fcnvfx.c

这个linux源代码是很全面的~基本完整了~使用c编译的~由于时间问题我没有亲自测试~但就算用来做参考资料也是非常好的

/*
 * Linux/PA-RISC Project (http://www.parisc-linux.org/)
 *
 * Floating-point emulation code
 *  Copyright (C) 2001 Hewlett-Packard (Paul Bame) <[e-mail]>
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2, or (at your option)
 *    any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
/*
 * BEGIN_DESC
 *
 *  File:
 *	@(#)	pa/spmath/fcnvfx.c		$Revision: 1.1 $
 *
 *  Purpose:
 *	Single Floating-point to Single Fixed-point
 *	Single Floating-point to Double Fixed-point 
 *	Double Floating-point to Single Fixed-point 
 *	Double Floating-point to Double Fixed-point 
 *
 *  External Interfaces:
 *	dbl_to_dbl_fcnvfx(srcptr,nullptr,dstptr,status)
 *	dbl_to_sgl_fcnvfx(srcptr,nullptr,dstptr,status)
 *	sgl_to_dbl_fcnvfx(srcptr,nullptr,dstptr,status)
 *	sgl_to_sgl_fcnvfx(srcptr,nullptr,dstptr,status)
 *
 *  Internal Interfaces:
 *
 *  Theory:
 *	<<please update with a overview of the operation of this file>>
 *
 * END_DESC
*/


#include "float.h"
#include "sgl_float.h"
#include "dbl_float.h"
#include "cnv_float.h"

/*
 *  Single Floating-point to Single Fixed-point 
 */
/*ARGSUSED*/
int
sgl_to_sgl_fcnvfx(
		    sgl_floating_point *srcptr,
		    sgl_floating_point *nullptr,
		    int *dstptr,
		    sgl_floating_point *status)
{
	register unsigned int src, temp;
	register int src_exponent, result;
	register boolean inexact = FALSE;

	src = *srcptr;
	src_exponent = Sgl_exponent(src) - SGL_BIAS;

	/* 
	 * Test for overflow
	 */
	if (src_exponent > SGL_FX_MAX_EXP) {
		/* check for MININT */
		if ((src_exponent > SGL_FX_MAX_EXP + 1) || 
		Sgl_isnotzero_mantissa(src) || Sgl_iszero_sign(src)) {
                        if (Sgl_iszero_sign(src)) result = 0x7fffffff;
                        else result = 0x80000000; 

	                if (Is_invalidtrap_enabled()) {
                            return(INVALIDEXCEPTION);
                        }
                        Set_invalidflag();
			*dstptr = result;
			return(NOEXCEPTION);
       		}
	}
	/*
	 * Generate result
	 */
	if (src_exponent >= 0) {
		temp = src;
		Sgl_clear_signexponent_set_hidden(temp);
		Int_from_sgl_mantissa(temp,src_exponent);
		if (Sgl_isone_sign(src))  result = -Sgl_all(temp);
		else result = Sgl_all(temp);

		/* check for inexact */
		if (Sgl_isinexact_to_fix(src,src_exponent)) {
			inexact = TRUE;
			/*  round result  */
			switch (Rounding_mode()) {
			case ROUNDPLUS:
			     if (Sgl_iszero_sign(src)) result++;
			     break;
			case ROUNDMINUS:
			     if (Sgl_isone_sign(src)) result--;
			     break;
			case ROUNDNEAREST:
			     if (Sgl_isone_roundbit(src,src_exponent)) {
			        if (Sgl_isone_stickybit(src,src_exponent) 
				|| (Sgl_isone_lowmantissa(temp)))
			           if (Sgl_iszero_sign(src)) result++;
			           else result--;
			     }
			} 
		}
	}
	else {
		result = 0;

		/* check for inexact */
		if (Sgl_isnotzero_exponentmantissa(src)) {
			inexact = TRUE;
			/*  round result  */
			switch (Rounding_mode()) {
			case ROUNDPLUS:
			     if (Sgl_iszero_sign(src)) result++;
			     break;
			case ROUNDMINUS:
			     if (Sgl_isone_sign(src)) result--;
			     break;
			case ROUNDNEAREST:
			     if (src_exponent == -1)
			        if (Sgl_isnotzero_mantissa(src))
			           if (Sgl_iszero_sign(src)) result++;
			           else result--;
			} 
		}
	}
	*dstptr = result;
	if (inexact) {
		if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
		else Set_inexactflag();
	}
	return(NOEXCEPTION);
}

/*
 *  Single Floating-point to Double Fixed-point 
 */
/*ARGSUSED*/
int
sgl_to_dbl_fcnvfx(
		sgl_floating_point *srcptr,
		unsigned int *nullptr,
		dbl_integer *dstptr,
		unsigned int *status)
{
	register int src_exponent, resultp1;
	register unsigned int src, temp, resultp2;
	register boolean inexact = FALSE;

	src = *srcptr;
	src_exponent = Sgl_exponent(src) - SGL_BIAS;

	/* 
	 * Test for overflow
	 */
	if (src_exponent > DBL_FX_MAX_EXP) {
		/* check for MININT */
		if ((src_exponent > DBL_FX_MAX_EXP + 1) || 
		Sgl_isnotzero_mantissa(src) || Sgl_iszero_sign(src)) {
                        if (Sgl_iszero_sign(src)) {
                              resultp1 = 0x7fffffff;
			      resultp2 = 0xffffffff;
			}
                        else {
			    resultp1 = 0x80000000; 
			    resultp2 = 0;
			}
	                if (Is_invalidtrap_enabled()) {
                            return(INVALIDEXCEPTION);
                        }
                        Set_invalidflag();
    		        Dint_copytoptr(resultp1,resultp2,dstptr);
			return(NOEXCEPTION);
		}
		Dint_set_minint(resultp1,resultp2);
		Dint_copytoptr(resultp1,resultp2,dstptr);
		return(NOEXCEPTION);
	}
	/*
	 * Generate result
	 */
	if (src_exponent >= 0) {
		temp = src;
		Sgl_clear_signexponent_set_hidden(temp);
		Dint_from_sgl_mantissa(temp,src_exponent,resultp1,resultp2);
		if (Sgl_isone_sign(src)) {
			Dint_setone_sign(resultp1,resultp2);
		}

		/* check for inexact */
		if (Sgl_isinexact_to_fix(src,src_exponent)) {
			inexact = TRUE;
                        /*  round result  */
                        switch (Rounding_mode()) {
                        case ROUNDPLUS:
                             if (Sgl_iszero_sign(src)) {
				Dint_increment(resultp1,resultp2);
			     }
                             break;
                        case ROUNDMINUS:
                             if (Sgl_isone_sign(src)) {
				Dint_decrement(resultp1,resultp2);
			     }
                             break;
                        case ROUNDNEAREST:
                             if (Sgl_isone_roundbit(src,src_exponent))
                                if (Sgl_isone_stickybit(src,src_exponent) || 
				(Dint_isone_lowp2(resultp2)))
				   if (Sgl_iszero_sign(src)) {
				      Dint_increment(resultp1,resultp2);
				   }
                                   else {
				      Dint_decrement(resultp1,resultp2);
				   }
                        }
                }
        }
	else {
		Dint_setzero(resultp1,resultp2);

		/* check for inexact */
		if (Sgl_isnotzero_exponentmantissa(src)) {
			inexact = TRUE;
                        /*  round result  */
                        switch (Rounding_mode()) {
                        case ROUNDPLUS:
                             if (Sgl_iszero_sign(src)) {
				Dint_increment(resultp1,resultp2);
			     }
                             break;
                        case ROUNDMINUS:
                             if (Sgl_isone_sign(src)) {
				Dint_decrement(resultp1,resultp2);
			     }
                             break;
                        case ROUNDNEAREST:
                             if (src_exponent == -1)
                                if (Sgl_isnotzero_mantissa(src))
                                   if (Sgl_iszero_sign(src)) {
				      Dint_increment(resultp1,resultp2);
				   }
                                   else {
				      Dint_decrement(resultp1,resultp2);
				   }
			}
		}
	}
	Dint_copytoptr(resultp1,resultp2,dstptr);
	if (inexact) {
		if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
		else Set_inexactflag();
	}
	return(NOEXCEPTION);
}

/*
 *  Double Floating-point to Single Fixed-point 
 */
/*ARGSUSED*/
int
dbl_to_sgl_fcnvfx(
		    dbl_floating_point *srcptr,
		    unsigned int *nullptr,
		    int *dstptr,
		    unsigned int *status)
{
	register unsigned int srcp1,srcp2, tempp1,tempp2;
	register int src_exponent, result;
	register boolean inexact = FALSE;

	Dbl_copyfromptr(srcptr,srcp1,srcp2);
	src_exponent = Dbl_exponent(srcp1) - DBL_BIAS;

	/* 
	 * Test for overflow
	 */
	if (src_exponent > SGL_FX_MAX_EXP) {
		/* check for MININT */
		if (Dbl_isoverflow_to_int(src_exponent,srcp1,srcp2)) {
                        if (Dbl_iszero_sign(srcp1)) result = 0x7fffffff;
                        else result = 0x80000000; 

	                if (Is_invalidtrap_enabled()) {
                            return(INVALIDEXCEPTION);
                        }
                        Set_invalidflag();
			*dstptr = result;
			return(NOEXCEPTION);
		}
	}
	/*
	 * Generate result
	 */
	if (src_exponent >= 0) {
		tempp1 = srcp1;
		tempp2 = srcp2;
		Dbl_clear_signexponent_set_hidden(tempp1);
		Int_from_dbl_mantissa(tempp1,tempp2,src_exponent);
		if (Dbl_isone_sign(srcp1) && (src_exponent <= SGL_FX_MAX_EXP))
			result = -Dbl_allp1(tempp1);
		else result = Dbl_allp1(tempp1);

		/* check for inexact */
		if (Dbl_isinexact_to_fix(srcp1,srcp2,src_exponent)) {
                        inexact = TRUE;
                        /*  round result  */
                        switch (Rounding_mode()) {
                        case ROUNDPLUS:
                             if (Dbl_iszero_sign(srcp1)) result++;
                             break;
                        case ROUNDMINUS:
                             if (Dbl_isone_sign(srcp1)) result--;
                             break;
                        case ROUNDNEAREST:
                             if (Dbl_isone_roundbit(srcp1,srcp2,src_exponent))
                                if (Dbl_isone_stickybit(srcp1,srcp2,src_exponent) || 
				(Dbl_isone_lowmantissap1(tempp1)))
                                   if (Dbl_iszero_sign(srcp1)) result++;
                                   else result--;
                        } 
			/* check for overflow */
			if ((Dbl_iszero_sign(srcp1) && result < 0) ||
			    (Dbl_isone_sign(srcp1) && result > 0)) {
			        
                          if (Dbl_iszero_sign(srcp1)) result = 0x7fffffff;
                          else result = 0x80000000; 

	                  if (Is_invalidtrap_enabled()) {
                            return(INVALIDEXCEPTION);
                          }
                          Set_invalidflag();
			  *dstptr = result;
			  return(NOEXCEPTION);
			}
                }
	}
	else {
		result = 0;

		/* check for inexact */
		if (Dbl_isnotzero_exponentmantissa(srcp1,srcp2)) {
                        inexact = TRUE;
                        /*  round result  */
                        switch (Rounding_mode()) {
                        case ROUNDPLUS:
                             if (Dbl_iszero_sign(srcp1)) result++;
                             break;
                        case ROUNDMINUS:
                             if (Dbl_isone_sign(srcp1)) result--;
                             break;
                        case ROUNDNEAREST:
                             if (src_exponent == -1)
                                if (Dbl_isnotzero_mantissa(srcp1,srcp2))
                                   if (Dbl_iszero_sign(srcp1)) result++;
                                   else result--;
			}
                }
	}
	*dstptr = result;
        if (inexact) {
                if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
		else Set_inexactflag();
        }
	return(NOEXCEPTION);
}

/*
 *  Double Floating-point to Double Fixed-point 
 */
/*ARGSUSED*/
int
dbl_to_dbl_fcnvfx(
		    dbl_floating_point *srcptr,
		    unsigned int *nullptr,
		    dbl_integer *dstptr,
		    unsigned int *status)
{
	register int src_exponent, resultp1;
	register unsigned int srcp1, srcp2, tempp1, tempp2, resultp2;
	register boolean inexact = FALSE;

	Dbl_copyfromptr(srcptr,srcp1,srcp2);
	src_exponent = Dbl_exponent(srcp1) - DBL_BIAS;

	/* 
	 * Test for overflow
	 */
	if (src_exponent > DBL_FX_MAX_EXP) {
		/* check for MININT */
		if ((src_exponent > DBL_FX_MAX_EXP + 1) || 
		Dbl_isnotzero_mantissa(srcp1,srcp2) || Dbl_iszero_sign(srcp1)) {
                        if (Dbl_iszero_sign(srcp1)) {
                              resultp1 = 0x7fffffff;
			      resultp2 = 0xffffffff;
			}
                        else {
			    resultp1 = 0x80000000; 
			    resultp2 = 0;
			}
	                if (Is_invalidtrap_enabled()) {
                            return(INVALIDEXCEPTION);
                        }
                        Set_invalidflag();
    		        Dint_copytoptr(resultp1,resultp2,dstptr);
			return(NOEXCEPTION);
		}
	}
 
	/*
	 * Generate result
	 */
	if (src_exponent >= 0) {
		tempp1 = srcp1;
		tempp2 = srcp2;
		Dbl_clear_signexponent_set_hidden(tempp1);
		Dint_from_dbl_mantissa(tempp1,tempp2,src_exponent,resultp1,
		resultp2);
		if (Dbl_isone_sign(srcp1)) {
			Dint_setone_sign(resultp1,resultp2);
		}

		/* check for inexact */
		if (Dbl_isinexact_to_fix(srcp1,srcp2,src_exponent)) {
                        inexact = TRUE;
                        /*  round result  */
                        switch (Rounding_mode()) {
                        case ROUNDPLUS:
                             if (Dbl_iszero_sign(srcp1)) {
				Dint_increment(resultp1,resultp2);
			     }
                             break;
                        case ROUNDMINUS:
                             if (Dbl_isone_sign(srcp1)) {
				Dint_decrement(resultp1,resultp2);
			     }
                             break;
                        case ROUNDNEAREST:
                             if (Dbl_isone_roundbit(srcp1,srcp2,src_exponent))
                                if (Dbl_isone_stickybit(srcp1,srcp2,src_exponent) || 
				(Dint_isone_lowp2(resultp2)))
                                   if (Dbl_iszero_sign(srcp1)) {
				      Dint_increment(resultp1,resultp2);
				   }
                                   else {
				      Dint_decrement(resultp1,resultp2);
				   }
                        } 
                }
	}
	else {
		Dint_setzero(resultp1,resultp2);

		/* check for inexact */
		if (Dbl_isnotzero_exponentmantissa(srcp1,srcp2)) {
                        inexact = TRUE;
                        /*  round result  */
                        switch (Rounding_mode()) {
                        case ROUNDPLUS:
                             if (Dbl_iszero_sign(srcp1)) {
				Dint_increment(resultp1,resultp2);
			     }
                             break;
                        case ROUNDMINUS:
                             if (Dbl_isone_sign(srcp1)) {
				Dint_decrement(resultp1,resultp2);
			     }
                             break;
                        case ROUNDNEAREST:
                             if (src_exponent == -1)
                                if (Dbl_isnotzero_mantissa(srcp1,srcp2))
                                   if (Dbl_iszero_sign(srcp1)) {
				      Dint_increment(resultp1,resultp2);
				   }
                                   else {
				      Dint_decrement(resultp1,resultp2);
				   }
			}
                }
	}
	Dint_copytoptr(resultp1,resultp2,dstptr);
        if (inexact) {
                if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
        	else Set_inexactflag();
        }
	return(NOEXCEPTION);
}