diff options
Diffstat (limited to 'gsl-1.9/ieee-utils/make_rep.c')
| -rw-r--r-- | gsl-1.9/ieee-utils/make_rep.c | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/gsl-1.9/ieee-utils/make_rep.c b/gsl-1.9/ieee-utils/make_rep.c new file mode 100644 index 0000000..59bf861 --- /dev/null +++ b/gsl-1.9/ieee-utils/make_rep.c @@ -0,0 +1,197 @@ +/* ieee-utils/make_rep.c + * + * Copyright (C) 1996, 1997, 1998, 1999, 2000 Brian Gough + * + * 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, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + */ + +#include <config.h> +#include <gsl/gsl_ieee_utils.h> + +#include "endian.c" +#include "standardize.c" + +static void sprint_nybble(int i, char *s) ; +static void sprint_byte(int i, char *s) ; +static int determine_ieee_type (int non_zero, int exponent, int max_exponent); + + +/* For the IEEE float format the bits are found from the following + masks, + + sign = 0x80000000 + exponent = 0x7f800000 + mantisssa = 0x007fffff + + For the IEEE double format the masks are, + + sign = 0x8000000000000000 + exponent = 0x7ff0000000000000 + mantissa = 0x000fffffffffffff + + */ + +void +gsl_ieee_float_to_rep (const float * x, gsl_ieee_float_rep * r) +{ + int e, non_zero; + + union { + float f; + struct { + unsigned char byte[4] ; + } ieee ; + } u; + + u.f = *x ; + + if (little_endian_p()) + make_float_bigendian(&(u.f)) ; + + /* note that r->sign is signed, u.ieee.byte is unsigned */ + + if (u.ieee.byte[3]>>7) + { + r->sign = 1 ; + } + else + { + r->sign = 0 ; + } + + e = (u.ieee.byte[3] & 0x7f) << 1 | (u.ieee.byte[2] & 0x80)>>7 ; + + r->exponent = e - 127 ; + + sprint_byte((u.ieee.byte[2] & 0x7f) << 1,r->mantissa) ; + sprint_byte(u.ieee.byte[1],r->mantissa + 7) ; + sprint_byte(u.ieee.byte[0],r->mantissa + 15) ; + + r->mantissa[23] = '\0' ; + + non_zero = u.ieee.byte[0] || u.ieee.byte[1] || (u.ieee.byte[2] & 0x7f); + + r->type = determine_ieee_type (non_zero, e, 255) ; +} + +void +gsl_ieee_double_to_rep (const double * x, gsl_ieee_double_rep * r) +{ + + int e, non_zero; + + union + { + double d; + struct { + unsigned char byte[8]; + } ieee ; + } u; + + u.d= *x ; + + if (little_endian_p()) + make_double_bigendian(&(u.d)) ; + + /* note that r->sign is signed, u.ieee.byte is unsigned */ + + if (u.ieee.byte[7]>>7) + { + r->sign = 1 ; + } + else + { + r->sign = 0 ; + } + + + e =(u.ieee.byte[7] & 0x7f)<<4 ^ (u.ieee.byte[6] & 0xf0)>>4 ; + + r->exponent = e - 1023 ; + + sprint_nybble(u.ieee.byte[6],r->mantissa) ; + sprint_byte(u.ieee.byte[5],r->mantissa + 4) ; + sprint_byte(u.ieee.byte[4],r->mantissa + 12) ; + sprint_byte(u.ieee.byte[3],r->mantissa + 20) ; + sprint_byte(u.ieee.byte[2],r->mantissa + 28) ; + sprint_byte(u.ieee.byte[1],r->mantissa + 36) ; + sprint_byte(u.ieee.byte[0],r->mantissa + 44) ; + + r->mantissa[52] = '\0' ; + + non_zero = (u.ieee.byte[0] || u.ieee.byte[1] || u.ieee.byte[2] + || u.ieee.byte[3] || u.ieee.byte[4] || u.ieee.byte[5] + || (u.ieee.byte[6] & 0x0f)) ; + + r->type = determine_ieee_type (non_zero, e, 2047) ; +} + +/* A table of character representations of nybbles */ + +static char nybble[16][5]={ /* include space for the \0 */ + "0000", "0001", "0010", "0011", + "0100", "0101", "0110", "0111", + "1000", "1001", "1010", "1011", + "1100", "1101", "1110", "1111" +} ; + +static void +sprint_nybble(int i, char *s) +{ + char *c ; + c=nybble[i & 0x0f ]; + *s=c[0] ; *(s+1)=c[1] ; *(s+2)=c[2] ; *(s+3)=c[3] ; +} + +static void +sprint_byte(int i, char *s) +{ + char *c ; + c=nybble[(i & 0xf0)>>4]; + *s=c[0] ; *(s+1)=c[1] ; *(s+2)=c[2] ; *(s+3)=c[3] ; + c=nybble[i & 0x0f]; + *(s+4)=c[0] ; *(s+5)=c[1] ; *(s+6)=c[2] ; *(s+7)=c[3] ; +} + +static int +determine_ieee_type (int non_zero, int exponent, int max_exponent) +{ + if (exponent == max_exponent) + { + if (non_zero) + { + return GSL_IEEE_TYPE_NAN ; + } + else + { + return GSL_IEEE_TYPE_INF ; + } + } + else if (exponent == 0) + { + if (non_zero) + { + return GSL_IEEE_TYPE_DENORMAL ; + } + else + { + return GSL_IEEE_TYPE_ZERO ; + } + } + else + { + return GSL_IEEE_TYPE_NORMAL ; + } +} |