sk_X509_num.pod

=pod

=head1 NAME

sk_X509_num, sk_X509_value, sk_X509_new, sk_X509_new_null, sk_X509_free,
sk_X509_zero, sk_X509_delete, sk_X509_delete_ptr, sk_X509_push,
sk_X509_unshift, sk_X509_pop, sk_X509_shift, sk_X509_pop_free, sk_X509_insert,
sk_X509_set, sk_X509_find, sk_X509_find_ex, sk_X509_sort, sk_X509_is_sorted,
sk_X509_dup, sk_X509_deep_copy, sk_X509_set_cmp_func - X509 stack

=head1 SYNOPSIS

 #include <openssl/x509.h>

 int sk_X509_num(const STACK_OF(X509) *sk);
 X509 *sk_X509_value(const STACK_OF(X509) *sk, int idx);
 STACK_OF(X509) *sk_X509_new(int (*cmpf)(const X509 * const *a,
                                         const X509 * const *b));
 STACK_OF(X509) *sk_X509_new_null(void);
 int (*sk_X509_set_cmp_func (STACK_OF(X509) *sk,
                             int (*cmpf) (const X509 * const *a,
                                          const X509 * const *b)))
                             (const X509 * const *, const X509 * const *);
 void sk_X509_free(const STACK_OF(X509) *sk);
 void sk_X509_zero(const STACK_OF(X509) *sk);
 void sk_X509_pop_free(STACK_OF(X509) *sk, void (*func) (X509 *a));
 X509 *sk_X509_delete(STACK_OF(X509) *sk, int i);
 X509 *sk_X509_delete_ptr(STACK_OF(X509) *sk, X509 *ptr);
 int sk_X509_insert(STACK_OF(X509) *sk, X509 *ptr, int idx);
 int sk_X509_push(STACK_OF(X509) *sk, X509 *ptr);
 int sk_X509_unshift(STACK_OF(X509) *sk, X509 *ptr);
 X509 *sk_X509_pop(STACK_OF(X509) *sk);
 X509 *sk_X509_shift(STACK_OF(X509) *sk);
 X509 *sk_X509_set(STACK_OF(X509) *sk, int idx, X509 *ptr);
 int sk_X509_find(STACK_OF(X509) *sk, X509 *ptr);
 int sk_X509_find_ex(STACK_OF(X509) *sk, X509 *ptr);
 void sk_X509_sort(const STACK_OF(X509) *sk);
 int sk_X509_is_sorted(const STACK_OF(X509) *sk);
 STACK_OF(X509) *sk_X509_dup(STACK_OF(X509) *sk);
 STACK_OF(X509) *sk_X509_deep_copy(STACK_OF(X509) *sk,
                                   X509 * (*copyfn) (const X509 *),
                                   void (*freefn) (X509 *));

=head1 DESCRIPTION

sk_X509_num() returns the number of elements in B<sk> or -1 if B<sk> is
B<NULL>.

sk_X509_value() returns element B<idx> in B<sk>. Where B<idx> runs from 0
to sk_X509_num(sk) - 1 inclusive. If B<idx> is out of range then B<NULL>
is returned.

sk_X509_new() allocates a new empty stack using comparison function B<cmpf>.
If B<cmpf> is B<0> then no comparison function is used.

sk_X509_new_null() allocates a new empty stack with no comparison function.

sk_X509_set_cmp_func() sets the comparison function of B<sk> to B<cmpf>.
The previous comparison function is returned or B<0> if there was
no previous comparison function.

sk_X509_free() frees up the B<sk> structure. It does B<not> free up any
elements of B<sk>. After this call B<sk> is no longer valid.

sk_X509_zero() sets the number of elements in B<sk> to zero. It does not free
B<sk> so after this call B<sk> is still valid.

sk_X509_pop_free() frees up all elements of B<sk> and B<sk> itself. The
free function func() is called on each element to free it.

sk_X509_delete() deletes element B<i> from B<sk>. It returns the deleted
element or B<NULL> if B<i> is out of range.

sk_X509_delete_ptr() deletes element matching B<ptr> from B<sk>. It returns
the deleted element or B<NULL> if no element matching B<ptr> was found.

sk_X509_insert() inserts B<ptr> into B<sk> at position B<idx>. Any existing
elements at or after B<idx> are moved downwards. If B<idx> is out of range
the new element is appended to B<sk>. sk_X509_insert() either returns the
number of elements in B<sk> after the new element is inserted or zero if
an error occurred: which will happen if there is a memory allocation failure.

sk_X509_push() appends B<ptr> to B<sk> it is equivalent to:

 sk_X509_insert(sk, ptr, -1);

sk_X509_unshift() inserts B<ptr> at the start of B<sk> it is equivalent to:

 sk_X509_insert(sk, ptr, 0);

sk_X509_pop() returns and removes the last element from B<sk>.

sk_X509_shift() returns and removes the first element from B<sk>.

sk_X509_set() sets element B<idx> of B<sk> to B<ptr> replacing the current
element. The new element value is returned or B<NULL> if an error occurred:
this will only happen if B<sk> is B<NULL> or B<idx> is out of range.

sk_X509_find() and int sk_X509_find_ex() search B<sk> using the supplied
comparison function for an element matching B<ptr>. sk_X509_find() returns
the index of the first matching element or B<-1> if there is no match.
sk_X509_find_ex() returns a matching element or the nearest element that
does not match B<ptr>. Note: if a comparison function is set then  B<sk> is
sorted before the search which may change its order. If no comparison
function is set then a linear search is made for a pointer matching B<ptr>
and the stack is not reordered.

sk_X509_sort() sorts B<sk> using the supplied comparison function.

sk_X509_is_sorted() returns B<1> if B<sk> is sorted and B<0> otherwise.

sk_X509_dup() returns a copy of B<sk>. Note the pointers in the copy
are identical to the original.

sk_X509_deep_copy() returns a new stack where each element has been copied.
Copying is performed by the supplied copyfn() and freeing by freefn(). The
function freefn() is only called if an error occurs.

=head1 NOTES

This manual page documents the functions which operate on a stack of
B<X509> pointers. A stack can contain pointers to any structure with B<X509>
replaced by the appropriate structure name.

Care should be taken when accessing stacks in multi-threaded environments.
Any operation which increases the size of a stack such as sk_X509_insert() or
sk_push() can "grow" the size of an internal array and cause race conditions
if the same stack is accessed in a different thread. Operations such as
sk_find() and sk_sort() can also reorder the stack.

Any comparison function supplied should use a metric suitable
for use in a binary search operation. That is it should return zero, a
positive or negative value if B<a> is equal to, greater than
or less than B<b> respectively.

Care should be taken when checking the return values of the functions
sk_X509_find() and sk_X509_find_ex(). They return an index to the
matching element. In particular B<0> indicates a matching first element.
A failed search is indicated by a B<-1> return value.

=head1 APPLICATION DEFINED STACKS

Applications can create and use their own stacks by placing any of the macros
described below in a header file.

DEFINE_STACK_OF(NAME) creates set of functions for a stack of B<NAME>. This
will mean that type B<NAME> is stored in each stack, the type is referenced by
STACK_OF(NAME) and each function name begins with sk_NAME_. For example:

 NAME *sk_NAME_value(STACK_OF(NAME) *sk, int idx);

DEFINE_STACK_OF_CONST(NAME) is identical to DEFINE_STACK_OF(NAME) except
each element is constant for example:

 const NAME *sk_name_value(STACK_OF(NAME) *sk, int idx);

DEFINE_SPECIAL_STACK_OF(FNAME, STNAME) defines a stack of B<STNAME> but
each function uses B<FNAME>. For example:

 STNAME *sk_FNAME_value(STACK_OF(STNAME) *sk, int idx);

=head1 RETURN VALUES

sk_X509_num() returns the number of elements in the stack or B<-1> if the
passed stack is B<NULL>.

sk_X509_value() returns a pointer to a stack element or B<NULL> if the
index is out of range.

sk_X509_new() and sk_X509_new_null() return an empty stack or B<NULL> if
an error occurs.

sk_X509_set_cmp_func() returns the old comparison function or B<NULL> if
there was no old comparison function.

sk_X509_free(), sk_X509_zero(), sk_X509_pop_free() and sk_X509_sort() do
not return values.

sk_X509_pop(), sk_X509_shift(), sk_X509_delete() and sk_X509_delete_ptr()
return a pointer to the deleted element or B<NULL> on error.

sk_X509_insert(), sk_X509_push() and sk_X509_unshift() return the total
number of elements in the stack and 0 if an error occurred.

sk_X509_set() returns a pointer to the replacement element or B<NULL> on
error.

sk_X509_find() and sk_X509_find_ex() return an index to the found element
or B<-1> on error.

sk_X509_is_sorted() returns B<1> if the stack is sorted and B<0> if it is
not.

sk_X509_dup() and sk_X509_deep_copy() return a pointer to the copy of the
stack.

=head1 HISTORY

Use of inline functions and application defined stacks first appeared in
OpenSSL 1.1.0. Previous versions of OpenSSL implemented stacks as macros.

=cut

=head1 COPYRIGHT

Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (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>.

=cut