Function getBinaryHeaderData

wasm/nodejs/src/module.js:17–48

(wasmBytes)

const PAGE_SIZE = 65536;

const getBinaryHeaderData = (wasmBytes) => {
  const magicBytes = new Uint32Array(new Uint8Array(wasmBytes.subarray(0, 24)).buffer);
  if (magicBytes[0] !== 0x6d736100) {
    console.error("Wasm magic number is missing!");
  }
  if (wasmBytes[8] !== 0) {
    log("Dylink section wasn't found in wasm binary, assuming static wasm.");
    return "static";
  }

  let next = 9;
  function getLEB() {
    let returnValue = 0;
    let mul = 1;
    while (1) {
      const byte = wasmBytes[next++];
      returnValue += (byte & 0x7f) * mul;
      mul *= 0x80;
      if (!(byte & 0x80)) break;
    }
    return returnValue;
  }
  const sectionSize = getLEB();
  // 6, size of "dylink" string = 7
  next += 7;
  const memorySize = getLEB();
  const memoryAlign = getLEB();
  const tableSize = getLEB();
  const tableAlign = getLEB();
  const neededDynlibsCount = getLEB();
  return { sectionSize, memorySize, memoryAlign, neededDynlibsCount, tableSize, tableAlign };
};

export default async function ({ withPlugins = [] }) {
  const fileBuffer = await readFilePromise(wasmDylibPath);