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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 Internal.TypeSystem;
using Debug = System.Diagnostics.Debug;
namespace Internal.IL
{
internal struct ILReader
{
private int _currentOffset;
private readonly byte[] _ilBytes;
public int Offset
{
get
{
return _currentOffset;
}
}
public int Size
{
get
{
return _ilBytes.Length;
}
}
public bool HasNext
{
get
{
return _currentOffset < _ilBytes.Length;
}
}
public ILReader(byte[] ilBytes, int currentOffset = 0)
{
_ilBytes = ilBytes;
_currentOffset = currentOffset;
}
//
// IL stream reading
//
public byte ReadILByte()
{
if (_currentOffset + 1 > _ilBytes.Length)
ThrowHelper.ThrowInvalidProgramException();
return _ilBytes[_currentOffset++];
}
public ushort ReadILUInt16()
{
if (_currentOffset + 2 > _ilBytes.Length)
ThrowHelper.ThrowInvalidProgramException();
ushort val = (ushort)(_ilBytes[_currentOffset] + (_ilBytes[_currentOffset + 1] << 8));
_currentOffset += 2;
return val;
}
public uint ReadILUInt32()
{
if (_currentOffset + 4 > _ilBytes.Length)
ThrowHelper.ThrowInvalidProgramException();
uint val = (uint)(_ilBytes[_currentOffset] + (_ilBytes[_currentOffset + 1] << 8) + (_ilBytes[_currentOffset + 2] << 16) + (_ilBytes[_currentOffset + 3] << 24));
_currentOffset += 4;
return val;
}
public int ReadILToken()
{
return (int)ReadILUInt32();
}
public ulong ReadILUInt64()
{
ulong value = ReadILUInt32();
value |= (((ulong)ReadILUInt32()) << 32);
return value;
}
public unsafe float ReadILFloat()
{
uint value = ReadILUInt32();
return *(float*)(&value);
}
public unsafe double ReadILDouble()
{
ulong value = ReadILUInt64();
return *(double*)(&value);
}
public ILOpcode ReadILOpcode()
{
ILOpcode opcode = (ILOpcode)ReadILByte();
if (opcode == ILOpcode.prefix1)
{
opcode = (ILOpcode)(0x100 + ReadILByte());
}
return opcode;
}
public ILOpcode PeekILOpcode()
{
ILOpcode opcode = (ILOpcode)_ilBytes[_currentOffset];
if (opcode == ILOpcode.prefix1)
{
if (_currentOffset + 2 > _ilBytes.Length)
ThrowHelper.ThrowInvalidProgramException();
opcode = (ILOpcode)(0x100 + _ilBytes[_currentOffset + 1]);
}
return opcode;
}
public void Skip(ILOpcode opcode)
{
if (!opcode.IsValid())
ThrowHelper.ThrowInvalidProgramException();
if (opcode != ILOpcode.switch_)
{
int opcodeSize = (byte)opcode != (int)opcode ? 2 : 1;
_currentOffset += opcode.GetSize() - opcodeSize;
}
else
{
// "switch" opcode is special
uint count = ReadILUInt32();
_currentOffset += checked((int)(count * 4));
}
}
public void Seek(int offset)
{
_currentOffset = offset;
}
public int ReadBranchDestination(ILOpcode currentOpcode)
{
if ((currentOpcode >= ILOpcode.br_s && currentOpcode <= ILOpcode.blt_un_s)
|| currentOpcode == ILOpcode.leave_s)
{
return (sbyte)ReadILByte() + Offset;
}
else
{
Debug.Assert((currentOpcode >= ILOpcode.br && currentOpcode <= ILOpcode.blt_un)
|| currentOpcode == ILOpcode.leave);
return (int)ReadILUInt32() + Offset;
}
}
}
}
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