NAME

       BN_CTX_start, BN_CTX_get, BN_CTX_end - use temporary BIGNUM variables

SYNOPSIS

        #include <openssl/bn.h>

        void BN_CTX_start(BN_CTX *ctx);

        BIGNUM *BN_CTX_get(BN_CTX *ctx);

        void BN_CTX_end(BN_CTX *ctx);

DESCRIPTION

       These functions are used to obtain temporary BIGNUM variables from a BN_CTX (which can
       been created by using BN_CTX_new(3)) in order to save the overhead of repeatedly creating
       and freeing BIGNUMs in functions that are called from inside a loop.

       A function must call BN_CTX_start() first. Then, BN_CTX_get() may be called repeatedly to
       obtain temporary BIGNUMs. All BN_CTX_get() calls must be made before calling any other
       functions that use the ctx as an argument.

       Finally, BN_CTX_end() must be called before returning from the function.  When
       BN_CTX_end() is called, the BIGNUM pointers obtained from BN_CTX_get() become invalid.

RETURN VALUES

       BN_CTX_start() and BN_CTX_end() return no values.

       BN_CTX_get() returns a pointer to the BIGNUM, or NULL on error.  Once BN_CTX_get() has
       failed, the subsequent calls will return NULL as well, so it is sufficient to check the
       return value of the last BN_CTX_get() call. In case of an error, an error code is set,
       which can be obtained by ERR_get_error(3).

SEE ALSO

       BN_CTX_new(3)

COPYRIGHT

       Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (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>.