MemoryHandle implementation. ( see hhvm/hsl-experimental#58 )

MemoryHandle.hack

namespace Nuxed\IO;

/*
 * This file is part of the Nuxed package.
 *
 * (c) Saif Eddin Gmati <azjezz@protonmail.org>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */
 
use namespace HH\Lib\{Experimental\IO, Math, Str};

class MemoryHandle implements IO\NonDisposableReadWriteHandle {
  private ?Awaitable<mixed> $lastOperation;
  protected int $position = 0;

  public function __construct(protected string $data = '') {}

  final protected function queuedAsync<T>(
    (function(): Awaitable<T>) $next,
  ): Awaitable<T> {
    $last = $this->lastOperation;
    $queue = async {
      await $last;
      return await $next();
    };
    $this->lastOperation = $queue;
    return $queue;
  }

  /**
   * Possibly write some of the string.
   *
   * Returns the number of bytes written, which may be 0.
   */
  final public function rawWriteBlocking(string $bytes): int {
    $length = Str\length($bytes);
    $this->data = Str\splice($this->data, $bytes, $this->position);
    $this->position += $length;

    return $length;
  }

  final public async function writeAsync(string $bytes): Awaitable<void> {
    await $this->queuedAsync(async () ==> $this->rawWriteBlocking($bytes));
  }

  final public function rawReadBlocking(?int $max_bytes = null): string {
    if ($this->isEndOfFile()) {
      return '';
    }

    $length = Str\length($this->data);
    $bytes = Str\slice($this->data, $this->position, $max_bytes);
    $postion = $this->position + Str\length($bytes);
    $this->position = $postion > $length ? $length : $postion;

    return $bytes;
  }

  final public async function readAsync(
    ?int $max_bytes = null,
  ): Awaitable<string> {
    return await $this->queuedAsync(async () ==> {
      return $this->rawReadBlocking($max_bytes);
    });
  }

  final public async function readLineAsync(
    ?int $max_bytes = null,
  ): Awaitable<string> {
    $eol = Str\search($this->data, "\n", $this->position);
    if ($max_bytes is null) {
      $read = $eol is null
        ? $this->readAsync()
        : $this->readAsync($this->position - $eol);
      return await $read;
    }

    if ($eol is null) {
      return await $this->readAsync($max_bytes);
    }

    $length = Str\length($this->data);
    $mb = $this->position + $max_bytes;
    if ($mb > $length) {
      $mb = $length;
    }

    $max_bytes = Math\minva($eol + 1, $mb);
    return await $this->readAsync($max_bytes);
  }

  final public function isEndOfFile(): bool {
    $length = Str\length($this->data);
    return $this->position >= $length;
  }

  final public async function closeAsync(): Awaitable<void> {
    // do nothing.
  }

  final public async function flushAsync(): Awaitable<void> {
    // do nothing.
  }
}