// C64 Constants and Utilities
// Color palette names
export const C64_COLORS = [
"black",
"white",
"red",
"cyan",
"purple",
"green",
"blue",
"yellow",
"orange",
"brown",
"light red",
"dark gray",
"gray",
"light green",
"light blue",
"light gray",
] as const;
export type C64Color = (typeof C64_COLORS)[number];
export function getColorName(value: number): C64Color {
return C64_COLORS[value & 0x0f];
}
export function getColorInfo(value: number): { value: number; name: C64Color } {
return {
value: value & 0x0f,
name: getColorName(value),
};
}
// PETSCII to ASCII conversion (screen codes, not PETSCII character codes)
// Screen codes are different from PETSCII - this handles the screen memory values
export function screenCodeToAscii(code: number): string {
// Screen codes 0-31: @, A-Z, [, £, ], ↑, ←
if (code <= 31) {
if (code === 0) return "@";
if (code <= 26) return String.fromCharCode(64 + code); // A-Z
if (code === 27) return "[";
if (code === 28) return "£";
if (code === 29) return "]";
if (code === 30) return "^"; // up arrow
if (code === 31) return "<"; // left arrow
}
// 32-63: space, !, ", #, $, %, &, ', (, ), *, +, ,, -, ., /, 0-9, :, ;, <, =, >, ?
if (code >= 32 && code <= 63) {
return String.fromCharCode(code);
}
// 64-95: horizontal line, graphics chars - use placeholders
if (code >= 64 && code <= 95) {
return "#"; // graphics placeholder
}
// 96-127: more graphics
if (code >= 96 && code <= 127) {
return "#"; // graphics placeholder
}
// 128-255: reverse video versions of 0-127
if (code >= 128) {
// Just show the base character (non-reversed)
return screenCodeToAscii(code - 128);
}
return "?";
}
// Convert screen RAM to text lines
export function screenToText(screenData: Buffer | number[]): string[] {
const data = Buffer.isBuffer(screenData) ? screenData : Buffer.from(screenData);
const lines: string[] = [];
for (let row = 0; row < 25; row++) {
const offset = row * 40;
let line = "";
for (let col = 0; col < 40; col++) {
if (offset + col < data.length) {
line += screenCodeToAscii(data[offset + col]);
}
}
// Trim trailing spaces but keep the line
lines.push(line.trimEnd());
}
return lines;
}
// VIC-II memory bank calculation
export function getVicBank(cia2PortA: number): { bank: number; baseAddress: number } {
// CIA2 port A bits 0-1 (inverted) select the bank
const bankBits = (~cia2PortA) & 0x03;
return {
bank: bankBits,
baseAddress: bankBits * 0x4000,
};
}
// Screen and character base from $D018
export function getVideoAddresses(
d018: number,
bankBase: number
): { screenAddress: number; charAddress: number } {
const screenOffset = ((d018 >> 4) & 0x0f) * 0x0400;
const charOffset = ((d018 >> 1) & 0x07) * 0x0800;
return {
screenAddress: bankBase + screenOffset,
charAddress: bankBase + charOffset,
};
}
// Graphics mode from D011 and D016
export function getGraphicsMode(d011: number, d016: number): {
mode: string;
bitmap: boolean;
multicolor: boolean;
extendedColor: boolean;
} {
const ecm = !!(d011 & 0x40);
const bmm = !!(d011 & 0x20);
const mcm = !!(d016 & 0x10);
let mode = "standard text";
if (ecm && !bmm && !mcm) mode = "extended background color";
else if (!ecm && !bmm && mcm) mode = "multicolor text";
else if (!ecm && bmm && !mcm) mode = "standard bitmap";
else if (!ecm && bmm && mcm) mode = "multicolor bitmap";
else if (ecm) mode = "invalid (ECM + other modes)";
return {
mode,
bitmap: bmm,
multicolor: mcm,
extendedColor: ecm,
};
}
// Sprite position visible range helpers
export const SPRITE_VISIBLE_X_MIN = 24;
export const SPRITE_VISIBLE_X_MAX = 343;
export const SPRITE_VISIBLE_Y_MIN = 50;
export const SPRITE_VISIBLE_Y_MAX = 249;
export function isSpriteVisible(x: number, y: number, enabled: boolean): {
visible: boolean;
reason?: string;
} {
if (!enabled) {
return { visible: false, reason: "Sprite is disabled ($D015)" };
}
if (x < SPRITE_VISIBLE_X_MIN || x > SPRITE_VISIBLE_X_MAX) {
return { visible: false, reason: `X position ${x} is outside visible range (${SPRITE_VISIBLE_X_MIN}-${SPRITE_VISIBLE_X_MAX})` };
}
if (y < SPRITE_VISIBLE_Y_MIN || y > SPRITE_VISIBLE_Y_MAX) {
return { visible: false, reason: `Y position ${y} is outside visible range (${SPRITE_VISIBLE_Y_MIN}-${SPRITE_VISIBLE_Y_MAX})` };
}
return { visible: true };
}
// Memory region descriptions
export function describeAddress(address: number): string {
if (address < 0x0100) return "Zero page";
if (address < 0x0200) return "Stack";
if (address >= 0x0400 && address < 0x0800) return "Default screen RAM";
if (address >= 0x0800 && address < 0x1000) return "Default char ROM shadow";
if (address >= 0xa000 && address < 0xc000) return "BASIC ROM / RAM";
if (address >= 0xd000 && address < 0xd400) return "VIC-II registers";
if (address >= 0xd400 && address < 0xd800) return "SID registers";
if (address >= 0xd800 && address < 0xdc00) return "Color RAM";
if (address >= 0xdc00 && address < 0xdd00) return "CIA1 registers";
if (address >= 0xdd00 && address < 0xde00) return "CIA2 registers";
if (address >= 0xe000) return "KERNAL ROM / RAM";
return "";
}
