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Diffstat (limited to 'codeflt1750.c')
| -rw-r--r-- | codeflt1750.c | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/codeflt1750.c b/codeflt1750.c new file mode 100644 index 0000000..40f488d --- /dev/null +++ b/codeflt1750.c @@ -0,0 +1,158 @@ +/***************************************************************************/ +/* */ +/* Project : Mil-Std-1750 Host Development Support Library */ +/* */ +/* Component : flt1750.c -- host independent float conversion routines */ +/* */ +/* Copyright : (C) Daimler-Benz Aerospace AG, 1994-97 */ +/* */ +/* Author : Oliver M. Kellogg, Dornier Satellite Systems, */ +/* Dept. RST13, D-81663 Munich, Germany. */ +/* Contact : oliver.kellogg@space.otn.dasa.de */ +/* */ +/* Disclaimer: */ +/* */ +/* 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 of the License, 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, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ +/* */ +/***************************************************************************/ + +/* These conversion functions have been tested on MIPS(ULTRIX), SPARC(Solaris), + i386(Linux/DOS), and VAX(VMS) machines. Should you encounter any problems + on other machines, please write to the e-mail contact address given above. + */ + + +#include "codeflt1750.h" +#include <math.h> +#define dfrexp frexp +#define pow2(exp) pow(2.0,(double)exp) + +#define ushort unsigned short +#define ulong unsigned long + +#define FLOATING_TWO_TO_THE_FIFTEEN 32768.0 +#define FLOATING_TWO_TO_THE_TWENTYTHREE 8388608.0 +#define FLOATING_TWO_TO_THE_THIRTYONE 2147483648.0 +#define FLOATING_TWO_TO_THE_THIRTYNINE 549755813888.0 + + + +double +from_1750flt (short *input) /* input : array of 2 shorts */ +{ + long int_mant; + double flt_mant, flt_exp; + signed char int_exp; + + int_exp = (signed char) (input[1] & 0xFF); + int_mant = ((long) input[0] << 8) | (((long) input[1] & 0xFF00L) >> 8); + /* printf("int_mant = 0x%08lx\n",int_mant); */ + flt_mant = (double) int_mant / FLOATING_TWO_TO_THE_TWENTYTHREE; + flt_exp = pow2 (int_exp); + return flt_mant * flt_exp; +} + +int +to_1750flt (double input, short output[2]) +{ + int exp; + long mant; + + input = dfrexp (input, &exp); + + if (exp < -128) + return -1; /* signalize underflow */ + else if (exp > 127) + return 1; /* signalize overflow */ + + if (input < 0.0 && input >= -0.5) /* prompted by UNIX frexp */ + { + input *= 2.0; + exp--; + } + + mant = (long) (input * FLOATING_TWO_TO_THE_THIRTYONE); + + /* printf("\n\tmant=%08lx\n",mant); */ + output[0] = (short) (mant >> 16); + output[1] = (short) (mant & 0xFF00) | (exp & 0xFF); + + return 0; /* success status */ +} + +double +from_1750eflt (short *input) /* input : array of 3 shorts */ +{ + long int_mant_hi, int_mant_lo; + double flt_mant, flt_exp; + signed char int_exp; + + int_exp = (signed char) (input[1] & 0xFF); + + int_mant_hi = (((long) input[0] << 16) | ((long) input[1] & 0xFF00L)) >> 8; + int_mant_lo = ((long) input[2] & 0xFFFFL); + + flt_mant = (double) int_mant_hi / FLOATING_TWO_TO_THE_TWENTYTHREE + + (double) int_mant_lo / FLOATING_TWO_TO_THE_THIRTYNINE; + flt_exp = pow2 (int_exp); +/* printf ("\tfrom: mant=%.12g, exp=%g\n", flt_mant, flt_exp); */ + + return flt_mant * flt_exp; +} + +int +to_1750eflt (double input, short output[3]) +{ + int exp; + int is_neg = 0; + ushort hlp; + + if (input < 0.0) + { + is_neg = 1; + input = -input - .03125 / FLOATING_TWO_TO_THE_THIRTYNINE; + } + + input = dfrexp (input, &exp); /* input is now normalized mantissa */ + + if (input == 1.0) /* prompted by VAX frexp */ + { + input = 0.5; + exp++; + } + + if (exp < -128) + return -1; /* signalize underflow */ + else if (exp > 127) + return 1; /* signalize overflow */ + + output[0] = (short) (input * FLOATING_TWO_TO_THE_FIFTEEN); + input -= (double) output[0] / FLOATING_TWO_TO_THE_FIFTEEN; + hlp = (ushort) (input * FLOATING_TWO_TO_THE_TWENTYTHREE); + output[1] = (short) ((hlp << 8) | (exp & 0xFF)); + input -= (double) hlp / FLOATING_TWO_TO_THE_TWENTYTHREE; + hlp = (ushort) (input * FLOATING_TWO_TO_THE_THIRTYNINE); + output[2] = (short) hlp; + + if (is_neg) + { + output[0] = ~output[0]; + output[1] = (~output[1] & 0xFF00) | (output[1] & 0x00FF); + output[2] = ~output[2]; + } + + return 0; /* success status */ +} + |