| =pod |
| |
| =head1 NAME |
| |
| BN_CTX_start, BN_CTX_get, BN_CTX_end - use temporary BIGNUM variables |
| |
| =head1 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); |
| |
| =head1 DESCRIPTION |
| |
| These functions are used to obtain temporary B<BIGNUM> variables from |
| a B<BN_CTX> (which can been created by using L<BN_CTX_new(3)|BN_CTX_new(3)>) |
| in order to save the overhead of repeatedly creating and |
| freeing B<BIGNUM>s 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 B<BIGNUM>s. All BN_CTX_get() |
| calls must be made before calling any other functions that use the |
| B<ctx> as an argument. |
| |
| Finally, BN_CTX_end() must be called before returning from the function. |
| When BN_CTX_end() is called, the B<BIGNUM> pointers obtained from |
| BN_CTX_get() become invalid. |
| |
| =head1 RETURN VALUES |
| |
| BN_CTX_start() and BN_CTX_end() return no values. |
| |
| BN_CTX_get() returns a pointer to the B<BIGNUM>, or B<NULL> on error. |
| Once BN_CTX_get() has failed, the subsequent calls will return B<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 L<ERR_get_error(3)|ERR_get_error(3)>. |
| |
| |
| =head1 SEE ALSO |
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| L<BN_CTX_new(3)|BN_CTX_new(3)> |
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| =head1 HISTORY |
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| BN_CTX_start(), BN_CTX_get() and BN_CTX_end() were added in OpenSSL 0.9.5. |
| |
| =cut |
