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.\" ========================================================================
.\"
.IX Title "BIO_S_CORE 3ossl"
.TH BIO_S_CORE 3ossl "2026-01-16" "3.5.1" "OpenSSL"
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.SH "NAME"
BIO_s_core, BIO_new_from_core_bio \- OSSL_CORE_BIO functions
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/bio.h>
\&
\& const BIO_METHOD *BIO_s_core(void);
\&
\& BIO *BIO_new_from_core_bio(OSSL_LIB_CTX *libctx, OSSL_CORE_BIO *corebio);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBBIO_s_core()\fR returns the core \s-1BIO\s0 method function.
.PP
A core \s-1BIO\s0 is treated as source/sink \s-1BIO\s0 which communicates to some external
\&\s-1BIO.\s0 This is primarily useful to provider authors. A number of calls from
libcrypto into a provider supply an \s-1OSSL_CORE_BIO\s0 parameter. This represents
a \s-1BIO\s0 within libcrypto, but cannot be used directly by a provider. Instead it
should be wrapped using a \fBBIO_s_core()\fR.
.PP
Once a \s-1BIO\s0 is constructed based on \fBBIO_s_core()\fR, the associated \s-1OSSL_CORE_BIO\s0
object should be set on it using \fBBIO_set_data\fR\|(3). Note that the \s-1BIO\s0 will only
operate correctly if it is associated with a library context constructed using
\&\fBOSSL_LIB_CTX_new_from_dispatch\fR\|(3). To associate the \s-1BIO\s0 with a library context
construct it using \fBBIO_new_ex\fR\|(3).
.PP
\&\fBBIO_new_from_core_bio()\fR is a convenience function that constructs a new \s-1BIO\s0
based on \fBBIO_s_core()\fR and that is associated with the given library context. It
then also sets the \s-1OSSL_CORE_BIO\s0 object on the \s-1BIO\s0 using \fBBIO_set_data\fR\|(3).
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBBIO_s_core()\fR return a core \s-1BIO\s0 \fB\s-1BIO_METHOD\s0\fR structure.
.PP
\&\fBBIO_new_from_core_bio()\fR returns a \s-1BIO\s0 structure on success or \s-1NULL\s0 on failure.
A failure will most commonly be because the library context was not constructed
using \fBOSSL_LIB_CTX_new_from_dispatch\fR\|(3).
.SH "HISTORY"
.IX Header "HISTORY"
\&\fBBIO_s_core()\fR and \fBBIO_new_from_core_bio()\fR were added in OpenSSL 3.0.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
Create a core \s-1BIO\s0 and write some data to it:
.PP
.Vb 2
\& int some_function(OSSL_LIB_CTX *libctx, OSSL_CORE_BIO *corebio) {
\&     BIO *cbio = BIO_new_from_core_bio(libctx, corebio);
\&
\&     if (cbio == NULL)
\&         return 0;
\&
\&     BIO_puts(cbio, "Hello World\en");
\&
\&     BIO_free(cbio);
\&     return 1;
\& }
.Ve
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2021\-2022 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the Apache License 2.0 (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.
