NAME    [Toc]    [Back]

       BN_CTX_start, BN_CTX_get, BN_CTX_end - use temporary
       BIGNUM variables

LIBRARY    [Toc]    [Back]

       libcrypto, -lcrypto

SYNOPSIS    [Toc]    [Back]

        #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    [Toc]    [Back]

       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    [Toc]    [Back]

       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    [Toc]    [Back]

       BN_CTX_new(3)

HISTORY    [Toc]    [Back]

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



2001-04-12                    0.9.6g              BN_CTX_start(3)