Function initWasm

src/componentize.js:538–580

* Initialize a WebAssembly binary, given the * * @param {Buffer} bin - WebAssembly binary bytes * @throws If a binary is invalid

(bin)

 * @throws If a binary is invalid
 */
async function initWasm(bin) {
  const eep = (name) => () => {
    throw new Error(
      `Internal error: unexpected call to "${name}" during Wasm verification`,
    );
  };

  let stderr = '';
  const wasmModule = await WebAssembly.compile(bin);

  const mockImports = {
    wasi_snapshot_preview1: {
      fd_write: function (fd, iovs, iovs_len, nwritten) {
        if (fd !== 2) return 0;
        const mem = new DataView(exports.memory.buffer);
        let written = 0;
        for (let i = 0; i < iovs_len; i++) {
          const bufPtr = mem.getUint32(iovs + i * 8, true);
          const bufLen = mem.getUint32(iovs + 4 + i * 8, true);
          stderr += new TextDecoder().decode(
            new Uint8Array(exports.memory.buffer, bufPtr, bufLen),
          );
          written += bufLen;
        }
        mem.setUint32(nwritten, written, true);
        return 1;
      },
    },
  };

  for (const { module, name } of WebAssembly.Module.imports(wasmModule)) {
    mockImports[module] = mockImports[module] || {};
    if (!mockImports[module][name]) mockImports[module][name] = eep(name);
  }

  const { exports } = await WebAssembly.instantiate(wasmModule, mockImports);
  return {
    exports,
    getStderr() {
      return stderr;
    },
  };
}

/**
 * Handle the output of `check_init()`