49 lines
1.0 KiB
Go
49 lines
1.0 KiB
Go
package apple2
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type textPages struct {
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pages [4]textPage
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}
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type textPage struct {
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dirty bool
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data [256]uint8
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}
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func (p *textPage) Peek(address uint8) uint8 {
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return p.data[address]
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}
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func (p *textPage) Poke(address uint8, value uint8) {
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p.data[address] = value
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// Note: we could avoid setting dirty on the 16 blocks of 8 hidden bytes
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p.dirty = true
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}
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func (tp *textPages) read(column uint8, line uint8) uint8 {
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page, address := tp.charAddress(column, line)
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return tp.pages[page].Peek(address)
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}
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func (tp *textPages) write(column uint8, line uint8, value uint8) {
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page, address := tp.charAddress(column, line)
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tp.pages[page].Poke(address, value)
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}
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func (tp *textPages) charAddress(column uint8, line uint8) (page uint8, address uint8) {
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page = (line % 8) / 2
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address = column + (line/8)*40 + (line%2)*128
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return
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}
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func (tp *textPages) strobe() bool {
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// Thread safe. May just mark more dirties than needed.
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dirty := false
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for i := 0; i < 4; i++ {
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if tp.pages[i].dirty {
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dirty = true
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tp.pages[i].dirty = false
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}
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}
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return dirty
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}
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