Class Buffer

io/buffer.ts:45–497

 * ```
 */
export class Buffer implements Writer, WriterSync, Reader, ReaderSync {
  #buf: Uint8Array; // contents are the bytes buf[off : len(buf)]
  #off = 0; // read at buf[off], write at buf[buf.byteLength]

  /**
   * Constructs a new instance with the specified {@linkcode ArrayBuffer} as its
   * initial contents.
   *
   * @param ab The ArrayBuffer to use as the initial contents of the buffer.
   */
  constructor(ab?: ArrayBufferLike | ArrayLike<number>) {
    if (ab === undefined) {
      this.#buf = new Uint8Array(0);
    } else if (ab instanceof SharedArrayBuffer) {
      // Note: This is necessary to avoid type error
      this.#buf = new Uint8Array(ab);
    } else {
      this.#buf = new Uint8Array(ab);
    }
  }

  /**
   * Returns a slice holding the unread portion of the buffer.
   *
   * The slice is valid for use only until the next buffer modification (that
   * is, only until the next call to a method like `read()`, `write()`,
   * `reset()`, or `truncate()`). If `options.copy` is false the slice aliases the buffer content at
   * least until the next buffer modification, so immediate changes to the
   * slice will affect the result of future reads.
   *
   * @example Usage
   * ```ts
   * import { Buffer } from "@std/io/buffer";
   * import { assertEquals } from "@std/assert/equals";
   *
   * const buf = new Buffer();
   * await buf.write(new TextEncoder().encode("Hello, world!"));
   *
   * const slice = buf.bytes();
   * assertEquals(new TextDecoder().decode(slice), "Hello, world!");
   * ```
   *
   * @param options The options for the slice.
   * @returns A slice holding the unread portion of the buffer.
   */
  bytes(options = { copy: true }): Uint8Array {
    if (options.copy === false) return this.#buf.subarray(this.#off);
    return this.#buf.slice(this.#off);
  }

  /**
   * Returns whether the unread portion of the buffer is empty.
   *
   * @example Usage
   * ```ts
   * import { Buffer } from "@std/io/buffer";
   * import { assertEquals } from "@std/assert/equals";
   *