[#ASN1_BIT_STRING_check]
= ASN1&lowbar;BIT&lowbar;STRING&lowbar;check
:mrdocs:

Verify that every set bit in `a` is allowed by the `flags` mask&period;

== Synopsis

Declared in `&lt;openssl&sol;asn1&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
ASN1&lowbar;BIT&lowbar;STRING&lowbar;check(
    xref:ASN1_BIT_STRING.adoc[ASN1&lowbar;BIT&lowbar;STRING] const* a,
    unsigned char const* flags,
    int flags&lowbar;len);
----

== Return Value

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

== Parameters

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


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