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 174case where no comparison function has been specified, the function 175performs a linear search for a pointer equal to I<ptr>. In the case 176where a comparison function has been specified, the function performs 177a search for a element that the comparison function indicates is a 178match. If the stack is sorted, a binary search is used, otherwise, a 179linear search is used. B<sk_I<TYPE>_find>() returns the index of a 180matching element or B<-1> if there is no match. 181 182B<sk_I<TYPE>_find_ex>() operates like B<sk_I<TYPE>_find>() except when a 183comparison function has been specified and no matching element is found. 184Instead of returning B<-1>, B<sk_I<TYPE>_find_ex>() returns the index of the 185element either before or after the location where I<ptr> would be if it were 186present in I<sk>. The function also does not guarantee that the first matching 187element in the sorted stack is returned. 188 189B<sk_I<TYPE>_find_all>() operates like B<sk_I<TYPE>_find>() but it also 190sets the I<*pnum> to number of matching elements in the stack. In case 191no comparison function has been specified the I<*pnum> will be always set 192to 1 if matching element was found, 0 otherwise. 193 194B<sk_I<TYPE>_sort>() sorts I<sk> using the supplied comparison function. 195 196B<sk_I<TYPE>_is_sorted>() returns B<1> if I<sk> is sorted and B<0> otherwise. 197 198B<sk_I<TYPE>_dup>() returns a shallow copy of I<sk> 199or an empty stack if the passed stack is NULL. 200Note the pointers in the copy are identical to the original. 201 202B<sk_I<TYPE>_deep_copy>() returns a new stack where each element has been 203copied or an empty stack if the passed stack is NULL. 204Copying is performed by the supplied copyfunc() and freeing by freefunc(). 205The function freefunc() is only called if an error occurs. 206 207=head1 NOTES 208 209Care should be taken when accessing stacks in multi-threaded environments. 210Any operation which increases the size of a stack such as B<sk_I<TYPE>_insert>() 211or B<sk_I<TYPE>_push>() can "grow" the size of an internal array and cause race 212conditions if the same stack is accessed in a different thread. Operations such 213as B<sk_I<TYPE>_find>() and B<sk_I<TYPE>_sort>() can also reorder the stack. 214 215Any comparison function supplied should use a metric suitable 216for use in a binary search operation. That is it should return zero, a 217positive or negative value if I<a> is equal to, greater than 218or less than I<b> respectively. 219 220Care should be taken when checking the return values of the functions 221B<sk_I<TYPE>_find>() and B<sk_I<TYPE>_find_ex>(). They return an index to the 222matching element. In particular B<0> indicates a matching first element. 223A failed search is indicated by a B<-1> return value. 224 225STACK_OF(), DEFINE_STACK_OF(), DEFINE_STACK_OF_CONST(), and 226DEFINE_SPECIAL_STACK_OF() are implemented as macros. 227 228It is not an error to call B<sk_I<TYPE>_num>(), B<sk_I<TYPE>_value>(), 229B<sk_I<TYPE>_free>(), B<sk_I<TYPE>_zero>(), B<sk_I<TYPE>_pop_free>(), 230B<sk_I<TYPE>_delete>(), B<sk_I<TYPE>_delete_ptr>(), B<sk_I<TYPE>_pop>(), 231B<sk_I<TYPE>_shift>(), B<sk_I<TYPE>_find>(), B<sk_I<TYPE>_find_ex>(), 232and B<sk_I<TYPE>_find_all>() on a NULL stack, empty stack, or with 233an invalid index. An error is not raised in these conditions. 234 235The underlying utility B<OPENSSL_sk_> API should not be used directly. 236It defines these functions: OPENSSL_sk_deep_copy(), 237OPENSSL_sk_delete(), OPENSSL_sk_delete_ptr(), OPENSSL_sk_dup(), 238OPENSSL_sk_find(), OPENSSL_sk_find_ex(), OPENSSL_sk_find_all(), 239OPENSSL_sk_free(), OPENSSL_sk_insert(), OPENSSL_sk_is_sorted(), 240OPENSSL_sk_new(), OPENSSL_sk_new_null(), OPENSSL_sk_new_reserve(), 241OPENSSL_sk_num(), OPENSSL_sk_pop(), OPENSSL_sk_pop_free(), OPENSSL_sk_push(), 242OPENSSL_sk_reserve(), OPENSSL_sk_set(), OPENSSL_sk_set_cmp_func(), 243OPENSSL_sk_shift(), OPENSSL_sk_sort(), OPENSSL_sk_unshift(), 244OPENSSL_sk_value(), OPENSSL_sk_zero(). 245 246=head1 RETURN VALUES 247 248B<sk_I<TYPE>_num>() returns the number of elements in the stack or B<-1> if the 249passed stack is NULL. 250 251B<sk_I<TYPE>_value>() returns a pointer to a stack element or NULL if the 252index is out of range. 253 254B<sk_I<TYPE>_new>(), B<sk_I<TYPE>_new_null>() and B<sk_I<TYPE>_new_reserve>() 255return an empty stack or NULL if an error occurs. 256 257B<sk_I<TYPE>_reserve>() returns B<1> on successful allocation of the required 258memory or B<0> on error. 259 260B<sk_I<TYPE>_set_cmp_func>() returns the old comparison function or NULL if 261there was no old comparison function. 262 263B<sk_I<TYPE>_free>(), B<sk_I<TYPE>_zero>(), B<sk_I<TYPE>_pop_free>() and 264B<sk_I<TYPE>_sort>() do not return values. 265 266B<sk_I<TYPE>_pop>(), B<sk_I<TYPE>_shift>(), B<sk_I<TYPE>_delete>() and 267B<sk_I<TYPE>_delete_ptr>() return a pointer to the deleted element or NULL 268on error. 269 270B<sk_I<TYPE>_insert>(), B<sk_I<TYPE>_push>() and B<sk_I<TYPE>_unshift>() return 271the total number of elements in the stack and 0 if an error occurred. 272 273B<sk_I<TYPE>_set>() returns a pointer to the replacement element or NULL on 274error. 275 276B<sk_I<TYPE>_find>() and B<sk_I<TYPE>_find_ex>() return an index to the found 277element or B<-1> on error. 278 279B<sk_I<TYPE>_is_sorted>() returns B<1> if the stack is sorted and B<0> if it is 280not. 281 282B<sk_I<TYPE>_dup>() and B<sk_I<TYPE>_deep_copy>() return a pointer to the copy 283of the stack or NULL on error. 284 285=head1 HISTORY 286 287Before OpenSSL 1.1.0, this was implemented via macros and not inline functions 288and was not a public API. 289 290B<sk_I<TYPE>_reserve>() and B<sk_I<TYPE>_new_reserve>() were added in OpenSSL 2911.1.1. 292 293From OpenSSL 3.2.0, the B<sk_I<TYPE>_find>(), B<sk_I<TYPE>_find_ex>() 294and B<sk_I<TYPE>_find_all>() calls are read-only and do not sort the 295stack. To avoid any performance implications this change introduces, 296B<sk_I<TYPE>_sort>() should be called before these find operations. 297 298Before OpenSSL 3.3.0 B<sk_I<TYPE>_push>() returned -1 if I<sk> was NULL. It 299was changed to return 0 in this condition as for other errors. 300 301=head1 COPYRIGHT 302 303Copyright 2000-2025 The OpenSSL Project Authors. All Rights Reserved. 304 305Licensed under the Apache License 2.0 (the "License"). You may not use 306this file except in compliance with the License. You can obtain a copy 307in the file LICENSE in the source distribution or at 308L<https://www.openssl.org/source/license.html>. 309 310=cut 311