xref: /openssl/doc/man3/DEFINE_STACK_OF.pod (revision b6461792) 
1=pod
2
3=head1 NAME
4
5DEFINE_STACK_OF, DEFINE_STACK_OF_CONST, DEFINE_SPECIAL_STACK_OF,
6DEFINE_SPECIAL_STACK_OF_CONST,
7sk_TYPE_num, sk_TYPE_value, sk_TYPE_new, sk_TYPE_new_null,
8sk_TYPE_reserve, sk_TYPE_free, sk_TYPE_zero, sk_TYPE_delete,
9sk_TYPE_delete_ptr, sk_TYPE_push, sk_TYPE_unshift, sk_TYPE_pop,
10sk_TYPE_shift, sk_TYPE_pop_free, sk_TYPE_insert, sk_TYPE_set,
11sk_TYPE_find, sk_TYPE_find_ex, sk_TYPE_find_all, sk_TYPE_sort,
12sk_TYPE_is_sorted, sk_TYPE_dup, sk_TYPE_deep_copy, sk_TYPE_set_cmp_func,
13sk_TYPE_new_reserve,
14OPENSSL_sk_deep_copy, OPENSSL_sk_delete, OPENSSL_sk_delete_ptr,
15OPENSSL_sk_dup, OPENSSL_sk_find, OPENSSL_sk_find_ex, OPENSSL_sk_find_all,
16OPENSSL_sk_free, OPENSSL_sk_insert, OPENSSL_sk_is_sorted, OPENSSL_sk_new,
17OPENSSL_sk_new_null, OPENSSL_sk_new_reserve, OPENSSL_sk_num, OPENSSL_sk_pop,
18OPENSSL_sk_pop_free, OPENSSL_sk_push, OPENSSL_sk_reserve, OPENSSL_sk_set,
19OPENSSL_sk_set_cmp_func, OPENSSL_sk_shift, OPENSSL_sk_sort,
20OPENSSL_sk_unshift, OPENSSL_sk_value, OPENSSL_sk_zero
21- stack container
22
23=head1 SYNOPSIS
24
25=for openssl generic
26
27 #include <openssl/safestack.h>
28
29 STACK_OF(TYPE)
30 DEFINE_STACK_OF(TYPE)
31 DEFINE_STACK_OF_CONST(TYPE)
32 DEFINE_SPECIAL_STACK_OF(FUNCTYPE, TYPE)
33 DEFINE_SPECIAL_STACK_OF_CONST(FUNCTYPE, TYPE)
34
35 typedef int (*sk_TYPE_compfunc)(const TYPE *const *a, const TYPE *const *b);
36 typedef TYPE * (*sk_TYPE_copyfunc)(const TYPE *a);
37 typedef void (*sk_TYPE_freefunc)(TYPE *a);
38
39 int sk_TYPE_num(const STACK_OF(TYPE) *sk);
40 TYPE *sk_TYPE_value(const STACK_OF(TYPE) *sk, int idx);
41 STACK_OF(TYPE) *sk_TYPE_new(sk_TYPE_compfunc compare);
42 STACK_OF(TYPE) *sk_TYPE_new_null(void);
43 int sk_TYPE_reserve(STACK_OF(TYPE) *sk, int n);
44 void sk_TYPE_free(STACK_OF(TYPE) *sk);
45 void sk_TYPE_zero(STACK_OF(TYPE) *sk);
46 TYPE *sk_TYPE_delete(STACK_OF(TYPE) *sk, int i);
47 TYPE *sk_TYPE_delete_ptr(STACK_OF(TYPE) *sk, TYPE *ptr);
48 int sk_TYPE_push(STACK_OF(TYPE) *sk, const TYPE *ptr);
49 int sk_TYPE_unshift(STACK_OF(TYPE) *sk, const TYPE *ptr);
50 TYPE *sk_TYPE_pop(STACK_OF(TYPE) *sk);
51 TYPE *sk_TYPE_shift(STACK_OF(TYPE) *sk);
52 void sk_TYPE_pop_free(STACK_OF(TYPE) *sk, sk_TYPE_freefunc freefunc);
53 int sk_TYPE_insert(STACK_OF(TYPE) *sk, TYPE *ptr, int idx);
54 TYPE *sk_TYPE_set(STACK_OF(TYPE) *sk, int idx, const TYPE *ptr);
55 int sk_TYPE_find(STACK_OF(TYPE) *sk, TYPE *ptr);
56 int sk_TYPE_find_ex(STACK_OF(TYPE) *sk, TYPE *ptr);
57 int sk_TYPE_find_all(STACK_OF(TYPE) *sk, TYPE *ptr, int *pnum);
58 void sk_TYPE_sort(const STACK_OF(TYPE) *sk);
59 int sk_TYPE_is_sorted(const STACK_OF(TYPE) *sk);
60 STACK_OF(TYPE) *sk_TYPE_dup(const STACK_OF(TYPE) *sk);
61 STACK_OF(TYPE) *sk_TYPE_deep_copy(const STACK_OF(TYPE) *sk,
62                                   sk_TYPE_copyfunc copyfunc,
63                                   sk_TYPE_freefunc freefunc);
64 sk_TYPE_compfunc (*sk_TYPE_set_cmp_func(STACK_OF(TYPE) *sk,
65                                         sk_TYPE_compfunc compare));
66 STACK_OF(TYPE) *sk_TYPE_new_reserve(sk_TYPE_compfunc compare, int n);
67
68=head1 DESCRIPTION
69
70Applications can create and use their own stacks by placing any of the macros
71described below in a header file. These macros define typesafe inline
72functions that wrap around the utility B<OPENSSL_sk_> API.
73In the description here, B<I<TYPE>> is used
74as a placeholder for any of the OpenSSL datatypes, such as B<X509>.
75
76The STACK_OF() macro returns the name for a stack of the specified B<I<TYPE>>.
77This is an opaque pointer to a structure declaration.
78This can be used in every header file that references the stack.
79There are several B<DEFINE...> macros that create static inline functions
80for all of the functions described on this page.
81This should normally be used in one source file, and the stack manipulation
82is wrapped with application-specific functions.
83
84DEFINE_STACK_OF() creates set of functions for a stack of B<I<TYPE>> elements.
85The type is referenced by
86B<STACK_OF>(B<I<TYPE>>) and each function name begins with B<sk_I<TYPE>_>.
87DEFINE_STACK_OF_CONST() is identical to DEFINE_STACK_OF() except
88each element is constant.
89
90 /* DEFINE_STACK_OF(TYPE) */
91 TYPE *sk_TYPE_value(STACK_OF(TYPE) *sk, int idx);
92 /* DEFINE_STACK_OF_CONST(TYPE) */
93 const TYPE *sk_TYPE_value(STACK_OF(TYPE) *sk, int idx);
94
95DEFINE_SPECIAL_STACK_OF() and DEFINE_SPECIAL_STACK_OF_CONST() are similar
96except B<FUNCNAME> is used in the function names:
97
98 /* DEFINE_SPECIAL_STACK_OF(TYPE, FUNCNAME) */
99 TYPE *sk_FUNCNAME_value(STACK_OF(TYPE) *sk, int idx);
100 /* DEFINE_SPECIAL_STACK_OF(TYPE, FUNCNAME) */
101 const TYPE *sk_FUNCNAME_value(STACK_OF(TYPE) *sk, int idx);
102
103B<sk_I<TYPE>_num>() returns the number of elements in I<sk> or -1 if I<sk> is
104NULL.
105
106B<sk_I<TYPE>_value>() returns element I<idx> in I<sk>, where I<idx> starts at
107zero. If I<idx> is out of range then NULL is returned.
108
109B<sk_I<TYPE>_new>() allocates a new empty stack using comparison function
110I<compare>. If I<compare> is NULL then no comparison function is used. This
111function is equivalent to B<sk_I<TYPE>_new_reserve>(I<compare>, 0).
112
113B<sk_I<TYPE>_new_null>() allocates a new empty stack with no comparison
114function. This function is equivalent to B<sk_I<TYPE>_new_reserve>(NULL, 0).
115
116B<sk_I<TYPE>_reserve>() allocates additional memory in the I<sk> structure
117such that the next I<n> calls to B<sk_I<TYPE>_insert>(), B<sk_I<TYPE>_push>()
118or B<sk_I<TYPE>_unshift>() will not fail or cause memory to be allocated
119or reallocated. If I<n> is zero, any excess space allocated in the
120I<sk> structure is freed. On error I<sk> is unchanged.
121
122B<sk_I<TYPE>_new_reserve>() allocates a new stack. The new stack will have
123additional memory allocated to hold I<n> elements if I<n> is positive.
124The next I<n> calls to B<sk_I<TYPE>_insert>(), B<sk_I<TYPE>_push>() or
125B<sk_I<TYPE>_unshift>() will not fail or cause memory to be allocated or
126reallocated. If I<n> is zero or less than zero, no memory is allocated.
127B<sk_I<TYPE>_new_reserve>() also sets the comparison function I<compare>
128to the newly created stack. If I<compare> is NULL then no comparison
129function is used.
130
131B<sk_I<TYPE>_set_cmp_func>() sets the comparison function of I<sk> to
132I<compare>. The previous comparison function is returned or NULL if there
133was no previous comparison function.
134
135B<sk_I<TYPE>_free>() frees up the I<sk> structure. It does I<not> free up any
136elements of I<sk>. After this call I<sk> is no longer valid.
137
138B<sk_I<TYPE>_zero>() sets the number of elements in I<sk> to zero. It does not
139free I<sk> so after this call I<sk> is still valid.
140
141B<sk_I<TYPE>_pop_free>() frees up all elements of I<sk> and I<sk> itself. The
142free function freefunc() is called on each element to free it.
143
144B<sk_I<TYPE>_delete>() deletes element I<i> from I<sk>. It returns the deleted
145element or NULL if I<i> is out of range.
146
147B<sk_I<TYPE>_delete_ptr>() deletes element matching I<ptr> from I<sk>. It
148returns the deleted element or NULL if no element matching I<ptr> was found.
149
150B<sk_I<TYPE>_insert>() inserts I<ptr> into I<sk> at position I<idx>. Any
151existing elements at or after I<idx> are moved downwards. If I<idx> is out
152of range the new element is appended to I<sk>. B<sk_I<TYPE>_insert>() either
153returns the number of elements in I<sk> after the new element is inserted or
154zero if an error (such as memory allocation failure) occurred.
155
156B<sk_I<TYPE>_push>() appends I<ptr> to I<sk> it is equivalent to:
157
158 sk_TYPE_insert(sk, ptr, -1);
159
160B<sk_I<TYPE>_unshift>() inserts I<ptr> at the start of I<sk> it is equivalent
161to:
162
163 sk_TYPE_insert(sk, ptr, 0);
164
165B<sk_I<TYPE>_pop>() returns and removes the last element from I<sk>.
166
167B<sk_I<TYPE>_shift>() returns and removes the first element from I<sk>.
168
169B<sk_I<TYPE>_set>() sets element I<idx> of I<sk> to I<ptr> replacing the current
170element. The new element value is returned or NULL if an error occurred:
171this will only happen if I<sk> is NULL or I<idx> is out of range.
172
173B<sk_I<TYPE>_find>() searches I<sk> for the element I<ptr>.  In the case
174where no comparison function has been specified, the function performs
175a linear search for a pointer equal to I<ptr>. The index of the first
176matching element is returned or B<-1> if there is no match. In the case
177where a comparison function has been specified, I<sk> is sorted and
178B<sk_I<TYPE>_find>() returns the index of a matching element or B<-1> if there
179is no match. Note that, in this case the comparison function will usually
180compare the values pointed to rather than the pointers themselves and
181the order of elements in I<sk> can change.
182
183B<sk_I<TYPE>_find_ex>() operates like B<sk_I<TYPE>_find>() except when a
184comparison function has been specified and no matching element is found.
185Instead of returning B<-1>, B<sk_I<TYPE>_find_ex>() returns the index of the
186element either before or after the location where I<ptr> would be if it were
187present in I<sk>. The function also does not guarantee that the first matching
188element in the sorted stack is returned.
189
190B<sk_I<TYPE>_find_all>() operates like B<sk_I<TYPE>_find>() but it also
191sets the I<*pnum> to number of matching elements in the stack. In case
192no comparison function has been specified the I<*pnum> will be always set
193to 1 if matching element was found, 0 otherwise.
194
195B<sk_I<TYPE>_sort>() sorts I<sk> using the supplied comparison function.
196
197B<sk_I<TYPE>_is_sorted>() returns B<1> if I<sk> is sorted and B<0> otherwise.
198
199B<sk_I<TYPE>_dup>() returns a shallow copy of I<sk>
200or an empty stack if the passed stack is NULL.
201Note the pointers in the copy are identical to the original.
202
203B<sk_I<TYPE>_deep_copy>() returns a new stack where each element has been
204copied or an empty stack if the passed stack is NULL.
205Copying is performed by the supplied copyfunc() and freeing by freefunc().
206The function freefunc() is only called if an error occurs.
207
208=head1 NOTES
209
210Care should be taken when accessing stacks in multi-threaded environments.
211Any operation which increases the size of a stack such as B<sk_I<TYPE>_insert>()
212or B<sk_I<TYPE>_push>() can "grow" the size of an internal array and cause race
213conditions if the same stack is accessed in a different thread. Operations such
214as B<sk_I<TYPE>_find>() and B<sk_I<TYPE>_sort>() can also reorder the stack.
215
216Any comparison function supplied should use a metric suitable
217for use in a binary search operation. That is it should return zero, a
218positive or negative value if I<a> is equal to, greater than
219or less than I<b> respectively.
220
221Care should be taken when checking the return values of the functions
222B<sk_I<TYPE>_find>() and B<sk_I<TYPE>_find_ex>(). They return an index to the
223matching element. In particular B<0> indicates a matching first element.
224A failed search is indicated by a B<-1> return value.
225
226STACK_OF(), DEFINE_STACK_OF(), DEFINE_STACK_OF_CONST(), and
227DEFINE_SPECIAL_STACK_OF() are implemented as macros.
228
229It is not an error to call B<sk_I<TYPE>_num>(), B<sk_I<TYPE>_value>(),
230B<sk_I<TYPE>_free>(), B<sk_I<TYPE>_zero>(), B<sk_I<TYPE>_pop_free>(),
231B<sk_I<TYPE>_delete>(), B<sk_I<TYPE>_delete_ptr>(), B<sk_I<TYPE>_pop>(),
232B<sk_I<TYPE>_shift>(), B<sk_I<TYPE>_find>(), B<sk_I<TYPE>_find_ex>(),
233and B<sk_I<TYPE>_find_all>() on a NULL stack, empty stack, or with
234an invalid index. An error is not raised in these conditions.
235
236The underlying utility B<OPENSSL_sk_> API should not be used directly.
237It defines these functions: OPENSSL_sk_deep_copy(),
238OPENSSL_sk_delete(), OPENSSL_sk_delete_ptr(), OPENSSL_sk_dup(),
239OPENSSL_sk_find(), OPENSSL_sk_find_ex(), OPENSSL_sk_find_all(),
240OPENSSL_sk_free(), OPENSSL_sk_insert(), OPENSSL_sk_is_sorted(),
241OPENSSL_sk_new(), OPENSSL_sk_new_null(), OPENSSL_sk_new_reserve(),
242OPENSSL_sk_num(), OPENSSL_sk_pop(), OPENSSL_sk_pop_free(), OPENSSL_sk_push(),
243OPENSSL_sk_reserve(), OPENSSL_sk_set(), OPENSSL_sk_set_cmp_func(),
244OPENSSL_sk_shift(), OPENSSL_sk_sort(), OPENSSL_sk_unshift(),
245OPENSSL_sk_value(), OPENSSL_sk_zero().
246
247=head1 RETURN VALUES
248
249B<sk_I<TYPE>_num>() returns the number of elements in the stack or B<-1> if the
250passed stack is NULL.
251
252B<sk_I<TYPE>_value>() returns a pointer to a stack element or NULL if the
253index is out of range.
254
255B<sk_I<TYPE>_new>(), B<sk_I<TYPE>_new_null>() and B<sk_I<TYPE>_new_reserve>()
256return an empty stack or NULL if an error occurs.
257
258B<sk_I<TYPE>_reserve>() returns B<1> on successful allocation of the required
259memory or B<0> on error.
260
261B<sk_I<TYPE>_set_cmp_func>() returns the old comparison function or NULL if
262there was no old comparison function.
263
264B<sk_I<TYPE>_free>(), B<sk_I<TYPE>_zero>(), B<sk_I<TYPE>_pop_free>() and
265B<sk_I<TYPE>_sort>() do not return values.
266
267B<sk_I<TYPE>_pop>(), B<sk_I<TYPE>_shift>(), B<sk_I<TYPE>_delete>() and
268B<sk_I<TYPE>_delete_ptr>() return a pointer to the deleted element or NULL
269on error.
270
271B<sk_I<TYPE>_insert>(), B<sk_I<TYPE>_push>() and B<sk_I<TYPE>_unshift>() return
272the total number of elements in the stack and 0 if an error occurred.
273
274B<sk_I<TYPE>_set>() returns a pointer to the replacement element or NULL on
275error.
276
277B<sk_I<TYPE>_find>() and B<sk_I<TYPE>_find_ex>() return an index to the found
278element or B<-1> on error.
279
280B<sk_I<TYPE>_is_sorted>() returns B<1> if the stack is sorted and B<0> if it is
281not.
282
283B<sk_I<TYPE>_dup>() and B<sk_I<TYPE>_deep_copy>() return a pointer to the copy
284of the stack or NULL on error.
285
286=head1 HISTORY
287
288Before OpenSSL 1.1.0, this was implemented via macros and not inline functions
289and was not a public API.
290
291B<sk_I<TYPE>_reserve>() and B<sk_I<TYPE>_new_reserve>() were added in OpenSSL
2921.1.1.
293
294From OpenSSL 3.2.0, the B<sk_I<TYPE>_find>(), B<sk_I<TYPE>_find_ex>()
295and B<sk_I<TYPE>_find_all>() calls are read-only and do not sort the
296stack.  To avoid any performance implications this change introduces,
297B<sk_I<TYPE>_sort>() should be called before these find operations.
298
299Before OpenSSL 3.3.0 B<sk_I<TYPE>_push>() returned -1 if I<sk> was NULL. It
300was changed to return 0 in this condition as for other errors.
301
302=head1 COPYRIGHT
303
304Copyright 2000-2024 The OpenSSL Project Authors. All Rights Reserved.
305
306Licensed under the Apache License 2.0 (the "License").  You may not use
307this file except in compliance with the License.  You can obtain a copy
308in the file LICENSE in the source distribution or at
309L<https://www.openssl.org/source/license.html>.
310
311=cut
312