自学教程：C++ xWrite8函数代码示例

__emitinline void xAdvancePtr( uint bytes ){	if( IsDevBuild )	{		// common debugger courtesy: advance with INT3 as filler.		for( uint i=0; i<bytes; i++ )			xWrite8( 0xcc );	}	else		x86Ptr += bytes;}

static void _g1_EmitOp( G1Type InstType, const xRegisterInt& to, int imm ){	to.prefix16();	if( !to.Is8BitOp() && is_s8( imm ) )	{		xWrite8( 0x83 );		EmitSibMagic( InstType, to );		xWrite<s8>( imm );	}	else	{		if( to.IsAccumulator() )			xWrite8( (to.Is8BitOp() ? 4 : 5) | (InstType<<3) );		else		{			xWrite8( to.Is8BitOp() ? 0x80 : 0x81 );			EmitSibMagic( InstType, to );		}		to.xWriteImm( imm );	}}

xForwardJumpBase::xForwardJumpBase(uint opsize, JccComparisonType cctype){    pxAssert(opsize == 1 || opsize == 4);    pxAssertDev(cctype != Jcc_Unknown, "Invalid ForwardJump conditional type.");    BasePtr = (s8 *)xGetPtr() +              ((opsize == 1) ? 2 :                           // j8's are always 2 bytes.                   ((cctype == Jcc_Unconditional) ? 5 : 6)); // j32's are either 5 or 6 bytes    if (opsize == 1)        xWrite8((cctype == Jcc_Unconditional) ? 0xeb : (0x70 | cctype));    else {        if (cctype == Jcc_Unconditional)            xWrite8(0xe9);        else {            xWrite8(0x0f);            xWrite8(0x80 | cctype);        }    }    xAdvancePtr(opsize);}

void xImpl_IncDec::operator()(const xRegisterInt &to) const{    if (to.Is8BitOp()) {        u8 regfield = isDec ? 1 : 0;        xOpWrite(to.GetPrefix16(), 0xfe, regfield, to);    } else {#ifdef __x86_64__        pxAssertMsg(0, "Single Byte INC/DEC aren't valid in 64 bits."                       "You need to use the ModR/M form (FF/0 FF/1 opcodes)");#endif        to.prefix16();        xWrite8((isDec ? 0x48 : 0x40) | to.Id);    }}

static void _imul_ImmStyle( const xRegisterInt& param1, const SrcType& param2, int imm ){	// for iMul OpSize is allowed to be 16 or 32 bit only.	const uint OpSize = param1.GetOperandSize();	pxAssert( OpSize == param2.GetOperandSize() );	pxAssert( OpSize > 1 );	xOpWrite0F( (OpSize == 2) ? 0x66 : 0, is_s8( imm ) ? 0x6b : 0x69, param1, param2 );	if( is_s8( imm ) )		xWrite8( (u8)imm );	else		param1.xWriteImm( imm );}

__fi void xCLC()	{ xWrite8( 0xF8 ); }

__fi void xSTC()	{ xWrite8( 0xF9 ); }

__emitinline void xPOP( const xIndirectVoid& from ){	xWrite8( 0x8f );	EmitSibMagic( 0, from );}

void xImpl_Group2::operator()( const xRegisterInt& to, const xRegisterCL& /* from */ ) const{	to.prefix16();	xWrite8( to.Is8BitOp() ? 0xd2 : 0xd3 );	EmitSibMagic( InstType, to );}

static void _g3_EmitOp( G3Type InstType, const xRegisterInt& from ){	from.prefix16();	xWrite8(from.Is8BitOp() ? 0xf6 : 0xf7 );	EmitSibMagic( InstType, from );}

// pops the EFLAGS register from the stack__fi void xPOPFD()						{ xWrite8( 0x9D ); }

__fi void xLEAVE()	{ xWrite8( 0xC9 ); }

__fi void xPUSH( xRegister32 from )	{ xWrite8( 0x50 | from.Id ); }

// pushes the EFLAGS register onto the stack__fi void xPUSHFD()					{ xWrite8( 0x9C ); }

// NOP 1-byte__fi void xNOP()	{ xWrite8(0x90); }

__fi void xRET()	{ xWrite8( 0xC3 ); }

// ------------------------------------------------------------------------// Emits a 32 bit jump, and returns a pointer to the 8 bit displacement.// (displacements should be assigned relative to the end of the jump instruction,// or in other words *(retval+1) )__emitinline s8* xJcc8( JccComparisonType comparison, s8 displacement ){	xWrite8( (comparison == Jcc_Unconditional) ? 0xeb : (0x70 | comparison) );	xWrite<s8>( displacement );	return (s8*)xGetPtr() - 1;}

__fi void xCDQ()	{ xWrite8( 0x99 ); }

void xImpl_Test::operator()( const xRegister32& to, const xRegister32& from ) const{	xWrite8( 0x85 );	EmitSibMagic( from, to );}

__fi void xLAHF()	{ xWrite8( 0x9f ); }

__fi void xSAHF()	{ xWrite8( 0x9e ); }

__fi void xCWDE()	{ xWrite8( 0x98 ); }