private void RewriteType(TypeDefinition type, ObserverReferences observer)
{
foreach (MethodDefinition method in type.Methods)
{
RewriteMethod(method, observer);
}
}
/// <summary>
/// Makes the <see cref="Observer"/> available to the given method as a variable and then
/// applies all of the individual rewriters to the method.
/// </summary>
private void RewriteMethod(MethodDefinition methodDefinition, ObserverReferences observer)
{
if (methodDefinition.DeclaringType == observer.InstanceField.DeclaringType)
{
return; // don't inject on our injected type.
}
if (!methodDefinition.HasBody || methodDefinition.Body.Instructions.Count == 0)
{
return; // don't inject on method without a Body
}
// Inject observer instance to method.
ILProcessor il = methodDefinition.Body.GetILProcessor();
var observerVariable = new VariableDefinition(observer.InstanceField.FieldType);
il.Body.Variables.Add(observerVariable);
Instruction start = methodDefinition.Body.Instructions[0];
il.InsertBefore(start, il.Create(OpCodes.Ldsfld, observer.InstanceField));
il.InsertBefore(start, il.CreateStlocBest(observerVariable));
var context = new ObserverRewriterContext(observer, observerVariable);
foreach (IObserverMethodRewriter rewriter in methodRewriters)
{
rewriter.Rewrite(methodDefinition, il, context);
}
}
/// <summary>
/// Adds a call to SpendGas from the RuntimeObserver before the given instruction.
/// </summary>
private static void AddSpendGasMethodBeforeInstruction(ILProcessor il, ObserverReferences observer, VariableDefinition variable, CodeSegment codeSegment)
{
Instruction first = codeSegment.Instructions.First();
Instruction newFirst = il.CreateLdlocBest(variable);
long segmentCost = (long)codeSegment.CalculateGasCost().Value;
il.Body.SimplifyMacros();
il.InsertBefore(first, newFirst); // load observer
il.InsertBefore(first, il.Create(OpCodes.Ldc_I8, (long)segmentCost)); // load gas amount
il.InsertBefore(first, il.Create(OpCodes.Call, observer.SpendGasMethod)); // trigger method
il.Body.OptimizeMacros();
}
public ModuleDefinition Rewrite(ModuleDefinition module)
{
Guid id = Guid.NewGuid();
FieldDefinition observerInstanceField = GetObserverInstance(module, id);
var observer = new ObserverReferences(observerInstanceField, module);
foreach (TypeDefinition type in module.Types)
{
RewriteType(type, observer);
}
ObserverInstances.Set(id, this.observerToInject);
return(module);
}
/// <summary>
/// Adds a call to SpendGas from the RuntimeObserver before the given instruction.
/// </summary>
private static void AddSpendGasMethodBeforeInstruction(MethodDefinition methodDefinition, ObserverReferences observer, VariableDefinition variable, Instruction instruction, Gas opcodeCount)
{
ILProcessor il = methodDefinition.Body.GetILProcessor();
il.Body.SimplifyMacros();
il.InsertBefore(instruction, il.CreateLdlocBest(variable)); // load observer
il.InsertBefore(instruction, il.Create(OpCodes.Ldc_I8, (long)opcodeCount.Value)); // load gas amount
il.InsertBefore(instruction, il.Create(OpCodes.Call, observer.SpendGasMethod)); // trigger method
il.Body.OptimizeMacros();
}
private void RewriteMethod(MethodDefinition methodDefinition, ObserverReferences observer)
{
if (methodDefinition.DeclaringType == observer.InstanceField.DeclaringType)
{
return; // don't inject on our injected type.
}
if (!methodDefinition.HasBody || methodDefinition.Body.Instructions.Count == 0)
{
return; // don't inject on method without a Body
}
List <Instruction> branches = methodDefinition.Body.Instructions.Where(x => BranchingOps.Contains(x.OpCode)).ToList();
List <Instruction> branchTos = branches.Select(x => (Instruction)x.Operand).ToList();
Instruction currentSegmentStart = methodDefinition.Body.Instructions.FirstOrDefault();
Gas gasTally = Gas.None;
Dictionary <Instruction, Gas> gasToSpendForSegment = new Dictionary <Instruction, Gas>();
// Inject observer instance to method.
ILProcessor il = methodDefinition.Body.GetILProcessor();
var observerVariable = new VariableDefinition(observer.InstanceField.FieldType);
il.Body.Variables.Add(observerVariable);
Instruction start = methodDefinition.Body.Instructions[0];
il.InsertBefore(start, il.Create(OpCodes.Ldsfld, observer.InstanceField));
il.InsertBefore(start, il.CreateStlocBest(observerVariable));
// Start at 2 because of the instructions we just added.
int position = 2;
while (position < methodDefinition.Body.Instructions.Count)
{
Instruction instruction = methodDefinition.Body.Instructions[position];
Gas instructionCost = GasPriceList.InstructionOperationCost(instruction);
// is the end of a segment. Include the current instruction in the count.
if (branches.Contains(instruction))
{
gasTally = (Gas)(gasTally + instructionCost);
gasToSpendForSegment.Add(currentSegmentStart, gasTally);
gasTally = Gas.None;
position++;
if (position == methodDefinition.Body.Instructions.Count)
{
break;
}
currentSegmentStart = methodDefinition.Body.Instructions[position];
}
// is the start of a new segment. Don't include the current instruction in count.
else if (branchTos.Contains(instruction) && instruction != currentSegmentStart)
{
gasToSpendForSegment.Add(currentSegmentStart, gasTally);
gasTally = Gas.None;
currentSegmentStart = instruction;
position++;
}
// is a call to another method
else if (CallingOps.Contains(instruction.OpCode))
{
var methodToCall = (MethodReference)instruction.Operand;
// If it's a method inside this contract then the gas will be injected no worries.
if (methodToCall.DeclaringType == methodDefinition.DeclaringType)
{
position++;
gasTally = (Gas)(gasTally + instructionCost);
}
// If it's a method outside this contract then we will need to get some average in future.
else
{
Gas methodCallCost = GasPriceList.MethodCallCost(methodToCall);
position++;
gasTally = (Gas)(gasTally + instructionCost + methodCallCost);
}
}
// any other instruction. just increase counter.
else
{
position++;
gasTally = (Gas)(gasTally + instructionCost);
}
}
if (!gasToSpendForSegment.ContainsKey(currentSegmentStart))
{
gasToSpendForSegment.Add(currentSegmentStart, gasTally);
}
foreach (Instruction instruction in gasToSpendForSegment.Keys)
{
Instruction injectAfterInstruction = instruction;
// If it's a constructor we need to skip the first 3 instructions.
// These will always be invoking the base constructor
// ldarg.0
// ldarg.0
// call SmartContract::ctor
if (methodDefinition.IsConstructor)
{
injectAfterInstruction = instruction.Next.Next.Next;
}
AddSpendGasMethodBeforeInstruction(methodDefinition, observer, observerVariable, injectAfterInstruction, gasToSpendForSegment[instruction]);
}
foreach (Instruction instruction in branches)
{
var oldReference = (Instruction)instruction.Operand;
Instruction newReference = oldReference.Previous.Previous.Previous; // 3 were inserted
Instruction newInstruction = il.Create(instruction.OpCode, newReference);
il.Replace(instruction, newInstruction);
}
}
public ObserverRewriterContext(ObserverReferences observer, VariableDefinition observerVariable)
{
this.Observer = observer;
this.ObserverVariable = observerVariable;
}