сравнить области памяти (compare memory areas)
Имя (Name)
memcmp - compare memory areas
Синопсис (Synopsis)
#include <string.h>
int memcmp(const void *s1, const void *s2, size_t n);
Описание (Description)
The memcmp() function compares the first n bytes (each
interpreted as unsigned char) of the memory areas s1 and s2.
Возвращаемое значение (Return value)
The memcmp() function returns an integer less than, equal to, or
greater than zero if the first n bytes of s1 is found,
respectively, to be less than, to match, or be greater than the
first n bytes of s2.
For a nonzero return value, the sign is determined by the sign of
the difference between the first pair of bytes (interpreted as
unsigned char) that differ in s1 and s2.
If n is zero, the return value is zero.
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│memcmp() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
Стандарты (Conforming to)
POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.
Примечание (Note)
Do not use memcmp() to compare security critical data, such as
cryptographic secrets, because the required CPU time depends on
the number of equal bytes. Instead, a function that performs
comparisons in constant time is required. Some operating systems
provide such a function (e.g., NetBSD's consttime_memequal()),
but no such function is specified in POSIX. On Linux, it may be
necessary to implement such a function oneself.
Смотри также (See also)
bcmp(3), bstring(3), strcasecmp(3), strcmp(3), strcoll(3),
strncasecmp(3), strncmp(3), wmemcmp(3)
