emacs/lib/intprops.h

/* intprops.h -- properties of integer types

   Copyright (C) 2001-2005, 2009-2011 Free Software Foundation, Inc.

   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 3 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, see <http://www.gnu.org/licenses/>.  */

/* Written by Paul Eggert.  */

#ifndef GL_INTPROPS_H
# define GL_INTPROPS_H

# include <limits.h>

/* The extra casts in the following macros work around compiler bugs,
   e.g., in Cray C 5.0.3.0.  */

/* True if the arithmetic type T is an integer type.  bool counts as
   an integer.  */
# define TYPE_IS_INTEGER(t) ((t) 1.5 == 1)

/* True if negative values of the signed integer type T use two's
   complement, ones' complement, or signed magnitude representation,
   respectively.  Much GNU code assumes two's complement, but some
   people like to be portable to all possible C hosts.  */
# define TYPE_TWOS_COMPLEMENT(t) ((t) ~ (t) 0 == (t) -1)
# define TYPE_ONES_COMPLEMENT(t) ((t) ~ (t) 0 == 0)
# define TYPE_SIGNED_MAGNITUDE(t) ((t) ~ (t) 0 < (t) -1)

/* True if the arithmetic type T is signed.  */
# define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))

/* The maximum and minimum values for the integer type T.  These
   macros have undefined behavior if T is signed and has padding bits.
   If this is a problem for you, please let us know how to fix it for
   your host.  */
# define TYPE_MINIMUM(t) \
  ((t) (! TYPE_SIGNED (t) \
        ? (t) 0 \
        : TYPE_SIGNED_MAGNITUDE (t) \
        ? ~ (t) 0 \
        : ~ TYPE_MAXIMUM (t)))
# define TYPE_MAXIMUM(t) \
  ((t) (! TYPE_SIGNED (t) \
        ? (t) -1 \
        : ((((t) 1 << (sizeof (t) * CHAR_BIT - 2)) - 1) * 2 + 1)))

/* Return zero if T can be determined to be an unsigned type.
   Otherwise, return 1.
   When compiling with GCC, INT_STRLEN_BOUND uses this macro to obtain a
   tighter bound.  Otherwise, it overestimates the true bound by one byte
   when applied to unsigned types of size 2, 4, 16, ... bytes.
   The symbol signed_type_or_expr__ is private to this header file.  */
# if __GNUC__ >= 2
#  define signed_type_or_expr__(t) TYPE_SIGNED (__typeof__ (t))
# else
#  define signed_type_or_expr__(t) 1
# endif

/* Bound on length of the string representing an unsigned integer
   value representable in B bits.  log10 (2.0) < 146/485.  The
   smallest value of B where this bound is not tight is 2621.  */
# define INT_BITS_STRLEN_BOUND(b) (((b) * 146 + 484) / 485)

/* Bound on length of the string representing an integer type or expression T.
   Subtract 1 for the sign bit if T is signed, and then add 1 more for
   a minus sign if needed.  */
# define INT_STRLEN_BOUND(t) \
  (INT_BITS_STRLEN_BOUND (sizeof (t) * CHAR_BIT - signed_type_or_expr__ (t)) \
   + signed_type_or_expr__ (t))

/* Bound on buffer size needed to represent an integer type or expression T,
   including the terminating null.  */
# define INT_BUFSIZE_BOUND(t) (INT_STRLEN_BOUND (t) + 1)

#endif /* GL_INTPROPS_H */