BN_CTX_start(3) - NetBSD Manual Pages

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BN_CTX_start(3)                     OpenSSL                    BN_CTX_start(3)




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>.



3.0.15                            2024-09-03                   BN_CTX_start(3)