mojo/public/mojom/base/string16_converter.ts

// Copyright 2025 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import type {String16DataView, String16TypeMapper} from './string16.mojom-converters.js';

export class String16Converter implements String16TypeMapper<string> {
  data(str: string): number[] {
    const arr: number[] = [];
    for (let i = 0; i < str.length; ++i) {
      arr.push(str.charCodeAt(i));
    }
    return arr;
  }

  convert(view: String16DataView): string {
    const data = view.data;

    return this.convertImpl(data);
  }

  // Exported for testing.
  // TODO(crbug.com/448737199): we should not have to expose a separate method
  // just to facilitate testing.
  convertImpl(data: number[]) {
    // Taken from chunk size used in goog.crypt.byteArrayToBinaryString in
    // Closure Library. The value is equal to 2^13.
    const CHUNK_SIZE = 8192;


    if (data.length < CHUNK_SIZE) {
      return String.fromCharCode(...data);
    }

    // Convert the array to a string in chunks, to avoid passing too many
    // arguments to String.fromCharCode() at once, which can exceed the max call
    // stack size (c.f. crbug.com/1509792).
    let str = '';
    for (let i = 0; i < data.length; i += CHUNK_SIZE) {
      const chunk = data.slice(i, i + CHUNK_SIZE);
      str += String.fromCharCode(...chunk);
    }
    return str;
  }
}