libc-pointer-arith.h (2866B) - Raw
1 /* Helper macros for pointer arithmetic. 2 Copyright (C) 2012-2025 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 /* Check if BASE is aligned on SIZE */ 64 #define PTR_IS_ALIGNED(base, size) \ 65 ((((uintptr_t) (base)) & (size - 1)) == 0) 66 67 /* Returns the ptrdiff_t difference between P1 and P2. */ 68 #define PTR_DIFF(p1, p2) \ 69 ((ptrdiff_t)((uintptr_t)(p1) - (uintptr_t)(p2))) 70 71 #endif