include/libc-pointer-arith.h

   1 /* Helper macros for pointer arithmetic.
   2    Copyright (C) 2012-2021 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 _LIBC_POINTER_ARITH_H
  20 #define _LIBC_POINTER_ARITH_H 1
  21
  22 #include <stdint.h>
  23
  24 /* 1 if 'type' is a pointer type, 0 otherwise.  */
  25 # define __pointer_type(type) (__builtin_classify_type ((type) 0) == 5)
  26
  27 /* intptr_t if P is true, or T if P is false.  */
  28 # define __integer_if_pointer_type_sub(T, P) \
  29   __typeof__ (*(0 ? (__typeof__ (0 ? (T *) 0 : (void *) (P))) 0 \
  30                   : (__typeof__ (0 ? (intptr_t *) 0 : (void *) (!(P)))) 0))
  31
  32 /* intptr_t if EXPR has a pointer type, or the type of EXPR otherwise.  */
  33 # define __integer_if_pointer_type(expr) \
  34   __integer_if_pointer_type_sub(__typeof__ ((__typeof__ (expr)) 0), \
  35                                 __pointer_type (__typeof__ (expr)))
  36
  37 /* Cast an integer or a pointer VAL to integer with proper type.  */
  38 # define cast_to_integer(val) ((__integer_if_pointer_type (val)) (val))
  39
  40 /* Cast an integer VAL to void * pointer.  */
  41 # define cast_to_pointer(val) ((void *) (uintptr_t) (val))
  42
  43 /* Align a value by rounding down to closest size.
  44    e.g. Using size of 4096, we get this behavior:
  45         {4095, 4096, 4097} = {0, 4096, 4096}.  */
  46 #define ALIGN_DOWN(base, size)  ((base) & -((__typeof__ (base)) (size)))
  47
  48 /* Align a value by rounding up to closest size.
  49    e.g. Using size of 4096, we get this behavior:
  50         {4095, 4096, 4097} = {4096, 4096, 8192}.
  51
  52   Note: The size argument has side effects (expanded multiple times).  */
  53 #define ALIGN_UP(base, size)    ALIGN_DOWN ((base) + (size) - 1, (size))
  54
  55 /* Same as ALIGN_DOWN(), but automatically casts when base is a pointer.  */
  56 #define PTR_ALIGN_DOWN(base, size) \
  57   ((__typeof__ (base)) ALIGN_DOWN ((uintptr_t) (base), (size)))
  58
  59 /* Same as ALIGN_UP(), but automatically casts when base is a pointer.  */
  60 #define PTR_ALIGN_UP(base, size) \
  61   ((__typeof__ (base)) ALIGN_UP ((uintptr_t) (base), (size)))
  62
  63 #endif