85 lines
1.8 KiB
Go
85 lines
1.8 KiB
Go
package izapple2
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import (
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"errors"
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)
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/*
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See:
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https://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Companies/Apple/Documentation/Apple%20Technical%20Information%20Library/a2til041.txt
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*/
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// CharacterGenerator represents the ROM wth the characters bitmaps
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type CharacterGenerator struct {
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data []uint8
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columnMap charColumnMap
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page int
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pageSize int
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}
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type charColumnMap func(column int) int
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func charGenColumnsMap2Plus(column int) int {
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return 6 - column
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}
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func charGenColumnsMap2e(column int) int {
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return column
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}
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const (
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charGenPageSize2Plus = 2048
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charGenPageSize2E = 2048 * 2
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)
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// NewCharacterGenerator instantiates a new Character Generator with the rom on the file given
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func newCharacterGenerator(filename string, order charColumnMap, isApple2e bool) (*CharacterGenerator, error) {
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var cg CharacterGenerator
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cg.columnMap = order
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cg.pageSize = charGenPageSize2Plus
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if isApple2e {
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cg.pageSize = charGenPageSize2E
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}
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err := cg.load(filename)
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if err != nil {
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return nil, err
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}
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return &cg, nil
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}
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func (cg *CharacterGenerator) load(filename string) error {
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bytes, _, err := LoadResource(filename)
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if err != nil {
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return err
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}
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size := len(bytes)
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if size < cg.pageSize {
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return errors.New("character ROM size not supported")
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}
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cg.data = bytes
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return nil
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}
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func (cg *CharacterGenerator) setPage(page int) {
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// Some clones had a switch to change codepage with extra characters
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pages := len(cg.data) / cg.pageSize
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cg.page = page % pages
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}
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func (cg *CharacterGenerator) getPage() int {
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return cg.page
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}
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func (cg *CharacterGenerator) nextPage() {
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cg.setPage(cg.page + 1)
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}
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func (cg *CharacterGenerator) getPixel(char uint8, row int, column int) bool {
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bits := cg.data[int(char)*8+row+cg.page*cg.pageSize]
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bit := cg.columnMap(column)
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value := bits >> uint(bit) & 1
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return value == 1
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}
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