pkg/dart2wasm/lib/js/runtime_blob.dart

// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

const jsRuntimeBlobPart1 = r'''

// Compiles a dart2wasm-generated main module from `source` which can then
// instantiatable via the `instantiate` method.
//
// `source` needs to be a `Response` object (or promise thereof) e.g. created
// via the `fetch()` JS API.
export async function compileStreaming(source) {
  const builtins = {builtins: ['js-string']};
  return new CompiledApp(
      await WebAssembly.compileStreaming(source, builtins), builtins);
}

// Compiles a dart2wasm-generated wasm modules from `bytes` which is then
// instantiatable via the `instantiate` method.
export async function compile(bytes) {
  const builtins = {builtins: ['js-string']};
  return new CompiledApp(await WebAssembly.compile(bytes, builtins), builtins);
}

// DEPRECATED: Please use `compile` or `compileStreaming` to get a compiled app,
// use `instantiate` method to get an instantiated app and then call
// `invokeMain` to invoke the main function.
export async function instantiate(modulePromise, importObjectPromise) {
  var moduleOrCompiledApp = await modulePromise;
  if (!(moduleOrCompiledApp instanceof CompiledApp)) {
    moduleOrCompiledApp = new CompiledApp(moduleOrCompiledApp);
  }
  const instantiatedApp = await moduleOrCompiledApp.instantiate(await importObjectPromise);
  return instantiatedApp.instantiatedModule;
}

// DEPRECATED: Please use `compile` or `compileStreaming` to get a compiled app,
// use `instantiate` method to get an instantiated app and then call
// `invokeMain` to invoke the main function.
export const invoke = (moduleInstance, ...args) => {
  moduleInstance.exports.$invokeMain(args);
}

class CompiledApp {
  constructor(module, builtins) {
    this.module = module;
    this.builtins = builtins;
  }

  // The second argument is an options object containing:
  // `loadDeferredWasm` is a JS function that takes a module name matching a
  //   wasm file produced by the dart2wasm compiler and returns the bytes to
  //   load the module. These bytes can be in either a format supported by
  //   `WebAssembly.compile` or `WebAssembly.compileStreaming`.
  async instantiate(additionalImports, {loadDeferredWasm} = {}) {
    let dartInstance;

    // Prints to the console
    function printToConsole(value) {
      if (typeof dartPrint == "function") {
        dartPrint(value);
        return;
      }
      if (typeof console == "object" && typeof console.log != "undefined") {
        console.log(value);
        return;
      }
      if (typeof print == "function") {
        print(value);
        return;
      }

      throw "Unable to print message: " + js;
    }

    // Converts a Dart List to a JS array. Any Dart objects will be converted, but
    // this will be cheap for JSValues.
    function arrayFromDartList(constructor, list) {
      const exports = dartInstance.exports;
      const read = exports.$listRead;
      const length = exports.$listLength(list);
      const array = new constructor(length);
      for (let i = 0; i < length; i++) {
        array[i] = read(list, i);
      }
      return array;
    }

    // A special symbol attached to functions that wrap Dart functions.
    const jsWrappedDartFunctionSymbol = Symbol("JSWrappedDartFunction");

    function finalizeWrapper(dartFunction, wrapped) {
      wrapped.dartFunction = dartFunction;
      wrapped[jsWrappedDartFunctionSymbol] = true;
      return wrapped;
    }

    // Imports
    const dart2wasm = {
''';

// We break inside the 'dart2wasm' object to enable injection of methods. We
// could use interpolation, but then we'd have to escape characters.
const jsRuntimeBlobPart2 = r'''
    };

    const baseImports = {
      dart2wasm: dart2wasm,
''';

// We break inside of `baseImports` to inject internalized strings.
const jsRuntimeBlobPart3 = r'''
      Math: Math,
      Date: Date,
      Object: Object,
      Array: Array,
      Reflect: Reflect,
    };

    const jsStringPolyfill = {
      "charCodeAt": (s, i) => s.charCodeAt(i),
      "compare": (s1, s2) => {
        if (s1 < s2) return -1;
        if (s1 > s2) return 1;
        return 0;
      },
      "concat": (s1, s2) => s1 + s2,
      "equals": (s1, s2) => s1 === s2,
      "fromCharCode": (i) => String.fromCharCode(i),
      "length": (s) => s.length,
      "substring": (s, a, b) => s.substring(a, b),
      "fromCharCodeArray": (a, start, end) => {
        if (end <= start) return '';

        const read = dartInstance.exports.$wasmI16ArrayGet;
        let result = '';
        let index = start;
        const chunkLength = Math.min(end - index, 500);
        let array = new Array(chunkLength);
        while (index < end) {
          const newChunkLength = Math.min(end - index, 500);
          for (let i = 0; i < newChunkLength; i++) {
            array[i] = read(a, index++);
          }
          if (newChunkLength < chunkLength) {
            array = array.slice(0, newChunkLength);
          }
          result += String.fromCharCode(...array);
        }
        return result;
      },
    };

    const deferredLibraryHelper = {
      "loadModule": async (moduleName) => {
        if (!loadDeferredWasm) {
          throw "No implementation of loadDeferredWasm provided.";
        }
        const source = await Promise.resolve(loadDeferredWasm(moduleName));
        const module = await ((source instanceof Response)
            ? WebAssembly.compileStreaming(source, this.builtins)
            : WebAssembly.compile(source, this.builtins));
        return await WebAssembly.instantiate(module, {
          ...baseImports,
          ...additionalImports,
          "wasm:js-string": jsStringPolyfill,
          "module0": dartInstance.exports,
        });
      },
    };

    dartInstance = await WebAssembly.instantiate(this.module, {
      ...baseImports,
      ...additionalImports,
      "deferredLibraryHelper": deferredLibraryHelper,
      "wasm:js-string": jsStringPolyfill,
    });

    return new InstantiatedApp(this, dartInstance);
  }
}

class InstantiatedApp {
  constructor(compiledApp, instantiatedModule) {
    this.compiledApp = compiledApp;
    this.instantiatedModule = instantiatedModule;
  }

  // Call the main function with the given arguments.
  invokeMain(...args) {
    this.instantiatedModule.exports.$invokeMain(args);
  }
}
''';