[#CRYPTO_memcmp]
= CRYPTO_memcmp
:mrdocs:

Compare two memory regions in constant time with respect to their contents.

== Synopsis

Declared in `<openssl/crypto.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
CRYPTO_memcmp(
    void const* in_a,
    void const* in_b,
    size_t len);
----

== Description

Runtime depends on `len` but not on the data at `in_a` / `in_b.` Unlike memcmp, the non‐zero return value must not be used to sort elements.

== Return Value

0 if the `len` bytes are equal; non‐zero otherwise (ordering is undefined).

== Parameters

[cols="1,4"]
|===
| Name| Description
| *in_a*
| First buffer.
| *in_b*
| Second buffer.
| *len*
| Number of bytes to compare.
|===


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