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Diffstat (limited to 'doc/crypto/stack.pod')
-rw-r--r-- | doc/crypto/stack.pod | 212 |
1 files changed, 212 insertions, 0 deletions
diff --git a/doc/crypto/stack.pod b/doc/crypto/stack.pod new file mode 100644 index 0000000000..1defff0328 --- /dev/null +++ b/doc/crypto/stack.pod @@ -0,0 +1,212 @@ +=pod + +=head1 NAME + +DEFINE_STACK_OF, DEFINE_STACK_OF_CONST, DEFINE_SPECIAL_STACK_OF, +sk_TYPE_num, sk_TYPE_value, sk_TYPE_new, sk_TYPE_new_null, 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 - +stack container + +=head1 SYNOPSIS + + #include <openssl/safestack.h> + + #define STACK_OF(TYPE) + #define DEFINE_STACK_OF + #define DEFINE_STACK_OF_CONST + #define DEFINE_SPECIAL_STACK_OF + + 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); + 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, TYPE *ptr); + int sk_TYPE_unshift(STACK_OF(TYPE) *sk, 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, 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(STACK_OF(TYPE) *sk); + STACK_OF(TYPE) *sk_TYPE_deep_copy(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); + +=head1 DESCRIPTION + +Applications can create and use their own stacks by placing any of the macros +described below in a header file. In the description below, I<TYPE> is used +as a placeholder for any of the OpenSSL datatypes, such as I<X509>. + +DEFINE_STACK_OF(TYPE) creates set of functions for a stack of B<TYPE>. This +will mean that type B<TYPE> is stored in each stack, the type is referenced by +STACK_OF(TYPE) and each function name begins with I<sk_TYPE_>. For example: + + TYPE *sk_TYPE_value(STACK_OF(TYPE) *sk, int idx); + +DEFINE_STACK_OF_CONST(TYPE) is identical to DEFINE_STACK_OF(TYPE) except +each element is constant. For example: + + const TYPE *sk_TYPE_value(STACK_OF(TYPE) *sk, int idx); + +DEFINE_SPECIAL_STACK_OF(FUNCNAME, TYPE) defines a stack of B<TYPE> but +each function uses B<FUNCNAME> in the function name. For example: + + TYPE *sk_FUNCNAME_value(STACK_OF(TYPE) *sk, int idx); + +sk_TYPE_num() returns the number of elements in B<sk> or -1 if B<sk> is +B<NULL>. + +sk_TYPE_value() returns element B<idx> in B<sk>, where B<idx> starts at +zero. If B<idx> is out of range then B<NULL> is returned. + +sk_TYPE_new() allocates a new empty stack using comparison function B<compar>. +If B<compar> is B<NULL> then no comparison function is used. + +sk_TYPE_new_null() allocates a new empty stack with no comparison function. + +sk_TYPE_set_cmp_func() sets the comparison function of B<sk> to B<compar>. +The previous comparison function is returned or B<NULL> if there was +no previous comparison function. + +sk_TYPE_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_TYPE_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_TYPE_pop_free() frees up all elements of B<sk> and B<sk> itself. The +free function freefunc() is called on each element to free it. + +sk_TYPE_delete() deletes element B<i> from B<sk>. It returns the deleted +element or B<NULL> if B<i> is out of range. + +sk_TYPE_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_TYPE_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_TYPE_insert() either returns the +number of elements in B<sk> after the new element is inserted or zero if +an error (such as memory allocation failure) occurred. + +sk_TYPE_push() appends B<ptr> to B<sk> it is equivalent to: + + sk_TYPE_insert(sk, ptr, -1); + +sk_TYPE_unshift() inserts B<ptr> at the start of B<sk> it is equivalent to: + + sk_TYPE_insert(sk, ptr, 0); + +sk_TYPE_pop() returns and removes the last element from B<sk>. + +sk_TYPE_shift() returns and removes the first element from B<sk>. + +sk_TYPE_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_TYPE_find() and sk_TYPE_find_ex() search B<sk> using the supplied +comparison function for an element matching B<ptr>. sk_TYPE_find() returns +the index of the first matching element or B<-1> if there is no match. +sk_TYPE_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_TYPE_sort() sorts B<sk> using the supplied comparison function. + +sk_TYPE_is_sorted() returns B<1> if B<sk> is sorted and B<0> otherwise. + +sk_TYPE_dup() returns a copy of B<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. + +=head1 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 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_TYPE_find() and sk_TYPE_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 RETURN VALUES + +sk_TYPE_num() returns the number of elements in the stack or B<-1> if the +passed stack is B<NULL>. + +sk_TYPE_value() returns a pointer to a stack element or B<NULL> if the +index is out of range. + +sk_TYPE_new() and sk_TYPE_new_null() return an empty stack or B<NULL> if +an error occurs. + +sk_TYPE_set_cmp_func() returns the old comparison function or B<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 B<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 B<NULL> on +error. + +sk_TYPE_find() and sk_TYPE_find_ex() return an index to the found element +or B<-1> on error. + +sk_TYPE_is_sorted() returns B<1> if the stack is sorted and B<0> if it is +not. + +sk_TYPE_dup() and sk_TYPE_deep_copy() return a pointer to the copy of the +stack. + +=head1 HISTORY + +Before OpenSSL 1.1.0, this was implemented via macros and not inline functions +and was not a public API. + +=head1 COPYRIGHT + +Copyright 2000-2016 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 |