[#BIO_asn1_get_prefix]
= BIO_asn1_get_prefix
:mrdocs:

Retrieve the ASN.1 prefix producer and optional free callback from a BIO.

== Synopsis

Declared in `<openssl/bio.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
BIO_asn1_get_prefix(
    xref:BIO.adoc[BIO]* b,
    xref:asn1_ps_func.adoc[asn1_ps_func]** pprefix,
    xref:asn1_ps_func.adoc[asn1_ps_func]** pprefix_free);
----

== Return Value

1 on success, or 0 on failure.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *b*
| ASN.1 filter BIO (BIO_f_asn1).
| *pprefix*
| Receives the prefix producer, or NULL if unset.
| *pprefix_free*
| Receives the matching free callback, or NULL if unset.
|===


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