doc/man3/DEFINE_STACK_OF.pod

   1 =pod
   2
   3 =head1 NAME
   4
   5 DEFINE_STACK_OF, DEFINE_STACK_OF_CONST, DEFINE_SPECIAL_STACK_OF,
   6 DEFINE_SPECIAL_STACK_OF_CONST,
   7 sk_TYPE_num, sk_TYPE_value, sk_TYPE_new, sk_TYPE_new_null,
   8 sk_TYPE_reserve, sk_TYPE_free, sk_TYPE_zero, sk_TYPE_delete,
   9 sk_TYPE_delete_ptr, sk_TYPE_push, sk_TYPE_unshift, sk_TYPE_pop,
  10 sk_TYPE_shift, sk_TYPE_pop_free, sk_TYPE_insert, sk_TYPE_set,
  11 sk_TYPE_find, sk_TYPE_find_ex, sk_TYPE_sort, sk_TYPE_is_sorted,
  12 sk_TYPE_dup, sk_TYPE_deep_copy, sk_TYPE_set_cmp_func, sk_TYPE_new_reserve
  13 - stack container
  14
  15 =head1 SYNOPSIS
  16
  17 =for openssl generic
  18
  19  #include <openssl/safestack.h>
  20
  21  STACK_OF(TYPE)
  22  DEFINE_STACK_OF(TYPE)
  23  DEFINE_STACK_OF_CONST(TYPE)
  24  DEFINE_SPECIAL_STACK_OF(FUNCTYPE, TYPE)
  25  DEFINE_SPECIAL_STACK_OF_CONST(FUNCTYPE, TYPE)
  26
  27  typedef int (*sk_TYPE_compfunc)(const TYPE *const *a, const TYPE *const *b);
  28  typedef TYPE * (*sk_TYPE_copyfunc)(const TYPE *a);
  29  typedef void (*sk_TYPE_freefunc)(TYPE *a);
  30
  31  int sk_TYPE_num(const STACK_OF(TYPE) *sk);
  32  TYPE *sk_TYPE_value(const STACK_OF(TYPE) *sk, int idx);
  33  STACK_OF(TYPE) *sk_TYPE_new(sk_TYPE_compfunc compare);
  34  STACK_OF(TYPE) *sk_TYPE_new_null(void);
  35  int sk_TYPE_reserve(STACK_OF(TYPE) *sk, int n);
  36  void sk_TYPE_free(const STACK_OF(TYPE) *sk);
  37  void sk_TYPE_zero(const STACK_OF(TYPE) *sk);
  38  TYPE *sk_TYPE_delete(STACK_OF(TYPE) *sk, int i);
  39  TYPE *sk_TYPE_delete_ptr(STACK_OF(TYPE) *sk, TYPE *ptr);
  40  int sk_TYPE_push(STACK_OF(TYPE) *sk, const TYPE *ptr);
  41  int sk_TYPE_unshift(STACK_OF(TYPE) *sk, const TYPE *ptr);
  42  TYPE *sk_TYPE_pop(STACK_OF(TYPE) *sk);
  43  TYPE *sk_TYPE_shift(STACK_OF(TYPE) *sk);
  44  void sk_TYPE_pop_free(STACK_OF(TYPE) *sk, sk_TYPE_freefunc freefunc);
  45  int sk_TYPE_insert(STACK_OF(TYPE) *sk, TYPE *ptr, int idx);
  46  TYPE *sk_TYPE_set(STACK_OF(TYPE) *sk, int idx, const TYPE *ptr);
  47  int sk_TYPE_find(STACK_OF(TYPE) *sk, TYPE *ptr);
  48  int sk_TYPE_find_ex(STACK_OF(TYPE) *sk, TYPE *ptr);
  49  void sk_TYPE_sort(const STACK_OF(TYPE) *sk);
  50  int sk_TYPE_is_sorted(const STACK_OF(TYPE) *sk);
  51  STACK_OF(TYPE) *sk_TYPE_dup(const STACK_OF(TYPE) *sk);
  52  STACK_OF(TYPE) *sk_TYPE_deep_copy(const STACK_OF(TYPE) *sk,
  53                                    sk_TYPE_copyfunc copyfunc,
  54                                    sk_TYPE_freefunc freefunc);
  55  sk_TYPE_compfunc (*sk_TYPE_set_cmp_func(STACK_OF(TYPE) *sk,
  56                                          sk_TYPE_compfunc compare));
  57  STACK_OF(TYPE) *sk_TYPE_new_reserve(sk_TYPE_compfunc compare, int n);
  58
  59 =head1 DESCRIPTION
  60
  61 Applications can create and use their own stacks by placing any of the macros
  62 described below in a header file. These macros define typesafe inline
  63 functions that wrap around the utility B<OPENSSL_sk_> API.
  64 In the description here, B<I<TYPE>> is used
  65 as a placeholder for any of the OpenSSL datatypes, such as B<X509>.
  66
  67 The STACK_OF() macro returns the name for a stack of the specified B<I<TYPE>>.
  68 This is an opaque pointer to a structure declaration.
  69 This can be used in every header file that references the stack.
  70 There are several B<DEFINE...> macros that create static inline functions
  71 for all of the functions described on this page.
  72 This should normally be used in one source file, and the stack manipulation
  73 is wrapped with application-specific functions.
  74
  75 DEFINE_STACK_OF() creates set of functions for a stack of B<I<TYPE>> elements.
  76 The type is referenced by
  77 B<STACK_OF>(B<I<TYPE>>) and each function name begins with B<sk_I<TYPE>_>.
  78 DEFINE_STACK_OF_CONST() is identical to DEFINE_STACK_OF() except
  79 each element is constant.
  80
  81  /* DEFINE_STACK_OF(TYPE) */
  82  TYPE *sk_TYPE_value(STACK_OF(TYPE) *sk, int idx);
  83  /* DEFINE_STACK_OF_CONST(TYPE) */
  84  const TYPE *sk_TYPE_value(STACK_OF(TYPE) *sk, int idx);
  85
  86 DEFINE_SPECIAL_STACK_OF() and DEFINE_SPECIAL_STACK_OF_CONST() are similar
  87 except B<FUNCNAME> is used in the function names:
  88
  89  /* DEFINE_SPECIAL_STACK_OF(TYPE, FUNCNAME) */
  90  TYPE *sk_FUNCNAME_value(STACK_OF(TYPE) *sk, int idx);
  91  /* DEFINE_SPECIAL_STACK_OF(TYPE, FUNCNAME) */
  92  const TYPE *sk_FUNCNAME_value(STACK_OF(TYPE) *sk, int idx);
  93
  94 B<sk_I<TYPE>_num>() returns the number of elements in I<sk> or -1 if I<sk> is
  95 NULL.
  96
  97 B<sk_I<TYPE>_value>() returns element I<idx> in I<sk>, where I<idx> starts at
  98 zero. If I<idx> is out of range then NULL is returned.
  99
 100 B<sk_I<TYPE>_new>() allocates a new empty stack using comparison function
 101 I<compare>. If I<compare> is NULL then no comparison function is used. This
 102 function is equivalent to B<sk_I<TYPE>_new_reserve>(I<compare>, 0).
 103
 104 B<sk_I<TYPE>_new_null>() allocates a new empty stack with no comparison
 105 function. This function is equivalent to B<sk_I<TYPE>_new_reserve>(NULL, 0).
 106
 107 B<sk_I<TYPE>_reserve>() allocates additional memory in the I<sk> structure
 108 such that the next I<n> calls to B<sk_I<TYPE>_insert>(), B<sk_I<TYPE>_push>()
 109 or B<sk_I<TYPE>_unshift>() will not fail or cause memory to be allocated
 110 or reallocated. If I<n> is zero, any excess space allocated in the
 111 I<sk> structure is freed. On error I<sk> is unchanged.
 112
 113 B<sk_I<TYPE>_new_reserve>() allocates a new stack. The new stack will have
 114 additional memory allocated to hold I<n> elements if I<n> is positive.
 115 The next I<n> calls to B<sk_I<TYPE>_insert>(), B<sk_I<TYPE>_push>() or
 116 B<sk_I<TYPE>_unshift>() will not fail or cause memory to be allocated or
 117 reallocated. If I<n> is zero or less than zero, no memory is allocated.
 118 B<sk_I<TYPE>_new_reserve>() also sets the comparison function I<compare>
 119 to the newly created stack. If I<compare> is NULL then no comparison
 120 function is used.
 121
 122 B<sk_I<TYPE>_set_cmp_func>() sets the comparison function of I<sk> to
 123 I<compare>. The previous comparison function is returned or NULL if there
 124 was no previous comparison function.
 125
 126 B<sk_I<TYPE>_free>() frees up the I<sk> structure. It does I<not> free up any
 127 elements of I<sk>. After this call I<sk> is no longer valid.
 128
 129 B<sk_I<TYPE>_zero>() sets the number of elements in I<sk> to zero. It does not
 130 free I<sk> so after this call I<sk> is still valid.
 131
 132 B<sk_I<TYPE>_pop_free>() frees up all elements of I<sk> and I<sk> itself. The
 133 free function freefunc() is called on each element to free it.
 134
 135 B<sk_I<TYPE>_delete>() deletes element I<i> from I<sk>. It returns the deleted
 136 element or NULL if I<i> is out of range.
 137
 138 B<sk_I<TYPE>_delete_ptr>() deletes element matching I<ptr> from I<sk>. It
 139 returns the deleted element or NULL if no element matching I<ptr> was found.
 140
 141 B<sk_I<TYPE>_insert>() inserts I<ptr> into I<sk> at position I<idx>. Any
 142 existing elements at or after I<idx> are moved downwards. If I<idx> is out
 143 of range the new element is appended to I<sk>. B<sk_I<TYPE>_insert>() either
 144 returns the number of elements in I<sk> after the new element is inserted or
 145 zero if an error (such as memory allocation failure) occurred.
 146
 147 B<sk_I<TYPE>_push>() appends I<ptr> to I<sk> it is equivalent to:
 148
 149  sk_TYPE_insert(sk, ptr, -1);
 150
 151 B<sk_I<TYPE>_unshift>() inserts I<ptr> at the start of I<sk> it is equivalent
 152 to:
 153
 154  sk_TYPE_insert(sk, ptr, 0);
 155
 156 B<sk_I<TYPE>_pop>() returns and removes the last element from I<sk>.
 157
 158 B<sk_I<TYPE>_shift>() returns and removes the first element from I<sk>.
 159
 160 B<sk_I<TYPE>_set>() sets element I<idx> of I<sk> to I<ptr> replacing the current
 161 element. The new element value is returned or NULL if an error occurred:
 162 this will only happen if I<sk> is NULL or I<idx> is out of range.
 163
 164 B<sk_I<TYPE>_find>() searches I<sk> for the element I<ptr>.  In the case
 165 where no comparison function has been specified, the function performs
 166 a linear search for a pointer equal to I<ptr>. The index of the first
 167 matching element is returned or B<-1> if there is no match. In the case
 168 where a comparison function has been specified, I<sk> is sorted then
 169 B<sk_I<TYPE>_find>() returns the index of a matching element or B<-1> if there
 170 is no match. Note that, in this case, the matching element returned is
 171 not guaranteed to be the first; the comparison function will usually
 172 compare the values pointed to rather than the pointers themselves and
 173 the order of elements in I<sk> could change.
 174
 175 B<sk_I<TYPE>_find_ex>() operates like B<sk_I<TYPE>_find>() except when a
 176 comparison function has been specified and no matching element is found.
 177 Instead of returning B<-1>, B<sk_I<TYPE>_find_ex>() returns the index of the
 178 element either before or after the location where I<ptr> would be if it were
 179 present in I<sk>.
 180
 181 B<sk_I<TYPE>_sort>() sorts I<sk> using the supplied comparison function.
 182
 183 B<sk_I<TYPE>_is_sorted>() returns B<1> if I<sk> is sorted and B<0> otherwise.
 184
 185 B<sk_I<TYPE>_dup>() returns a shallow copy of I<sk>
 186 or an empty stack if the passed stack is NULL.
 187 Note the pointers in the copy are identical to the original.
 188
 189 B<sk_I<TYPE>_deep_copy>() returns a new stack where each element has been
 190 copied or an empty stack if the passed stack is NULL.
 191 Copying is performed by the supplied copyfunc() and freeing by freefunc().
 192 The function freefunc() is only called if an error occurs.
 193
 194 =head1 NOTES
 195
 196 Care should be taken when accessing stacks in multi-threaded environments.
 197 Any operation which increases the size of a stack such as B<sk_I<TYPE>_insert>()
 198 or B<sk_I<TYPE>_push>() can "grow" the size of an internal array and cause race
 199 conditions if the same stack is accessed in a different thread. Operations such
 200 as B<sk_I<TYPE>_find>() and B<sk_I<TYPE>_sort>() can also reorder the stack.
 201
 202 Any comparison function supplied should use a metric suitable
 203 for use in a binary search operation. That is it should return zero, a
 204 positive or negative value if I<a> is equal to, greater than
 205 or less than I<b> respectively.
 206
 207 Care should be taken when checking the return values of the functions
 208 B<sk_I<TYPE>_find>() and B<sk_I<TYPE>_find_ex>(). They return an index to the
 209 matching element. In particular B<0> indicates a matching first element.
 210 A failed search is indicated by a B<-1> return value.
 211
 212 STACK_OF(), DEFINE_STACK_OF(), DEFINE_STACK_OF_CONST(), and
 213 DEFINE_SPECIAL_STACK_OF() are implemented as macros.
 214
 215 The underlying utility B<OPENSSL_sk_> API should not be used directly.
 216 It defines these functions: OPENSSL_sk_deep_copy(),
 217 OPENSSL_sk_delete(), OPENSSL_sk_delete_ptr(), OPENSSL_sk_dup(),
 218 OPENSSL_sk_find(), OPENSSL_sk_find_ex(), OPENSSL_sk_free(),
 219 OPENSSL_sk_insert(), OPENSSL_sk_is_sorted(), OPENSSL_sk_new(),
 220 OPENSSL_sk_new_null(), OPENSSL_sk_num(), OPENSSL_sk_pop(),
 221 OPENSSL_sk_pop_free(), OPENSSL_sk_push(), OPENSSL_sk_reserve(),
 222 OPENSSL_sk_set(), OPENSSL_sk_set_cmp_func(), OPENSSL_sk_shift(),
 223 OPENSSL_sk_sort(), OPENSSL_sk_unshift(), OPENSSL_sk_value(),
 224 OPENSSL_sk_zero().
 225
 226 =head1 RETURN VALUES
 227
 228 B<sk_I<TYPE>_num>() returns the number of elements in the stack or B<-1> if the
 229 passed stack is NULL.
 230
 231 B<sk_I<TYPE>_value>() returns a pointer to a stack element or NULL if the
 232 index is out of range.
 233
 234 B<sk_I<TYPE>_new>(), B<sk_I<TYPE>_new_null>() and B<sk_I<TYPE>_new_reserve>()
 235 return an empty stack or NULL if an error occurs.
 236
 237 B<sk_I<TYPE>_reserve>() returns B<1> on successful allocation of the required
 238 memory or B<0> on error.
 239
 240 B<sk_I<TYPE>_set_cmp_func>() returns the old comparison function or NULL if
 241 there was no old comparison function.
 242
 243 B<sk_I<TYPE>_free>(), B<sk_I<TYPE>_zero>(), B<sk_I<TYPE>_pop_free>() and
 244 B<sk_I<TYPE>_sort>() do not return values.
 245
 246 B<sk_I<TYPE>_pop>(), B<sk_I<TYPE>_shift>(), B<sk_I<TYPE>_delete>() and
 247 B<sk_I<TYPE>_delete_ptr>() return a pointer to the deleted element or NULL
 248 on error.
 249
 250 B<sk_I<TYPE>_insert>(), B<sk_I<TYPE>_push>() and B<sk_I<TYPE>_unshift>() return
 251 the total number of elements in the stack and 0 if an error occurred.
 252
 253 B<sk_I<TYPE>_set>() returns a pointer to the replacement element or NULL on
 254 error.
 255
 256 B<sk_I<TYPE>_find>() and B<sk_I<TYPE>_find_ex>() return an index to the found
 257 element or B<-1> on error.
 258
 259 B<sk_I<TYPE>_is_sorted>() returns B<1> if the stack is sorted and B<0> if it is
 260 not.
 261
 262 B<sk_I<TYPE>_dup>() and B<sk_I<TYPE>_deep_copy>() return a pointer to the copy
 263 of the stack or NULL on error.
 264
 265 =head1 HISTORY
 266
 267 Before OpenSSL 1.1.0, this was implemented via macros and not inline functions
 268 and was not a public API.
 269
 270 B<sk_I<TYPE>_reserve>() and B<sk_I<TYPE>_new_reserve>() were added in OpenSSL
 271 1.1.1.
 272
 273 =head1 COPYRIGHT
 274
 275 Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
 276
 277 Licensed under the Apache License 2.0 (the "License").  You may not use
 278 this file except in compliance with the License.  You can obtain a copy
 279 in the file LICENSE in the source distribution or at
 280 L<https://www.openssl.org/source/license.html>.
 281
 282 =cut