Provided by: libssl-doc_1.0.1-4ubuntu3_all bug


       BN_CTX_start, BN_CTX_get, BN_CTX_end - use temporary BIGNUM variables


        #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);


       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.


       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).




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