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ptrtag.h
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1/*
2 * Copyright (C) 2020 Otto-von-Guericke-Universität Magdeburg
3 *
4 * This file is subject to the terms and conditions of the GNU Lesser General
5 * Public License v2.1. See the file LICENSE in the top level directory for more
6 * details.
7 */
8
61#ifndef PTRTAG_H
62#define PTRTAG_H
63
64#include <assert.h>
65#include <inttypes.h>
66#include <stdint.h>
67
68#ifdef __cplusplus
69extern "C" {
70#endif
71
77#define PTRTAG __attribute__((aligned(4)))
78
90static inline void * ptrtag(void *ptr, uint8_t tag)
91{
92 uintptr_t tmp = (uintptr_t)ptr;
93 /* ensure ptr is aligned to four bytes and tag fits in two bits */
94 assert((tag < 4) && !(tmp & 0x3));
95 return (void *)(tmp | tag);
96}
97
103static inline void * ptrtag_ptr(void *tagged_ptr)
104{
105 uintptr_t tagged = (uintptr_t)tagged_ptr;
106 const uintptr_t mask = 0x3;
107 return (void *)(tagged & (~mask));
108}
109
115static inline uint8_t ptrtag_tag(void *tagged_ptr)
116{
117 uintptr_t tagged = (uintptr_t)tagged_ptr;
118 return tagged & 0x3;
119}
120
121#ifdef __cplusplus
122}
123#endif
124
125#endif /* PTRTAG_H */
POSIX.1-2008 compliant version of the assert macro.
#define assert(cond)
abort the program if assertion is false
Definition assert.h:136
static uint8_t ptrtag_tag(void *tagged_ptr)
Extract the tag from a tagged pointer.
Definition ptrtag.h:115
static void * ptrtag_ptr(void *tagged_ptr)
Extract the original pointer from a tagged pointer.
Definition ptrtag.h:103
static void * ptrtag(void *ptr, uint8_t tag)
Create a tagged pointer.
Definition ptrtag.h:90
Adds include for missing inttype definitions.