public/dart/zircon/lib/src/vmo.dart

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

part of zircon;

// ignore_for_file: public_member_api_docs

/// Typed wrapper around a Zircon vmo object.
class Vmo extends _HandleWrapper<Vmo> {
  Vmo(Handle handle) : super(handle);

  GetSizeResult getSize() {
    if (handle == null) {
      return const GetSizeResult(ZX.ERR_INVALID_ARGS);
    }

    return System.vmoGetSize(handle);
  }

  int setSize(int size) {
    if (handle == null || size < 0) {
      return ZX.ERR_INVALID_ARGS;
    }

    return System.vmoSetSize(handle, size);
  }

  int write(ByteData data, [int vmoOffset = 0]) {
    if (handle == null) {
      return ZX.ERR_INVALID_ARGS;
    }

    return System.vmoWrite(handle, vmoOffset, data);
  }

  /// Duplicate this [Vmo] with the given rights.
  Vmo duplicate(int rights) {
    return Vmo(handle.duplicate(rights));
  }

  ReadResult read(int numBytes, [int vmoOffset = 0]) {
    if (handle == null) {
      return const ReadResult(ZX.ERR_INVALID_ARGS);
    }

    return System.vmoRead(handle, vmoOffset, numBytes);
  }

  /// Maps the Vmo into the process's root vmar, and returns it as a typed data
  /// array.
  ///
  /// The returned [Uint8List] is read-only. Attempts to write to it will
  /// result in an UnsupportedError exception.
  Uint8List map() {
    if (handle == null) {
      const int status = ZX.ERR_INVALID_ARGS;
      throw ZxStatusException(status, getStringForStatus(status));
    }
    MapResult r = System.vmoMap(handle);
    if (r.status != ZX.OK) {
      throw ZxStatusException(r.status, getStringForStatus(r.status));
    }
    return UnmodifiableUint8ListView(r.data);
  }
}

/// Typed wrapper around a Zircon vmo object, which also tracks its size.
class SizedVmo extends Vmo {
  final int _size;

  SizedVmo(Handle handle, this._size) : super(handle);

  /// Uses fdio_get_vmo_clone() to get a VMO for the file at `path` in the
  /// current Isolate's namespace.
  ///
  /// The returned Vmo is read-only.
  factory SizedVmo.fromFile(String path) {
    FromFileResult r = System.vmoFromFile(path);
    if (r.status != ZX.OK) {
      throw ZxStatusException(r.status, getStringForStatus(r.status));
    }
    return SizedVmo(r.handle, r.numBytes);
  }

  /// Constructs a VMO using the given [bytes]. The returned Vmo is read-only.
  factory SizedVmo.fromUint8List(Uint8List bytes) {
    HandleResult r = System.vmoCreate(bytes.length);
    if (r.status != ZX.OK) {
      throw ZxStatusException(r.status, getStringForStatus(r.status));
    }
    return SizedVmo(r.handle, bytes.length)
      ..write(bytes.buffer.asByteData());
  }

  /// Size of the Vmo in bytes.
  int get size => _size;
}