pdf.js.mirror/src/core/data_builder.js

/* Copyright 2026 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import { assert } from "../shared/util.js";
import { MathClamp } from "../shared/math_clamp.js";

class DataBuilder {
  #buf;

  #bufLength = 1024;

  #hasExactLength = false;

  #pos = 0;

  #view;

  constructor({ exactLength = 0, minLength = 0 }) {
    this.#hasExactLength = !!exactLength;
    this.#initBuf(exactLength || minLength);
  }

  #initBuf(minLength) {
    if (this.#hasExactLength) {
      this.#bufLength = minLength;
    } else {
      // Compute the first power of two that is as big as the `minLength`.
      while (this.#bufLength < minLength) {
        this.#bufLength *= 2;
      }
    }
    const newBuf = new Uint8Array(this.#bufLength);

    if (this.#buf) {
      newBuf.set(this.#buf, 0);
    }
    this.#buf = newBuf;
    this.#view = new DataView(newBuf.buffer);
  }

  get data() {
    return this.#buf.subarray(0, this.#pos);
  }

  get length() {
    return this.#pos;
  }

  skip(n) {
    this.#pos += n;
  }

  setArray(arr) {
    const newPos = this.#pos + arr.length;

    if (!this.#hasExactLength && newPos > this.#bufLength) {
      this.#initBuf(newPos);
    }
    this.#buf.set(arr, this.#pos);
    this.#pos = newPos;
  }

  setInt16(val) {
    if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
      assert(
        typeof val === "number" && Math.abs(val) < 2 ** 16,
        `setInt16: Unexpected input "${val}".`
      );
    }
    const newPos = this.#pos + 2;

    if (!this.#hasExactLength && newPos > this.#bufLength) {
      this.#initBuf(newPos);
    }
    this.#view.setInt16(this.#pos, val);
    this.#pos = newPos;
  }

  setSafeInt16(val) {
    if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
      assert(
        typeof val === "number" && !Number.isNaN(val),
        `safeString16: Unexpected input "${val}".`
      );
    }
    const newPos = this.#pos + 2;

    if (!this.#hasExactLength && newPos > this.#bufLength) {
      this.#initBuf(newPos);
    }
    // clamp value to the 16-bit int range
    this.#view.setInt16(this.#pos, MathClamp(val, -0x8000, 0x7fff));
    this.#pos = newPos;
  }

  setInt32(val) {
    if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
      assert(
        typeof val === "number" && Math.abs(val) < 2 ** 32,
        `setInt32: Unexpected input "${val}".`
      );
    }
    const newPos = this.#pos + 4;

    if (!this.#hasExactLength && newPos > this.#bufLength) {
      this.#initBuf(newPos);
    }
    this.#view.setInt32(this.#pos, val);
    this.#pos = newPos;
  }
}

export { DataBuilder };