// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
// for details. 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 dart.ffi;

/// A dynamically loaded native library.
///
/// A dynamically loaded library is a mapping from symbols to memory addresses.
/// These memory addresses can be accessed through [lookup].
class DynamicLibrary {
  /// Creates a dynamic library holding all global symbols.
  ///
  /// Any symbol in a library currently loaded with global visibility
  /// (including the executable itself) may be resolved through this library.
  ///
  /// This feature is not available on Windows.
  external factory DynamicLibrary.process();

  /// Creates a dynamic library containing all the symbols of the running
  /// executable.
  external factory DynamicLibrary.executable();

  /// Loads a library file and provides access to its symbols.
  ///
  /// The [path] must refer to a native library file which can be successfully
  /// loaded.
  ///
  /// Calling this function multiple times with the same [path], even across
  /// different isolates, only loads the library into the DartVM process once.
  /// Multiple loads of the same library file produces [DynamicLibrary] objects
  /// which are equal (`==`), but not [identical].
  external factory DynamicLibrary.open(String path);

  /// Looks up a symbol in the [DynamicLibrary] and returns its address in
  /// memory.
  ///
  /// Similar to the functionality of the
  /// [dlsym(3)](https://man7.org/linux/man-pages/man3/dlsym.3.html) system
  /// call.
  ///
  /// The symbol must be provided by the dynamic library. To check whether
  /// the library provides such symbol, use [hasSymbol].
  external Pointer<T> lookup<T extends NativeType>(String symbolName);

  /// Checks whether this dynamic library provides a symbol with the given
  /// name.
  @Since('2.14')
  external bool providesSymbol(String symbolName);

  /// Dynamic libraries are equal if they load the same library.
  external bool operator ==(Object other);

  /// The hash code for a [DynamicLibrary] only depends on the loaded library.
  external int get hashCode;

  /// The opaque handle to the dynamic library.
  ///
  /// Similar to the return value of
  /// [dlopen(3)](https://man7.org/linux/man-pages/man3/dlopen.3.html).
  /// Can be used as arguments to other functions in the `dlopen` API
  /// through FFI calls.
  external Pointer<Void> get handle;
}

/// Method which must not be invoked dynamically.
extension DynamicLibraryExtension on DynamicLibrary {
  /// Looks up a native function and returns it as a Dart function.
  ///
  /// [T] is the C function signature, and [F] is the Dart function signature.
  /// For example:
  ///
  /// ```c
  /// int32_t add(int32_t a, int32_t b) {
  ///   return a + b;
  /// }
  /// ```
  ///
  /// ```dart
  /// DynamicLibrary dylib;
  /// final add = dylib.lookupFunction<Int32 Function(Int32, Int32),
  ///                                  int Function(int, int)>('add');
  /// ```
  external F lookupFunction<T extends Function, F extends Function>(
      String symbolName,
      {bool isLeaf: false});
}