1#region Copyright notice and license
2// Protocol Buffers - Google's data interchange format
3// Copyright 2015 Google Inc.  All rights reserved.
4// https://developers.google.com/protocol-buffers/
5//
6// Redistribution and use in source and binary forms, with or without
7// modification, are permitted provided that the following conditions are
8// met:
9//
10//     * Redistributions of source code must retain the above copyright
11// notice, this list of conditions and the following disclaimer.
12//     * Redistributions in binary form must reproduce the above
13// copyright notice, this list of conditions and the following disclaimer
14// in the documentation and/or other materials provided with the
15// distribution.
16//     * Neither the name of Google Inc. nor the names of its
17// contributors may be used to endorse or promote products derived from
18// this software without specific prior written permission.
19//
20// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
23// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
24// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
25// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
26// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
30// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31#endregion
32
33using System;
34using System.Reflection;
35using Google.Protobuf.Compatibility;
36
37namespace Google.Protobuf.Reflection
38{
39    /// <summary>
40    /// Accessor for single fields.
41    /// </summary>
42    internal sealed class SingleFieldAccessor : FieldAccessorBase
43    {
44        // All the work here is actually done in the constructor - it creates the appropriate delegates.
45        // There are various cases to consider, based on the property type (message, string/bytes, or "genuine" primitive)
46        // and proto2 vs proto3 for non-message types, as proto3 doesn't support "full" presence detection or default
47        // values.
48
49        private readonly Action<IMessage, object> setValueDelegate;
50        private readonly Action<IMessage> clearDelegate;
51        private readonly Func<IMessage, bool> hasDelegate;
52
53        internal SingleFieldAccessor(PropertyInfo property, FieldDescriptor descriptor) : base(property, descriptor)
54        {
55            if (!property.CanWrite)
56            {
57                throw new ArgumentException("Not all required properties/methods available");
58            }
59            setValueDelegate = ReflectionUtil.CreateActionIMessageObject(property.GetSetMethod());
60
61            // Note: this looks worrying in that we access the containing oneof, which isn't valid until cross-linking
62            // is complete... but field accessors aren't created until after cross-linking.
63            // The oneof itself won't be cross-linked yet, but that's okay: the oneof accessor is created
64            // earlier.
65
66            // Message fields always support presence, via null checks.
67            if (descriptor.FieldType == FieldType.Message)
68            {
69                hasDelegate = message => GetValue(message) != null;
70                clearDelegate = message => SetValue(message, null);
71            }
72            // Oneof fields always support presence, via case checks.
73            // Note that clearing the field is a no-op unless that specific field is the current "case".
74            else if (descriptor.RealContainingOneof != null)
75            {
76                var oneofAccessor = descriptor.RealContainingOneof.Accessor;
77                hasDelegate = message => oneofAccessor.GetCaseFieldDescriptor(message) == descriptor;
78                clearDelegate = message =>
79                {
80                    // Clear on a field only affects the oneof itself if the current case is the field we're accessing.
81                    if (oneofAccessor.GetCaseFieldDescriptor(message) == descriptor)
82                    {
83                        oneofAccessor.Clear(message);
84                    }
85                };
86            }
87            // Primitive fields always support presence in proto2, and support presence in proto3 for optional fields.
88            else if (descriptor.File.Syntax == Syntax.Proto2 || descriptor.Proto.Proto3Optional)
89            {
90                MethodInfo hasMethod = property.DeclaringType.GetRuntimeProperty("Has" + property.Name).GetMethod;
91                if (hasMethod == null)
92                {
93                    throw new ArgumentException("Not all required properties/methods are available");
94                }
95                hasDelegate = ReflectionUtil.CreateFuncIMessageBool(hasMethod);
96                MethodInfo clearMethod = property.DeclaringType.GetRuntimeMethod("Clear" + property.Name, ReflectionUtil.EmptyTypes);
97                if (clearMethod == null)
98                {
99                    throw new ArgumentException("Not all required properties/methods are available");
100                }
101                clearDelegate = ReflectionUtil.CreateActionIMessage(clearMethod);
102            }
103            // What's left?
104            // Primitive proto3 fields without the optional keyword, which aren't in oneofs.
105            else
106            {
107                hasDelegate = message => { throw new InvalidOperationException("Presence is not implemented for this field"); };
108
109                // While presence isn't supported, clearing still is; it's just setting to a default value.
110                var clrType = property.PropertyType;
111
112                object defaultValue =
113                    clrType == typeof(string) ? ""
114                    : clrType == typeof(ByteString) ? ByteString.Empty
115                    : Activator.CreateInstance(clrType);
116                clearDelegate = message => SetValue(message, defaultValue);
117            }
118        }
119
120        public override void Clear(IMessage message) => clearDelegate(message);
121        public override bool HasValue(IMessage message) => hasDelegate(message);
122        public override void SetValue(IMessage message, object value) => setValueDelegate(message, value);
123    }
124}
125