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DEFINE_STACK_OF(3)		    OpenSSL		    DEFINE_STACK_OF(3)

NAME
       DEFINE_STACK_OF,	DEFINE_STACK_OF_CONST, DEFINE_SPECIAL_STACK_OF,
       DEFINE_SPECIAL_STACK_OF_CONST, sk_TYPE_num, sk_TYPE_value, sk_TYPE_new,
       sk_TYPE_new_null, sk_TYPE_reserve, sk_TYPE_free,	sk_TYPE_zero,
       sk_TYPE_delete, sk_TYPE_delete_ptr, sk_TYPE_push, sk_TYPE_unshift,
       sk_TYPE_pop, sk_TYPE_shift, sk_TYPE_pop_free, sk_TYPE_insert,
       sk_TYPE_set, sk_TYPE_find, sk_TYPE_find_ex, sk_TYPE_sort,
       sk_TYPE_is_sorted, sk_TYPE_dup, sk_TYPE_deep_copy,
       sk_TYPE_set_cmp_func, sk_TYPE_new_reserve - stack container

SYNOPSIS
	#include <openssl/safestack.h>

	STACK_OF(TYPE)
	DEFINE_STACK_OF(TYPE)
	DEFINE_STACK_OF_CONST(TYPE)
	DEFINE_SPECIAL_STACK_OF(FUNCTYPE, TYPE)
	DEFINE_SPECIAL_STACK_OF_CONST(FUNCTYPE,	TYPE)

	typedef	int (*sk_TYPE_compfunc)(const TYPE *const *a, const TYPE *const	*b);
	typedef	TYPE * (*sk_TYPE_copyfunc)(const TYPE *a);
	typedef	void (*sk_TYPE_freefunc)(TYPE *a);

	int sk_TYPE_num(const STACK_OF(TYPE) *sk);
	TYPE *sk_TYPE_value(const STACK_OF(TYPE) *sk, int idx);
	STACK_OF(TYPE) *sk_TYPE_new(sk_TYPE_compfunc compare);
	STACK_OF(TYPE) *sk_TYPE_new_null(void);
	int sk_TYPE_reserve(STACK_OF(TYPE) *sk,	int n);
	void sk_TYPE_free(const	STACK_OF(TYPE) *sk);
	void sk_TYPE_zero(const	STACK_OF(TYPE) *sk);
	TYPE *sk_TYPE_delete(STACK_OF(TYPE) *sk, int i);
	TYPE *sk_TYPE_delete_ptr(STACK_OF(TYPE)	*sk, TYPE *ptr);
	int sk_TYPE_push(STACK_OF(TYPE)	*sk, const TYPE	*ptr);
	int sk_TYPE_unshift(STACK_OF(TYPE) *sk,	const TYPE *ptr);
	TYPE *sk_TYPE_pop(STACK_OF(TYPE) *sk);
	TYPE *sk_TYPE_shift(STACK_OF(TYPE) *sk);
	void sk_TYPE_pop_free(STACK_OF(TYPE) *sk, sk_TYPE_freefunc freefunc);
	int sk_TYPE_insert(STACK_OF(TYPE) *sk, TYPE *ptr, int idx);
	TYPE *sk_TYPE_set(STACK_OF(TYPE) *sk, int idx, const TYPE *ptr);
	int sk_TYPE_find(STACK_OF(TYPE)	*sk, TYPE *ptr);
	int sk_TYPE_find_ex(STACK_OF(TYPE) *sk,	TYPE *ptr);
	void sk_TYPE_sort(const	STACK_OF(TYPE) *sk);
	int sk_TYPE_is_sorted(const STACK_OF(TYPE) *sk);
	STACK_OF(TYPE) *sk_TYPE_dup(const STACK_OF(TYPE) *sk);
	STACK_OF(TYPE) *sk_TYPE_deep_copy(const	STACK_OF(TYPE) *sk,
					  sk_TYPE_copyfunc copyfunc,
					  sk_TYPE_freefunc freefunc);
	sk_TYPE_compfunc (*sk_TYPE_set_cmp_func(STACK_OF(TYPE) *sk,
						sk_TYPE_compfunc compare));
	STACK_OF(TYPE) *sk_TYPE_new_reserve(sk_TYPE_compfunc compare, int n);

DESCRIPTION
       Applications can	create and use their own stacks	by placing any of the
       macros described	below in a header file.	These macros define typesafe
       inline functions	that wrap around the utility OPENSSL_sk_ API.  In the
       description here, TYPE is used as a placeholder for any of the OpenSSL
       datatypes, such as X509.

       STACK_OF() returns the name for a stack of the specified	TYPE.
       DEFINE_STACK_OF() creates set of	functions for a	stack of TYPE. This
       will mean that type TYPE	is stored in each stack, the type is
       referenced by STACK_OF(TYPE) and	each function name begins with
       sk_TYPE_. For example:

	TYPE *sk_TYPE_value(STACK_OF(TYPE) *sk,	int idx);

       DEFINE_STACK_OF_CONST() is identical to DEFINE_STACK_OF() except	each
       element is constant. For	example:

	const TYPE *sk_TYPE_value(STACK_OF(TYPE) *sk, int idx);

       DEFINE_SPECIAL_STACK_OF() defines a stack of TYPE but each function
       uses FUNCNAME in	the function name. For example:

	TYPE *sk_FUNCNAME_value(STACK_OF(TYPE) *sk, int	idx);

       DEFINE_SPECIAL_STACK_OF_CONST() is similar except that each element is
       constant:

	const TYPE *sk_FUNCNAME_value(STACK_OF(TYPE) *sk, int idx);

       sk_TYPE_num() returns the number	of elements in sk or -1	if sk is NULL.

       sk_TYPE_value() returns element idx in sk, where	idx starts at zero. If
       idx is out of range then	NULL is	returned.

       sk_TYPE_new() allocates a new empty stack using comparison function
       compare.	 If compare is NULL then no comparison function	is used. This
       function	is equivalent to sk_TYPE_new_reserve(compare, 0).

       sk_TYPE_new_null() allocates a new empty	stack with no comparison
       function. This function is equivalent to	sk_TYPE_new_reserve(NULL, 0).

       sk_TYPE_reserve() allocates additional memory in	the sk structure such
       that the	next n calls to	sk_TYPE_insert(), sk_TYPE_push() or
       sk_TYPE_unshift() will not fail or cause	memory to be allocated or
       reallocated. If n is zero, any excess space allocated in	the sk
       structure is freed. On error sk is unchanged.

       sk_TYPE_new_reserve() allocates a new stack. The	new stack will have
       additional memory allocated to hold n elements if n is positive.	The
       next n calls to sk_TYPE_insert(), sk_TYPE_push()	or sk_TYPE_unshift()
       will not	fail or	cause memory to	be allocated or	reallocated. If	n is
       zero or less than zero, no memory is allocated. sk_TYPE_new_reserve()
       also sets the comparison	function compare to the	newly created stack.
       If compare is NULL then no comparison function is used.

       sk_TYPE_set_cmp_func() sets the comparison function of sk to compare.
       The previous comparison function	is returned or NULL if there was no
       previous	comparison function.

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

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

       sk_TYPE_pop_free() frees	up all elements	of sk and sk itself. The free
       function	freefunc() is called on	each element to	free it.

       sk_TYPE_delete()	deletes	element	i from sk. It returns the deleted
       element or NULL if i is out of range.

       sk_TYPE_delete_ptr() deletes element matching ptr from sk. It returns
       the deleted element or NULL if no element matching ptr was found.

       sk_TYPE_insert()	inserts	ptr into sk at position	idx. Any existing
       elements	at or after idx	are moved downwards. If	idx is out of range
       the new element is appended to sk. sk_TYPE_insert() either returns the
       number of elements in sk	after the new element is inserted or zero if
       an error	(such as memory	allocation failure) occurred.

       sk_TYPE_push() appends ptr to sk	it is equivalent to:

	sk_TYPE_insert(sk, ptr,	-1);

       sk_TYPE_unshift() inserts ptr at	the start of sk	it is equivalent to:

	sk_TYPE_insert(sk, ptr,	0);

       sk_TYPE_pop() returns and removes the last element from sk.

       sk_TYPE_shift() returns and removes the first element from sk.

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

       sk_TYPE_find() searches sk for the element ptr.	In the case where no
       comparison function has been specified, the function performs a linear
       search for a pointer equal to ptr. The index of the first matching
       element is returned or -1 if there is no	match. In the case where a
       comparison function has been specified, sk is sorted then
       sk_TYPE_find() returns the index	of a matching element or -1 if there
       is no match. Note that, in this case, the matching element returned is
       not guaranteed to be the	first; the comparison function will usually
       compare the values pointed to rather than the pointers themselves and
       the order of elements in	sk could change.

       sk_TYPE_find_ex() operates like sk_TYPE_find() except when a comparison
       function	has been specified and no matching element is found. Instead
       of returning -1,	sk_TYPE_find_ex() returns the index of the element
       either before or	after the location where ptr would be if it were
       present in sk.

       sk_TYPE_sort() sorts sk using the supplied comparison function.

       sk_TYPE_is_sorted() returns 1 if	sk is sorted and 0 otherwise.

       sk_TYPE_dup() returns a copy of sk. Note	the pointers in	the copy are
       identical to the	original.

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

NOTES
       Care should be taken when accessing stacks in multi-threaded
       environments.  Any operation which increases the	size of	a stack	such
       as sk_TYPE_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 a is equal to, greater than	or less	than b
       respectively.

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

       STACK_OF(), DEFINE_STACK_OF(), DEFINE_STACK_OF_CONST(), and
       DEFINE_SPECIAL_STACK_OF() are implemented as macros.

       The underlying utility OPENSSL_sk_ API should not be used directly.  It
       defines these functions:	OPENSSL_sk_deep_copy(),	OPENSSL_sk_delete(),
       OPENSSL_sk_delete_ptr(),	OPENSSL_sk_dup(), OPENSSL_sk_find(),
       OPENSSL_sk_find_ex(), OPENSSL_sk_free(),	OPENSSL_sk_insert(),
       OPENSSL_sk_is_sorted(), OPENSSL_sk_new(), OPENSSL_sk_new_null(),
       OPENSSL_sk_num(), OPENSSL_sk_pop(), OPENSSL_sk_pop_free(),
       OPENSSL_sk_push(), OPENSSL_sk_reserve(),	OPENSSL_sk_set(),
       OPENSSL_sk_set_cmp_func(), OPENSSL_sk_shift(), OPENSSL_sk_sort(),
       OPENSSL_sk_unshift(), OPENSSL_sk_value(), OPENSSL_sk_zero().

RETURN VALUES
       sk_TYPE_num() returns the number	of elements in the stack or -1 if the
       passed stack is NULL.

       sk_TYPE_value() returns a pointer to a stack element or NULL if the
       index is	out of range.

       sk_TYPE_new(), sk_TYPE_new_null() and sk_TYPE_new_reserve() return an
       empty stack or NULL if an error occurs.

       sk_TYPE_reserve() returns 1 on successful allocation of the required
       memory or 0 on error.

       sk_TYPE_set_cmp_func() returns the old comparison function or NULL if
       there was no old	comparison function.

       sk_TYPE_free(), sk_TYPE_zero(), sk_TYPE_pop_free() and sk_TYPE_sort()
       do not return values.

       sk_TYPE_pop(), sk_TYPE_shift(), sk_TYPE_delete()	and
       sk_TYPE_delete_ptr() return a pointer to	the deleted element or NULL on
       error.

       sk_TYPE_insert(), sk_TYPE_push()	and sk_TYPE_unshift() return the total
       number of elements in the stack and 0 if	an error occurred.

       sk_TYPE_set() returns a pointer to the replacement element or NULL on
       error.

       sk_TYPE_find() and sk_TYPE_find_ex() return an index to the found
       element or -1 on	error.

       sk_TYPE_is_sorted() returns 1 if	the stack is sorted and	0 if it	is
       not.

       sk_TYPE_dup() and sk_TYPE_deep_copy() return a pointer to the copy of
       the stack.

HISTORY
       Before OpenSSL 1.1.0, this was implemented via macros and not inline
       functions and was not a public API.

       sk_TYPE_reserve() and sk_TYPE_new_reserve() were	added in OpenSSL
       1.1.1.

COPYRIGHT
       Copyright 2000-2017 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
       <https://www.openssl.org/source/license.html>.

1.1.1a				  2018-11-20		    DEFINE_STACK_OF(3)

NAME | SYNOPSIS | DESCRIPTION | NOTES | RETURN VALUES | HISTORY | COPYRIGHT

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