=head1 DESCRIPTION
-A B<BN_CTX> is a structure that holds temporary variables used by
-library functions. Thus, it can be avoided to create and destroy
-the temporary B<BIGNUM> objects whenever a library function is
-called.
+A B<BN_CTX> is a structure that holds B<BIGNUM> temporary variables used by
+library functions. Since dynamic memory allocation to create B<BIGNUM>s
+is rather expensive when used in conjunction with repeated subroutine
+calls, the B<BN_CTX> structure is used.
-BN_CTX_new() allocated and initializes a B<BN_CTX>
+BN_CTX_new() allocates and initializes a B<BN_CTX>
structure. BN_CTX_init() initializes an existing uninitialized
B<BN_CTX>.
BN_CTX_free() frees the components of the B<BN_CTX>, and if it was
created by BN_CTX_new(), also the structure itself.
+If L<BN_CTX_start(3)|BN_CTX_start(3)> has been used on the B<BN_CTX>,
+L<BN_CTX_end(3)|BN_CTX_end(3)> must be called before the B<BN_CTX>
+may be freed by BN_CTX_free().
+
=head1 RETURN VALUES
BN_CTX_new() returns a pointer to the B<BN_CTX>. If the allocation fails,
it returns B<NULL> and sets an error code that can be obtained by
-ERR_get_error(3).
+L<ERR_get_error(3)|ERR_get_error(3)>.
BN_CTX_init() and BN_CTX_free() have no return values.
=head1 SEE ALSO
-bn(3), err(3), BN_add(3)
+L<bn(3)|bn(3)>, L<err(3)|err(3)>, L<BN_add(3)|BN_add(3)>,
+L<BN_CTX_start(3)|BN_CTX_start(3)>
=head1 HISTORY
-BN_CTX_new() and BN_CTX_free() are availabe in all versions on SSLeay
+BN_CTX_new() and BN_CTX_free() are available in all versions on SSLeay
and OpenSSL. BN_CTX_init() was added in SSLeay 0.9.1b.
=cut
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