fcnvfxt.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/fcnvfxt.c		$Revision: 1.1 $
 *
 *  Purpose:
 *	Single Floating-point to Single Fixed-point /w truncated result
 *	Single Floating-point to Double Fixed-point /w truncated result
 *	Double Floating-point to Single Fixed-point /w truncated result
 *	Double Floating-point to Double Fixed-point /w truncated result
 *
 *  External Interfaces:
 *	dbl_to_dbl_fcnvfxt(srcptr,nullptr,dstptr,status)
 *	dbl_to_sgl_fcnvfxt(srcptr,nullptr,dstptr,status)
 *	sgl_to_dbl_fcnvfxt(srcptr,nullptr,dstptr,status)
 *	sgl_to_sgl_fcnvfxt(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"

/*
 *  Convert single floating-point to single fixed-point format
 *  with truncated result
 */
/*ARGSUSED*/
int
sgl_to_sgl_fcnvfxt(
		    sgl_floating_point *srcptr,
		    unsigned int *nullptr,
		    int *dstptr,
		    unsigned int *status)
{
	register unsigned int src, temp;
	register int src_exponent, result;

	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);
		*dstptr = result;

		/* check for inexact */
		if (Sgl_isinexact_to_fix(src,src_exponent)) {
			if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
			else Set_inexactflag();
		}
	}
	else {
		*dstptr = 0;

		/* check for inexact */
		if (Sgl_isnotzero_exponentmantissa(src)) {
			if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
			else Set_inexactflag();
		}
	}
	return(NOEXCEPTION);
}

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

	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);
		}
		Dint_copytoptr(resultp1,resultp2,dstptr);

		/* check for inexact */
		if (Sgl_isinexact_to_fix(src,src_exponent)) {
			if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
			else Set_inexactflag();
		}
	}
	else {
		Dint_setzero(resultp1,resultp2);
		Dint_copytoptr(resultp1,resultp2,dstptr);

		/* check for inexact */
		if (Sgl_isnotzero_exponentmantissa(src)) {
			if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
			else Set_inexactflag();
		}
	}
	return(NOEXCEPTION);
}

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

	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);
		*dstptr = result;

		/* check for inexact */
		if (Dbl_isinexact_to_fix(srcp1,srcp2,src_exponent)) {
			if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
			else Set_inexactflag();
		}
	}
	else {
		*dstptr = 0;

		/* check for inexact */
		if (Dbl_isnotzero_exponentmantissa(srcp1,srcp2)) {
			if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
			else Set_inexactflag();
		}
	}
	return(NOEXCEPTION);
}

/*
 *  Double Floating-point to Double Fixed-point 
 */
/*ARGSUSED*/
int
dbl_to_dbl_fcnvfxt(
			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;

	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);
		}
		Dint_copytoptr(resultp1,resultp2,dstptr);

		/* check for inexact */
		if (Dbl_isinexact_to_fix(srcp1,srcp2,src_exponent)) {
			if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
			else Set_inexactflag();
		}
	}
	else {
		Dint_setzero(resultp1,resultp2);
		Dint_copytoptr(resultp1,resultp2,dstptr);

		/* check for inexact */
		if (Dbl_isnotzero_exponentmantissa(srcp1,srcp2)) {
			if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
			else Set_inexactflag();
		}
	}
	return(NOEXCEPTION);
}