waltSource = `// WAVE EQUATION - Click and drag on the canvas. // Compare this to the version generated by Emscripten: https://webassembly.studio/?f=kv3dhnahf1 import { getCanvasWidth: GetSizeType, getCanvasHeight: GetSizeType, log: LogType } from 'env'; type LogType = (i32) => void; type GetSizeType = () => i32; export const memory: Memory<{initial: 1}>; const HEAP_START: i32 = 65536; let width: i32; let height: i32; let wh: i32; let image: i32[]; let force: i32[]; let status: i32[]; let u: i32[]; let vel: i32[]; let colorRamp: i32[]; let iStart: i32; let iEnd: i32; let useColorRamp: i32; export function init(_useColorRamp : i32) : void { useColorRamp = _useColorRamp; width = getCanvasWidth(); height = getCanvasHeight(); wh = width * height; image = HEAP_START; force = HEAP_START + 4 * wh; status = HEAP_START + 8 * wh; u = HEAP_START + 12 * wh; vel = HEAP_START + 16 * wh; colorRamp = HEAP_START + 20 * wh; let i: i32; // Draw walls // top row for (i = 0; i < width; i += 1) { status[i] = 1; } // columns for(i = width; i < wh; i += width){ // exploit that array wraps around to next row status[i-1] = 1; status[i] = 1; } // bottom row for (i = wh - width; i < wh; i += 1) { status[i] = 1; } iStart = width + 1; iEnd = wh - width - 2; } function applyCap(x: i32) : i32 { // branchless bit-twiddling code below // if (x < -0x40000000) { // return -0x40000000; // } // if (x > 0x3FFFFFFF) { // return 0x3FFFFFFF; // } // return x; // const mask : i32 = x >> 31; // if ((x^mask) > 0x3FFFFFFF) { // return 0x3FFFFFFF^mask; // } // return x; const mask : i32 = x >> 31; x = x^mask; // "absolute" value of x (applying one's complement to a two's complement nr) const absMask : i32 = (x<<1)>>31; // abs(x) > 0x3FFFFFFF? x = (x | absMask) & 0x3FFFFFFF; return x^mask; } function toRGB(x: i32) : i32 { // branchless bit-twiddling code below // const val: i32 = x >> 22; // if (val < 0) { // return ((-(val + 1)) | 0xFF000000); //red // } // return (((val << 8) | (val << 16)) | 0xFF000000); // cyan let val: i32 = x >> 22; let sign: i32 = x >> 31; // branchless absolute value & color selection let absVal: i32 = (val^sign) + (sign&1); sign = (sign&8)^sign; absVal = absVal + (absVal << sign); return 0xFF000000 | (absVal << sign); } function toColorRamp(x: i32) : i32 { let val: i32 = (x >> 23) + 128; return colorRamp[val]; } export function applyBrush(x: i32, y: i32, radius: i32) : void { const width: i32 = getCanvasWidth(); const height: i32 = getCanvasHeight(); const wh: i32 = width * height; const force: i32[] = HEAP_START + 4 * wh; if (radius < 0) radius = -radius; const radius2: i32 = radius*radius; const rMul: i32 = 0x3FFFFFFF / radius2; let xi: i32 = x - radius; let yj: i32 = y - radius; let i: i32; let j: i32; for (i = -radius; xi < 0 && i <= radius; i += 1) { xi = x + i+1; } for (j = -radius; yj < 0 && j <= radius; j += 1) { yj = y + j+1; } const i0: i32 = i; const j0: i32 = j; for (j = j0; yj < height && j <= radius; j += 1){ const j2: i32 = j * j; for (i = i0; xi < width && i <= radius; i += 1){ const r2: i32 = j2 + i*i; if (r2 <= radius2) { const f: i32 = force[xi + yj * width]; //force[xi + yj * width] = applyCap(f + 0x3FFFFFFF - rMul*r2); // manually inlined applyCap let cap : i32 = f + 0x3FFFFFFF - rMul*r2; const mask : i32 = cap >> 31; cap = cap^mask; // abs(cap) const absMask : i32 = (cap<<1)>>31; // abs(x) > 0x3FFFFFFF? cap = (cap | absMask) & 0x3FFFFFFF; force[xi + yj * width] = cap^mask; } xi = x + i; } yj = y + j; } } export function step() : void { let i: i32 = iStart; // Calculate velocity change while (i < iEnd) { let uCen: i32 = u[i-1]; let uEast: i32 = u[i]; while (status[i] == 0) { const uNorth: i32 = u[i - width]; const uWest: i32 = uCen; uCen = uEast; uEast = u[i + 1]; const uSouth: i32 = u[i + width]; const uxx: i32 = ((uWest + uEast + 1) >> 1) - uCen; const uyy: i32 = ((uNorth + uSouth + 1) >> 1) - uCen; vel[i] = applyCap(vel[i] + (uxx+1 >> 1) + (uyy+1 >> 1)); i += 1; } i += 1; } // Apply forces i = iStart; while (i < iEnd) { while (status[i] == 0) { const f: i32 = force[i]; u[i] = applyCap(f + applyCap(u[i] + vel[i])); force[i] = f >> 1; i += 1; } i += 1; } // Generate image i = iStart; if (useColorRamp) { while (i < iEnd) { while (status[i] == 0) { // inlined toColorRamp image[i] = colorRamp[128 + (u[i]>>23)]; i += 1; } i += 1; } } else { let val: i32; let sign: i32; let absVal: i32; while (i < iEnd) { while (status[i] == 0) { image[i] = toRGB(u[i]); // manually inlined toRGB const rawVal: i32 = u[i]; val = rawVal >> 22; sign = rawVal >> 31; absVal = (val^sign) + (sign&1); sign = (sign&8)^8; absVal = absVal | (absVal << sign); image[i] = 0xFF000000 | (absVal << sign); i += 1; } i += 1; } } } `