52 lines
1.1 KiB
Go
52 lines
1.1 KiB
Go
package storage
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/*
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See:
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"Beneath Apple DOS" https://fabiensanglard.net/fd_proxy/prince_of_persia/Beneath%20Apple%20DOS.pdf
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https://github.com/TomHarte/CLK/wiki/Apple-GCR-disk-encoding
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*/
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type diskette16sectorWritable struct {
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nib *fileNib
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position int
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// Needed to write back
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hasDirtyTrack bool
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dirtyTrack int
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}
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func (d *diskette16sectorWritable) PowerOn(cycle uint64) {
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// Not used
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}
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func (d *diskette16sectorWritable) PowerOff(_ uint64) {
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d.commit()
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}
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func (d *diskette16sectorWritable) Read(quarterTrack int, cycle uint64) uint8 {
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track := d.nib.track[quarterTrack/4]
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value := track[d.position]
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d.position = (d.position + 1) % nibBytesPerTrack
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return value
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}
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func (d *diskette16sectorWritable) Write(quarterTrack int, value uint8, _ uint64) {
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track := quarterTrack / 4
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if d.hasDirtyTrack && track != d.dirtyTrack {
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d.commit()
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}
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d.nib.track[track][d.position] = value
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d.position = (d.position + 1) % nibBytesPerTrack
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d.hasDirtyTrack = true
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d.dirtyTrack = track
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}
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func (d *diskette16sectorWritable) commit() {
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if d.hasDirtyTrack {
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d.nib.saveTrack(d.dirtyTrack)
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d.hasDirtyTrack = false
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}
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}
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