[#BIO_nwrite]
= BIO_nwrite
:mrdocs:

Obtain a writable buffer from a memory BIO and advance its write pointer.

== Synopsis

Declared in `<openssl/bio.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
BIO_nwrite(
    xref:BIO.adoc[BIO]* bio,
    char** buf,
    int num);
----

== Return Value

Number of bytes made available at *`buf,` or a negative value on error.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *bio*
| Memory BIO to write into.
| *buf*
| Receives a pointer into the BIO's internal buffer.
| *num*
| Maximum number of bytes to reserve.
|===


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