/*
 * safe_mem.h
 *
 * A header-only library (macro collection) for safer memory management.
 *
 * Author: Intel A80486DX2-66
 * License: Creative Commons Zero 1.0 Universal
 */

#ifndef _SAFE_MEM_H
#define _SAFE_MEM_H

#include <stdlib.h>

#define SAFE_FREE_ERROR_HOOK /* user-defined */

#define safe_free(ptr) do {                                                   \
    /* prevents NULL-freeing and double freeing */                            \
    if (ptr != NULL) {                                                        \
        free(ptr);                                                            \
        ptr = NULL;                                                           \
    } else { SAFE_FREE_ERROR_HOOK; }                                          \
} while (0)

#define precise_malloc(nmemb, size)                                           \
    /* prevents incorrect casting */                                          \
    malloc((size_t) nmemb * (size_t) size)

/* secure_erase(dest, count): erases memory explicitly */
#if defined(__FreeBSD__)
# define NO_SECURE_ERASE_WARRANTY 0
# define SECURE_ERASE_WARRANTY "OpenBSD/FreeBSD: explicit_bzero"

# include <strings.h>
# define secure_erase explicit_bzero
#elif defined(_WIN32)
# define NO_SECURE_ERASE_WARRANTY 0
# define SECURE_ERASE_WARRANTY "Microsoft Windows: SecureZeroMemory"

# include <windows.h>
# define secure_erase SecureZeroMemory
#elif defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L)
# define NO_SECURE_ERASE_WARRANTY 0
# define SECURE_ERASE_WARRANTY "C11+: memset_s"

# define secure_erase(dest, count) memset_s(dest, count, 0, count)
#else
# define NO_SECURE_ERASE_WARRANTY 1

# define __observe__(ptr) do {                                                \
    if (*ptr == 0) {                                                          \
        ++(*ptr);                                                             \
        fprintf(stderr, "");                                                  \
    } else                                                                    \
        --(*ptr);                                                             \
} while (0)

# define secure_erase(dest, count) do {                                       \
    memset(dest, 0, count);                                                   \
    for (size_t i = 0; i < count; i++)                                        \
        __observe__(dest[i]);                                                 \
} while (0)
#endif

#endif /* _SAFE_MEM_H */