/usr/man/cat.3/BN_CTX_get.3

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.  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.

1.0.2t               Last change: 2019-09-10                    1

See also BN_CTX_end(3)
See also BN_CTX_start(3)