lib/intprops.h

   1 /* intprops.h -- properties of integer types
   2
   3    Copyright (C) 2001-2005, 2009-2011 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program 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
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Paul Eggert.  */
  19
  20 #ifndef GL_INTPROPS_H
  21 # define GL_INTPROPS_H
  22
  23 # include <limits.h>
  24
  25 /* The extra casts in the following macros work around compiler bugs,
  26    e.g., in Cray C 5.0.3.0.  */
  27
  28 /* True if the arithmetic type T is an integer type.  bool counts as
  29    an integer.  */
  30 # define TYPE_IS_INTEGER(t) ((t) 1.5 == 1)
  31
  32 /* True if negative values of the signed integer type T use two's
  33    complement, ones' complement, or signed magnitude representation,
  34    respectively.  Much GNU code assumes two's complement, but some
  35    people like to be portable to all possible C hosts.  */
  36 # define TYPE_TWOS_COMPLEMENT(t) ((t) ~ (t) 0 == (t) -1)
  37 # define TYPE_ONES_COMPLEMENT(t) ((t) ~ (t) 0 == 0)
  38 # define TYPE_SIGNED_MAGNITUDE(t) ((t) ~ (t) 0 < (t) -1)
  39
  40 /* True if the arithmetic type T is signed.  */
  41 # define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
  42
  43 /* The maximum and minimum values for the integer type T.  These
  44    macros have undefined behavior if T is signed and has padding bits.
  45    If this is a problem for you, please let us know how to fix it for
  46    your host.  */
  47 # define TYPE_MINIMUM(t) \
  48   ((t) (! TYPE_SIGNED (t) \
  49         ? (t) 0 \
  50         : TYPE_SIGNED_MAGNITUDE (t) \
  51         ? ~ (t) 0 \
  52         : ~ TYPE_MAXIMUM (t)))
  53 # define TYPE_MAXIMUM(t) \
  54   ((t) (! TYPE_SIGNED (t) \
  55         ? (t) -1 \
  56         : ((((t) 1 << (sizeof (t) * CHAR_BIT - 2)) - 1) * 2 + 1)))
  57
  58 /* Return zero if T can be determined to be an unsigned type.
  59    Otherwise, return 1.
  60    When compiling with GCC, INT_STRLEN_BOUND uses this macro to obtain a
  61    tighter bound.  Otherwise, it overestimates the true bound by one byte
  62    when applied to unsigned types of size 2, 4, 16, ... bytes.
  63    The symbol signed_type_or_expr__ is private to this header file.  */
  64 # if __GNUC__ >= 2
  65 #  define signed_type_or_expr__(t) TYPE_SIGNED (__typeof__ (t))
  66 # else
  67 #  define signed_type_or_expr__(t) 1
  68 # endif
  69
  70 /* Bound on length of the string representing an unsigned integer
  71    value representable in B bits.  log10 (2.0) < 146/485.  The
  72    smallest value of B where this bound is not tight is 2621.  */
  73 # define INT_BITS_STRLEN_BOUND(b) (((b) * 146 + 484) / 485)
  74
  75 /* Bound on length of the string representing an integer type or expression T.
  76    Subtract 1 for the sign bit if T is signed, and then add 1 more for
  77    a minus sign if needed.  */
  78 # define INT_STRLEN_BOUND(t) \
  79   (INT_BITS_STRLEN_BOUND (sizeof (t) * CHAR_BIT - signed_type_or_expr__ (t)) \
  80    + signed_type_or_expr__ (t))
  81
  82 /* Bound on buffer size needed to represent an integer type or expression T,
  83    including the terminating null.  */
  84 # define INT_BUFSIZE_BOUND(t) (INT_STRLEN_BOUND (t) + 1)
  85
  86 #endif /* GL_INTPROPS_H */