BN_CTX_end(3)

     BN_CTX_start(3)        0.9.6h (2000-07-11)        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.

     Page 1                                         (printed 1/19/103)