x1f:0x21])
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if err := fd.LastMod.fromBytes(buf[0x21:0x25]); err != nil {
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return fmt.Errorf("unable to unmarshal last modification date/time of FileDescriptor %q: %v", fd.Filename(), err)
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}
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fd.HeaderPointer = binary.LittleEndian.Uint16(buf[0x25:0x27])
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return nil
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}
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// An index block contains 256 16-bit block numbers, pointing to other
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// blocks. The LSBs are stored in the first half, MSBs in the second.
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type IndexBlock Block
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@ -173,3 +347,145 @@ func (i IndexBlock) Set(blockNum byte, block uint16) {
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i[blockNum] = byte(block)
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i[256+int(blockNum)] = byte(block >> 8)
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}
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// SubdirectoryKeyBlock is the struct used to hold the first entry in
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// a subdirectory structure.
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type SubdirectoryKeyBlock struct {
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Prev uint16 // Pointer to previous block (always zero: the KeyBlock is the first Volume Directory block
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Next uint16 // Pointer to next block in the Volume Directory
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Header SubdirectoryHeader
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Descriptors [12]FileDescriptor
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}
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// ToBlock marshals the SubdirectoryKeyBlock to a Block of bytes.
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func (skb SubdirectoryKeyBlock) ToBlock() Block {
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var block Block
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binary.LittleEndian.PutUint16(block[0x0:0x2], skb.Prev)
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binary.LittleEndian.PutUint16(block[0x2:0x4], skb.Next)
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copyBytes(block[0x04:0x02b], skb.Header.toBytes())
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for i, desc := range skb.Descriptors {
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copyBytes(block[0x2b+i*0x27:0x2b+(i+1)*0x27], desc.toBytes())
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}
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return block
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}
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// FromBlock unmarshals a Block of bytes into a SubdirectoryKeyBlock.
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func (skb *SubdirectoryKeyBlock) FromBlock(block Block) error {
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skb.Prev = binary.LittleEndian.Uint16(block[0x0:0x2])
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if skb.Prev != 0 {
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return fmt.Errorf("Subdirectory Key Block should have a `Previous` block of 0, got $%04x", skb.Prev)
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}
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skb.Next = binary.LittleEndian.Uint16(block[0x2:0x4])
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if err := skb.Header.fromBytes(block[0x04:0x2b]); err != nil {
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return err
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}
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for i := range skb.Descriptors {
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if err := skb.Descriptors[i].fromBytes(block[0x2b+i*0x27 : 0x2b+(i+1)*0x27]); err != nil {
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return fmt.Errorf("cannot deserialize file descriptor %d of Subdirectory Key Block: %v", err)
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}
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}
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return nil
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}
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// SubdirectoryBlock is a normal (non-key) segment in a Subdirectory.
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type SubdirectoryBlock struct {
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Prev uint16 // Pointer to previous block in the Volume Directory.
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Next uint16 // Pointer to next block in the Volume Directory.
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Descriptors [13]FileDescriptor
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}
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// ToBlock marshals a SubdirectoryBlock to a Block of bytes.
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func (sb SubdirectoryBlock) ToBlock() Block {
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var block Block
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binary.LittleEndian.PutUint16(block[0x0:0x2], sb.Prev)
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binary.LittleEndian.PutUint16(block[0x2:0x4], sb.Next)
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for i, desc := range sb.Descriptors {
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copyBytes(block[0x04+i*0x27:0x04+(i+1)*0x27], desc.toBytes())
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}
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return block
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}
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// FromBlock unmarshals a Block of bytes into a SubdirectoryBlock.
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func (sb *SubdirectoryBlock) FromBlock(block Block) error {
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sb.Prev = binary.LittleEndian.Uint16(block[0x0:0x2])
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sb.Next = binary.LittleEndian.Uint16(block[0x2:0x4])
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for i := range sb.Descriptors {
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if err := sb.Descriptors[i].fromBytes(block[0x4+i*0x27 : 0x4+(i+1)*0x27]); err != nil {
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return fmt.Errorf("cannot deserialize file descriptor %d of Volume Directory Block: %v", err)
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}
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}
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return nil
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}
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type SubdirectoryHeader struct {
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TypeAndNameLength byte // Storage type (top four bits) and subdirectory name length (lower four).
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SubdirectoryName [15]byte // Subdirectory name (actual length defined in TypeAndNameLength)
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SeventyFive byte // Must contain $75 (!?)
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Unused1 [7]byte
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Creation DateTime // Date and time volume was formatted
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Version byte
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MinVersion byte
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Access Access
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EntryLength byte // Length of each entry in the Subdirectory: usually $27
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EntriesPerBlock byte // Usually $0D
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FileCount uint16 // Number of active entries in the Subdirectory, not counting the Subdirectory Header
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ParentPointer uint16 // The block number of the key (first) block of the directory that contains the entry that describes this subdirectory
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ParentEntry byte // Index in the parent directory for this subdirectory's entry (counting from parent header = 0)
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ParentEntryLength byte // Usually $27
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}
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// toBytes converts a SubdirectoryHeader to a slice of bytes.
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func (sh SubdirectoryHeader) toBytes() []byte {
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buf := make([]byte, 0x27)
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buf[0] = sh.TypeAndNameLength
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copyBytes(buf[1:0x10], sh.SubdirectoryName[:])
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buf[0x10] = sh.SeventyFive
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copyBytes(buf[0x11:0x18], sh.Unused1[:])
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copyBytes(buf[0x18:0x1c], sh.Creation.toBytes())
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buf[0x1c] = sh.Version
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buf[0x1d] = sh.MinVersion
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buf[0x1e] = byte(sh.Access)
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buf[0x1f] = sh.EntryLength
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buf[0x20] = sh.EntriesPerBlock
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binary.LittleEndian.PutUint16(buf[0x20:0x22], sh.FileCount)
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binary.LittleEndian.PutUint16(buf[0x22:0x24], sh.ParentPointer)
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buf[0x24] = sh.ParentEntry
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buf[0x25] = sh.ParentEntryLength
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return buf
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}
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// fromBytes unmarshals a slice of bytes into a SubdirectoryHeader.
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func (sh *SubdirectoryHeader) fromBytes(buf []byte) error {
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if len(buf) != 0x27 {
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return fmt.Errorf("VolumeDirectoryHeader should be 0x27 bytes long; got 0x%02x", len(buf))
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}
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sh.TypeAndNameLength = buf[0]
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copyBytes(sh.SubdirectoryName[:], buf[1:0x10])
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if buf[0x10] != 0x75 {
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return fmt.Errorf("the byte after subdirectory name should be 0x75; got 0x%02x", buf[0x10])
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}
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sh.SeventyFive = buf[0x10]
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copyBytes(sh.Unused1[:], buf[0x11:0x18])
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if err := sh.Creation.fromBytes(buf[0x18:0x1c]); err != nil {
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return fmt.Errorf("unable to deserialize Subdirectory Header Creation date/time: %v", err)
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}
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sh.Version = buf[0x1c]
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sh.MinVersion = buf[0x1d]
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sh.Access = Access(buf[0x1e])
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sh.EntryLength = buf[0x1f]
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sh.EntriesPerBlock = buf[0x20]
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sh.FileCount = binary.LittleEndian.Uint16(buf[0x20:0x22])
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sh.ParentPointer = binary.LittleEndian.Uint16(buf[0x22:0x24])
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sh.ParentEntry = buf[0x24]
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sh.ParentEntryLength = buf[0x25]
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return nil
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}
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// copyBytes is just like the builtin copy, but just for byte slices,
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// and it checks that dst and src have the same length.
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func copyBytes(dst, src []byte) int {
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if len(dst) != len(src) {
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panic(fmt.Sprintf("copyBytes called with differing lengths %d and %d", len(dst), len(src)))
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}
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return copy(dst, src)
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}
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