Include support for .woz disk images

[st3fan]

If the file format is publicly documented.

[kerthunk]

The most recent version of the spec can always be found here: woz reference

Some test images are currently available here: images

Feel free to hit me up if you have any questions.

[st3fan]

Some more sources:

• MAME Code to read Woz Images
• Chapter 9 of Understanding the Apple II by Sather (PDF)

[st3fan]

Some things I can already work on until I fully understand how all this fits together:

• Add an EWM_DSK_TYPE_WOZ
• Add a function to verify and load a .woz image
• Convert track bitstream to a nibble stream

[kerthunk]

This is the code that I use in Applesauce to convert from a DSK to a bitstream. The NibbleStream class that this is referencing is an abstraction layer that sits over the bitstream.

    static func makeNibbleStream(fromDSK: Data, trackNum: Int, useGap1Size: Int) -> NibbleStream {
        let sectorInterleave = [0x00, 0x07, 0x0e, 0x06, 0x0d, 0x05, 0x0c, 0x04, 0x0b, 0x03, 0x0a, 0x02, 0x09, 0x01, 0x08, 0x0f]
        let nibs = NibbleStream()
        // gap 1
        nibs.appendRepeating(value: 0xff, bitCount: 10, count: useGap1Size)
        for sector_num in 0..<16 {
            // write the address field prolog
            nibs.append(value: 0xd5, bitCount: 8)
            nibs.append(value: 0xaa, bitCount: 8)
            nibs.append(value: 0x96, bitCount: 8)
            // write the address field data
            var afd = Data()
            let vol = UInt8(254)
            afd.append(vol)
            let trk = UInt8(trackNum)
            afd.append(trk)
            let sec = UInt8(sector_num)
            afd.append(sec)
            let chk = vol ^ trk ^ sec
            afd.append(chk)
            if let encoded_afd = NibbleCodec.codec44.encode(data: afd, start: 0, length: 4).nibbles {
                nibs.appendData(data: encoded_afd, bitCount: 8)
            }
            // write the address field epilog
            nibs.append(value: 0xde, bitCount: 8)
            nibs.append(value: 0xaa, bitCount: 8)
            nibs.append(value: 0xeb, bitCount: 8)
            // write gap 2
            nibs.appendRepeating(value: 0xff, bitCount: 10, count: 7)
            // write the data field prolog
            nibs.append(value: 0xd5, bitCount: 8)
            nibs.append(value: 0xaa, bitCount: 8)
            nibs.append(value: 0xad, bitCount: 8)
            // write the data
            let sector_start = (trackNum * 4096) + (sectorInterleave[sector_num] * 256)
            if let encoded_data = NibbleCodec.codec62.encode(data: fromDSK, start: sector_start).nibbles {
                nibs.appendData(data: encoded_data, bitCount: 8)
            }
            // write the data field epilog
            nibs.append(value: 0xde, bitCount: 8)
            nibs.append(value: 0xaa, bitCount: 8)
            nibs.append(value: 0xeb, bitCount: 8)
            // write gap 3
            nibs.appendRepeating(value: 0xff, bitCount: 10, count: 16)
        }
        return nibs
    }