text: /* 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"
  
  #include "openssl/type_check.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
  // of a specific type of object has type |STACK_OF(type)|. This can be defined
  // (once) with |DEFINE_STACK_OF(type)| and declared where needed with
  // |DECLARE_STACK_OF(type)|. For example:
  //
  //   typedef struct foo_st {
  //     int bar;
  //   } FOO;
  //
  //   DEFINE_STACK_OF(FOO);
  //
  // Although note that the stack will contain /pointers/ to |FOO|.
  //
  // A macro will be defined for each of the sk_* functions below. For
  // STACK_OF(FOO), the macros would be sk_FOO_new, sk_FOO_pop etc.
  
  
  // stack_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 (*stack_free_func)(void *ptr);
  
  // stack_copy_func is a function that copies an element in a stack. Note its
  // actual type is T *(*)(T *) for some T. Low-level |sk_*| functions will be
  // passed a type-specific wrapper to call it correctly.
  typedef void *(*stack_copy_func)(void *ptr);
  
  // stack_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 **, const T **). Low-level |sk_*|
  // functions will be passed a type-specific wrapper to call it correctly.
  typedef int (*stack_cmp_func)(const void **a, const void **b);
  
  // 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.
    stack_cmp_func comp;
  } _STACK;
  
  
  #define STACK_OF(type) struct stack_st_##type
  
  #define DECLARE_STACK_OF(type) STACK_OF(type);
  
  // These are the raw stack functions, you shouldn't be using them. Rather you
  // should be using the type stack macros implemented above.
  
  // sk_new creates a new, empty stack with the given comparison function, which
  // may be zero. It returns the new stack or NULL on allocation failure.
  OPENSSL_EXPORT _STACK *sk_new(stack_cmp_func comp);
  
  // sk_new_null creates a new, empty stack. It returns the new stack or NULL on
  // allocation failure.
  OPENSSL_EXPORT _STACK *sk_new_null(void);
  
  // sk_num returns the number of elements in |s|.
  OPENSSL_EXPORT size_t sk_num(const _STACK *sk);
  
  // sk_zero resets |sk| to the empty state but does nothing to free the
  // individual elements themselves.
  OPENSSL_EXPORT void sk_zero(_STACK *sk);
  
  // sk_value returns the |i|th pointer in |sk|, or NULL if |i| is out of
  // range.
  OPENSSL_EXPORT void *sk_value(const _STACK *sk, size_t i);
  
  // sk_set sets the |i|th pointer in |sk| to |p| and returns |p|. If |i| is out
  // of range, it returns NULL.
  OPENSSL_EXPORT void *sk_set(_STACK *sk, size_t i, void *p);
  
  // sk_free frees the given stack and array of pointers, but does nothing to
  // free the individual elements. Also see |sk_pop_free_ex|.
  OPENSSL_EXPORT void sk_free(_STACK *sk);
  
  // sk_pop_free_ex calls |free_func| on each element in the stack and then frees
  // the stack itself. Note this corresponds to |sk_FOO_pop_free|. It is named
  // |sk_pop_free_ex| as a workaround for existing code calling an older version
  // of |sk_pop_free|.
  OPENSSL_EXPORT void sk_pop_free_ex(_STACK *sk,
                                     void (*call_free_func)(stack_free_func,
                                                            void *),
                                     stack_free_func free_func);
  
  // sk_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.
  OPENSSL_EXPORT size_t sk_insert(_STACK *sk, void *p, size_t where);
  
  // sk_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.
  OPENSSL_EXPORT void *sk_delete(_STACK *sk, size_t where);
  
  // sk_delete_ptr removes, at most, one instance of |p| from the stack based on
  // pointer equality. If an instance of |p| is found then |p| is returned,
  // otherwise it returns NULL.
  OPENSSL_EXPORT void *sk_delete_ptr(_STACK *sk, const void *p);
  
  // sk_find returns the first value in the stack equal to |p|. If a comparison
  // function has been set on the stack, equality is defined by it, otherwise
  // pointer equality is used. If the stack is sorted, then a binary search is
  // used, otherwise a linear search is performed. If a matching element is found,
  // its index is written to
  // |*out_index| (if |out_index| is not NULL) and one is returned. Otherwise zero
  // is returned.
  //
  // Note this differs from OpenSSL. The type signature is slightly different, and
  // OpenSSL's sk_find will implicitly sort |sk| if it has a comparison function
  // defined.
  OPENSSL_EXPORT int sk_find(const _STACK *sk, size_t *out_index, const void *p,
                             int (*call_cmp_func)(stack_cmp_func, const void **,
                                                  const void **));
  
  // sk_shift removes and returns the first element in the stack, or returns NULL
  // if the stack is empty.
  OPENSSL_EXPORT void *sk_shift(_STACK *sk);
  
  // sk_push appends |p| to the stack and returns the length of the new stack, or
  // 0 on allocation failure.
  OPENSSL_EXPORT size_t sk_push(_STACK *sk, void *p);
  
  // sk_pop returns and removes the last element on the stack, or NULL if the
  // stack is empty.
  OPENSSL_EXPORT void *sk_pop(_STACK *sk);
  
  // sk_dup performs a shallow copy of a stack and returns the new stack, or NULL
  // on error.
  OPENSSL_EXPORT _STACK *sk_dup(const _STACK *sk);
  
  // sk_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.
  OPENSSL_EXPORT void sk_sort(_STACK *sk);
  
  // sk_is_sorted returns one if |sk| is known to be sorted and zero
  // otherwise.
  OPENSSL_EXPORT int sk_is_sorted(const _STACK *sk);
  
  // sk_set_cmp_func sets the comparison function to be used by |sk| and returns
  // the previous one.
  OPENSSL_EXPORT stack_cmp_func sk_set_cmp_func(_STACK *sk, stack_cmp_func comp);
  
  // sk_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, |free_func| is used to free
  // any copies already made and NULL is returned.
  OPENSSL_EXPORT _STACK *sk_deep_copy(
      const _STACK *sk, void *(*call_copy_func)(stack_copy_func, void *),
      stack_copy_func copy_func, void (*call_free_func)(stack_free_func, void *),
      stack_free_func free_func);
  
  
  // Deprecated functions.
  
  // 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, stack_free_func free_func);
  
  
  // Defining stack types.
  //
  // This set of macros is used to emit the typed functions that act on a
  // |STACK_OF(T)|.
  
  #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)            \
    DECLARE_STACK_OF(name)                                                       \
                                                                                 \
    typedef void (*stack_##name##_free_func)(ptrtype);                           \
    typedef ptrtype (*stack_##name##_copy_func)(ptrtype);                        \
    typedef int (*stack_##name##_cmp_func)(constptrtype *a, constptrtype *b);    \
                                                                                 \
    OPENSSL_INLINE void sk_##name##_call_free_func(stack_free_func free_func,    \
                                                   void *ptr) {                  \
      ((stack_##name##_free_func)free_func)((ptrtype)ptr);                       \
    }                                                                            \
                                                                                 \
    OPENSSL_INLINE void *sk_##name##_call_copy_func(stack_copy_func copy_func,   \
                                                    void *ptr) {                 \
      return (void *)((stack_##name##_copy_func)copy_func)((ptrtype)ptr);        \
    }                                                                            \
                                                                                 \
    OPENSSL_INLINE int sk_##name##_call_cmp_func(                                \
        stack_cmp_func cmp_func, const void **a, const void **b) {               \
      constptrtype a_ptr = (constptrtype)*a;                                     \
      constptrtype b_ptr = (constptrtype)*b;                                     \
      return ((stack_##name##_cmp_func)cmp_func)(&a_ptr, &b_ptr);                \
    }                                                                            \
                                                                                 \
    OPENSSL_INLINE STACK_OF(name) *                                              \
        sk_##name##_new(stack_##name##_cmp_func comp) {                          \
      return (STACK_OF(name) *)sk_new((stack_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, stack_##name##_free_func free_func) {               \
      sk_pop_free_ex((_STACK *)sk, sk_##name##_call_free_func,                   \
                     (stack_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 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);                                                     \
    }                                                                            \
                                                                                 \
    OPENSSL_INLINE int sk_##name##_is_sorted(const STACK_OF(name) *sk) {         \
      return sk_is_sorted((const _STACK *)sk);                                   \
    }                                                                            \
                                                                                 \
    OPENSSL_INLINE stack_##name##_cmp_func sk_##name##_set_cmp_func(             \
        STACK_OF(name) *sk, stack_##name##_cmp_func comp) {                      \
      return (stack_##name##_cmp_func)sk_set_cmp_func((_STACK *)sk,              \
                                                      (stack_cmp_func)comp);     \
    }                                                                            \
                                                                                 \
    OPENSSL_INLINE STACK_OF(name) *                                              \
        sk_##name##_deep_copy(const STACK_OF(name) *sk,                          \
                              ptrtype(*copy_func)(ptrtype),                      \
                              void (*free_func)(ptrtype)) {                      \
      return (STACK_OF(name) *)sk_deep_copy(                                     \
          (const _STACK *)sk, sk_##name##_call_copy_func,                        \
          (stack_copy_func)copy_func, sk_##name##_call_free_func,                \
          (stack_free_func)free_func);                                           \
    }
  
  // DEFINE_NAMED_STACK_OF defines |STACK_OF(name)| to be a stack whose elements
  // are |type| *.
  #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| *.
  #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| *.
  #define DEFINE_CONST_STACK_OF(type)                                \
    BORINGSSL_DEFINE_STACK_OF_IMPL(type, const type *, const type *) \
    BORINGSSL_DEFINE_STACK_TRAITS(type, const type, true)
  
  // DEFINE_SPECIAL_STACK_OF defines |STACK_OF(type)| to be a stack whose elements
  // are |type|, where |type| must be a typedef for a pointer.
  #define DEFINE_SPECIAL_STACK_OF(type)                   \
    OPENSSL_STATIC_ASSERT(sizeof(type) == sizeof(void *), \
                          #type " is not a pointer");     \
    BORINGSSL_DEFINE_STACK_OF_IMPL(type, type, const type)
  
  
  typedef char *OPENSSL_STRING;
  
  DEFINE_STACK_OF(void)
  DEFINE_SPECIAL_STACK_OF(OPENSSL_STRING)
  
  
  #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, typename std::enable_if<StackTraits<Stack>::kIsConst>::type> {
    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, typename std::enable_if<!StackTraits<Stack>::kIsConst>::type> {
    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),
                     [](stack_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 = typename std::enable_if<StackTraits<Stack>::kIsStack,
                                                StackIteratorImpl<Stack>>::type;
  
  }  // namespace internal
  
  // PushToStack pushes |elem| to |sk|. It returns true on success and false on
  // allocation failure.
  template <typename Stack>
  inline
      typename std::enable_if<!internal::StackTraits<Stack>::kIsConst, bool>::type
      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
  