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.  If ctx is NULL,
       nothing is done.  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 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>.