95 lines
1.8 KiB
Go
95 lines
1.8 KiB
Go
// convert.go contains routines to convert from character ROMs to text and back.
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package videoscan
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import (
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"fmt"
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"strings"
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)
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var chars = []rune{'.', '#'}
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func reverseByte(in byte) byte {
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hi := in & 0x80
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var out byte
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for i := 0; i < 7; i++ {
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out = out << 1
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out = out | in&1
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in = in >> 1
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}
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out |= hi
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return out
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}
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func BytesToText(rom []byte, reverse bool) []byte {
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result := []byte{}
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for i, b := range rom {
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if reverse {
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b = reverseByte(b)
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}
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if i > 0 && i%8 == 0 {
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result = append(result, '\n')
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}
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if b >= 0x80 {
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result = append(result, 'i')
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} else {
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result = append(result, 'n')
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}
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result = append(result, ' ')
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for i := 0; i < 7; i++ {
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result = append(result, byte(chars[b&1]))
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b = b >> 1
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}
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result = append(result, '\n')
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}
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return result
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}
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func TextToBytes(text []byte, reverse bool) ([]byte, error) {
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result := []byte{}
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lines := strings.Split(string(text), "\n")
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for i, l := range lines {
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l = strings.TrimSpace(l)
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lines[i] = l
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if i != 0 && i%9 == 8 {
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if l != "" {
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return nil, fmt.Errorf("line %d: expected empty line, got '%s'", i+1, l)
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}
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continue
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}
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if len(l) != 9 {
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return nil, fmt.Errorf("line %d: expected 9 characters, got %d: '%s'", i+1, len(l), l)
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}
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var hi byte
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switch l[0] {
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case 'i':
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hi = 0x80
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case 'n':
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default:
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return nil, fmt.Errorf("line %d: should start with 'n' or 'i'; got '%s'", i+1, l[0])
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}
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if l[1] != ' ' {
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return nil, fmt.Errorf("line %d: second char should be space; got '%s'", i+1, l[1])
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}
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var b byte
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var bit byte = 1
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for _, c := range l[2:] {
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switch c {
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case chars[0]: // do nothing
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case chars[1]:
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b |= bit
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default:
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return nil, fmt.Errorf("line %d: expected character: '%s'", i+1, c)
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}
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bit <<= 1
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}
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b |= hi
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if reverse {
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b = reverseByte(b)
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}
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result = append(result, b)
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}
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return result, nil
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}
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