Initial Commit

openssl-1.0.2f/doc/crypto/BN_CTX_start.pod

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+=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
+
+L<BN_CTX_new(3)|BN_CTX_new(3)>
+
+=head1 HISTORY
+
+BN_CTX_start(), BN_CTX_get() and BN_CTX_end() were added in OpenSSL 0.9.5.
+
+=cut