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InstructionEncoder.cs
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/
InstructionEncoder.cs
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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Diagnostics;
namespace System.Reflection.Metadata.Ecma335
{
/// <summary>
/// Encodes instructions.
/// </summary>
public readonly struct InstructionEncoder
{
/// <summary>
/// Underlying builder where encoded instructions are written to.
/// </summary>
public BlobBuilder CodeBuilder { get; }
/// <summary>
/// Builder tracking labels, branches and exception handlers.
/// </summary>
/// <remarks>
/// If null the encoder doesn't support construction of control flow.
/// </remarks>
public ControlFlowBuilder? ControlFlowBuilder { get; }
/// <summary>
/// Creates an encoder backed by code and control-flow builders.
/// </summary>
/// <param name="codeBuilder">Builder to write encoded instructions to.</param>
/// <param name="controlFlowBuilder">
/// Builder tracking labels, branches and exception handlers.
/// Must be specified to be able to use some of the control-flow factory methods of <see cref="InstructionEncoder"/>,
/// such as <see cref="Branch(ILOpCode, LabelHandle)"/>, <see cref="DefineLabel"/>, <see cref="MarkLabel(LabelHandle)"/> etc.
/// </param>
public InstructionEncoder(BlobBuilder codeBuilder, ControlFlowBuilder? controlFlowBuilder = null)
{
if (codeBuilder == null)
{
Throw.BuilderArgumentNull();
}
CodeBuilder = codeBuilder;
ControlFlowBuilder = controlFlowBuilder;
}
/// <summary>
/// Offset of the next encoded instruction.
/// </summary>
public int Offset => CodeBuilder.Count;
/// <summary>
/// Encodes specified op-code.
/// </summary>
public void OpCode(ILOpCode code)
{
if (unchecked((byte)code) == (ushort)code)
{
CodeBuilder.WriteByte((byte)code);
}
else
{
// IL opcodes that occupy two bytes are written to
// the byte stream with the high-order byte first,
// in contrast to the little-endian format of the
// numeric arguments and tokens.
CodeBuilder.WriteUInt16BE((ushort)code);
}
}
/// <summary>
/// Encodes a token.
/// </summary>
public void Token(EntityHandle handle)
{
Token(MetadataTokens.GetToken(handle));
}
/// <summary>
/// Encodes a token.
/// </summary>
public void Token(int token)
{
CodeBuilder.WriteInt32(token);
}
/// <summary>
/// Encodes <code>ldstr</code> instruction and its operand.
/// </summary>
public void LoadString(UserStringHandle handle)
{
OpCode(ILOpCode.Ldstr);
Token(MetadataTokens.GetToken(handle));
}
/// <summary>
/// Encodes <code>call</code> instruction and its operand.
/// </summary>
public void Call(EntityHandle methodHandle)
{
if (methodHandle.Kind != HandleKind.MethodDefinition &&
methodHandle.Kind != HandleKind.MethodSpecification &&
methodHandle.Kind != HandleKind.MemberReference)
{
Throw.InvalidArgument_Handle(nameof(methodHandle));
}
OpCode(ILOpCode.Call);
Token(methodHandle);
}
/// <summary>
/// Encodes <code>call</code> instruction and its operand.
/// </summary>
public void Call(MethodDefinitionHandle methodHandle)
{
OpCode(ILOpCode.Call);
Token(methodHandle);
}
/// <summary>
/// Encodes <code>call</code> instruction and its operand.
/// </summary>
public void Call(MethodSpecificationHandle methodHandle)
{
OpCode(ILOpCode.Call);
Token(methodHandle);
}
/// <summary>
/// Encodes <code>call</code> instruction and its operand.
/// </summary>
public void Call(MemberReferenceHandle methodHandle)
{
OpCode(ILOpCode.Call);
Token(methodHandle);
}
/// <summary>
/// Encodes <code>calli</code> instruction and its operand.
/// </summary>
public void CallIndirect(StandaloneSignatureHandle signature)
{
OpCode(ILOpCode.Calli);
Token(signature);
}
/// <summary>
/// Encodes <see cref="int"/> constant load instruction.
/// </summary>
public void LoadConstantI4(int value)
{
ILOpCode code;
switch (value)
{
case -1: code = ILOpCode.Ldc_i4_m1; break;
case 0: code = ILOpCode.Ldc_i4_0; break;
case 1: code = ILOpCode.Ldc_i4_1; break;
case 2: code = ILOpCode.Ldc_i4_2; break;
case 3: code = ILOpCode.Ldc_i4_3; break;
case 4: code = ILOpCode.Ldc_i4_4; break;
case 5: code = ILOpCode.Ldc_i4_5; break;
case 6: code = ILOpCode.Ldc_i4_6; break;
case 7: code = ILOpCode.Ldc_i4_7; break;
case 8: code = ILOpCode.Ldc_i4_8; break;
default:
if (unchecked((sbyte)value == value))
{
OpCode(ILOpCode.Ldc_i4_s);
CodeBuilder.WriteSByte((sbyte)value);
}
else
{
OpCode(ILOpCode.Ldc_i4);
CodeBuilder.WriteInt32(value);
}
return;
}
OpCode(code);
}
/// <summary>
/// Encodes <see cref="long"/> constant load instruction.
/// </summary>
public void LoadConstantI8(long value)
{
OpCode(ILOpCode.Ldc_i8);
CodeBuilder.WriteInt64(value);
}
/// <summary>
/// Encodes <see cref="float"/> constant load instruction.
/// </summary>
public void LoadConstantR4(float value)
{
OpCode(ILOpCode.Ldc_r4);
CodeBuilder.WriteSingle(value);
}
/// <summary>
/// Encodes <see cref="double"/> constant load instruction.
/// </summary>
public void LoadConstantR8(double value)
{
OpCode(ILOpCode.Ldc_r8);
CodeBuilder.WriteDouble(value);
}
/// <summary>
/// Encodes local variable load instruction.
/// </summary>
/// <param name="slotIndex">Index of the local variable slot.</param>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="slotIndex"/> is negative.</exception>
public void LoadLocal(int slotIndex)
{
switch (slotIndex)
{
case 0: OpCode(ILOpCode.Ldloc_0); break;
case 1: OpCode(ILOpCode.Ldloc_1); break;
case 2: OpCode(ILOpCode.Ldloc_2); break;
case 3: OpCode(ILOpCode.Ldloc_3); break;
default:
if (unchecked((uint)slotIndex) <= byte.MaxValue)
{
OpCode(ILOpCode.Ldloc_s);
CodeBuilder.WriteByte((byte)slotIndex);
}
else if (slotIndex > 0)
{
OpCode(ILOpCode.Ldloc);
CodeBuilder.WriteInt32(slotIndex);
}
else
{
Throw.ArgumentOutOfRange(nameof(slotIndex));
}
break;
}
}
/// <summary>
/// Encodes local variable store instruction.
/// </summary>
/// <param name="slotIndex">Index of the local variable slot.</param>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="slotIndex"/> is negative.</exception>
public void StoreLocal(int slotIndex)
{
switch (slotIndex)
{
case 0: OpCode(ILOpCode.Stloc_0); break;
case 1: OpCode(ILOpCode.Stloc_1); break;
case 2: OpCode(ILOpCode.Stloc_2); break;
case 3: OpCode(ILOpCode.Stloc_3); break;
default:
if (unchecked((uint)slotIndex) <= byte.MaxValue)
{
OpCode(ILOpCode.Stloc_s);
CodeBuilder.WriteByte((byte)slotIndex);
}
else if (slotIndex > 0)
{
OpCode(ILOpCode.Stloc);
CodeBuilder.WriteInt32(slotIndex);
}
else
{
Throw.ArgumentOutOfRange(nameof(slotIndex));
}
break;
}
}
/// <summary>
/// Encodes local variable address load instruction.
/// </summary>
/// <param name="slotIndex">Index of the local variable slot.</param>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="slotIndex"/> is negative.</exception>
public void LoadLocalAddress(int slotIndex)
{
if (unchecked((uint)slotIndex) <= byte.MaxValue)
{
OpCode(ILOpCode.Ldloca_s);
CodeBuilder.WriteByte((byte)slotIndex);
}
else if (slotIndex > 0)
{
OpCode(ILOpCode.Ldloca);
CodeBuilder.WriteInt32(slotIndex);
}
else
{
Throw.ArgumentOutOfRange(nameof(slotIndex));
}
}
/// <summary>
/// Encodes argument load instruction.
/// </summary>
/// <param name="argumentIndex">Index of the argument.</param>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="argumentIndex"/> is negative.</exception>
public void LoadArgument(int argumentIndex)
{
switch (argumentIndex)
{
case 0: OpCode(ILOpCode.Ldarg_0); break;
case 1: OpCode(ILOpCode.Ldarg_1); break;
case 2: OpCode(ILOpCode.Ldarg_2); break;
case 3: OpCode(ILOpCode.Ldarg_3); break;
default:
if (unchecked((uint)argumentIndex) <= byte.MaxValue)
{
OpCode(ILOpCode.Ldarg_s);
CodeBuilder.WriteByte((byte)argumentIndex);
}
else if (argumentIndex > 0)
{
OpCode(ILOpCode.Ldarg);
CodeBuilder.WriteInt32(argumentIndex);
}
else
{
Throw.ArgumentOutOfRange(nameof(argumentIndex));
}
break;
}
}
/// <summary>
/// Encodes argument address load instruction.
/// </summary>
/// <param name="argumentIndex">Index of the argument.</param>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="argumentIndex"/> is negative.</exception>
public void LoadArgumentAddress(int argumentIndex)
{
if (unchecked((uint)argumentIndex) <= byte.MaxValue)
{
OpCode(ILOpCode.Ldarga_s);
CodeBuilder.WriteByte((byte)argumentIndex);
}
else if (argumentIndex > 0)
{
OpCode(ILOpCode.Ldarga);
CodeBuilder.WriteInt32(argumentIndex);
}
else
{
Throw.ArgumentOutOfRange(nameof(argumentIndex));
}
}
/// <summary>
/// Encodes argument store instruction.
/// </summary>
/// <param name="argumentIndex">Index of the argument.</param>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="argumentIndex"/> is negative.</exception>
public void StoreArgument(int argumentIndex)
{
if (unchecked((uint)argumentIndex) <= byte.MaxValue)
{
OpCode(ILOpCode.Starg_s);
CodeBuilder.WriteByte((byte)argumentIndex);
}
else if (argumentIndex > 0)
{
OpCode(ILOpCode.Starg);
CodeBuilder.WriteInt32(argumentIndex);
}
else
{
Throw.ArgumentOutOfRange(nameof(argumentIndex));
}
}
/// <summary>
/// Defines a label that can later be used to mark and refer to a location in the instruction stream.
/// </summary>
/// <returns>Label handle.</returns>
/// <exception cref="InvalidOperationException"><see cref="ControlFlowBuilder"/> is null.</exception>
public LabelHandle DefineLabel()
{
return GetBranchBuilder().AddLabel();
}
/// <summary>
/// Encodes a branch instruction.
/// </summary>
/// <param name="code">Branch instruction to encode.</param>
/// <param name="label">Label of the target location in instruction stream.</param>
/// <exception cref="ArgumentException"><paramref name="code"/> is not a branch instruction.</exception>
/// <exception cref="ArgumentException"><paramref name="label"/> was not defined by this encoder.</exception>
/// <exception cref="InvalidOperationException"><see cref="ControlFlowBuilder"/> is null.</exception>
/// <exception cref="ArgumentNullException"><paramref name="label"/> has default value.</exception>
public void Branch(ILOpCode code, LabelHandle label)
{
// throws if code is not a branch:
int size = code.GetBranchOperandSize();
GetBranchBuilder().AddBranch(Offset, label, code);
OpCode(code);
// -1 points in the middle of the branch instruction and is thus invalid.
// We want to produce invalid IL so that if the caller doesn't patch the branches
// the branch instructions will be invalid in an obvious way.
if (size == 1)
{
CodeBuilder.WriteSByte(-1);
}
else
{
Debug.Assert(size == 4);
CodeBuilder.WriteInt32(-1);
}
}
/// <summary>
/// Associates specified label with the current IL offset.
/// </summary>
/// <param name="label">Label to mark.</param>
/// <remarks>
/// A single label may be marked multiple times, the last offset wins.
/// </remarks>
/// <exception cref="InvalidOperationException"><see cref="ControlFlowBuilder"/> is null.</exception>
/// <exception cref="ArgumentException"><paramref name="label"/> was not defined by this encoder.</exception>
/// <exception cref="ArgumentNullException"><paramref name="label"/> has default value.</exception>
public void MarkLabel(LabelHandle label)
{
GetBranchBuilder().MarkLabel(Offset, label);
}
private ControlFlowBuilder GetBranchBuilder()
{
if (ControlFlowBuilder == null)
{
Throw.ControlFlowBuilderNotAvailable();
}
return ControlFlowBuilder;
}
}
}