string_utils.h

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/*
 * SPDX-FileCopyrightText: 2022 Otto-von-Guericke-Universität Magdeburg
 * SPDX-FileCopyrightText: 2022-2026 ML!PA Consulting GmbH
 * SPDX-License-Identifier: LGPL-2.1-only
 */
 
#pragma once

 
#include <assert.h>
#include <stdint.h>
/* if explicit_bzero() is provided by standard C lib, it may be defined in
 * either `string.h` or `strings.h`, so just include both here */
#include <string.h>
#include <strings.h>
#include <sys/types.h>
 
#include "compiler_hints.h"
#include "flash_utils.h"
#include "modules.h"
 
#ifdef __cplusplus
extern "C" {
#endif

typedef struct {
    const char *start;  
    char *position;     
    size_t capacity;    
} string_writer_t;

ACCESS(write_only, 2, 3)
static inline void string_writer_init(string_writer_t *sw, void *buffer, size_t len)
{
    assert(buffer && len);
 
    sw->start = buffer;
    sw->position = buffer;
    sw->capacity = len;
    sw->position[0] = 0;
}

static inline size_t string_writer_len(const string_writer_t *sw)
{
    return sw->position - sw->start;
}

static inline const char *string_writer_str(const string_writer_t *sw)
{
    return sw->start;
}
 
#ifndef DOXYGEN
#  if IS_ACTIVE(HAS_FLASH_UTILS_ARCH)
#    define __swprintf flash_swprintf
#  else
#    define __swprintf swprintf
__attribute__((format(printf, 2, 3)))
#  endif
int __swprintf(string_writer_t *sw, FLASH_ATTR const char *restrict format, ...);
#else
int swprintf(string_writer_t *sw, FLASH_ATTR const char *restrict format, ...);
#endif /* DOXYGEN */
 
#if IS_ACTIVE(HAS_FLASH_UTILS_ARCH)
#  define swprintf(sw, fmt, ...) flash_swprintf(sw, TO_FLASH(fmt), ##__VA_ARGS__)
#endif
 
/* explicit_bzero is provided if:
 * - glibc is used as C lib (only with board natvie)
 * - newlib is used and __BSD_VISIBLE is set
 *      - except for ESP8266, which is using an old version of newlib without it
 * - picolibc is used and __BSD_VISIBLE is set
 *
 * for all other cases, we provide it here
 */
#if !defined(CPU_NATIVE) \
    && !(IS_USED(MODULE_PICOLIBC) && __BSD_VISIBLE) \
    && !(IS_USED(MODULE_NEWLIB) && __BSD_VISIBLE && !defined(CPU_ESP8266))

static inline void explicit_bzero(void *dest, size_t n_bytes)
{
    volatile uint8_t *tmp = dest;
    for (size_t i = 0; i < n_bytes; i++) {
        tmp[i] = 0;
    }
}
#endif

ACCESS(write_only, 1, 3)
ssize_t strscpy(char *dest, const char *src, size_t count);

ACCESS(read_only, 1, 3)
const void *memchk(const void *data, uint8_t c, size_t len);

ACCESS(read_write, 1, 2)
void reverse_buf(void *buf, size_t len);

ACCESS(read_write, 1, 3)
ACCESS(read_only, 2, 3)
void memxor(void *dst, void *src, size_t size);

ACCESS(write_only, 1, 3)
ACCESS(read_only, 2, 3)
void memcpy_reversed(void *restrict dst, const void *restrict src, size_t size);
 
#ifdef __cplusplus
}
#endif