stdlib/fpioconst.h

   1 /* Header file for constants used in floating point <-> decimal conversions.
   2    Copyright (C) 1995-2023 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _FPIOCONST_H
  20 #define _FPIOCONST_H
  21
  22 #include <float.h>
  23 #include <math.h>
  24 #include <gmp.h>
  25
  26
  27 /* These values are used by __printf_fp, where they are noncritical (if the
  28    value is not large enough, it will just be slower); and by
  29    strtof/strtod/strtold, where it is critical (it's used for overflow
  30    detection).
  31
  32    XXX These should be defined in <float.h>.  For the time being, we have the
  33    IEEE754 values here.  */
  34
  35 #if !defined __NO_LONG_DOUBLE_MATH && __LDBL_MAX_EXP__ > 1024
  36 # define LDBL_MAX_10_EXP_LOG    12 /* = floor(log_2(LDBL_MAX_10_EXP)) */
  37 #else
  38 # define LDBL_MAX_10_EXP_LOG    8 /* = floor(log_2(LDBL_MAX_10_EXP)) */
  39 #endif
  40 #define DBL_MAX_10_EXP_LOG      8 /* = floor(log_2(DBL_MAX_10_EXP)) */
  41 #define FLT_MAX_10_EXP_LOG      5 /* = floor(log_2(FLT_MAX_10_EXP)) */
  42
  43 /* On some machines, _Float128 may be ABI-distinct from long double (e.g
  44    IBM extended precision).  */
  45 #include <bits/floatn.h>
  46
  47 #if __HAVE_DISTINCT_FLOAT128
  48 # define FLT128_MAX_10_EXP_LOG  12 /* = floor(log_2(FLT128_MAX_10_EXP)) */
  49 #endif
  50
  51 /* For strtold, we need powers of 10 up to floor (log_2 (LDBL_MANT_DIG
  52    - LDBL_MIN_EXP + 2)).  When _Float128 is enabled in libm and it is
  53    ABI-distinct from long double (e.g. on powerpc64le), we also need powers
  54    of 10 up to floor (log_2 (FLT128_MANT_DIG - FLT128_MIN_EXP + 2)).  */
  55 #if (!defined __NO_LONG_DOUBLE_MATH && __LDBL_MAX_EXP__ > 1024) \
  56     || __HAVE_DISTINCT_FLOAT128
  57 # define FPIOCONST_HAVE_EXTENDED_RANGE 1
  58 #else
  59 # define FPIOCONST_HAVE_EXTENDED_RANGE 0
  60 #endif
  61
  62 #if FPIOCONST_HAVE_EXTENDED_RANGE
  63 # define FPIOCONST_POW10_ARRAY_SIZE     15
  64 #else
  65 # define FPIOCONST_POW10_ARRAY_SIZE     11
  66 #endif
  67
  68 /* The array with the number representation. */
  69 extern const mp_limb_t __tens[] attribute_hidden;
  70
  71 /* Table of powers of ten.  This is used by __printf_fp and by
  72    strtof/strtod/strtold.  */
  73 struct mp_power
  74   {
  75     size_t arrayoff;            /* Offset in `__tens'.  */
  76     mp_size_t arraysize;        /* Size of the array.  */
  77     int p_expo;                 /* Exponent of the number 10^(2^i).  */
  78     int m_expo;                 /* Exponent of the number 10^-(2^i-1).  */
  79   };
  80 extern const struct mp_power _fpioconst_pow10[FPIOCONST_POW10_ARRAY_SIZE]
  81      attribute_hidden;
  82
  83 /* The constants in the array `_fpioconst_pow10' have an offset.  */
  84 #if BITS_PER_MP_LIMB == 32
  85 # define _FPIO_CONST_OFFSET     2
  86 #else
  87 # define _FPIO_CONST_OFFSET     1
  88 #endif
  89
  90
  91 #endif  /* fpioconst.h */