ptrtag.h
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1 /*
2  * SPDX-FileCopyrightText: 2020 Otto-von-Guericke-Universität Magdeburg
3  * SPDX-License-Identifier: LGPL-2.1-only
4  */
5 
6 #pragma once
7 
60 #include <assert.h>
61 #include <inttypes.h>
62 #include <stdint.h>
63 
64 #ifdef __cplusplus
65 extern "C" {
66 #endif
67 
73 #define PTRTAG __attribute__((aligned(4)))
74 
86 static inline void * ptrtag(void *ptr, uint8_t tag)
87 {
88  uintptr_t tmp = (uintptr_t)ptr;
89  /* ensure ptr is aligned to four bytes and tag fits in two bits */
90  assert((tag < 4) && !(tmp & 0x3));
91  return (void *)(tmp | tag);
92 }
93 
99 static inline void * ptrtag_ptr(void *tagged_ptr)
100 {
101  uintptr_t tagged = (uintptr_t)tagged_ptr;
102  const uintptr_t mask = 0x3;
103  return (void *)(tagged & (~mask));
104 }
105 
111 static inline uint8_t ptrtag_tag(void *tagged_ptr)
112 {
113  uintptr_t tagged = (uintptr_t)tagged_ptr;
114  return tagged & 0x3;
115 }
116 
117 #ifdef __cplusplus
118 }
119 #endif
120 
assert.h
POSIX.1-2008 compliant version of the assert macro.
assert
#define assert(cond)
abort the program if assertion is false
Definition: assert.h:143
ptrtag_tag
static uint8_t ptrtag_tag(void *tagged_ptr)
Extract the tag from a tagged pointer.
Definition: ptrtag.h:111
ptrtag_ptr
static void * ptrtag_ptr(void *tagged_ptr)
Extract the original pointer from a tagged pointer.
Definition: ptrtag.h:99
ptrtag
static void * ptrtag(void *ptr, uint8_t tag)
Create a tagged pointer.
Definition: ptrtag.h:86
inttypes.h
Adds include for missing inttype definitions.