2949a96e11
Bit layout [atlas:8][tile_id:20][rot:2][res:2] matches lib-core.maps init.lua so JS-produced GIDs are byte-identical to engine-produced ones. >>> 0 forces unsigned u32 output.
31 lines
795 B
JavaScript
31 lines
795 B
JavaScript
'use strict';
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const MAX_ATLAS = 255;
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const MAX_TILE = 1048575;
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const MAX_ROT = 3;
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const MAX_U32 = 0xFFFFFFFF;
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function checkInt(name, value, min, max) {
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if (!Number.isInteger(value) || value < min || value > max) {
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throw new RangeError(`${name} ${value} out of range [${min},${max}]`);
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}
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}
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function encodeGid(atlas, tile, rotation = 0) {
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checkInt('atlas', atlas, 0, MAX_ATLAS);
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checkInt('tile', tile, 0, MAX_TILE);
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checkInt('rotation', rotation, 0, MAX_ROT);
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return ((atlas << 24) | (tile << 4) | (rotation << 2)) >>> 0;
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}
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function decodeGid(gid) {
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checkInt('gid', gid, 0, MAX_U32);
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return {
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atlas: (gid >>> 24) & 0xFF,
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tile: (gid >>> 4) & 0xFFFFF,
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rotation: (gid >>> 2) & 0x3,
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};
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}
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module.exports = { encodeGid, decodeGid, MAX_ATLAS, MAX_TILE, MAX_ROT };
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