Nuclex.Support/Source/Cloning/ExpressionTreeCloner.FieldBased.cs

602 lines
25 KiB
C#

#region CPL License
/*
Nuclex Framework
Copyright (C) 2002-2010 Nuclex Development Labs
This library is free software; you can redistribute it and/or
modify it under the terms of the IBM Common Public License as
published by the IBM Corporation; either version 1.0 of the
License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
IBM Common Public License for more details.
You should have received a copy of the IBM Common Public
License along with this library
*/
#endregion
#if !(XBOX360 || WINDOWS_PHONE)
using System;
using System.Collections.Generic;
using System.Linq.Expressions;
using System.Reflection;
using System.Runtime.Serialization;
namespace Nuclex.Support.Cloning {
partial class ExpressionTreeCloner : ICloneFactory {
/// <summary>Compiles a method that creates a deep clone of an object</summary>
/// <param name="clonedType">Type for which a clone method will be created</param>
/// <returns>A method that clones an object of the provided type</returns>
/// <remarks>
/// <para>
/// The 'null' check is supposed to take place before running the cloner. This
/// avoids having redundant 'null' checks on nested types - first before calling
/// GetType() on the field to be cloned and second when runner the matching
/// cloner for the field.
/// </para>
/// <para>
/// This design also enables the cloning of nested value types (which can never
/// be null) without any null check whatsoever.
/// </para>
/// </remarks>
private static Func<object, object> createDeepFieldBasedCloner(Type clonedType) {
ParameterExpression original = Expression.Parameter(typeof(object), "original");
var transferExpressions = new List<Expression>();
var variables = new List<ParameterExpression>();
if(clonedType.IsPrimitive || (clonedType == typeof(string))) {
// Primitives and strings are copied on direct assignment
transferExpressions.Add(original);
} else if(clonedType.IsArray) {
// Arrays need to be cloned element-by-element
Type elementType = clonedType.GetElementType();
if(elementType.IsPrimitive || (elementType == typeof(string))) {
// For primitive arrays, the Array.Clone() method is sufficient
transferExpressions.Add(
generateFieldBasedPrimitiveArrayTransferExpressions(
clonedType, original, variables, transferExpressions
)
);
} else {
// To access the fields of the original type, we need it to be of the actual
// type instead of an object, so perform a downcast
ParameterExpression typedOriginal = Expression.Variable(clonedType);
variables.Add(typedOriginal);
transferExpressions.Add(
Expression.Assign(typedOriginal, Expression.Convert(original, clonedType))
);
// Arrays of complex types require manual cloning
transferExpressions.Add(
generateFieldBasedComplexArrayTransferExpressions(
clonedType, typedOriginal, variables, transferExpressions
)
);
}
} else {
// We need a variable to hold the clone because due to the assignments it
// won't be last in the block when we're finished
ParameterExpression clone = Expression.Variable(clonedType);
variables.Add(clone);
// Give it a new instance of the type being cloned
MethodInfo getUninitializedObjectMethodInfo = typeof(FormatterServices).GetMethod(
"GetUninitializedObject", BindingFlags.Static | BindingFlags.Public
);
transferExpressions.Add(
Expression.Assign(
clone,
Expression.Convert(
Expression.Call(
getUninitializedObjectMethodInfo, Expression.Constant(clonedType)
),
clonedType
)
)
);
// To access the fields of the original type, we need it to be of the actual
// type instead of an object, so perform a downcast
ParameterExpression typedOriginal = Expression.Variable(clonedType);
variables.Add(typedOriginal);
transferExpressions.Add(
Expression.Assign(typedOriginal, Expression.Convert(original, clonedType))
);
// Generate the expressions required to transfer the type field by field
generateFieldBasedComplexTypeTransferExpressions(
clonedType, typedOriginal, clone, variables, transferExpressions
);
// Make sure the clone is the last thing in the block to set the return value
transferExpressions.Add(clone);
}
// Turn all transfer expressions into a single block if necessary
Expression resultExpression;
if((transferExpressions.Count == 1) && (variables.Count == 0)) {
resultExpression = transferExpressions[0];
} else {
resultExpression = Expression.Block(variables, transferExpressions);
}
// Value types require manual boxing
if(clonedType.IsValueType) {
resultExpression = Expression.Convert(resultExpression, typeof(object));
}
return Expression.Lambda<Func<object, object>>(resultExpression, original).Compile();
}
/// <summary>Compiles a method that creates a shallow clone of an object</summary>
/// <param name="clonedType">Type for which a clone method will be created</param>
/// <returns>A method that clones an object of the provided type</returns>
private static Func<object, object> createShallowFieldBasedCloner(Type clonedType) {
ParameterExpression original = Expression.Parameter(typeof(object), "original");
var transferExpressions = new List<Expression>();
var variables = new List<ParameterExpression>();
if(clonedType.IsPrimitive || clonedType.IsValueType || (clonedType == typeof(string))) {
// Primitives and strings are copied on direct assignment
transferExpressions.Add(original);
} else if(clonedType.IsArray) {
transferExpressions.Add(
generateFieldBasedPrimitiveArrayTransferExpressions(
clonedType, original, variables, transferExpressions
)
);
} else {
// We need a variable to hold the clone because due to the assignments it
// won't be last in the block when we're finished
ParameterExpression clone = Expression.Variable(clonedType);
variables.Add(clone);
// To access the fields of the original type, we need it to be of the actual
// type instead of an object, so perform a downcast
ParameterExpression typedOriginal = Expression.Variable(clonedType);
variables.Add(typedOriginal);
transferExpressions.Add(
Expression.Assign(typedOriginal, Expression.Convert(original, clonedType))
);
// Give it a new instance of the type being cloned
MethodInfo getUninitializedObjectMethodInfo = typeof(FormatterServices).GetMethod(
"GetUninitializedObject", BindingFlags.Static | BindingFlags.Public
);
transferExpressions.Add(
Expression.Assign(
clone,
Expression.Convert(
Expression.Call(
getUninitializedObjectMethodInfo, Expression.Constant(clonedType)
),
clonedType
)
)
);
// Enumerate all of the type's fields and generate transfer expressions for each
FieldInfo[] fieldInfos = clonedType.GetFields(
BindingFlags.Public | BindingFlags.NonPublic |
BindingFlags.Instance | BindingFlags.FlattenHierarchy
);
for(int index = 0; index < fieldInfos.Length; ++index) {
FieldInfo fieldInfo = fieldInfos[index];
transferExpressions.Add(
Expression.Assign(
Expression.Field(clone, fieldInfo),
Expression.Field(typedOriginal, fieldInfo)
)
);
}
// Make sure the clone is the last thing in the block to set the return value
transferExpressions.Add(clone);
}
// Turn all transfer expressions into a single block if necessary
Expression resultExpression;
if((transferExpressions.Count == 1) && (variables.Count == 0)) {
resultExpression = transferExpressions[0];
} else {
resultExpression = Expression.Block(variables, transferExpressions);
}
// Value types require manual boxing
if(clonedType.IsValueType) {
resultExpression = Expression.Convert(resultExpression, typeof(object));
}
return Expression.Lambda<Func<object, object>>(resultExpression, original).Compile();
}
/// <summary>
/// Generates state transfer expressions to copy an array of primitive types
/// </summary>
/// <param name="clonedType">Type of array that will be cloned</param>
/// <param name="original">Variable expression for the original array</param>
/// <param name="variables">Receives variables used by the transfer expressions</param>
/// <param name="transferExpressions">Receives the generated transfer expressions</param>
/// <returns>The variable holding the cloned array</returns>
private static Expression generateFieldBasedPrimitiveArrayTransferExpressions(
Type clonedType,
Expression original,
ICollection<ParameterExpression> variables,
ICollection<Expression> transferExpressions
) {
MethodInfo arrayCloneMethodInfo = typeof(Array).GetMethod("Clone");
return Expression.Convert(
Expression.Call(
Expression.Convert(original, typeof(Array)), arrayCloneMethodInfo
),
clonedType
);
}
/// <summary>
/// Generates state transfer expressions to copy an array of complex types
/// </summary>
/// <param name="clonedType">Type of array that will be cloned</param>
/// <param name="original">Variable expression for the original array</param>
/// <param name="variables">Receives variables used by the transfer expressions</param>
/// <param name="transferExpressions">Receives the generated transfer expressions</param>
/// <returns>The variable holding the cloned array</returns>
private static ParameterExpression generateFieldBasedComplexArrayTransferExpressions(
Type clonedType,
Expression original,
IList<ParameterExpression> variables,
ICollection<Expression> transferExpressions
) {
// We need a temporary variable in order to transfer the elements of the array
ParameterExpression clone = Expression.Variable(clonedType);
variables.Add(clone);
int dimensionCount = clonedType.GetArrayRank();
int baseVariableIndex = variables.Count;
Type elementType = clonedType.GetElementType();
var lengths = new List<ParameterExpression>();
var indexes = new List<ParameterExpression>();
var labels = new List<LabelTarget>();
// Retrieve the length of each of the array's dimensions
MethodInfo arrayGetLengthMethodInfo = typeof(Array).GetMethod("GetLength");
for(int index = 0; index < dimensionCount; ++index) {
// Obtain the length of the array in the current dimension
lengths.Add(Expression.Variable(typeof(int)));
variables.Add(lengths[index]);
transferExpressions.Add(
Expression.Assign(
lengths[index],
Expression.Call(
original, arrayGetLengthMethodInfo, Expression.Constant(index)
)
)
);
// Set up a variable to index the array in this dimension
indexes.Add(Expression.Variable(typeof(int)));
variables.Add(indexes[index]);
// Also set up a label than can be used to break out of the dimension's
// transfer loop
labels.Add(Expression.Label());
}
// Create a new (empty) array with the same dimensions and lengths as the original
transferExpressions.Add(
Expression.Assign(clone, Expression.NewArrayBounds(elementType, lengths))
);
// Initialize the indexer of the outer loop (indexers are initialized one up
// in the loops (ie. before the loop using it begins), so we have to set this
// one outside of the loop building code.
transferExpressions.Add(
Expression.Assign(indexes[0], Expression.Constant(0))
);
// Build the nested loops (one for each dimension) from the inside out
Expression innerLoop = null;
for(int index = dimensionCount - 1; index >= 0; --index) {
var loopVariables = new List<ParameterExpression>();
var loopExpressions = new List<Expression>();
// If we reached the end of the current array dimension, break the loop
loopExpressions.Add(
Expression.IfThen(
Expression.GreaterThanOrEqual(indexes[index], lengths[index]),
Expression.Break(labels[index])
)
);
if(innerLoop == null) {
// The innermost loop clones an actual array element
if(elementType.IsPrimitive || (elementType == typeof(string))) {
// Primitive array elements can be copied by simple assignment. This case
// should not occur since Array.Clone() should be used instead.
loopExpressions.Add(
Expression.Assign(
Expression.ArrayAccess(clone, indexes),
Expression.ArrayAccess(original, indexes)
)
);
} else if(elementType.IsValueType) {
// Arrays of complex value types can be transferred by assigning all fields
// of the source array element to the destination array element (cloning
// any nested reference types appropriately)
generateFieldBasedComplexTypeTransferExpressions(
elementType,
Expression.ArrayAccess(original, indexes),
Expression.ArrayAccess(clone, indexes),
variables,
loopExpressions
);
} else {
// Arrays of reference types need to be cloned by creating a new instance
// of the reference type and then transferring the fields over
ParameterExpression originalElement = Expression.Variable(elementType);
loopVariables.Add(originalElement);
loopExpressions.Add(
Expression.Assign(originalElement, Expression.ArrayAccess(original, indexes))
);
var nestedVariables = new List<ParameterExpression>();
var nestedTransferExpressions = new List<Expression>();
// A nested array should be cloned by directly creating a new array (not invoking
// a cloner) since you cannot derive from an array
if(elementType.IsArray) {
Expression clonedElement;
Type nestedElementType = elementType.GetElementType();
if(nestedElementType.IsPrimitive || (nestedElementType == typeof(string))) {
clonedElement = generateFieldBasedPrimitiveArrayTransferExpressions(
elementType, originalElement, nestedVariables, nestedTransferExpressions
);
} else {
clonedElement = generateFieldBasedComplexArrayTransferExpressions(
elementType, originalElement, nestedVariables, nestedTransferExpressions
);
}
nestedTransferExpressions.Add(
Expression.Assign(Expression.ArrayAccess(clone, indexes), clonedElement)
);
} else {
// Complex types are cloned by checking their actual, concrete type (fields
// may be typed to an interface or base class) and requesting a cloner for that
// type during runtime
MethodInfo getOrCreateClonerMethodInfo = typeof(ExpressionTreeCloner).GetMethod(
"getOrCreateDeepFieldBasedCloner",
BindingFlags.NonPublic | BindingFlags.Static
);
MethodInfo getTypeMethodInfo = typeof(object).GetMethod("GetType");
MethodInfo invokeMethodInfo = typeof(Func<object, object>).GetMethod("Invoke");
// Generate expressions to do this:
// clone.SomeField = getOrCreateDeepFieldBasedCloner(
// original.SomeField.GetType()
// ).Invoke(original.SomeField);
nestedTransferExpressions.Add(
Expression.Assign(
Expression.ArrayAccess(clone, indexes),
Expression.Convert(
Expression.Call(
Expression.Call(
getOrCreateClonerMethodInfo,
Expression.Call(originalElement, getTypeMethodInfo)
),
invokeMethodInfo,
originalElement
),
elementType
)
)
);
}
// Whether array-in-array of reference-type-in-array, we need a null check before
// doing anything to avoid NullReferenceExceptions for unset members
loopExpressions.Add(
Expression.IfThen(
Expression.NotEqual(originalElement, Expression.Constant(null)),
Expression.Block(
nestedVariables,
nestedTransferExpressions
)
)
);
}
} else {
// Outer loops of any level just reset the inner loop's indexer and execute
// the inner loop
loopExpressions.Add(
Expression.Assign(indexes[index + 1], Expression.Constant(0))
);
loopExpressions.Add(innerLoop);
}
// Each time we executed the loop instructions, increment the indexer
loopExpressions.Add(Expression.PreIncrementAssign(indexes[index]));
// Build the loop using the expressions recorded above
innerLoop = Expression.Loop(
Expression.Block(loopVariables, loopExpressions),
labels[index]
);
}
// After the loop builder has finished, the innerLoop variable contains
// the entire hierarchy of nested loops, so add this to the clone expressions.
transferExpressions.Add(innerLoop);
return clone;
}
/// <summary>Generates state transfer expressions to copy a complex type</summary>
/// <param name="clonedType">Complex type that will be cloned</param>
/// <param name="original">Variable expression for the original instance</param>
/// <param name="clone">Variable expression for the cloned instance</param>
/// <param name="variables">Receives variables used by the transfer expressions</param>
/// <param name="transferExpressions">Receives the generated transfer expressions</param>
private static void generateFieldBasedComplexTypeTransferExpressions(
Type clonedType, // Actual, concrete type (not declared type)
Expression original, // Expected to be an object
Expression clone, // As actual, concrete type
IList<ParameterExpression> variables,
ICollection<Expression> transferExpressions
) {
// Enumerate all of the type's fields and generate transfer expressions for each
FieldInfo[] fieldInfos = clonedType.GetFields(
BindingFlags.Public | BindingFlags.NonPublic |
BindingFlags.Instance | BindingFlags.FlattenHierarchy
);
for(int index = 0; index < fieldInfos.Length; ++index) {
FieldInfo fieldInfo = fieldInfos[index];
Type fieldType = fieldInfo.FieldType;
if(fieldType.IsPrimitive || (fieldType == typeof(string))) {
// Primitive types and strings can be transferred by simple assignment
transferExpressions.Add(
Expression.Assign(
Expression.Field(clone, fieldInfo),
Expression.Field(original, fieldInfo)
)
);
} else if(fieldType.IsValueType) {
// A nested value type is part of the parent and will have its fields directly
// assigned without boxing, new instance creation or anything like that.
generateFieldBasedComplexTypeTransferExpressions(
fieldType,
Expression.Field(original, fieldInfo),
Expression.Field(clone, fieldInfo),
variables,
transferExpressions
);
} else {
generateFieldBasedReferenceTypeTransferExpressions(
original, clone, transferExpressions, fieldInfo, fieldType
);
}
}
}
/// <summary>
/// Generates the expressions to transfer a reference type (array or class)
/// </summary>
/// <param name="original">Original value that will be cloned</param>
/// <param name="clone">Variable that will receive the cloned value</param>
/// <param name="transferExpressions">
/// Receives the expression generated to transfer the values
/// </param>
/// <param name="fieldInfo">Reflection informations about the field being cloned</param>
/// <param name="fieldType">Type of the field being cloned</param>
private static void generateFieldBasedReferenceTypeTransferExpressions(
Expression original,
Expression clone,
ICollection<Expression> transferExpressions,
FieldInfo fieldInfo,
Type fieldType
) {
// Reference types and arrays require special care because they can be null,
// so gather the transfer expressions in a separate block for the null check
var fieldTransferExpressions = new List<Expression>();
var fieldVariables = new List<ParameterExpression>();
if(fieldType.IsArray) {
// Arrays need to be cloned element-by-element
Expression fieldClone;
Type elementType = fieldType.GetElementType();
if(elementType.IsPrimitive || (elementType == typeof(string))) {
// For primitive arrays, the Array.Clone() method is sufficient
fieldClone = generateFieldBasedPrimitiveArrayTransferExpressions(
fieldType,
Expression.Field(original, fieldInfo),
fieldVariables,
fieldTransferExpressions
);
} else {
// Arrays of complex types require manual cloning
fieldClone = generateFieldBasedComplexArrayTransferExpressions(
fieldType,
Expression.Field(original, fieldInfo),
fieldVariables,
fieldTransferExpressions
);
}
// Add the assignment to the transfer expressions. The array transfer expression
// generator will either have set up a temporary variable to hold the array or
// returned the conversion expression straight away
fieldTransferExpressions.Add(
Expression.Assign(Expression.Field(clone, fieldInfo), fieldClone)
);
} else {
// Complex types are cloned by checking their actual, concrete type (fields
// may be typed to an interface or base class) and requesting a cloner for that
// type during runtime
MethodInfo getOrCreateClonerMethodInfo = typeof(ExpressionTreeCloner).GetMethod(
"getOrCreateDeepFieldBasedCloner",
BindingFlags.NonPublic | BindingFlags.Static
);
MethodInfo getTypeMethodInfo = typeof(object).GetMethod("GetType");
MethodInfo invokeMethodInfo = typeof(Func<object, object>).GetMethod("Invoke");
// Generate expressions to do this:
// clone.SomeField = getOrCreateDeepFieldBasedCloner(
// original.SomeField.GetType()
// ).Invoke(original.SomeField);
fieldTransferExpressions.Add(
Expression.Assign(
Expression.Field(clone, fieldInfo),
Expression.Convert(
Expression.Call(
Expression.Call(
getOrCreateClonerMethodInfo,
Expression.Call(
Expression.Field(original, fieldInfo), getTypeMethodInfo
)
),
invokeMethodInfo,
Expression.Field(original, fieldInfo)
),
fieldType
)
)
);
}
// Wrap up the generated array or complex reference type transfer expressions
// in a null check so the field is skipped if it is not holding an instance.
transferExpressions.Add(
Expression.IfThen(
Expression.NotEqual(
Expression.Field(original, fieldInfo), Expression.Constant(null)
),
Expression.Block(fieldVariables, fieldTransferExpressions)
)
);
}
}
} // namespace Nuclex.Support.Cloning
#endif // !(XBOX360 || WINDOWS_PHONE)