formats/ctf/types/float.c

   1 /*
   2  * Common Trace Format
   3  *
   4  * Floating point read/write functions.
   5  *
   6  * Copyright (c) 2010 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  *
  22  * Reference: ISO C99 standard 5.2.4
  23  */
  24
  25 #include <babeltrace/ctf/types.h>
  26 #include <glib.h>
  27 #include <float.h>      /* C99 floating point definitions */
  28 #include <limits.h>     /* C99 limits */
  29 #include <endian.h>
  30
  31 /*
  32  * This library is limited to binary representation of floating point values.
  33  * Sign-extension of the exponents is assumed to keep the NaN, +inf, -inf
  34  * values, but this should be double-checked (TODO).
  35  */
  36
  37 /*
  38  * Aliasing float/double and unsigned long is not strictly permitted by strict
  39  * aliasing, but in practice type prunning is well supported, and this permits
  40  * us to use per-word read/writes rather than per-byte.
  41  */
  42
  43 #if defined(__GNUC__) || defined(__MINGW32__) || defined(_MSC_VER)
  44 #define HAS_TYPE_PRUNING
  45 #endif
  46
  47 #if (FLT_RADIX != 2)
  48
  49 #error "Unsupported floating point radix"
  50
  51 #endif
  52
  53 union doubleIEEE754 {
  54         double v;
  55 #ifdef HAS_TYPE_PRUNING
  56         unsigned long bits[(sizeof(double) + sizeof(unsigned long) - 1) / sizeof(unsigned long)];
  57 #else
  58         unsigned char bits[sizeof(double)];
  59 #endif
  60 };
  61
  62 union ldoubleIEEE754 {
  63         long double v;
  64 #ifdef HAS_TYPE_PRUNING
  65         unsigned long bits[(sizeof(long double) + sizeof(unsigned long) - 1) / sizeof(unsigned long)];
  66 #else
  67         unsigned char bits[sizeof(long double)];
  68 #endif
  69 };
  70
  71 struct pos_len {
  72         size_t sign_start, exp_start, mantissa_start, len;
  73 };
  74
  75 void _ctf_float_copy(struct stream_pos *destp,
  76                      const struct type_class_float *dest_class,
  77                      struct stream_pos *srcp,
  78                      const struct type_class_float *src_class)
  79 {
  80         uint8_t sign;
  81         int64_t exp;
  82         uint64_t mantissa;
  83
  84         /* Read */
  85         if (src->byte_order == LITTLE_ENDIAN) {
  86                 mantissa = ctf_uint_read(srcp, src_class->mantissa);
  87                 exp = ctf_int_read(srcp, src_class->exp);
  88                 sign = ctf_uint_read(srcp, src_class->sign);
  89         } else {
  90                 sign = ctf_uint_read(srcp, src_class->sign);
  91                 exp = ctf_int_read(srcp, src_class->exp);
  92                 mantissa = ctf_uint_read(srcp, src_class->mantissa);
  93         }
  94         /* Write */
  95         if (dest->byte_order == LITTLE_ENDIAN) {
  96                 ctf_uint_write(destp, dest_class->mantissa, mantissa);
  97                 ctf_int_write(destp, dest_class->exp, exp);
  98                 ctf_uint_write(destp, dest_class->sign, sign);
  99         } else {
 100                 ctf_uint_write(destp, dest_class->sign, sign);
 101                 ctf_int_write(destp, dest_class->exp, exp);
 102                 ctf_uint_write(destp, dest_class->mantissa, mantissa);
 103         }
 104 }
 105
 106 void ctf_float_copy(struct stream_pos *dest, struct stream_pos *src,
 107                     const struct type_class_float *float_class)
 108 {
 109         align_pos(src, float_class->p.alignment);
 110         align_pos(dest, float_class->p.alignment);
 111         _ctf_float_copy(dest, float_class, src, float_class);
 112 }
 113
 114 double ctf_double_read(struct stream_pos *srcp,
 115                        const struct type_class_float *float_class)
 116 {
 117         union doubleIEEE754 u;
 118         struct ctf_float *dest_class = float_type_new(NULL,
 119                                 DBL_MANT_DIG,
 120                                 sizeof(double) * CHAR_BIT - DBL_MANT_DIG,
 121                                 BYTE_ORDER,
 122                                 __alignof__(double));
 123         struct stream_pos destp;
 124
 125         align_pos(srcp, float_class->p.alignment);
 126         init_pos(&destp, &u.bits);
 127         _ctf_float_copy(&destp, dest_class, srcp, float_class);
 128         float_type_free(dest_class);
 129         return u.v;
 130 }
 131
 132 void ctf_double_write(struct stream_pos *destp,
 133                       const struct type_class_float *float_class,
 134                       double v)
 135 {
 136         union doubleIEEE754 u;
 137         struct ctf_float *src_class = float_type_new(NULL,
 138                                 DBL_MANT_DIG,
 139                                 sizeof(double) * CHAR_BIT - DBL_MANT_DIG,
 140                                 BYTE_ORDER,
 141                                 __alignof__(double));
 142         struct stream_pos srcp;
 143
 144         u.v = v;
 145         align_pos(destp, float_class->p.alignment);
 146         init_pos(&srcp, &u.bits);
 147         _ctf_float_copy(destp, float_class, &srcp, src_class);
 148         float_type_free(src_class);
 149 }
 150
 151 long double ctf_ldouble_read(struct stream_pos *srcp,
 152                              const struct type_class_float *float_class)
 153 {
 154         union ldoubleIEEE754 u;
 155         struct ctf_float *dest_class = float_type_new(NULL,
 156                                 LDBL_MANT_DIG,
 157                                 sizeof(long double) * CHAR_BIT - LDBL_MANT_DIG,
 158                                 BYTE_ORDER,
 159                                 __alignof__(long double));
 160         struct stream_pos destp;
 161
 162         align_pos(srcp, float_class->p.alignment);
 163         init_pos(&destp, &u.bits);
 164         _ctf_float_copy(&destp, dest_class, srcp, float_class);
 165         float_type_free(dest_class);
 166         return u.v;
 167 }
 168
 169 void ctf_ldouble_write(struct stream_pos *destp,
 170                        const struct type_class_float *float_class,
 171                        long double v)
 172 {
 173         union ldoubleIEEE754 u;
 174         struct ctf_float *src_class = float_type_new(NULL,
 175                                 LDBL_MANT_DIG,
 176                                 sizeof(long double) * CHAR_BIT - LDBL_MANT_DIG,
 177                                 BYTE_ORDER,
 178                                 __alignof__(long double));
 179         struct stream_pos srcp;
 180
 181         u.v = v;
 182         align_pos(destp, float_class->p.alignment);
 183         init_pos(&srcp, &u.bits);
 184         _ctf_float_copy(destp, float_class, &srcp, src_class);
 185         float_type_free(src_class);
 186 }