C# EventReader.Allow方法代码示例

        public bool Deserialize(EventReader reader, Type expectedType, Func<EventReader, Type, object> nestedObjectDeserializer, out object value)
        {
            if (reader == null)
            {
                value = null;
                return false;
            }

            // only try this if we're targeting a boolean or an untyped object
            if (expectedType == typeof(object) || expectedType == typeof(bool) ) 
            {
                // peek at the current token
                Scalar scalar = reader.Peek<Scalar>();

                // if it's unquoted 
                if (scalar != null && scalar.Style == ScalarStyle.Plain)
                {
                    // and the value is actually true or false
                    switch (scalar.Value.ToUpperInvariant())
                    {
                        case "TRUE":
                            value = true;
                            reader.Allow<Scalar>();
                            return true;
                        case "FALSE":
                            value = false;
                            reader.Allow<Scalar>();
                            return true;

                    }
                }
            }

            // otherwise, fall thru
            value = null;
            return false;
        }

		bool INodeDeserializer.Deserialize(EventReader reader, Type expectedType, Func<EventReader, Type, object> nestedObjectDeserializer, out object value)
		{
			var mapping = reader.Allow<MappingStart>();
			if (mapping == null)
			{
				value = null;
				return false;
			}
			
			value = _objectFactory.Create(expectedType);
			while (!reader.Accept<MappingEnd>())
			{
				var propertyName = reader.Expect<Scalar>();
				var property = _typeDescriptor.GetProperty(expectedType, null, propertyName.Value, _ignoreUnmatched);
				if (property == null)
				{
					reader.SkipThisAndNestedEvents();
					continue;
				}

				var propertyValue = nestedObjectDeserializer(reader, property.Type);
				var propertyValuePromise = propertyValue as IValuePromise;
				if (propertyValuePromise == null)
				{
					var convertedValue = TypeConverter.ChangeType(propertyValue, property.Type);
					property.Write(value, convertedValue);
				}
				else
				{
					var valueRef = value;
					propertyValuePromise.ValueAvailable += v =>
					{
						var convertedValue = TypeConverter.ChangeType(v, property.Type);
						property.Write(valueRef, convertedValue);
					};
				}
			}

			reader.Expect<MappingEnd>();
			return true;
		}

        public static bool MigrateAssetIfNeeded(AssetMigrationContext context, PackageLoadingAssetFile loadAsset)
        {
            var assetFullPath = loadAsset.FilePath.FullPath;

            // Determine if asset was Yaml or not
            var assetFileExtension = Path.GetExtension(assetFullPath);
            if (assetFileExtension == null)
                return false;

            assetFileExtension = assetFileExtension.ToLowerInvariant();

            var serializer = AssetSerializer.FindSerializer(assetFileExtension);
            if (!(serializer is AssetYamlSerializer))
                return false;

            // We've got a Yaml asset, let's get expected and serialized versions
            var serializedVersion = 0;
            int expectedVersion;
            Type assetType;

            // Read from Yaml file the asset version and its type (to get expected version)
            // Note: It tries to read as few as possible (SerializedVersion is expected to be right after Id, so it shouldn't try to read further than that)
            using (var assetStream = loadAsset.OpenStream())
            using (var streamReader = new StreamReader(assetStream))
            {
                var yamlEventReader = new EventReader(new Parser(streamReader));

                // Skip header
                yamlEventReader.Expect<StreamStart>();
                yamlEventReader.Expect<DocumentStart>();
                var mappingStart = yamlEventReader.Expect<MappingStart>();

                var yamlSerializerSettings = YamlSerializer.GetSerializerSettings();
                var tagTypeRegistry = yamlSerializerSettings.TagTypeRegistry;
                bool typeAliased;
                assetType = tagTypeRegistry.TypeFromTag(mappingStart.Tag, out typeAliased);

                expectedVersion = AssetRegistry.GetCurrentFormatVersion(assetType);

                Scalar assetKey;
                while ((assetKey = yamlEventReader.Allow<Scalar>()) != null)
                {
                    // Only allow Id before SerializedVersion
                    if (assetKey.Value == "Id")
                    {
                        yamlEventReader.Skip();
                        continue;
                    }
                    if (assetKey.Value == "SerializedVersion")
                    {
                        serializedVersion = Convert.ToInt32(yamlEventReader.Expect<Scalar>().Value, CultureInfo.InvariantCulture);
                        break;
                    }
                }
            }

            if (serializedVersion > expectedVersion)
            {
                // Try to open an asset newer than what we support (probably generated by a newer Paradox)
                throw new InvalidOperationException(string.Format("Asset of type {0} has been serialized with newer version {1}, but only version {2} is supported. Was this asset created with a newer version of Paradox?", assetType, serializedVersion, expectedVersion));
            }

            if (serializedVersion < expectedVersion)
            {
                // Perform asset upgrade
                context.Log.Verbose("{0} needs update, from version {1} to version {2}", Path.GetFullPath(assetFullPath), serializedVersion, expectedVersion);

                // transform the stream into string.
                string assetAsString;
                using (var assetStream = loadAsset.OpenStream())
                using (var assetStreamReader = new StreamReader(assetStream, Encoding.UTF8))
                {
                    assetAsString = assetStreamReader.ReadToEnd();
                }

                // Load the asset as a YamlNode object
                var input = new StringReader(assetAsString);
                var yamlStream = new YamlStream();
                yamlStream.Load(input);
                var yamlRootNode = (YamlMappingNode)yamlStream.Documents[0].RootNode;

                // Check if there is any asset updater
                var assetUpgraders = AssetRegistry.GetAssetUpgraders(assetType);
                if (assetUpgraders == null)
                {
                    throw new InvalidOperationException(string.Format("Asset of type {0} should be updated from version {1} to {2}, but no asset migration path was found", assetType, serializedVersion, expectedVersion));
                }

                // Instantiate asset updaters
                var currentVersion = serializedVersion;
                while (currentVersion != expectedVersion)
                {
                    int targetVersion;
                    // This will throw an exception if no upgrader is available for the given version, exiting the loop in case of error.
                    var upgrader = assetUpgraders.GetUpgrader(currentVersion, out targetVersion);
                    upgrader.Upgrade(context, currentVersion, targetVersion, yamlRootNode, loadAsset);
                    currentVersion = targetVersion;
                }

                // Make sure asset is updated to latest version
//.........这里部分代码省略.........

        /// <summary>
        /// Deserializes an object of the specified type.
        /// </summary>
        /// <param name="reader">The <see cref="EventReader" /> where to deserialize the object.</param>
        /// <param name="type">The static type of the object to deserialize.</param>
        /// <param name="options">Options that control how the deserialization is to be performed.</param>
        /// <returns>Returns the deserialized object.</returns>
        public object Deserialize(EventReader reader, Type type, DeserializationOptions options = DeserializationOptions.None)
        {
            if (reader == null)
            {
                throw new ArgumentNullException("reader");
            }

            if (type == null)
            {
                throw new ArgumentNullException("type");
            }

            var hasStreamStart = reader.Allow<StreamStart>() != null;

            var hasDocumentStart = reader.Allow<DocumentStart>() != null;

            if (hasDocumentStart)
            {
                reader.Expect<DocumentEnd>();
            }

            if (hasStreamStart)
            {
                reader.Expect<StreamEnd>();
            }
        }

		bool INodeDeserializer.Deserialize(EventReader reader, Type expectedType, Func<EventReader, Type, object> nestedObjectDeserializer, out object value)
		{
			var scalar = reader.Allow<Scalar>();
			if (scalar == null)
			{
				value = null;
				return false;
			}

			if (expectedType.IsEnum())
			{
				value = Enum.Parse(expectedType, scalar.Value);
			}
			else
			{
				TypeCode typeCode = expectedType.GetTypeCode();
				switch (typeCode)
				{
					case TypeCode.Boolean:
						value = bool.Parse(scalar.Value);
						break;

					case TypeCode.Byte:
					case TypeCode.Int16:
					case TypeCode.Int32:
					case TypeCode.Int64:
					case TypeCode.SByte:
					case TypeCode.UInt16:
					case TypeCode.UInt32:
					case TypeCode.UInt64:
						value = DeserializeIntegerHelper(typeCode, scalar.Value, YamlFormatter.NumberFormat);
						break;

					case TypeCode.Single:
						value = Single.Parse(scalar.Value, YamlFormatter.NumberFormat);
						break;

					case TypeCode.Double:
						value = Double.Parse(scalar.Value, YamlFormatter.NumberFormat);
						break;

					case TypeCode.Decimal:
						value = Decimal.Parse(scalar.Value, YamlFormatter.NumberFormat);
						break;

					case TypeCode.String:
						value = scalar.Value;
						break;

					case TypeCode.Char:
						value = scalar.Value[0];
						break;

					case TypeCode.DateTime:
						// TODO: This is probably incorrect. Use the correct regular expression.
						value = DateTime.Parse(scalar.Value, CultureInfo.InvariantCulture);
						break;

					default:
						if (expectedType == typeof(object))
						{
							// Default to string
							value = scalar.Value;
						}
						else
						{
							value = TypeConverter.ChangeType(scalar.Value, expectedType);
						}
						break;
				}
			}
			return true;
		}

        public static bool MigrateAssetIfNeeded(AssetMigrationContext context, PackageLoadingAssetFile loadAsset, string dependencyName, PackageVersion untilVersion = null)
        {
            var assetFullPath = loadAsset.FilePath.FullPath;

            // Determine if asset was Yaml or not
            var assetFileExtension = Path.GetExtension(assetFullPath);
            if (assetFileExtension == null)
                return false;

            assetFileExtension = assetFileExtension.ToLowerInvariant();

            var serializer = AssetFileSerializer.FindSerializer(assetFileExtension);
            if (!(serializer is YamlAssetSerializer))
                return false;

            // We've got a Yaml asset, let's get expected and serialized versions
            var serializedVersion = PackageVersion.Zero;
            PackageVersion expectedVersion;
            Type assetType;

            // Read from Yaml file the asset version and its type (to get expected version)
            // Note: It tries to read as few as possible (SerializedVersion is expected to be right after Id, so it shouldn't try to read further than that)
            using (var assetStream = loadAsset.OpenStream())
            using (var streamReader = new StreamReader(assetStream))
            {
                var yamlEventReader = new EventReader(new Parser(streamReader));

                // Skip header
                yamlEventReader.Expect<StreamStart>();
                yamlEventReader.Expect<DocumentStart>();
                var mappingStart = yamlEventReader.Expect<MappingStart>();

                var tagTypeRegistry = AssetYamlSerializer.Default.GetSerializerSettings().TagTypeRegistry;
                bool typeAliased;
                assetType = tagTypeRegistry.TypeFromTag(mappingStart.Tag, out typeAliased);

                var expectedVersions = AssetRegistry.GetCurrentFormatVersions(assetType);
                expectedVersion = expectedVersions?.FirstOrDefault(x => x.Key == dependencyName).Value ?? PackageVersion.Zero;

                Scalar assetKey;
                while ((assetKey = yamlEventReader.Allow<Scalar>()) != null)
                {
                    // Only allow Id before SerializedVersion
                    if (assetKey.Value == nameof(Asset.Id))
                    {
                        yamlEventReader.Skip();
                    }
                    else if (assetKey.Value == nameof(Asset.SerializedVersion))
                    {
                        // Check for old format: only a scalar
                        var scalarVersion = yamlEventReader.Allow<Scalar>();
                        if (scalarVersion != null)
                        {
                            serializedVersion = PackageVersion.Parse("0.0." + Convert.ToInt32(scalarVersion.Value, CultureInfo.InvariantCulture));

                            // Let's update to new format
                            using (var yamlAsset = loadAsset.AsYamlAsset())
                            {
                                yamlAsset.DynamicRootNode.RemoveChild(nameof(Asset.SerializedVersion));
                                AssetUpgraderBase.SetSerializableVersion(yamlAsset.DynamicRootNode, dependencyName, serializedVersion);

                                var baseBranch = yamlAsset.DynamicRootNode["~Base"];
                                if (baseBranch != null)
                                {
                                    var baseAsset = baseBranch["Asset"];
                                    if (baseAsset != null)
                                    {
                                        baseAsset.RemoveChild(nameof(Asset.SerializedVersion));
                                        AssetUpgraderBase.SetSerializableVersion(baseAsset, dependencyName, serializedVersion);
                                    }
                                }
                            }
                        }
                        else
                        {
                            // New format: package => version mapping
                            yamlEventReader.Expect<MappingStart>();

                            while (!yamlEventReader.Accept<MappingEnd>())
                            {
                                var packageName = yamlEventReader.Expect<Scalar>().Value;
                                var packageVersion = PackageVersion.Parse(yamlEventReader.Expect<Scalar>().Value);

                                // For now, we handle only one dependency at a time
                                if (packageName == dependencyName)
                                {
                                    serializedVersion = packageVersion;
                                }
                            }

                            yamlEventReader.Expect<MappingEnd>();
                        }
                        break;
                    }
                    else
                    {
                        // If anything else than Id or SerializedVersion, let's stop
                        break;
                    }
                }
//.........这里部分代码省略.........