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ref(wasm): shared decode util
Nate Moore
(Jun 1, 2026, 3:16 PM -0500)
8aad2225
9b7e4ac7
+43
-7
+4
-7
tasks/bundle-wasm.ts
+4
-7
tasks/bundle-wasm.ts
···
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const z85 = encodeZ85(compressed);
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// Decoder uses division instead of >>> to avoid 32-bit truncation on values near 0xFFFFFFFF.
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const source = `import{brotliDecompressSync}from"node:zlib";
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const Z="0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ.-:+=^!/*?&<>()[]{}@%$#";
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const T=new Uint8Array(128);for(let i=0;i<85;i++)T[Z.charCodeAt(i)]=i;
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function d(s:string,n:number){const b=new Uint8Array(n);let o=0;for(let i=0;i<s.length&&o<n;i+=5){const v=T[s.charCodeAt(i)]*52200625+T[s.charCodeAt(i+1)]*614125+T[s.charCodeAt(i+2)]*7225+T[s.charCodeAt(i+3)]*85+T[s.charCodeAt(i+4)];if(o<n)b[o++]=Math.floor(v/16777216);if(o<n)b[o++]=Math.floor(v/65536)%256;if(o<n)b[o++]=Math.floor(v/256)%256;if(o<n)b[o++]=v%256;}return b;}
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const compressed=d(${JSON.stringify(z85)},${compressed.byteLength});
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export const compiled=await WebAssembly.compile(new Uint8Array(brotliDecompressSync(compressed)));
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// args separated to keep deno fmt happy
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const args = `${JSON.stringify(z85)}, ${compressed.byteLength}`;
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const source = `import { decode } from "./wasm-decode.ts";
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export const compiled = await decode(${args});
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`;
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await Deno.writeTextFile(output, source);
+39
wasm-decode.ts
+39
wasm-decode.ts
···
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import { brotliDecompressSync } from "node:zlib";
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const Z85 =
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"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ.-:+=^!/*?&<>()[]{}@%$#";
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const DECODE = new Uint8Array(128);
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for (let i = 0; i < 85; i++) DECODE[Z85.charCodeAt(i)] = i;
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// Division instead of >>> avoids 32-bit truncation on values near 0xFFFFFFFF.
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function decodeZ85(s: string, n: number): Uint8Array {
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let bytes = new Uint8Array(n);
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let o = 0;
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for (let i = 0; i < s.length && o < n; i += 5) {
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let v = DECODE[s.charCodeAt(i)] * 52200625 +
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DECODE[s.charCodeAt(i + 1)] * 614125 +
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DECODE[s.charCodeAt(i + 2)] * 7225 +
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DECODE[s.charCodeAt(i + 3)] * 85 +
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DECODE[s.charCodeAt(i + 4)];
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if (o < n) bytes[o++] = Math.floor(v / 16777216);
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if (o < n) bytes[o++] = Math.floor(v / 65536) % 256;
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if (o < n) bytes[o++] = Math.floor(v / 256) % 256;
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if (o < n) bytes[o++] = v % 256;
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}
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return bytes;
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}
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/**
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* Decode an inlined WASM blob: z85 → brotli-decompress → compile.
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*
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* `byteLength` is the brotli-compressed length, used to size the z85
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* decode buffer before decompression restores the original module.
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*/
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export function decode(
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z85: string,
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byteLength: number,
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): Promise<WebAssembly.Module> {
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let compressed = decodeZ85(z85, byteLength);
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return WebAssembly.compile(new Uint8Array(brotliDecompressSync(compressed)));
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}