File: ctrl87.h

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/*
 * This file is part of ms-dos port for XaoS
 * ctrl87.h
 *
 */


#ifndef __CONTROL87_H__


#define __CONTROL87_H__


#ifdef __CONTROL87_C__
#define EXTERN
#else
#define EXTERN extern
#endif


/* 8087/80287 Status Word format   */

#define SW_INVALID      0x0001	/* Invalid operation            */
#define SW_DENORMAL     0x0002	/* Denormalized operand         */
#define SW_ZERODIVIDE   0x0004	/* Zero divide                  */
#define SW_OVERFLOW     0x0008	/* Overflow                     */
#define SW_UNDERFLOW    0x0010	/* Underflow                    */
#define SW_INEXACT      0x0020	/* Precision (Inexact result)   */

/* 8087/80287 Control Word format */

#define MCW_EM              0x003f	/* interrupt Exception Masks */
#define     EM_INVALID      0x0001	/*   invalid                */
#define     EM_DENORMAL     0x0002	/*   denormal               */
#define     EM_ZERODIVIDE   0x0004	/*   zero divide            */
#define     EM_OVERFLOW     0x0008	/*   overflow               */
#define     EM_UNDERFLOW    0x0010	/*   underflow              */
#define     EM_INEXACT      0x0020	/*   inexact (precision)    */

#define MCW_IC              0x1000	/* Infinity Control */
#define     IC_AFFINE       0x1000	/*   affine         */
#define     IC_PROJECTIVE   0x0000	/*   projective     */

#define MCW_RC          0x0c00	/* Rounding Control     */
#define     RC_CHOP     0x0c00	/*   chop               */
#define     RC_UP       0x0800	/*   up                 */
#define     RC_DOWN     0x0400	/*   down               */
#define     RC_NEAR     0x0000	/*   near               */

#define MCW_PC          0x0300	/* Precision Control    */
#define     PC_24       0x0000	/*    24 bits           */
#define     PC_53       0x0200	/*    53 bits           */
#define     PC_64       0x0300	/*    64 bits           */

/**************************************************************************/
/*************************   Type declarations   **************************/
/**************************************************************************/

/**************************************************************************/
/************************   Function declarations   ***********************/
/**************************************************************************/

/*
   _control87 changes floating-point control word.

   Declaration:
   ------------
   unsigned short _control87(unsigned short newcw, unsigned short mask);

   Remarks:
   --------
   _control87 retrieves or changes the floating-point control word.

   The floating-point control word is an unsigned short that specifies the
   following modes in the 80x87 FPU:
   o  allowed exceptions
   o  infinity mode
   o  rounding mode
   o  precision mode

   Changing these modes allows you to mask or unmask floating-point exceptions.

   _control87 matches the bits in mask to the bits in newcw.

   If any mask bit = 1, the corresponding bit in newcw contains the new value
   for the same bit in the floating-point control word.

   If mask = 0000, _control87 returns the floating-point control word without
   altering it.

   Examples:
   ---------
   Switching to projective infinity mode:
   _control87(IC_PROJECTIVE, MCW_IC);

   Disabling all exceptions:
   _control87(MCW_EM, MCW_EM);

   Return Value:
   -------------
   The bits in the value returned reflect the new floating-point control word.
 */
EXTERN unsigned short _control87(unsigned short, unsigned short);


/**************************************************************************/
/**************************   Global variables   **************************/
/**************************************************************************/



#ifdef __CONTROL87_C__
#else
#endif


#undef EXTERN


#endif