Relocate nametable and attributes to blank space 👽. (#15)

* Relocate nametable and attributes to blank space 👽.

---------

Co-authored-by: Gamaiel Zavala <ceriumz@hotmail.com>

experiments/relocateNtAttrs.js

@@ -0,0 +1,136 @@
+#!/usr/bin/env node --experimental-json-modules
+
+import { parseArgs } from 'node:util';
+import { basename } from 'node:path';
+import { loadRom, saveRom, expandRom, inject } from '../src/lib/cliUtils.js';
+import parseRoom from '../src/lib/parser/parseRooms.js';
+import { zeroPad, hex } from '../src/lib/utils.js';
+
+/*
+Relocate nametable and attributes:
+  Move nametable and attributes out of the room payloads to a new section of the ROM.
+  Update the NES ASM to read from the new location
+  It creates a new ROM file called 'relocated-nt-attr.nes' in current path.
+*/
+
+const BANK_SIZE = 0x4000;
+const output = 'relocated-nt-attr.nes';
+const { values } = parseArgs({
+  options: {
+    input: {
+      type: 'string',
+      short: 'i',
+    },
+    'base-rom': {
+      type: 'string',
+      short: 'b',
+    },
+  },
+  strict: true,
+});
+
+if (!values.input) {
+  console.log(`\x1b[1mRelocate nametable and attributes:\x1b[0m
+  Move nametable and attributes out of the room payloads to a new section of the ROM.
+  Update the NES ASM to read from the new location
+  It creates a new ROM file called '${output}' in current path.
+
+\x1b[1mUsage\x1b[0m
+  node ${basename(import.meta.url)} --input path/to/rom [--base-rom xx]`);
+  process.exit(0);
+}
+
+// Load the input file.
+let rom, res;
+try {
+  ({ rom, res } = await loadRom(values.input, values['base-rom']));
+} catch (err) {
+  console.error(`Input ROM file could not be opened.`);
+  console.error(err);
+  process.exit(1);
+}
+
+rom = expandRom(rom);
+
+// Write the nametable and attributes from bank 16 onwards.
+const view = new DataView(rom);
+const roomNum = 55;
+let bank = 17;
+let bankOffset = 0;
+console.log('Bank:', bank);
+
+for (let i = 0; i < roomNum; i++) {
+  const [offset, length] = res.rooms[i];
+
+  if (!length) {
+    continue;
+  }
+
+  const roomBuffer = rom.slice(offset, offset + length);
+  const resources = parseRoom(roomBuffer, i, offset, res.characters);
+  let from, to;
+
+  // Nametable
+  ({ from, to } = resources.map.find(({ type }) => type === 'nametable'));
+  from += 17; // Skip the tileset id and palette.
+  const nametableLength = to - from;
+  const nametableBuffer = roomBuffer.slice(from, to);
+  for (let i = offset + from; i < offset + to; i++) {
+    view.setUint8(i, 0xff);
+  }
+
+  // Attributes
+  ({ from, to } = resources.map.find(({ type }) => type === 'attributes'));
+  const attrsLength = to - from;
+  const attrsBuffer = roomBuffer.slice(from, to);
+  for (let i = offset + from; i < offset + to; i++) {
+    view.setUint8(i, 0xff);
+  }
+
+  if (bankOffset + nametableLength + attrsLength > BANK_SIZE) {
+    bank++;
+    bankOffset = 0;
+    console.log('Bank:', bank);
+  }
+
+  const ntOffset = bank * BANK_SIZE + bankOffset;
+  const atOffset = ntOffset + nametableLength;
+  inject(rom, nametableBuffer, ntOffset, nametableLength);
+  inject(rom, attrsBuffer, atOffset, attrsLength);
+
+  // Update room header.
+  view.setUint16(offset + 0x08, bankOffset + BANK_SIZE * 2, true); // unk3
+  view.setUint16(
+    offset + 0x0c,
+    bankOffset + BANK_SIZE * 2 + nametableLength,
+    true,
+  ); // unk4
+  view.setUint8(offset + 0x12, bank - 16); // unk5
+
+  const headerLength = 0x10;
+  console.log(
+    'Room %s (%s) @ 0x%s: bank %s, nt offset 0x%s @ 0x%s (%s bytes), attrs offset 0x%s @ 0x%s (%s bytes)',
+    hex(i, 2),
+    zeroPad(i),
+    hex(offset + headerLength),
+    hex(bank - 16, 2),
+    hex(bankOffset, 4),
+    hex(ntOffset + headerLength),
+    nametableLength,
+    hex(bankOffset + nametableLength, 4),
+    hex(atOffset + headerLength),
+    attrsLength
+  );
+  bankOffset += nametableLength;
+  bankOffset += attrsLength;
+}
+
+try {
+  await saveRom(output, rom);
+} catch (err) {
+  console.error(`Output ROM file could not be saved.`);
+  console.error(err);
+  process.exit(1);
+}
+
+console.log('Output file successfully written.');