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=head1 NAME

X509_chain_up_ref,
X509_new, X509_free, X509_up_ref - X509 certificate ASN1 allocation functions

=head1 SYNOPSIS

 #include <openssl/x509.h>

 X509 *X509_new(void);
 void X509_free(X509 *a);
 int X509_up_ref(X509 *a);
 STACK_OF(X509) *X509_chain_up_ref(STACK_OF(X509) *x);

=head1 DESCRIPTION

The X509 ASN1 allocation routines, allocate and free an
X509 structure, which represents an X509 certificate.

X509_new() allocates and initializes a X509 structure with reference count
B<1>.

X509_free() decrements the reference count of B<X509> structure B<a> and
frees it up if the reference count is zero. If B<a> is NULL nothing is done.

X509_up_ref() increments the reference count of B<a>.

X509_chain_up_ref() increases the reference count of all certificates in
chain B<x> and returns a copy of the stack.

=head1 NOTES

The function X509_up_ref() if useful if a certificate structure is being
used by several different operations each of which will free it up after
use: this avoids the need to duplicate the entire certificate structure.

The function X509_chain_up_ref() doesn't just up the reference count of
each certificate it also returns a copy of the stack, using sk_X509_dup(),
but it serves a similar purpose: the returned chain persists after the
original has been freed.

=head1 RETURN VALUES

If the allocation fails, X509_new() returns B<NULL> and sets an error
code that can be obtained by L<ERR_get_error(3)>.
Otherwise it returns a pointer to the newly allocated structure.

X509_up_ref() returns 1 for success and 0 for failure.

X509_chain_up_ref() returns a copy of the stack or B<NULL> if an error
occurred.

=head1 SEE ALSO

L<d2i_X509(3)>,
L<ERR_get_error(3)>,
L<X509_CRL_get0_by_serial(3)>,
L<X509_get0_signature(3)>,
L<X509_get_ext_d2i(3)>,
L<X509_get_extension_flags(3)>,
L<X509_get_pubkey(3)>,
L<X509_get_subject_name(3)>,
L<X509_get_version(3)>,
L<X509_NAME_add_entry_by_txt(3)>,
L<X509_NAME_ENTRY_get_object(3)>,
L<X509_NAME_get_index_by_NID(3)>,
L<X509_NAME_print_ex(3)>,
L<X509_sign(3)>,
L<X509V3_get_d2i(3)>,
L<X509_verify_cert(3)>

=head1 COPYRIGHT

Copyright 2002-2016 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file LICENSE in the source distribution or at
L<https://www.openssl.org/source/license.html>.

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