41 lines
1.3 KiB
Go
41 lines
1.3 KiB
Go
package storage
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type diskette16sectorTimed struct {
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nib *fileNib
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cycleOn uint64 // Cycle when the disk was last turned on
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}
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func (d *diskette16sectorTimed) PowerOn(cycle uint64) {
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d.cycleOn = cycle
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}
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func (d *diskette16sectorTimed) PowerOff(_ uint64) {
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// Not needed
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}
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func (d *diskette16sectorTimed) getBitPositionInTrack(cycle uint64) int {
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// Calculate how long the disk has been spinning. We move one bit every 4 cycles.
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// In this implementation we don't take into account how long the motor takes to be at full speed.
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cycles := cycle - d.cycleOn
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position := cycles / cyclesPerBit
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return int(position % (8 * nibBytesPerTrack)) // Ignore full turns
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}
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func (d *diskette16sectorTimed) Read(quarterTrack int, cycle uint64) uint8 {
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track := d.nib.track[quarterTrack/4]
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bitPosition := d.getBitPositionInTrack(cycle)
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bytePosition := bitPosition / 8
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shift := uint(bitPosition % 8)
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if shift == 1 {
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// We continue having the unshifted byte for a little longer (4 cycles)
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shift = 0
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}
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value := track[bytePosition]
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value >>= shift
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//fmt.Printf("%v, %v, %v, %x\n", bitPosition, shift, bytePosition, uint8(value))
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return value
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}
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func (d *diskette16sectorTimed) Write(quarterTrack int, value uint8, _ uint64) {
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panic("Write not implemented on time based disk implementation")
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}
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