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I didn't think it made sense, but I found something that used it, so apparently it's a thing. This updates the operand editor to let you choose PETSCII+DCI, and updates the assemblers to handle it correctly (really just 64tass, since the others either don't have a DCI directive or don't deal with PETSCII at all). Changed the char-encoding sample from "bad dcI" to "pet dcI", and updated the documentation.
296 lines
12 KiB
C#
296 lines
12 KiB
C#
/*
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* Copyright 2019 faddenSoft
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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using System;
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using System.Diagnostics;
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namespace Asm65 {
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/// <summary>
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/// Character encoding helper methods.
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/// </summary>
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public static class CharEncoding {
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public const char UNPRINTABLE_CHAR = '\ufffd'; // Unicode REPLACEMENT CHARACTER
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/// <summary>
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/// Determines whether the byte represents a member of the character set. The
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/// specifics (e.g. printable only) are defined by the method.
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/// </summary>
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public delegate bool InclusionTest(byte val);
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/// <summary>
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/// Converts the byte to a printable character. Returns UNPRINTABLE_CHAR if the value
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/// does not map to something printable.
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/// </summary>
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/// <remarks>
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/// Yes, I'm assuming it all fits in a UTF-16 char. PETSCII has some glyphs that
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/// aren't part of the BMP, but we're targeting a variety of cross-assemblers with
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/// potentially different notions of Unicode mappings, so anything non-ASCII is
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/// getting hexified anyway.
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/// </remarks>
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public delegate char Convert(byte val);
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/// <summary>
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/// Character encoding.
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/// </summary>
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public enum Encoding {
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Unknown = 0,
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Ascii,
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HighAscii,
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C64Petscii,
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C64ScreenCode,
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}
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//
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// Plain ASCII.
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//
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// We recognize BELL, LF, and CR as control characters that may be present in
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// text strings. This allows use to generate:
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//
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// .str "hello",$0d
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//
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// instead of:
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//
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// .str "hello"
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// .dd1 $0d
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//
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public static bool IsPrintableAscii(byte val) {
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return (val >= 0x20 && val < 0x7f);
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}
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public static bool IsExtendedAscii(byte val) {
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return IsPrintableAscii(val) || val == 0x07 || val == 0x0a || val == 0x0d;
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}
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public static char ConvertAscii(byte val) {
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if (IsPrintableAscii(val)) {
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return (char)val;
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} else {
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return UNPRINTABLE_CHAR;
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}
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}
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//
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// High ASCII: plain ASCII with the high bit set.
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//
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public static bool IsPrintableHighAscii(byte val) {
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return (val >= 0xa0 && val < 0xff);
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}
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public static bool IsExtendedHighAscii(byte val) {
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return IsPrintableHighAscii(val) || val == 0x87 || val == 0x8a || val == 0x8d;
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}
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public static char ConvertHighAscii(byte val) {
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if (IsPrintableHighAscii(val)) {
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return (char)(val & 0x7f);
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} else {
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return UNPRINTABLE_CHAR;
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}
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}
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//
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// High and/or low ASCII.
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//
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public static bool IsPrintableLowOrHighAscii(byte val) {
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return IsPrintableAscii((byte)(val & 0x7f));
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}
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public static bool IsExtendedLowOrHighAscii(byte val) {
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return IsExtendedAscii((byte)(val & 0x7f));
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}
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public static char ConvertLowAndHighAscii(byte val) {
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//if (IsPrintableAscii(val) || IsPrintableHighAscii(val)) {
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// return (char)(val & 0x7f);
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//} else {
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// return UNPRINTABLE_CHAR;
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//}
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return ConvertAscii((byte)(val & 0x7f));
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}
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//
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// ATASCII (Atari 400/800)
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//
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// Substantially similar to ASCII, but with printable symbols in the control character
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// range ($00-1f). Characters $60 and $7b-7f don't correspond to ASCII symbols.
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//
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// Characters with the high bit set are shown with colors reversed.
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//
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//
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// PETSCII (C64 variant)
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//
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// Assemblers like ACME use the C64 character set 2, a/k/a shifted mode, lower case
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// mode, or text mode.
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//
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// Comparison to ASCII:
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// $00-1f: control codes, many with C64-specific meanings
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// $20-3f: same as ASCII
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// $40-5f: lower case letters (rather than upper case); backslash, caret, and underscore
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// replaced with non-ASCII symbols (though the up-arrow in place of caret is close)
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// $60-7f: upper case letters (rather than lower case); backquote, curly braces,
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// vertical bar, and tilde replaced with non-ASCII symbols
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// $80-9f: more control codes
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// $a0-bf: non-ASCII symbols
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// $c0-df: clone of $60-7f; by convention this is used for upper case, since it's
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// equal to lower case with the high bit set
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// $e0-ff: non-ASCII symbols (mostly a clone of $a0-bf)
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//
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// The printable ASCII set (glyphs in [$20,$7e]) is [$20,$5b]+$5d+[$c1,$da].
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// (Looks like the Pet had $5c=backslash, but C64 went with a \u00a3 POUND SIGN instead.)
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// Anything outside that range will get printed as hex to ensure proper conversion.
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//
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// Note for the pedantic: in ASCII-1963, up-arrow and left-arrow characters were
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// assigned to the caret and underscore values. So arguably those are "ASCII" as
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// well, unless you're sane and define ASCII more narrowly.
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//
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// Control codes that we might expect to appear in the middle of a string:
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// $05 1c 1e 1f 81 90 95 96 97 98 99 9a 9b 9c 9e 9f - set text color
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// $93 - clear
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// $12 92 - reverse on/off
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// $07 0a 0d - bell, LF, CR (note CR is favored for EOL)
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//
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// Other Commodore systems use variants on PETSCII, but the ASCII correspondence remains
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// the same -- only the non-ASCII symbols change. (On the original PET, $60-7f was a
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// duplicate of $20-3f rather than a duplicate of the upper-case letters, which might be
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// why $c0-df is preferred for upper case.)
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//
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// For full details, see the chart at https://www.aivosto.com/articles/petscii.pdf
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//
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private static bool[] sPrintablePetscii = CreatePrintablePetsciiMap();
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private static bool[] sExtendedPetscii = CreateExtendedPetsciiMap();
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private static bool[] CreatePrintablePetsciiMap() {
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bool[] map = new bool[256];
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for (int i = 0x20; i <= 0x5b; i++) {
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map[i] = true;
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}
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map[0x5d] = true;
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for (int i = 0xc1; i <= 0xda; i++) {
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map[i] = true;
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}
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return map;
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}
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private static bool[] CreateExtendedPetsciiMap() {
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bool[] map = CreatePrintablePetsciiMap();
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// control codes that we might expect to find in strings
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map[0x05] = map[0x1c] = map[0x1e] = map[0x1f] = map[0x81] = map[0x90] = map[0x95] =
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map[0x96] = map[0x97] = map[0x98] = map[0x99] = map[0x9a] = map[0x9b] =
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map[0x9c] = map[0x9e] = map[0x9f] = true;
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map[0x93] = map[0x12] = map[0x92] = true;
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map[0x07] = map[0x0a] = map[0x0d] = true;
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return map;
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}
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public static bool IsPrintableC64Petscii(byte val) {
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return sPrintablePetscii[val];
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}
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public static bool IsExtendedC64Petscii(byte val) {
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return sExtendedPetscii[val];
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}
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private static char[] sPetsciiToUnicode = CreatePetsciiToUnicodeMap();
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private static char[] CreatePetsciiToUnicodeMap() {
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// There are performance arguments for doing this with and without a table. For
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// x64 with fast memory and large caches, table seems reasonable.
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char[] map = new char[256];
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for (int val = 0; val < 256; val++) {
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char ch;
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if ((val >= 0x20 && val <= 0x40) || val == 0x5b || val == 0x5d) {
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ch = (char)val; // number/symbols, '[', ']'
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} else if (val >= 0x41 && val <= 0x5a) {
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ch = (char)(val + 0x20); // lower case
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} else if (val >= 0xc1 && val <= 0xda) {
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ch = (char)(val - 0x80); // upper case
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} else {
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Debug.Assert(!IsPrintableC64Petscii((byte)val));
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ch = UNPRINTABLE_CHAR;
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}
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map[val] = ch;
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}
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return map;
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}
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public static char ConvertC64Petscii(byte val) {
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return sPetsciiToUnicode[val];
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}
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public static char ConvertLowAndHighC64Petscii(byte val) {
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// This is an odd one. Some programs use DCI with PETSCII, which means the
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// string is allow lower case except for the last letteR.
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//
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// There's no such thing as "high PETSCII", in the same sense that ASCII or
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// C64 screen codes have it, but I'm giving the method a similar name for
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// the sake of consistency.
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return ConvertC64Petscii((byte)(val & 0x7f));
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}
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//
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// C64 Screen Codes
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//
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// Using character set 2, which includes lower case letters.
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//
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// $00-1f: lower case letters (PETSCII $40-5f)
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// $20-3f: same as ASCII (PETSCII $20-3f)
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// $40-5f: upper case letters (PETSCII $60-7f / $c0-df)
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// $60-7f: non-ASCII symbols (PETSCII $a0-bf)
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//
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// With the high bit set, character colors are reversed. The printable ASCII set
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// is [$00,$1b]+$1d+[$20,$3f]+[$41,$5a]. By definition, only printable characters
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// are included in the set, so there are no control codes.
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//
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// For full details, see the chart at https://www.aivosto.com/articles/petscii.pdf
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//
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private static bool[] sPrintableScreenCode = CreatePrintableScreenCodeMap();
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private static bool[] CreatePrintableScreenCodeMap() {
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bool[] map = new bool[256];
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for (int i = 0x00; i <= 0x1b; i++) {
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map[i] = true;
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}
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map[0x1d] = true;
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for (int i = 0x20; i <= 0x3f; i++) {
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map[i] = true;
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}
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for (int i = 0x41; i <= 0x5a; i++) {
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map[i] = true;
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}
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return map;
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}
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public static bool IsPrintableC64ScreenCode(byte val) {
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return sPrintableScreenCode[val];
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}
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public static bool IsExtendedC64ScreenCode(byte val) {
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return sPrintableScreenCode[val];
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}
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private static char[] sScreenCodeToUnicode = CreateScreenCodeToUnicodeMap();
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private static char[] CreateScreenCodeToUnicodeMap() {
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char[] map = new char[256];
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for (int val = 0; val < 256; val++) {
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char ch;
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if (val == 0x00 || val == 0x1b || val == 0x1d) {
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ch = (char)(val + 0x40); // '@', '[', ']'
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} else if (val >= 0x01 && val <= 0x1a) {
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ch = (char)(val + 0x60); // lower case
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} else if (val >= 0x20 && val <= 0x3f) {
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ch = (char)(val); // numbers/symbols
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} else if (val >= 0x41 && val <= 0x5a) {
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ch = (char)(val); // upper case
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} else {
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Debug.Assert(!IsPrintableC64ScreenCode((byte)val));
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ch = UNPRINTABLE_CHAR;
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}
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map[val] = ch;
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}
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return map;
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}
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public static char ConvertC64ScreenCode(byte val) {
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return sScreenCodeToUnicode[val];
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}
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public static char ConvertLowAndHighC64ScreenCode(byte val) {
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return ConvertC64ScreenCode((byte)(val & 0x7f));
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}
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}
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}
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