NAME    [Toc]    [Back]

       BN_CTX_start,   BN_CTX_get,  BN_CTX_end  -  Use  temporary
       BIGNUM variables

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 the
       BN_CTX_new() function) 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]

       The  BN_CTX_start()  and  BN_CTX_end() functions return no
       values.

       The BN_CTX_get() function 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().

HISTORY    [Toc]    [Back]

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

SEE ALSO    [Toc]    [Back]

       Functions: BN_CTX_new(3)



                                                  BN_CTX_start(3)