public void JumpToNear(X86Condition condition)
{
_jNearCondition = condition;
_jNearPosition = _stream.Position;
_jNearLength = Assembler.GetJccLength(0);
_stream.Seek(_jNearLength, SeekOrigin.Current);
}
public void JumpHere()
{
long currentPosition = _stream.Position;
_stream.Seek(_jNearPosition, SeekOrigin.Begin);
long offset = currentPosition - (_jNearPosition + _jNearLength);
Debug.Assert(_jNearLength == Assembler.GetJccLength(offset), "Relative offset doesn't fit on near jump.");
Assembler.Jcc(_jNearCondition, offset);
_stream.Seek(currentPosition, SeekOrigin.Begin);
}
public byte[] GetCode()
{
// Write jump relative offsets.
bool modified;
do
{
modified = false;
for (int index = 0; index < _jumps.Count; index++)
{
Jump jump = _jumps[index];
long jumpTarget = _blockOffsets[jump.Target.Index];
long offset = jumpTarget - jump.JumpPosition;
if (offset < 0)
{
for (int index2 = index - 1; index2 >= 0; index2--)
{
Jump jump2 = _jumps[index2];
if (jump2.JumpPosition < jumpTarget)
{
break;
}
offset -= jump2.InstSize - ReservedBytesForJump;
}
}
else
{
for (int index2 = index + 1; index2 < _jumps.Count; index2++)
{
Jump jump2 = _jumps[index2];
if (jump2.JumpPosition >= jumpTarget)
{
break;
}
offset += jump2.InstSize - ReservedBytesForJump;
}
offset -= ReservedBytesForJump;
}
if (jump.IsConditional)
{
jump.InstSize = Assembler.GetJccLength(offset);
}
else
{
jump.InstSize = Assembler.GetJmpLength(offset);
}
// The jump is relative to the next instruction, not the current one.
// Since we didn't know the next instruction address when calculating
// the offset (as the size of the current jump instruction was not know),
// we now need to compensate the offset with the jump instruction size.
// It's also worth to note that:
// - This is only needed for backward jumps.
// - The GetJmpLength and GetJccLength also compensates the offset
// internally when computing the jump instruction size.
if (offset < 0)
{
offset -= jump.InstSize;
}
if (jump.RelativeOffset != offset)
{
modified = true;
}
jump.RelativeOffset = offset;
_jumps[index] = jump;
}
}while (modified);
// Write the code, ignoring the dummy bytes after jumps, into a new stream.
_stream.Seek(0, SeekOrigin.Begin);
using (MemoryStream codeStream = new MemoryStream())
{
Assembler assembler = new Assembler(codeStream);
byte[] buffer;
for (int index = 0; index < _jumps.Count; index++)
{
Jump jump = _jumps[index];
buffer = new byte[jump.JumpPosition - _stream.Position];
_stream.Read(buffer, 0, buffer.Length);
_stream.Seek(ReservedBytesForJump, SeekOrigin.Current);
codeStream.Write(buffer);
if (jump.IsConditional)
{
assembler.Jcc(jump.Condition, jump.RelativeOffset);
}
else
{
assembler.Jmp(jump.RelativeOffset);
}
}
buffer = new byte[_stream.Length - _stream.Position];
_stream.Read(buffer, 0, buffer.Length);
codeStream.Write(buffer);
return(codeStream.ToArray());
}
}