[#ASN1_BIT_STRING_check]
= ASN1_BIT_STRING_check
:mrdocs:

Verify that every set bit in `a` is allowed by the `flags` mask.

== Synopsis

Declared in `<openssl/asn1.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
ASN1_BIT_STRING_check(
    xref:ASN1_BIT_STRING.adoc[ASN1_BIT_STRING] const* a,
    unsigned char const* flags,
    int flags_len);
----

== Return Value

1 if all set bits are allowed (or `a` is empty), or 0 if any disallowed bit is set.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *a*
| Bit string to check; NULL or empty is treated as valid.
| *flags*
| Byte mask of permitted bits (1 = allowed).
| *flags_len*
| Length of `flags` in bytes.
|===


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