/*
* Secure Memory Buffers
* (C) 1999-2007,2012 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#ifndef BOTAN_SECURE_MEMORY_BUFFERS_H__
#define BOTAN_SECURE_MEMORY_BUFFERS_H__

#include <botan/mem_ops.h>
#include <algorithm>
#include <vector>
#include <deque>
#include <type_traits>

#if defined(BOTAN_HAS_LOCKING_ALLOCATOR)
  #include <botan/locking_allocator.h>
#endif

namespace Botan {

template<typename T>
class secure_allocator
   {
   public:
      /*
      * Assert exists to prevent someone from doing something that will
      * probably crash anyway (like secure_vector<non_POD_t> where ~non_POD_t
      * deletes a member pointer which was zeroed before it ran).
      * MSVC in debug mode uses non-integral proxy types in container types
      * like std::vector, thus we disable the check there.
      */
#if !defined(_ITERATOR_DEBUG_LEVEL) || _ITERATOR_DEBUG_LEVEL == 0
      static_assert(std::is_integral<T>::value, "secure_allocator supports only integer types");
#endif

      typedef T          value_type;

      typedef T*         pointer;
      typedef const T*   const_pointer;

      typedef T&         reference;
      typedef const T&   const_reference;

      typedef std::size_t     size_type;
      typedef std::ptrdiff_t  difference_type;

      secure_allocator() BOTAN_NOEXCEPT {}

      template<typename U>
      secure_allocator(const secure_allocator<U>&) BOTAN_NOEXCEPT {}

      ~secure_allocator() BOTAN_NOEXCEPT {}

      pointer address(reference x) const BOTAN_NOEXCEPT
         { return std::addressof(x); }

      const_pointer address(const_reference x) const BOTAN_NOEXCEPT
         { return std::addressof(x); }

      pointer allocate(size_type n, const void* = 0)
         {
#if defined(BOTAN_HAS_LOCKING_ALLOCATOR)
         if(pointer p = static_cast<pointer>(mlock_allocator::instance().allocate(n, sizeof(T))))
            return p;
#endif

         pointer p = new T[n];
         clear_mem(p, n);
         return p;
         }

      void deallocate(pointer p, size_type n)
         {
         zero_mem(p, n);

#if defined(BOTAN_HAS_LOCKING_ALLOCATOR)
         if(mlock_allocator::instance().deallocate(p, n, sizeof(T)))
            return;
#endif

         delete [] p;
         }

      size_type max_size() const BOTAN_NOEXCEPT
         {
         return static_cast<size_type>(-1) / sizeof(T);
         }

      template<typename U, typename... Args>
      void construct(U* p, Args&&... args)
         {
         ::new(static_cast<void*>(p)) U(std::forward<Args>(args)...);
         }

#ifdef _MSC_VER
#pragma warning(push)
#pragma warning(disable: 4100)
      template<typename U> void destroy(U* p) { p->~U(); }
#pragma warning(pop)
#endif
   };

template<typename T, typename U> inline bool
operator==(const secure_allocator<T>&, const secure_allocator<U>&)
   { return true; }

template<typename T, typename U> inline bool
operator!=(const secure_allocator<T>&, const secure_allocator<U>&)
   { return false; }

template<typename T> using secure_vector = std::vector<T, secure_allocator<T>>;
template<typename T> using secure_deque = std::deque<T, secure_allocator<T>>;

template<typename T>
std::vector<T> unlock(const secure_vector<T>& in)
   {
   std::vector<T> out(in.size());
   copy_mem(out.data(), in.data(), in.size());
   return out;
   }

template<typename T, typename Alloc>
size_t buffer_insert(std::vector<T, Alloc>& buf,
                     size_t buf_offset,
                     const T input[],
                     size_t input_length)
   {
   const size_t to_copy = std::min(input_length, buf.size() - buf_offset);
   if (to_copy > 0)
      {
      copy_mem(&buf[buf_offset], input, to_copy);
      }
   return to_copy;
   }

template<typename T, typename Alloc, typename Alloc2>
size_t buffer_insert(std::vector<T, Alloc>& buf,
                     size_t buf_offset,
                     const std::vector<T, Alloc2>& input)
   {
   const size_t to_copy = std::min(input.size(), buf.size() - buf_offset);
   if (to_copy > 0)
      {
      copy_mem(&buf[buf_offset], input.data(), to_copy);
      }
   return to_copy;
   }

template<typename T, typename Alloc, typename Alloc2>
std::vector<T, Alloc>&
operator+=(std::vector<T, Alloc>& out,
           const std::vector<T, Alloc2>& in)
   {
   const size_t copy_offset = out.size();
   out.resize(out.size() + in.size());
   if (in.size() > 0)
      {
      copy_mem(&out[copy_offset], in.data(), in.size());
      }
   return out;
   }

template<typename T, typename Alloc>
std::vector<T, Alloc>& operator+=(std::vector<T, Alloc>& out, T in)
   {
   out.push_back(in);
   return out;
   }

template<typename T, typename Alloc, typename L>
std::vector<T, Alloc>& operator+=(std::vector<T, Alloc>& out,
                                  const std::pair<const T*, L>& in)
   {
   const size_t copy_offset = out.size();
   out.resize(out.size() + in.second);
   if (in.second > 0)
      {
      copy_mem(&out[copy_offset], in.first, in.second);
      }
   return out;
   }

template<typename T, typename Alloc, typename L>
std::vector<T, Alloc>& operator+=(std::vector<T, Alloc>& out,
                                  const std::pair<T*, L>& in)
   {
   const size_t copy_offset = out.size();
   out.resize(out.size() + in.second);
   if (in.second > 0)
      {
      copy_mem(&out[copy_offset], in.first, in.second);
      }
   return out;
   }

/**
* Zeroise the values; length remains unchanged
* @param vec the vector to zeroise
*/
template<typename T, typename Alloc>
void zeroise(std::vector<T, Alloc>& vec)
   {
   clear_mem(vec.data(), vec.size());
   }

/**
* Zeroise the values then free the memory
* @param vec the vector to zeroise and free
*/
template<typename T, typename Alloc>
void zap(std::vector<T, Alloc>& vec)
   {
   zeroise(vec);
   vec.clear();
   vec.shrink_to_fit();
   }

}

#endif