- NAME
- SYNOPSIS
- DESCRIPTION
- RETURN VALUES
- HISTORY
- EXAMPLES
- COPYRIGHT

# NAME

BIO_s_core, BIO_new_from_core_bio - OSSL_CORE_BIO functions

# SYNOPSIS

     #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);

# DESCRIPTION

`BIO_s_core()` returns the core BIO method function.

A core BIO is treated as source/sink BIO which communicates to some external BIO. This is primarily useful to provider authors. A number of calls from libcrypto into a provider supply an OSSL_CORE_BIO parameter. This represents a BIO within libcrypto, but cannot be used directly by a provider. Instead it should be wrapped using a `BIO_s_core()`.

Once a BIO is constructed based on `BIO_s_core()`, the associated OSSL_CORE_BIO object should be set on it using `BIO_set_data(3)`. Note that the BIO will only operate correctly if it is associated with a library context constructed using `OSSL_LIB_CTX_new_from_dispatch(3)`. To associate the BIO with a library context construct it using `BIO_new_ex(3)`.

`BIO_new_from_core_bio()` is a convenience function that constructs a new BIO based on `BIO_s_core()` and that is associated with the given library context. It then also sets the OSSL_CORE_BIO object on the BIO using `BIO_set_data(3)`.

# RETURN VALUES

`BIO_s_core()` return a core BIO BIO_METHOD structure.

`BIO_new_from_core_bio()` returns a BIO structure on success or NULL on failure. A failure will most commonly be because the library context was not constructed using `OSSL_LIB_CTX_new_from_dispatch(3)`.

# HISTORY

`BIO_s_core()` and `BIO_new_from_core_bio()` were added in OpenSSL 3.0.

# EXAMPLES

Create a core BIO and write some data to it:

     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\n");

         BIO_free(cbio);
         return 1;
     }

# COPYRIGHT

Copyright 2021-2022 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at https://www.openssl.org/source/license.html.