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 repeat-
       edly 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 tempo-
       rary BIGNUMs. All BN_CTX_get() calls must be made before
       calling any other functions that use the ctx as an argu-
       ment.

       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)

HISTORY
       BN_CTX_start(), BN_CTX_get() and BN_CTX_end() were added
       in OpenSSL 0.9.5.



0.9.7c                     2000-07-11           BN_CTX_start(3)
