55 lines
1.6 KiB
JavaScript
55 lines
1.6 KiB
JavaScript
// Generate seizzle tables
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//
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// Maps an 8-bit value of wwxxyyzz to a lookup table that takes each 2-bit
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// value to a 16-bit pixel index. Zero always maps to zero. The input
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// is three 4-bit values that define the targets for 1, 2, and 3.
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// Run as: node swizzle.js label val1 val2 val3
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if (process.argv.length !== 6) {
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console.log(process.argv);
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process.exit(1);
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}
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const output = process.stdout;
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const values = [
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0,
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Number(process.argv[3]),
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Number(process.argv[4]),
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Number(process.argv[5]),
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];
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output.write(process.argv[2] + '\n');
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for (let w = 0; w < 4; w++) {
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for (let x = 0; x < 4; x++) {
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output.write(' dw ');
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const row = [];
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for (let y = 0; y < 4; y++) {
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for (let z = 0; z < 4; z++) {
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// Because the NES PPU bits define the pixel order from high bit to low bit, but the
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// 65816 is little endian, we need to swap the byte order in the mapping
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/*
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const target =
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(values[w] * 4096) +
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(values[x] * 256) +
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(values[y] * 16) +
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values[z];
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*/
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const target =
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(values[w] * 16) +
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(values[x] * 1) +
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(values[y] * 4096) +
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(values[z] * 256);
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row.push(target);
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}
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}
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// Output the values
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output.write(row.map(s => '$' + s.toString(16).padStart(4, '0')).join(','));
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// Line break
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output.write('\n');
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}
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}
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