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// Copyright (c) 2011 AlphaSierraPapa for the SharpDevelop Team
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
using System;
using System.Collections.Generic;
using System.Diagnostics;
using Mono.Cecil;
namespace ICSharpCode.Decompiler.ILAst
{
/// <summary>
/// This exception is thrown when we find something else than we expect from the C# compiler.
/// This aborts the analysis and makes the whole transform fail.
/// </summary>
internal class SymbolicAnalysisFailedException : Exception {}
internal enum SymbolicValueType
{
/// <summary>
/// Unknown value
/// </summary>
Unknown,
/// <summary>
/// int: Constant (result of ldc.i4)
/// </summary>
IntegerConstant,
/// <summary>
/// int: State + Constant
/// </summary>
State,
/// <summary>
/// This pointer (result of ldarg.0)
/// </summary>
This,
/// <summary>
/// bool: State == Constant
/// </summary>
StateEquals,
/// <summary>
/// bool: State != Constant
/// </summary>
StateInEquals
}
internal struct SymbolicValue
{
public readonly int Constant;
public readonly SymbolicValueType Type;
public SymbolicValue(SymbolicValueType type, int constant = 0)
{
Type = type;
Constant = constant;
}
public SymbolicValue AsBool()
{
if (Type == SymbolicValueType.State) {
// convert state integer to bool:
// if (state + c) = if (state + c != 0) = if (state != -c)
return new SymbolicValue(SymbolicValueType.StateInEquals, unchecked(-Constant));
}
return this;
}
public override string ToString()
{
return string.Format("[SymbolicValue {0}: {1}]", Type, Constant);
}
}
internal class SymbolicEvaluationContext
{
readonly FieldDefinition stateField;
readonly List<ILVariable> stateVariables = new List<ILVariable>();
public SymbolicEvaluationContext(FieldDefinition stateField)
{
this.stateField = stateField;
}
public void AddStateVariable(ILVariable v)
{
if (!stateVariables.Contains(v))
stateVariables.Add(v);
}
SymbolicValue Failed()
{
return new SymbolicValue(SymbolicValueType.Unknown);
}
public SymbolicValue Eval(ILExpression expr)
{
SymbolicValue left, right;
switch (expr.Code) {
case ILCode.Sub:
left = Eval(expr.Arguments[0]);
right = Eval(expr.Arguments[1]);
if (left.Type != SymbolicValueType.State && left.Type != SymbolicValueType.IntegerConstant)
return Failed();
if (right.Type != SymbolicValueType.IntegerConstant)
return Failed();
return new SymbolicValue(left.Type, unchecked ( left.Constant - right.Constant ));
case ILCode.Ldfld:
if (Eval(expr.Arguments[0]).Type != SymbolicValueType.This)
return Failed();
if (CecilExtensions.ResolveWithinSameModule(expr.Operand as FieldReference) != stateField)
return Failed();
return new SymbolicValue(SymbolicValueType.State);
case ILCode.Ldloc:
ILVariable loadedVariable = (ILVariable)expr.Operand;
if (stateVariables.Contains(loadedVariable))
return new SymbolicValue(SymbolicValueType.State);
else if (loadedVariable.IsParameter && loadedVariable.OriginalParameter.Index < 0)
return new SymbolicValue(SymbolicValueType.This);
else
return Failed();
case ILCode.Ldc_I4:
return new SymbolicValue(SymbolicValueType.IntegerConstant, (int)expr.Operand);
case ILCode.Ceq:
case ILCode.Cne:
left = Eval(expr.Arguments[0]);
right = Eval(expr.Arguments[1]);
if (left.Type != SymbolicValueType.State || right.Type != SymbolicValueType.IntegerConstant)
return Failed();
// bool: (state + left.Constant == right.Constant)
// bool: (state == right.Constant - left.Constant)
return new SymbolicValue(expr.Code == ILCode.Ceq ? SymbolicValueType.StateEquals : SymbolicValueType.StateInEquals, unchecked(right.Constant - left.Constant));
case ILCode.LogicNot:
SymbolicValue val = Eval(expr.Arguments[0]).AsBool();
if (val.Type == SymbolicValueType.StateEquals)
return new SymbolicValue(SymbolicValueType.StateInEquals, val.Constant);
else if (val.Type == SymbolicValueType.StateInEquals)
return new SymbolicValue(SymbolicValueType.StateEquals, val.Constant);
else
return Failed();
default:
return Failed();
}
}
}
}
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