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106 lines
2.5 KiB
C
106 lines
2.5 KiB
C
/*
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* Copyright (C) 2019 Kaspar Schleiser <kaspar@schleiser.de>
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @defgroup sys_unaligned unaligned memory access methods
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* @ingroup sys
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* @brief Provides functions for safe unaligned memory accesses
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*
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* This header provides functions to read values from pointers that are not
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* necessarily aligned to the type's alignment requirements.
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*
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* E.g.,
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*
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* uint16_t *foo = 0x123;
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* printf("%u\n", *foo);
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*
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* ... might cause an unaligned access, if `uint16_t` is usually aligned at
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* 2-byte-boundaries, as foo has an odd address.
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*
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* The current implementation casts a pointer to a packed struct, which forces
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* the compiler to deal with possibly unalignedness. Idea taken from linux
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* kernel sources.
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*
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* @{
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*
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* @file
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* @brief Unaligned but safe memory access functions
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*
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* @author Kaspar Schleiser <kaspar@schleiser.de>
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*/
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#ifndef UNALIGNED_H
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#define UNALIGNED_H
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/** @brief Unaligned access helper struct (uint16_t version) */
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typedef struct __attribute__((packed)) {
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uint16_t val; /**< value */
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} uint16_una_t;
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/** @brief Unaligned access helper struct (uint32_t version) */
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typedef struct __attribute__((packed)) {
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uint32_t val; /**< value */
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} uint32_una_t;
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/** @brief Unaligned access helper struct (uint64_t version) */
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typedef struct __attribute__((packed)) {
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uint64_t val; /**< value */
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} uint64_una_t;
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/**
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* @brief Get uint16_t from possibly unaligned pointer
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*
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* @param[in] ptr pointer to read from
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*
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* @returns value read from @p ptr
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*/
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static inline uint16_t unaligned_get_u16(const void *ptr)
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{
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const uint16_una_t *tmp = (const uint16_una_t *)ptr;
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return tmp->val;
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}
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/**
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* @brief Get uint32_t from possibly unaligned pointer
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*
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* @param[in] ptr pointer to read from
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*
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* @returns value read from @p ptr
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*/
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static inline uint32_t unaligned_get_u32(const void *ptr)
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{
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const uint32_una_t *tmp = (const uint32_una_t *)ptr;
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return tmp->val;
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}
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/**
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* @brief Get uint64_t from possibly unaligned pointer
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*
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* @param[in] ptr pointer to read from
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*
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* @returns value read from @p ptr
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*/
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static inline uint64_t unaligned_get_u64(const void *ptr)
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{
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const uint64_una_t *tmp = (const uint64_una_t *)ptr;
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return tmp->val;
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}
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#ifdef __cplusplus
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}
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#endif
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/** @} */
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#endif /* UNALIGNED_H */
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