include/openssl/stack.h

/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 *
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 *
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 *
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.] */

#ifndef OPENSSL_HEADER_STACK_H
#define OPENSSL_HEADER_STACK_H

#include <openssl/base.h>

#if defined(__cplusplus)
extern "C" {
#endif


// A stack, in OpenSSL, is an array of pointers. They are the most commonly
// used collection object.
//
// This file defines macros for type-safe use of the stack functions. A stack
// type is named like |STACK_OF(FOO)| and is accessed with functions named
// like |sk_FOO_*|. Note the stack will typically contain /pointers/ to |FOO|.
//
// The |DECLARE_STACK_OF| macro makes |STACK_OF(FOO)| available, and
// |DEFINE_STACK_OF| makes the corresponding functions available.


// Defining stacks.

// STACK_OF expands to the stack type for |type|.
#define STACK_OF(type) struct stack_st_##type

// DECLARE_STACK_OF declares the |STACK_OF(type)| type. It does not make the
// corresponding |sk_type_*| functions available. This macro should be used in
// files which only need the type.
#define DECLARE_STACK_OF(type) STACK_OF(type);

// DEFINE_NAMED_STACK_OF defines |STACK_OF(name)| to be a stack whose elements
// are |type| *. This macro makes the |sk_name_*| functions available.
//
// It is not necessary to use |DECLARE_STACK_OF| in files which use this macro.
#define DEFINE_NAMED_STACK_OF(name, type)                    \
  BORINGSSL_DEFINE_STACK_OF_IMPL(name, type *, const type *) \
  BORINGSSL_DEFINE_STACK_TRAITS(name, type, false)

// DEFINE_STACK_OF defines |STACK_OF(type)| to be a stack whose elements are
// |type| *. This macro makes the |sk_type_*| functions available.
//
// It is not necessary to use |DECLARE_STACK_OF| in files which use this macro.
#define DEFINE_STACK_OF(type) DEFINE_NAMED_STACK_OF(type, type)

// DEFINE_CONST_STACK_OF defines |STACK_OF(type)| to be a stack whose elements
// are const |type| *. This macro makes the |sk_type_*| functions available.
//
// It is not necessary to use |DECLARE_STACK_OF| in files which use this macro.
#define DEFINE_CONST_STACK_OF(type)                                \
  BORINGSSL_DEFINE_STACK_OF_IMPL(type, const type *, const type *) \
  BORINGSSL_DEFINE_STACK_TRAITS(type, const type, true)


// Using stacks.
//
// After the |DEFINE_STACK_OF| macro is used, the following functions are
// available.

#if 0  // Sample

// sk_SAMPLE_free_func is a callback to free an element in a stack.
typedef void (*sk_SAMPLE_free_func)(SAMPLE *);

// sk_SAMPLE_copy_func is a callback to copy an element in a stack. It should
// return the copy or NULL on error.
typedef SAMPLE *(*sk_SAMPLE_copy_func)(const SAMPLE *);

// sk_SAMPLE_cmp_func is a callback to compare |*a| to |*b|. It should return a
// value < 0, 0, or > 0 if |*a| is less than, equal to, or greater than |*b|,
// respectively.  Note the extra indirection - the function is given a pointer
// to a pointer to the element. This is the |qsort|/|bsearch| comparison
// function applied to an array of |SAMPLE*|.
//
// TODO(https://crbug.com/boringssl/498): The parameters should be
// |const SAMPLE *const *|.
typedef int (*sk_SAMPLE_cmp_func)(const SAMPLE **a, const SAMPLE **b);

// sk_SAMPLE_new creates a new, empty stack with the given comparison function,
// which may be NULL. It returns the new stack or NULL on allocation failure.
STACK_OF(SAMPLE) *sk_SAMPLE_new(sk_SAMPLE_cmp_func comp);

// sk_SAMPLE_new_null creates a new, empty stack. It returns the new stack or
// NULL on allocation failure.
STACK_OF(SAMPLE) *sk_SAMPLE_new_null(void);

// sk_SAMPLE_num returns the number of elements in |sk|.
size_t sk_SAMPLE_num(const STACK_OF(SAMPLE) *sk);

// sk_SAMPLE_zero resets |sk| to the empty state but does nothing to free the
// individual elements themselves.
void sk_SAMPLE_zero(STACK_OF(SAMPLE) *sk);

// sk_SAMPLE_value returns the |i|th pointer in |sk|, or NULL if |i| is out of
// range.
SAMPLE *sk_SAMPLE_value(const STACK_OF(SAMPLE) *sk, size_t i);

// sk_SAMPLE_set sets the |i|th pointer in |sk| to |p| and returns |p|. If |i|
// is out of range, it returns NULL.
SAMPLE *sk_SAMPLE_set(STACK_OF(SAMPLE) *sk, size_t i, SAMPLE *p);

// sk_SAMPLE_free frees |sk|, but does nothing to free the individual elements.
// Use |sk_SAMPLE_pop_free| to also free the elements.
void sk_SAMPLE_free(STACK_OF(SAMPLE) *sk);

// sk_SAMPLE_pop_free calls |free_func| on each element in |sk| and then
// frees the stack itself.
void sk_SAMPLE_pop_free(STACK_OF(SAMPLE) *sk, sk_SAMPLE_free_func free_func);

// sk_SAMPLE_insert inserts |p| into the stack at index |where|, moving existing
// elements if needed. It returns the length of the new stack, or zero on
// error.
size_t sk_SAMPLE_insert(STACK_OF(SAMPLE) *sk, SAMPLE *p, size_t where);

// sk_SAMPLE_delete removes the pointer at index |where|, moving other elements
// down if needed. It returns the removed pointer, or NULL if |where| is out of
// range.
SAMPLE *sk_SAMPLE_delete(STACK_OF(SAMPLE) *sk, size_t where);

// sk_SAMPLE_delete_ptr removes, at most, one instance of |p| from |sk| based on
// pointer equality. If an instance of |p| is found then |p| is returned,
// otherwise it returns NULL.
SAMPLE *sk_SAMPLE_delete_ptr(STACK_OF(SAMPLE) *sk, const SAMPLE *p);

// sk_SAMPLE_delete_if_func is the callback function for |sk_SAMPLE_delete_if|.
// It should return one to remove |p| and zero to keep it.
typedef int (*sk_SAMPLE_delete_if_func)(SAMPLE *p, void *data);

// sk_SAMPLE_delete_if calls |func| with each element of |sk| and removes the
// entries where |func| returned one. This function does not free or return
// removed pointers so, if |sk| owns its contents, |func| should release the
// pointers prior to returning one.
void sk_SAMPLE_delete_if(STACK_OF(SAMPLE) *sk, sk_SAMPLE_delete_if_func func,
                         void *data);

// sk_SAMPLE_find find the first value in |sk| equal to |p|. |sk|'s comparison
// function determines equality, or pointer equality if |sk| has no comparison
// function.
//
// If the stack is sorted (see |sk_SAMPLE_sort|), this function uses a binary
// search. Otherwise it performs a linear search. If it finds a matching
// element, it writes the index to |*out_index| (if |out_index| is not NULL) and
// returns one. Otherwise, it returns zero.
//
// Note this differs from OpenSSL. The type signature is slightly different, and
// OpenSSL's version will implicitly sort |sk| if it has a comparison function
// defined.
int sk_SAMPLE_find(const STACK_OF(SAMPLE) *sk, size_t *out_index,
                   const SAMPLE *p);

// sk_SAMPLE_shift removes and returns the first element in |sk|, or NULL if
// |sk| is empty.
SAMPLE *sk_SAMPLE_shift(STACK_OF(SAMPLE) *sk);

// sk_SAMPLE_push appends |p| to |sk| and returns the length of the new stack,
// or 0 on allocation failure.
size_t sk_SAMPLE_push(STACK_OF(SAMPLE) *sk, SAMPLE *p);

// sk_SAMPLE_pop removes and returns the last element of |sk|, or NULL if |sk|
// is empty.
SAMPLE *sk_SAMPLE_pop(STACK_OF(SAMPLE) *sk);

// sk_SAMPLE_dup performs a shallow copy of a stack and returns the new stack,
// or NULL on error. Use |sk_SAMPLE_deep_copy| to also copy the elements.
STACK_OF(SAMPLE) *sk_SAMPLE_dup(const STACK_OF(SAMPLE) *sk);

// sk_SAMPLE_sort sorts the elements of |sk| into ascending order based on the
// comparison function. The stack maintains a "sorted" flag and sorting an
// already sorted stack is a no-op.
void sk_SAMPLE_sort(STACK_OF(SAMPLE) *sk);

// sk_SAMPLE_is_sorted returns one if |sk| is known to be sorted and zero
// otherwise.
int sk_SAMPLE_is_sorted(const STACK_OF(SAMPLE) *sk);

// sk_SAMPLE_set_cmp_func sets the comparison function to be used by |sk| and
// returns the previous one.
sk_SAMPLE_cmp_func sk_SAMPLE_set_cmp_func(STACK_OF(SAMPLE) *sk,
                                          sk_SAMPLE_cmp_func comp);

// sk_SAMPLE_deep_copy performs a copy of |sk| and of each of the non-NULL
// elements in |sk| by using |copy_func|. If an error occurs, it calls
// |free_func| to free any copies already made and returns NULL.
STACK_OF(SAMPLE) *sk_SAMPLE_deep_copy(const STACK_OF(SAMPLE) *sk,
                                      sk_SAMPLE_copy_func copy_func,
                                      sk_SAMPLE_free_func free_func);

#endif  // Sample


// Private functions.
//
// TODO(https://crbug.com/boringssl/499): Rename to |OPENSSL_sk_foo|, after
// external code that calls them is fixed.

// OPENSSL_sk_free_func is a function that frees an element in a stack. Note its
// actual type is void (*)(T *) for some T. Low-level |sk_*| functions will be
// passed a type-specific wrapper to call it correctly.
typedef void (*OPENSSL_sk_free_func)(void *ptr);

// OPENSSL_sk_copy_func is a function that copies an element in a stack. Note
// its actual type is T *(*)(const T *) for some T. Low-level |sk_*| functions
// will be passed a type-specific wrapper to call it correctly.
typedef void *(*OPENSSL_sk_copy_func)(const void *ptr);

// OPENSSL_sk_cmp_func is a comparison function that returns a value < 0, 0 or >
// 0 if |*a| is less than, equal to or greater than |*b|, respectively.  Note
// the extra indirection - the function is given a pointer to a pointer to the
// element. This differs from the usual qsort/bsearch comparison function.
//
// Note its actual type is |int (*)(const T **a, const T **b)|. Low-level |sk_*|
// functions will be passed a type-specific wrapper to call it correctly.
//
// TODO(https://crbug.com/boringssl/498): This type should be
// |const T *const *|. It is already fixed in OpenSSL 1.1.1, so hopefully we can
// fix this compatibly.
typedef int (*OPENSSL_sk_cmp_func)(const void **a, const void **b);

// OPENSSL_sk_delete_if_func is the generic version of
// |sk_SAMPLE_delete_if_func|.
typedef int (*OPENSSL_sk_delete_if_func)(void *obj, void *data);

// The following function types call the above type-erased signatures with the
// true types.
typedef void (*OPENSSL_sk_call_free_func)(OPENSSL_sk_free_func, void *);
typedef void *(*OPENSSL_sk_call_copy_func)(OPENSSL_sk_copy_func, const void *);
typedef int (*OPENSSL_sk_call_cmp_func)(OPENSSL_sk_cmp_func,
                                        const void *const *,
                                        const void *const *);
typedef int (*OPENSSL_sk_call_delete_if_func)(OPENSSL_sk_delete_if_func, void *,
                                              void *);

// stack_st contains an array of pointers. It is not designed to be used
// directly, rather the wrapper macros should be used.
typedef struct stack_st {
  // num contains the number of valid pointers in |data|.
  size_t num;
  void **data;
  // sorted is non-zero if the values pointed to by |data| are in ascending
  // order, based on |comp|.
  int sorted;
  // num_alloc contains the number of pointers allocated in the buffer pointed
  // to by |data|, which may be larger than |num|.
  size_t num_alloc;
  // comp is an optional comparison function.
  OPENSSL_sk_cmp_func comp;
} _STACK;

// The following are raw stack functions. They implement the corresponding typed
// |sk_SAMPLE_*| functions generated by |DEFINE_STACK_OF|. Callers shouldn't be
// using them. Rather, callers should use the typed functions.
OPENSSL_EXPORT _STACK *sk_new(OPENSSL_sk_cmp_func comp);
OPENSSL_EXPORT _STACK *sk_new_null(void);
OPENSSL_EXPORT size_t sk_num(const _STACK *sk);
OPENSSL_EXPORT void sk_zero(_STACK *sk);
OPENSSL_EXPORT void *sk_value(const _STACK *sk, size_t i);
OPENSSL_EXPORT void *sk_set(_STACK *sk, size_t i, void *p);
OPENSSL_EXPORT void sk_free(_STACK *sk);
OPENSSL_EXPORT void sk_pop_free_ex(_STACK *sk,
                                   OPENSSL_sk_call_free_func call_free_func,
                                   OPENSSL_sk_free_func free_func);
OPENSSL_EXPORT size_t sk_insert(_STACK *sk, void *p, size_t where);
OPENSSL_EXPORT void *sk_delete(_STACK *sk, size_t where);
OPENSSL_EXPORT void *sk_delete_ptr(_STACK *sk, const void *p);
OPENSSL_EXPORT void sk_delete_if(_STACK *sk,
                                 OPENSSL_sk_call_delete_if_func call_func,
                                 OPENSSL_sk_delete_if_func func, void *data);
OPENSSL_EXPORT int sk_find(const _STACK *sk, size_t *out_index, const void *p,
                           OPENSSL_sk_call_cmp_func call_cmp_func);
OPENSSL_EXPORT void *sk_shift(_STACK *sk);
OPENSSL_EXPORT size_t sk_push(_STACK *sk, void *p);
OPENSSL_EXPORT void *sk_pop(_STACK *sk);
OPENSSL_EXPORT _STACK *sk_dup(const _STACK *sk);
OPENSSL_EXPORT void sk_sort(_STACK *sk, OPENSSL_sk_call_cmp_func call_cmp_func);
OPENSSL_EXPORT int sk_is_sorted(const _STACK *sk);
OPENSSL_EXPORT OPENSSL_sk_cmp_func sk_set_cmp_func(_STACK *sk,
                                                   OPENSSL_sk_cmp_func comp);
OPENSSL_EXPORT _STACK *sk_deep_copy(const _STACK *sk,
                                    OPENSSL_sk_call_copy_func call_copy_func,
                                    OPENSSL_sk_copy_func copy_func,
                                    OPENSSL_sk_call_free_func call_free_func,
                                    OPENSSL_sk_free_func free_func);

// sk_pop_free behaves like |sk_pop_free_ex| but performs an invalid function
// pointer cast. It exists because some existing callers called |sk_pop_free|
// directly.
//
// TODO(davidben): Migrate callers to bssl::UniquePtr and remove this.
OPENSSL_EXPORT void sk_pop_free(_STACK *sk, OPENSSL_sk_free_func free_func);

#if !defined(BORINGSSL_NO_CXX)
extern "C++" {
BSSL_NAMESPACE_BEGIN
namespace internal {
template <typename T>
struct StackTraits {};
}
BSSL_NAMESPACE_END
}

#define BORINGSSL_DEFINE_STACK_TRAITS(name, type, is_const) \
  extern "C++" {                                            \
  BSSL_NAMESPACE_BEGIN                                      \
  namespace internal {                                      \
  template <>                                               \
  struct StackTraits<STACK_OF(name)> {                      \
    static constexpr bool kIsStack = true;                  \
    using Type = type;                                      \
    static constexpr bool kIsConst = is_const;              \
  };                                                        \
  }                                                         \
  BSSL_NAMESPACE_END                                        \
  }

#else
#define BORINGSSL_DEFINE_STACK_TRAITS(name, type, is_const)
#endif

#define BORINGSSL_DEFINE_STACK_OF_IMPL(name, ptrtype, constptrtype)           \
  /* We disable MSVC C4191 in this macro, which warns when pointers are cast  \
   * to the wrong type. While the cast itself is valid, it is often a bug     \
   * because calling it through the cast is UB. However, we never actually    \
   * call functions as |OPENSSL_sk_cmp_func|. The type is just a type-erased  \
   * function pointer. (C does not guarantee function pointers fit in         \
   * |void*|, and GCC will warn on this.) Thus we just disable the false      \
   * positive warning. */                                                     \
  OPENSSL_MSVC_PRAGMA(warning(push))                                          \
  OPENSSL_MSVC_PRAGMA(warning(disable : 4191))                                \
                                                                              \
  DECLARE_STACK_OF(name)                                                      \
                                                                              \
  typedef void (*sk_##name##_free_func)(ptrtype);                             \
  typedef ptrtype (*sk_##name##_copy_func)(constptrtype);                     \
  typedef int (*sk_##name##_cmp_func)(constptrtype *, constptrtype *);        \
  typedef int (*sk_##name##_delete_if_func)(ptrtype, void *);                 \
                                                                              \
  OPENSSL_INLINE void sk_##name##_call_free_func(                             \
      OPENSSL_sk_free_func free_func, void *ptr) {                            \
    ((sk_##name##_free_func)free_func)((ptrtype)ptr);                         \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE void *sk_##name##_call_copy_func(                            \
      OPENSSL_sk_copy_func copy_func, const void *ptr) {                      \
    return (void *)((sk_##name##_copy_func)copy_func)((constptrtype)ptr);     \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE int sk_##name##_call_cmp_func(OPENSSL_sk_cmp_func cmp_func,  \
                                               const void *const *a,          \
                                               const void *const *b) {        \
    /* The data is actually stored as |void*| pointers, so read the pointer   \
     * as |void*| and then pass the corrected type into the caller-supplied   \
     * function, which expects |constptrtype*|. */                            \
    constptrtype a_ptr = (constptrtype)*a;                                    \
    constptrtype b_ptr = (constptrtype)*b;                                    \
    return ((sk_##name##_cmp_func)cmp_func)(&a_ptr, &b_ptr);                  \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE int sk_##name##_call_delete_if_func(                         \
      OPENSSL_sk_delete_if_func func, void *obj, void *data) {                \
    return ((sk_##name##_delete_if_func)func)((ptrtype)obj, data);            \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE STACK_OF(name) *sk_##name##_new(sk_##name##_cmp_func comp) { \
    return (STACK_OF(name) *)sk_new((OPENSSL_sk_cmp_func)comp);               \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE STACK_OF(name) *sk_##name##_new_null(void) {                 \
    return (STACK_OF(name) *)sk_new_null();                                   \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE size_t sk_##name##_num(const STACK_OF(name) *sk) {           \
    return sk_num((const _STACK *)sk);                                        \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE void sk_##name##_zero(STACK_OF(name) *sk) {                  \
    sk_zero((_STACK *)sk);                                                    \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE ptrtype sk_##name##_value(const STACK_OF(name) *sk,          \
                                           size_t i) {                        \
    return (ptrtype)sk_value((const _STACK *)sk, i);                          \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE ptrtype sk_##name##_set(STACK_OF(name) *sk, size_t i,        \
                                         ptrtype p) {                         \
    return (ptrtype)sk_set((_STACK *)sk, i, (void *)p);                       \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE void sk_##name##_free(STACK_OF(name) *sk) {                  \
    sk_free((_STACK *)sk);                                                    \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE void sk_##name##_pop_free(STACK_OF(name) *sk,                \
                                           sk_##name##_free_func free_func) { \
    sk_pop_free_ex((_STACK *)sk, sk_##name##_call_free_func,                  \
                   (OPENSSL_sk_free_func)free_func);                          \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE size_t sk_##name##_insert(STACK_OF(name) *sk, ptrtype p,     \
                                           size_t where) {                    \
    return sk_insert((_STACK *)sk, (void *)p, where);                         \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE ptrtype sk_##name##_delete(STACK_OF(name) *sk,               \
                                            size_t where) {                   \
    return (ptrtype)sk_delete((_STACK *)sk, where);                           \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE ptrtype sk_##name##_delete_ptr(STACK_OF(name) *sk,           \
                                                constptrtype p) {             \
    return (ptrtype)sk_delete_ptr((_STACK *)sk, (const void *)p);             \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE void sk_##name##_delete_if(                                  \
      STACK_OF(name) *sk, sk_##name##_delete_if_func func, void *data) {      \
    sk_delete_if((_STACK *)sk, sk_##name##_call_delete_if_func,               \
                 (OPENSSL_sk_delete_if_func)func, data);                      \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE int sk_##name##_find(const STACK_OF(name) *sk,               \
                                      size_t *out_index, constptrtype p) {    \
    return sk_find((const _STACK *)sk, out_index, (const void *)p,            \
                   sk_##name##_call_cmp_func);                                \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE ptrtype sk_##name##_shift(STACK_OF(name) *sk) {              \
    return (ptrtype)sk_shift((_STACK *)sk);                                   \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE size_t sk_##name##_push(STACK_OF(name) *sk, ptrtype p) {     \
    return sk_push((_STACK *)sk, (void *)p);                                  \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE ptrtype sk_##name##_pop(STACK_OF(name) *sk) {                \
    return (ptrtype)sk_pop((_STACK *)sk);                                     \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE STACK_OF(name) *sk_##name##_dup(const STACK_OF(name) *sk) {  \
    return (STACK_OF(name) *)sk_dup((const _STACK *)sk);                      \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE void sk_##name##_sort(STACK_OF(name) *sk) {                  \
    sk_sort((_STACK *)sk, sk_##name##_call_cmp_func);                         \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE int sk_##name##_is_sorted(const STACK_OF(name) *sk) {        \
    return sk_is_sorted((const _STACK *)sk);                                  \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE sk_##name##_cmp_func sk_##name##_set_cmp_func(               \
      STACK_OF(name) *sk, sk_##name##_cmp_func comp) {                        \
    return (sk_##name##_cmp_func)sk_set_cmp_func((_STACK *)sk,                \
                                                 (OPENSSL_sk_cmp_func)comp);  \
  }                                                                           \
                                                                              \
  OPENSSL_INLINE STACK_OF(name) *sk_##name##_deep_copy(                       \
      const STACK_OF(name) *sk, sk_##name##_copy_func copy_func,              \
      sk_##name##_free_func free_func) {                                      \
    return (STACK_OF(name) *)sk_deep_copy(                                    \
        (const _STACK *)sk, sk_##name##_call_copy_func,                       \
        (OPENSSL_sk_copy_func)copy_func, sk_##name##_call_free_func,          \
        (OPENSSL_sk_free_func)free_func);                                     \
  }                                                                           \
                                                                              \
  OPENSSL_MSVC_PRAGMA(warning(pop))


// Built-in stacks.

typedef char *OPENSSL_STRING;

DEFINE_STACK_OF(void)
DEFINE_NAMED_STACK_OF(OPENSSL_STRING, char)


#if defined(__cplusplus)
}  // extern C
#endif

#if !defined(BORINGSSL_NO_CXX)
extern "C++" {

#include <type_traits>

BSSL_NAMESPACE_BEGIN

namespace internal {

// Stacks defined with |DEFINE_CONST_STACK_OF| are freed with |sk_free|.
template <typename Stack>
struct DeleterImpl<Stack, std::enable_if_t<StackTraits<Stack>::kIsConst>> {
  static void Free(Stack *sk) { sk_free(reinterpret_cast<_STACK *>(sk)); }
};

// Stacks defined with |DEFINE_STACK_OF| are freed with |sk_pop_free| and the
// corresponding type's deleter.
template <typename Stack>
struct DeleterImpl<Stack, std::enable_if_t<!StackTraits<Stack>::kIsConst>> {
  static void Free(Stack *sk) {
    // sk_FOO_pop_free is defined by macros and bound by name, so we cannot
    // access it from C++ here.
    using Type = typename StackTraits<Stack>::Type;
    sk_pop_free_ex(reinterpret_cast<_STACK *>(sk),
                   [](OPENSSL_sk_free_func /* unused */, void *ptr) {
                     DeleterImpl<Type>::Free(reinterpret_cast<Type *>(ptr));
                   },
                   nullptr);
  }
};

template <typename Stack>
class StackIteratorImpl {
 public:
  using Type = typename StackTraits<Stack>::Type;
  // Iterators must be default-constructable.
  StackIteratorImpl() : sk_(nullptr), idx_(0) {}
  StackIteratorImpl(const Stack *sk, size_t idx) : sk_(sk), idx_(idx) {}

  bool operator==(StackIteratorImpl other) const {
    return sk_ == other.sk_ && idx_ == other.idx_;
  }
  bool operator!=(StackIteratorImpl other) const {
    return !(*this == other);
  }

  Type *operator*() const {
    return reinterpret_cast<Type *>(
        sk_value(reinterpret_cast<const _STACK *>(sk_), idx_));
  }

  StackIteratorImpl &operator++(/* prefix */) {
    idx_++;
    return *this;
  }

  StackIteratorImpl operator++(int /* postfix */) {
    StackIteratorImpl copy(*this);
    ++(*this);
    return copy;
  }

 private:
  const Stack *sk_;
  size_t idx_;
};

template <typename Stack>
using StackIterator =
    std::enable_if_t<StackTraits<Stack>::kIsStack, StackIteratorImpl<Stack>>;

}  // namespace internal

// PushToStack pushes |elem| to |sk|. It returns true on success and false on
// allocation failure.
template <typename Stack>
inline std::enable_if_t<!internal::StackTraits<Stack>::kIsConst, bool>
PushToStack(Stack *sk,
            UniquePtr<typename internal::StackTraits<Stack>::Type> elem) {
  if (!sk_push(reinterpret_cast<_STACK *>(sk), elem.get())) {
    return false;
  }
  // sk_push takes ownership on success.
  elem.release();
  return true;
}

BSSL_NAMESPACE_END

// Define begin() and end() for stack types so C++ range for loops work.
template <typename Stack>
inline bssl::internal::StackIterator<Stack> begin(const Stack *sk) {
  return bssl::internal::StackIterator<Stack>(sk, 0);
}

template <typename Stack>
inline bssl::internal::StackIterator<Stack> end(const Stack *sk) {
  return bssl::internal::StackIterator<Stack>(
      sk, sk_num(reinterpret_cast<const _STACK *>(sk)));
}

}  // extern C++
#endif

#endif  // OPENSSL_HEADER_STACK_H