path: root/csharp/src/Google.Protobuf/Compatibility/TypeExtensions.cs

#region Copyright notice and license
// Protocol Buffers - Google's data interchange format
// Copyright 2015 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#endregion

using System;
using System.Reflection;

namespace Google.Protobuf.Compatibility
{
    /// <summary>
    /// Provides extension methods on Type that just proxy to TypeInfo.
    /// These are used to support the new type system from .NET 4.5, without
    /// having calls to GetTypeInfo all over the place. While the methods here are meant to be
    /// broadly compatible with the desktop framework, there are some subtle differences in behaviour - but
    /// they're not expected to affect our use cases. While the class is internal, that should be fine: we can
    /// evaluate each new use appropriately.
    /// </summary>
    internal static class TypeExtensions
    {
        /// <summary>
        /// Returns true if the target type is a value type, including a nullable value type or an enum, or false
        /// if it's a reference type (class, delegate, interface - including System.ValueType and System.Enum).
        /// </summary>
#if DOTNET35
        internal static bool IsValueType(this Type target) {
            return target.IsValueType;
        }
#else
        internal static bool IsValueType(this Type target)
        {
            return target.GetTypeInfo().IsValueType;
        }

        /// <summary>
        /// See https://msdn.microsoft.com/en-us/library/system.type.isassignablefrom
        /// </summary>
        internal static bool IsAssignableFrom(this Type target, Type c)
        {
            return target.GetTypeInfo().IsAssignableFrom(c.GetTypeInfo());
        }

        /// <summary>
        /// Returns a representation of the public property associated with the given name in the given type,
        /// including inherited properties or null if there is no such public property.
        /// Here, "public property" means a property where either the getter, or the setter, or both, is public.
        /// </summary>
        internal static PropertyInfo GetProperty(this Type target, string name)
        {
            // GetDeclaredProperty only returns properties declared in the given type, so we need to recurse.
            while (target != null)
            {
                var typeInfo = target.GetTypeInfo();
                var ret = typeInfo.GetDeclaredProperty(name);
                if (ret != null && ((ret.CanRead && ret.GetMethod.IsPublic) || (ret.CanWrite && ret.SetMethod.IsPublic)))
                {
                    return ret;
                }
                target = typeInfo.BaseType;
            }
            return null;
        }

        /// <summary>
        /// Returns a representation of the public method associated with the given name in the given type,
        /// including inherited methods.
        /// </summary>
        /// <remarks>
        /// This has a few differences compared with Type.GetMethod in the desktop framework. It will throw
        /// if there is an ambiguous match even between a private method and a public one, but it *won't* throw
        /// if there are two overloads at different levels in the type hierarchy (e.g. class Base declares public void Foo(int) and
        /// class Child : Base declares public void Foo(long)).
        /// </remarks>
        /// <exception cref="AmbiguousMatchException">One type in the hierarchy declared more than one method with the same name</exception>
        internal static MethodInfo GetMethod(this Type target, string name)
        {
            // GetDeclaredMethod only returns methods declared in the given type, so we need to recurse.
            while (target != null)
            {
                var typeInfo = target.GetTypeInfo();
                var ret = typeInfo.GetDeclaredMethod(name);
                if (ret != null && ret.IsPublic)
                {
                    return ret;
                }
                target = typeInfo.BaseType;
            }
            return null;
        }
#endif
    }
}