source: trunk/src-cryptopp/secblock.h

// secblock.h - written and placed in the public domain by Wei Dai

//! \file secblock.h
//! \brief Classes and functions for secure memory allocations.

#ifndef CRYPTOPP_SECBLOCK_H
#define CRYPTOPP_SECBLOCK_H

#include "config.h"
#include "stdcpp.h"
#include "misc.h"

#if CRYPTOPP_MSC_VERSION
# pragma warning(push)
# pragma warning(disable: 4700)
# if (CRYPTOPP_MSC_VERSION >= 1400)
#  pragma warning(disable: 6386)
# endif
#endif

NAMESPACE_BEGIN(CryptoPP)

// ************** secure memory allocation ***************

//! \class AllocatorBase
//! \brief Base class for all allocators used by SecBlock
//! \tparam T the class or type
template<class T>
class AllocatorBase
{
public:
        typedef T value_type;
        typedef size_t size_type;
#ifdef CRYPTOPP_MSVCRT6
        typedef ptrdiff_t difference_type;
#else
        typedef std::ptrdiff_t difference_type;
#endif
        typedef T * pointer;
        typedef const T * const_pointer;
        typedef T & reference;
        typedef const T & const_reference;

        pointer address(reference r) const {return (&r);}
        const_pointer address(const_reference r) const {return (&r); }
        void construct(pointer p, const T& val) {new (p) T(val);}
        void destroy(pointer p) {CRYPTOPP_UNUSED(p); p->~T();}

        //! \brief Returns the maximum number of elements the allocator can provide
        //! \returns the maximum number of elements the allocator can provide
        //! \details Internally, preprocessor macros are used rather than std::numeric_limits
        //!   because the latter is \a not a \a constexpr. Some compilers, like Clang, do not
        //!   optimize it well under all circumstances. Compilers like GCC, ICC and MSVC appear
        //!   to optimize it well in either form.
        CRYPTOPP_CONSTEXPR size_type max_size() const {return (SIZE_MAX/sizeof(T));}

#if defined(CRYPTOPP_CXX11_VARIADIC_TEMPLATES) || defined(CRYPTOPP_DOXYGEN_PROCESSING)

        //! \brief Constructs a new U using variadic arguments
        //! \tparam U the type to be forwarded
        //! \tparam Args the arguments to be forwarded
        //! \param ptr pointer to type U
        //! \param args variadic arguments
        //! \details This is a C++11 feature. It is available when CRYPTOPP_CXX11_VARIADIC_TEMPLATES
        //!   is defined. The define is controlled by compiler versions detected in config.h.
    template<typename U, typename... Args>
    void construct(U* ptr, Args&&... args) {::new ((void*)ptr) U(std::forward<Args>(args)...);}

        //! \brief Destroys an U constructed with variadic arguments
        //! \tparam U the type to be forwarded
        //! \details This is a C++11 feature. It is available when CRYPTOPP_CXX11_VARIADIC_TEMPLATES
        //!   is defined. The define is controlled by compiler versions detected in config.h.
    template<typename U>
    void destroy(U* ptr) {if(ptr) ptr->~U();}

#endif

protected:

        //! \brief Verifies the allocator can satisfy a request based on size
        //! \param size the size of the allocation, in elements
        //! \throws InvalidArgument
        //! \details CheckSize verifies the number of elements requested is valid.
        //! \details If size is greater than max_size(), then InvalidArgument is thrown.
        //!   The library throws InvalidArgument if the size is too large to satisfy.
        //! \details Internally, preprocessor macros are used rather than std::numeric_limits
        //!   because the latter is \a not a \a constexpr. Some compilers, like Clang, do not
        //!   optimize it well under all circumstances. Compilers like GCC, ICC and MSVC appear
        //!   to optimize it well in either form.
        //! \note size is the count of elements, and not the number of bytes
        static void CheckSize(size_t size)
        {
                // C++ throws std::bad_alloc (C++03) or std::bad_array_new_length (C++11) here.
                if (size > (SIZE_MAX/sizeof(T)))
                        throw InvalidArgument("AllocatorBase: requested size would cause integer overflow");
        }
};

#define CRYPTOPP_INHERIT_ALLOCATOR_TYPES        \
typedef typename AllocatorBase<T>::value_type value_type;\
typedef typename AllocatorBase<T>::size_type size_type;\
typedef typename AllocatorBase<T>::difference_type difference_type;\
typedef typename AllocatorBase<T>::pointer pointer;\
typedef typename AllocatorBase<T>::const_pointer const_pointer;\
typedef typename AllocatorBase<T>::reference reference;\
typedef typename AllocatorBase<T>::const_reference const_reference;

//! \brief Reallocation function
//! \tparam T the class or type
//! \tparam A the class or type's allocator
//! \param alloc the allocator
//! \param oldPtr the previous allocation
//! \param oldSize the size of the previous allocation
//! \param newSize the new, requested size
//! \param preserve flag that indicates if the old allocation should be preserved
//! \note oldSize and newSize are the count of elements, and not the
//!   number of bytes.
template <class T, class A>
typename A::pointer StandardReallocate(A& alloc, T *oldPtr, typename A::size_type oldSize, typename A::size_type newSize, bool preserve)
{
        CRYPTOPP_ASSERT((oldPtr && oldSize) || !(oldPtr || oldSize));
        if (oldSize == newSize)
                return oldPtr;

        if (preserve)
        {
                typename A::pointer newPointer = alloc.allocate(newSize, NULL);
                const size_t copySize = STDMIN(oldSize, newSize) * sizeof(T);

                if (oldPtr && newPointer) {memcpy_s(newPointer, copySize, oldPtr, copySize);}
                alloc.deallocate(oldPtr, oldSize);
                return newPointer;
        }
        else
        {
                alloc.deallocate(oldPtr, oldSize);
                return alloc.allocate(newSize, NULL);
        }
}

//! \class AllocatorWithCleanup
//! \brief Allocates a block of memory with cleanup
//! \tparam T class or type
//! \tparam T_Align16 boolean that determines whether allocations should be aligned on 16-byte boundaries
//! \details If T_Align16 is true, then AllocatorWithCleanup calls AlignedAllocate()
//!    for memory allocations. If T_Align16 is false, then AllocatorWithCleanup() calls
//!    UnalignedAllocate() for memory allocations.
//! \details Template parameter T_Align16 is effectively controlled by cryptlib.h and mirrors
//!    CRYPTOPP_BOOL_ALIGN16. CRYPTOPP_BOOL_ALIGN16 is often used as the template parameter.
template <class T, bool T_Align16 = false>
class AllocatorWithCleanup : public AllocatorBase<T>
{
public:
        CRYPTOPP_INHERIT_ALLOCATOR_TYPES

        //! \brief Allocates a block of memory
        //! \param ptr the size of the allocation
        //! \param size the size of the allocation, in elements
        //! \returns a memory block
        //! \throws InvalidArgument
        //! \details allocate() first checks the size of the request. If it is non-0
        //!   and less than max_size(), then an attempt is made to fulfill the request using either
        //!   AlignedAllocate() or UnalignedAllocate().
        //! \details AlignedAllocate() is used if T_Align16 is true.
        //!   UnalignedAllocate() used if T_Align16 is false.
        //! \details This is the C++ *Placement New* operator. ptr is not used, and the function
        //!   CRYPTOPP_ASSERTs in Debug builds if ptr is non-NULL.
        //! \sa CallNewHandler() for the methods used to recover from a failed
        //!   allocation attempt.
        //! \note size is the count of elements, and not the number of bytes
        pointer allocate(size_type size, const void *ptr = NULL)
        {
                CRYPTOPP_UNUSED(ptr); CRYPTOPP_ASSERT(ptr == NULL);
                this->CheckSize(size);
                if (size == 0)
                        return NULL;

#if CRYPTOPP_BOOL_ALIGN16
                // TODO: should this need the test 'size*sizeof(T) >= 16'?
                if (T_Align16 && size*sizeof(T) >= 16)
                        return (pointer)AlignedAllocate(size*sizeof(T));
#endif

                return (pointer)UnalignedAllocate(size*sizeof(T));
        }

        //! \brief Deallocates a block of memory
        //! \param ptr the pointer for the allocation
        //! \param size the size of the allocation, in elements
        //! \details Internally, SecureWipeArray() is called before deallocating the memory.
        //!   Once the memory block is wiped or zeroized, AlignedDeallocate() or
        //!   UnalignedDeallocate() is called.
        //! \details AlignedDeallocate() is used if T_Align16 is true.
        //!   UnalignedDeallocate() used if T_Align16 is false.
        void deallocate(void *ptr, size_type size)
        {
                CRYPTOPP_ASSERT((ptr && size) || !(ptr || size));
                SecureWipeArray((pointer)ptr, size);

#if CRYPTOPP_BOOL_ALIGN16
                if (T_Align16 && size*sizeof(T) >= 16)
                        return AlignedDeallocate(ptr);
#endif

                UnalignedDeallocate(ptr);
        }

        //! \brief Reallocates a block of memory
        //! \param oldPtr the previous allocation
        //! \param oldSize the size of the previous allocation
        //! \param newSize the new, requested size
        //! \param preserve flag that indicates if the old allocation should be preserved
        //! \returns pointer to the new memory block
        //! \details Internally, reallocate() calls StandardReallocate().
        //! \details If preserve is true, then index 0 is used to begin copying the
        //!   old memory block to the new one. If the block grows, then the old array
        //!   is copied in its entirety. If the block shrinks, then only newSize
        //!   elements are copied from the old block to the new one.
        //! \note oldSize and newSize are the count of elements, and not the
        //!   number of bytes.
        pointer reallocate(T *oldPtr, size_type oldSize, size_type newSize, bool preserve)
        {
                CRYPTOPP_ASSERT((oldPtr && oldSize) || !(oldPtr || oldSize));
                return StandardReallocate(*this, oldPtr, oldSize, newSize, preserve);
        }

        //! \brief Template class memeber Rebind
        //! \tparam T allocated class or type
        //! \tparam T_Align16 boolean that determines whether allocations should be aligned on 16-byte boundaries
        //! \tparam U bound class or type
        //! \details Rebind allows a container class to allocate a different type of object
        //!   to store elements. For example, a std::list will allocate std::list_node to
        //!   store elements in the list.
        //! \details VS.NET STL enforces the policy of "All STL-compliant allocators
        //!   have to provide a template class member called rebind".
    template <class U> struct rebind { typedef AllocatorWithCleanup<U, T_Align16> other; };
#if _MSC_VER >= 1500
        AllocatorWithCleanup() {}
        template <class U, bool A> AllocatorWithCleanup(const AllocatorWithCleanup<U, A> &) {}
#endif
};

CRYPTOPP_DLL_TEMPLATE_CLASS AllocatorWithCleanup<byte>;
CRYPTOPP_DLL_TEMPLATE_CLASS AllocatorWithCleanup<word16>;
CRYPTOPP_DLL_TEMPLATE_CLASS AllocatorWithCleanup<word32>;
CRYPTOPP_DLL_TEMPLATE_CLASS AllocatorWithCleanup<word64>;
#if defined(CRYPTOPP_WORD128_AVAILABLE)
CRYPTOPP_DLL_TEMPLATE_CLASS AllocatorWithCleanup<word128, true>; // for Integer
#endif
#if CRYPTOPP_BOOL_X86
CRYPTOPP_DLL_TEMPLATE_CLASS AllocatorWithCleanup<word, true>;    // for Integer
#endif

//! \class NullAllocator
//! \brief NULL allocator
//! \tparam T class or type
//! \details A NullAllocator is useful for fixed-size, stack based allocations
//!   (i.e., static arrays used by FixedSizeAllocatorWithCleanup).
//! \details A NullAllocator always returns 0 for max_size(), and always returns
//!   NULL for allocation requests. Though the allocator does not allocate at
//!   runtime, it does perform a secure wipe or zeroization during cleanup.
template <class T>
class NullAllocator : public AllocatorBase<T>
{
public:
        //LCOV_EXCL_START
        CRYPTOPP_INHERIT_ALLOCATOR_TYPES

        // TODO: should this return NULL or throw bad_alloc? Non-Windows C++ standard
        // libraries always throw. And late mode Windows throws. Early model Windows
        // (circa VC++ 6.0) returned NULL.
        pointer allocate(size_type n, const void* unused = NULL)
        {
                CRYPTOPP_UNUSED(n); CRYPTOPP_UNUSED(unused);
                CRYPTOPP_ASSERT(false); return NULL;
        }

        void deallocate(void *p, size_type n)
        {
                CRYPTOPP_UNUSED(p); CRYPTOPP_UNUSED(n);
                CRYPTOPP_ASSERT(false);
        }

        CRYPTOPP_CONSTEXPR size_type max_size() const {return 0;}
        //LCOV_EXCL_STOP
};

//! \class FixedSizeAllocatorWithCleanup
//! \brief Static secure memory block with cleanup
//! \tparam T class or type
//! \tparam S fixed-size of the stack-based memory block, in elements
//! \tparam A AllocatorBase derived class for allocation and cleanup
//! \details FixedSizeAllocatorWithCleanup provides a fixed-size, stack-
//!    based allocation at compile time. The class can grow its memory
//!    block at runtime if a suitable allocator is available. If size
//!    grows beyond S and a suitable allocator is available, then the
//!    statically allocated array is obsoleted.
//! \note This allocator can't be used with standard collections because
//!   they require that all objects of the same allocator type are equivalent.
template <class T, size_t S, class A = NullAllocator<T>, bool T_Align16 = false>
class FixedSizeAllocatorWithCleanup : public AllocatorBase<T>
{
public:
        CRYPTOPP_INHERIT_ALLOCATOR_TYPES

        //! \brief Constructs a FixedSizeAllocatorWithCleanup
        FixedSizeAllocatorWithCleanup() : m_allocated(false) {}

        //! \brief Allocates a block of memory
        //! \param size size of the memory block, in elements
        //! \details FixedSizeAllocatorWithCleanup provides a fixed-size, stack-based
        //!   allocation at compile time. If size is less than or equal to
        //!   <tt>S</tt>, then a pointer to the static array is returned.
        //! \details The class can grow its memory block at runtime if a suitable
        //!   allocator is available. If size grows beyond S and a suitable
        //!   allocator is available, then the statically allocated array is
        //!   obsoleted. If a suitable allocator is \a not available, as with a
        //!   NullAllocator, then the function returns NULL and a runtime error
        //!   eventually occurs.
        //! \sa reallocate(), SecBlockWithHint
        pointer allocate(size_type size)
        {
                CRYPTOPP_ASSERT(IsAlignedOn(m_array, 8));

                if (size <= S && !m_allocated)
                {
                        m_allocated = true;
                        return GetAlignedArray();
                }
                else
                        return m_fallbackAllocator.allocate(size);
        }

        //! \brief Allocates a block of memory
        //! \param size size of the memory block, in elements
        //! \param hint an unused hint
        //! \details FixedSizeAllocatorWithCleanup provides a fixed-size, stack-
        //!   based allocation at compile time. If size is less than or equal to
        //!   S, then a pointer to the static array is returned.
        //! \details The class can grow its memory block at runtime if a suitable
        //!   allocator is available. If size grows beyond S and a suitable
        //!   allocator is available, then the statically allocated array is
        //!   obsoleted. If a suitable allocator is \a not available, as with a
        //!   NullAllocator, then the function returns NULL and a runtime error
        //!   eventually occurs.
        //! \sa reallocate(), SecBlockWithHint
        pointer allocate(size_type size, const void *hint)
        {
                if (size <= S && !m_allocated)
                {
                        m_allocated = true;
                        return GetAlignedArray();
                }
                else
                        return m_fallbackAllocator.allocate(size, hint);
        }

        //! \brief Deallocates a block of memory
        //! \param ptr a pointer to the memory block to deallocate
        //! \param size size of the memory block, in elements
        //! \details The memory block is wiped or zeroized before deallocation.
        //!   If the statically allocated memory block is active, then no
        //!   additional actions are taken after the wipe.
        //! \details If a dynamic memory block is active, then the pointer and
        //!   size are passed to the allocator for deallocation.
        void deallocate(void *ptr, size_type size)
        {
                if (ptr == GetAlignedArray())
                {
                        CRYPTOPP_ASSERT(size <= S);
                        CRYPTOPP_ASSERT(m_allocated);
                        m_allocated = false;
                        SecureWipeArray((pointer)ptr, size);
                }
                else
                        m_fallbackAllocator.deallocate(ptr, size);
        }

        //! \brief Reallocates a block of memory
        //! \param oldPtr the previous allocation
        //! \param oldSize the size of the previous allocation
        //! \param newSize the new, requested size
        //! \param preserve flag that indicates if the old allocation should be preserved
        //! \returns pointer to the new memory block
        //! \details FixedSizeAllocatorWithCleanup provides a fixed-size, stack-
        //!   based allocation at compile time. If size is less than or equal to
        //!   S, then a pointer to the static array is returned.
        //! \details The class can grow its memory block at runtime if a suitable
        //!   allocator is available. If size grows beyond S and a suitable
        //!   allocator is available, then the statically allocated array is
        //!   obsoleted. If a suitable allocator is \a not available, as with a
        //!   NullAllocator, then the function returns NULL and a runtime error
        //!   eventually occurs.
        //! \note size is the count of elements, and not the number of bytes.
        //! \sa reallocate(), SecBlockWithHint
        pointer reallocate(pointer oldPtr, size_type oldSize, size_type newSize, bool preserve)
        {
                if (oldPtr == GetAlignedArray() && newSize <= S)
                {
                        CRYPTOPP_ASSERT(oldSize <= S);
                        if (oldSize > newSize)
                                SecureWipeArray(oldPtr+newSize, oldSize-newSize);
                        return oldPtr;
                }

                pointer newPointer = allocate(newSize, NULL);
                if (preserve && newSize)
                {
                        const size_t copySize = STDMIN(oldSize, newSize);
                        memcpy_s(newPointer, sizeof(T)*newSize, oldPtr, sizeof(T)*copySize);
                }
                deallocate(oldPtr, oldSize);
                return newPointer;
        }

        CRYPTOPP_CONSTEXPR size_type max_size() const {return STDMAX(m_fallbackAllocator.max_size(), S);}

private:

#ifdef __BORLANDC__
        T* GetAlignedArray() {return m_array;}
        T m_array[S];
#else
        T* GetAlignedArray() {return (CRYPTOPP_BOOL_ALIGN16 && T_Align16) ? (T*)(void *)(((byte *)m_array) + (0-(size_t)m_array)%16) : m_array;}
        CRYPTOPP_ALIGN_DATA(8) T m_array[(CRYPTOPP_BOOL_ALIGN16 && T_Align16) ? S+8/sizeof(T) : S];
#endif

        A m_fallbackAllocator;
        bool m_allocated;
};

//! \class SecBlock
//! \brief Secure memory block with allocator and cleanup
//! \tparam T a class or type
//! \tparam A AllocatorWithCleanup derived class for allocation and cleanup
template <class T, class A = AllocatorWithCleanup<T> >
class SecBlock
{
public:
        typedef typename A::value_type value_type;
        typedef typename A::pointer iterator;
        typedef typename A::const_pointer const_iterator;
        typedef typename A::size_type size_type;

        //! \brief Construct a SecBlock with space for size elements.
        //! \param size the size of the allocation, in elements
        //! \throws std::bad_alloc
        //! \details The elements are not initialized.
        //! \note size is the count of elements, and not the number of bytes
        explicit SecBlock(size_type size=0)
                : m_size(size), m_ptr(m_alloc.allocate(size, NULL)) { }

        //! \brief Copy construct a SecBlock from another SecBlock
        //! \param t the other SecBlock
        //! \throws std::bad_alloc
        SecBlock(const SecBlock<T, A> &t)
                : m_size(t.m_size), m_ptr(m_alloc.allocate(t.m_size, NULL)) {
                        CRYPTOPP_ASSERT((!t.m_ptr && !m_size) || (t.m_ptr && m_size));
                        if (t.m_ptr) {memcpy_s(m_ptr, m_size*sizeof(T), t.m_ptr, t.m_size*sizeof(T));}
                }

        //! \brief Construct a SecBlock from an array of elements.
        //! \param ptr a pointer to an array of T
        //! \param len the number of elements in the memory block
        //! \throws std::bad_alloc
        //! \details If <tt>ptr!=NULL</tt> and <tt>len!=0</tt>, then the block is initialized from the pointer ptr.
        //!    If <tt>ptr==NULL</tt> and <tt>len!=0</tt>, then the block is initialized to 0.
        //!    Otherwise, the block is empty and \a not initialized.
        //! \note size is the count of elements, and not the number of bytes
        SecBlock(const T *ptr, size_type len)
                : m_size(len), m_ptr(m_alloc.allocate(len, NULL)) {
                        CRYPTOPP_ASSERT((!m_ptr && !m_size) || (m_ptr && m_size));
                        if (ptr && m_ptr)
                                memcpy_s(m_ptr, m_size*sizeof(T), ptr, len*sizeof(T));
                        else if (m_size)
                                memset(m_ptr, 0, m_size*sizeof(T));
                }

        ~SecBlock()
                {m_alloc.deallocate(m_ptr, m_size);}

#ifdef __BORLANDC__
        operator T *() const
                {return (T*)m_ptr;}
#else
        operator const void *() const
                {return m_ptr;}
        operator void *()
                {return m_ptr;}

        operator const T *() const
                {return m_ptr;}
        operator T *()
                {return m_ptr;}
#endif

        //! \brief Provides an iterator pointing to the first element in the memory block
        //! \returns iterator pointing to the first element in the memory block
        iterator begin()
                {return m_ptr;}
        //! \brief Provides a constant iterator pointing to the first element in the memory block
        //! \returns constant iterator pointing to the first element in the memory block
        const_iterator begin() const
                {return m_ptr;}
        //! \brief Provides an iterator pointing beyond the last element in the memory block
        //! \returns iterator pointing beyond the last element in the memory block
        iterator end()
                {return m_ptr+m_size;}
        //! \brief Provides a constant iterator pointing beyond the last element in the memory block
        //! \returns constant iterator pointing beyond the last element in the memory block
        const_iterator end() const
                {return m_ptr+m_size;}

        //! \brief Provides a pointer to the first element in the memory block
        //! \returns pointer to the first element in the memory block
        typename A::pointer data() {return m_ptr;}
        //! \brief Provides a pointer to the first element in the memory block
        //! \returns constant pointer to the first element in the memory block
        typename A::const_pointer data() const {return m_ptr;}

        //! \brief Provides the count of elements in the SecBlock
        //! \returns number of elements in the memory block
        //! \note the return value is the count of elements, and not the number of bytes
        size_type size() const {return m_size;}
        //! \brief Determines if the SecBlock is empty
        //! \returns true if number of elements in the memory block is 0, false otherwise
        bool empty() const {return m_size == 0;}

        //! \brief Provides a byte pointer to the first element in the memory block
        //! \returns byte pointer to the first element in the memory block
        byte * BytePtr() {return (byte *)m_ptr;}
        //! \brief Return a byte pointer to the first element in the memory block
        //! \returns constant byte pointer to the first element in the memory block
        const byte * BytePtr() const {return (const byte *)m_ptr;}
        //! \brief Provides the number of bytes in the SecBlock
        //! \return the number of bytes in the memory block
        //! \note the return value is the number of bytes, and not count of elements.
        size_type SizeInBytes() const {return m_size*sizeof(T);}

        //! \brief Set contents and size from an array
        //! \param ptr a pointer to an array of T
        //! \param len the number of elements in the memory block
        //! \details If the memory block is reduced in size, then the reclaimed memory is set to 0.
        void Assign(const T *ptr, size_type len)
        {
                New(len);
                if (m_ptr && ptr && len)
                        {memcpy_s(m_ptr, m_size*sizeof(T), ptr, len*sizeof(T));}
        }

        //! \brief Copy contents from another SecBlock
        //! \param t the other SecBlock
        //! \details Assign checks for self assignment.
        //! \details If the memory block is reduced in size, then the reclaimed memory is set to 0.
        void Assign(const SecBlock<T, A> &t)
        {
                if (this != &t)
                {
                        New(t.m_size);
                        if (m_ptr && t.m_ptr && t.m_size)
                                {memcpy_s(m_ptr, m_size*sizeof(T), t, t.m_size*sizeof(T));}
                }
        }

        //! \brief Assign contents from another SecBlock
        //! \param t the other SecBlock
        //! \details Internally, operator=() calls Assign().
        //! \details If the memory block is reduced in size, then the reclaimed memory is set to 0.
        SecBlock<T, A>& operator=(const SecBlock<T, A> &t)
        {
                // Assign guards for self-assignment
                Assign(t);
                return *this;
        }

        //! \brief Append contents from another SecBlock
        //! \param t the other SecBlock
        //! \details Internally, this SecBlock calls Grow and then appends t.
        SecBlock<T, A>& operator+=(const SecBlock<T, A> &t)
        {
                CRYPTOPP_ASSERT((!t.m_ptr && !t.m_size) || (t.m_ptr && t.m_size));

                if(t.m_size)
                {
                        const size_type oldSize = m_size;
                        if(this != &t)  // s += t
                        {
                                Grow(m_size+t.m_size);
                                memcpy_s(m_ptr+oldSize, (m_size-oldSize)*sizeof(T), t.m_ptr, t.m_size*sizeof(T));
                        }
                        else            // t += t
                        {
                                Grow(m_size*2);
                                memcpy_s(m_ptr+oldSize, (m_size-oldSize)*sizeof(T), m_ptr, oldSize*sizeof(T));
                        }
                }
                return *this;
        }

        //! \brief Construct a SecBlock from this and another SecBlock
        //! \param t the other SecBlock
        //! \returns a newly constructed SecBlock that is a conacentation of this and t
        //! \details Internally, a new SecBlock is created from this and a concatenation of t.
        SecBlock<T, A> operator+(const SecBlock<T, A> &t)
        {
                CRYPTOPP_ASSERT((!m_ptr && !m_size) || (m_ptr && m_size));
                CRYPTOPP_ASSERT((!t.m_ptr && !t.m_size) || (t.m_ptr && t.m_size));
                if(!t.m_size) return SecBlock(*this);

                SecBlock<T, A> result(m_size+t.m_size);
                if(m_size) {memcpy_s(result.m_ptr, result.m_size*sizeof(T), m_ptr, m_size*sizeof(T));}
                memcpy_s(result.m_ptr+m_size, (result.m_size-m_size)*sizeof(T), t.m_ptr, t.m_size*sizeof(T));
                return result;
        }

        //! \brief Bitwise compare two SecBlocks
        //! \param t the other SecBlock
        //! \returns true if the size and bits are equal, false otherwise
        //! \details Uses a constant time compare if the arrays are equal size. The constant time
        //!    compare is VerifyBufsEqual() found in misc.h.
        //! \sa operator!=()
        bool operator==(const SecBlock<T, A> &t) const
        {
                return m_size == t.m_size &&
                        VerifyBufsEqual(reinterpret_cast<const byte*>(m_ptr), reinterpret_cast<const byte*>(t.m_ptr), m_size*sizeof(T));
        }

        //! \brief Bitwise compare two SecBlocks
        //! \param t the other SecBlock
        //! \returns true if the size and bits are equal, false otherwise
        //! \details Uses a constant time compare if the arrays are equal size. The constant time
        //!    compare is VerifyBufsEqual() found in misc.h.
        //! \details Internally, operator!=() returns the inverse of operator==().
        //! \sa operator==()
        bool operator!=(const SecBlock<T, A> &t) const
        {
                return !operator==(t);
        }

        //! \brief Change size without preserving contents
        //! \param newSize the new size of the memory block
        //! \details Old content is \a not preserved. If the memory block is reduced in size,
        //!    then the reclaimed memory is set to 0. If the memory block grows in size, then
        //!    the new memory is \a not initialized.
        //! \details Internally, this SecBlock calls reallocate().
        //! \sa New(), CleanNew(), Grow(), CleanGrow(), resize()
        void New(size_type newSize)
        {
                m_ptr = m_alloc.reallocate(m_ptr, m_size, newSize, false);
                m_size = newSize;
        }

        //! \brief Change size without preserving contents
        //! \param newSize the new size of the memory block
        //! \details Old content is \a not preserved. If the memory block is reduced in size,
        //!    then the reclaimed content is set to 0. If the memory block grows in size, then
        //!    the new memory is initialized to 0.
        //! \details Internally, this SecBlock calls New().
        //! \sa New(), CleanNew(), Grow(), CleanGrow(), resize()
        void CleanNew(size_type newSize)
        {
                New(newSize);
                if (m_ptr) {memset_z(m_ptr, 0, m_size*sizeof(T));}
        }

        //! \brief Change size and preserve contents
        //! \param newSize the new size of the memory block
        //! \details Old content is preserved. New content is not initialized.
        //! \details Internally, this SecBlock calls reallocate() when size must increase. If the
        //!    size does not increase, then Grow() does not take action. If the size must
        //!    change, then use resize().
        //! \sa New(), CleanNew(), Grow(), CleanGrow(), resize()
        void Grow(size_type newSize)
        {
                if (newSize > m_size)
                {
                        m_ptr = m_alloc.reallocate(m_ptr, m_size, newSize, true);
                        m_size = newSize;
                }
        }

        //! \brief Change size and preserve contents
        //! \param newSize the new size of the memory block
        //! \details Old content is preserved. New content is initialized to 0.
        //! \details Internally, this SecBlock calls reallocate() when size must increase. If the
        //!    size does not increase, then CleanGrow() does not take action. If the size must
        //!    change, then use resize().
        //! \sa New(), CleanNew(), Grow(), CleanGrow(), resize()
        void CleanGrow(size_type newSize)
        {
                if (newSize > m_size)
                {
                        m_ptr = m_alloc.reallocate(m_ptr, m_size, newSize, true);
                        memset_z(m_ptr+m_size, 0, (newSize-m_size)*sizeof(T));
                        m_size = newSize;
                }
        }

        //! \brief Change size and preserve contents
        //! \param newSize the new size of the memory block
        //! \details Old content is preserved. If the memory block grows in size, then
        //!    new memory is \a not initialized.
        //! \details Internally, this SecBlock calls reallocate().
        //! \sa New(), CleanNew(), Grow(), CleanGrow(), resize()
        void resize(size_type newSize)
        {
                m_ptr = m_alloc.reallocate(m_ptr, m_size, newSize, true);
                m_size = newSize;
        }

        //! \brief Swap contents with another SecBlock
        //! \param b the other SecBlock
        //! \details Internally, std::swap() is called on m_alloc, m_size and m_ptr.
        void swap(SecBlock<T, A> &b)
        {
                // Swap must occur on the allocator in case its FixedSize that spilled into the heap.
                std::swap(m_alloc, b.m_alloc);
                std::swap(m_size, b.m_size);
                std::swap(m_ptr, b.m_ptr);
        }

// protected:
        A m_alloc;
        size_type m_size;
        T *m_ptr;
};

#ifdef CRYPTOPP_DOXYGEN_PROCESSING
//! \class SecByteBlock
//! \brief \ref SecBlock "SecBlock<byte>" typedef.
class SecByteBlock : public SecBlock<byte> {};
//! \class SecWordBlock
//! \brief \ref SecBlock "SecBlock<word>" typedef.
class SecWordBlock : public SecBlock<word> {};
//! \class AlignedSecByteBlock
//! \brief SecBlock using \ref AllocatorWithCleanup "AllocatorWithCleanup<byte, true>" typedef
class AlignedSecByteBlock : public SecBlock<byte, AllocatorWithCleanup<byte, true> > {};
#else
typedef SecBlock<byte> SecByteBlock;
typedef SecBlock<word> SecWordBlock;
typedef SecBlock<byte, AllocatorWithCleanup<byte, true> > AlignedSecByteBlock;
#endif

// No need for move semantics on derived class *if* the class does not add any
//   data members; see http://stackoverflow.com/q/31755703, and Rule of {0|3|5}.

//! \class FixedSizeSecBlock
//! \brief Fixed size stack-based SecBlock
//! \tparam T class or type
//! \tparam S fixed-size of the stack-based memory block, in elements
//! \tparam A AllocatorBase derived class for allocation and cleanup
template <class T, unsigned int S, class A = FixedSizeAllocatorWithCleanup<T, S> >
class FixedSizeSecBlock : public SecBlock<T, A>
{
public:
        //! \brief Construct a FixedSizeSecBlock
        explicit FixedSizeSecBlock() : SecBlock<T, A>(S) {}
};

//! \class FixedSizeAlignedSecBlock
//! \brief Fixed size stack-based SecBlock with 16-byte alignment
//! \tparam T class or type
//! \tparam S fixed-size of the stack-based memory block, in elements
//! \tparam A AllocatorBase derived class for allocation and cleanup
template <class T, unsigned int S, bool T_Align16 = true>
class FixedSizeAlignedSecBlock : public FixedSizeSecBlock<T, S, FixedSizeAllocatorWithCleanup<T, S, NullAllocator<T>, T_Align16> >
{
};

//! \class SecBlockWithHint
//! \brief Stack-based SecBlock that grows into the heap
//! \tparam T class or type
//! \tparam S fixed-size of the stack-based memory block, in elements
//! \tparam A AllocatorBase derived class for allocation and cleanup
template <class T, unsigned int S, class A = FixedSizeAllocatorWithCleanup<T, S, AllocatorWithCleanup<T> > >
class SecBlockWithHint : public SecBlock<T, A>
{
public:
        //! construct a SecBlockWithHint with a count of elements
        explicit SecBlockWithHint(size_t size) : SecBlock<T, A>(size) {}
};

template<class T, bool A, class U, bool B>
inline bool operator==(const CryptoPP::AllocatorWithCleanup<T, A>&, const CryptoPP::AllocatorWithCleanup<U, B>&) {return (true);}
template<class T, bool A, class U, bool B>
inline bool operator!=(const CryptoPP::AllocatorWithCleanup<T, A>&, const CryptoPP::AllocatorWithCleanup<U, B>&) {return (false);}

NAMESPACE_END

NAMESPACE_BEGIN(std)
template <class T, class A>
inline void swap(CryptoPP::SecBlock<T, A> &a, CryptoPP::SecBlock<T, A> &b)
{
        a.swap(b);
}

#if defined(_STLP_DONT_SUPPORT_REBIND_MEMBER_TEMPLATE) || (defined(_STLPORT_VERSION) && !defined(_STLP_MEMBER_TEMPLATE_CLASSES))
// working for STLport 5.1.3 and MSVC 6 SP5
template <class _Tp1, class _Tp2>
inline CryptoPP::AllocatorWithCleanup<_Tp2>&
__stl_alloc_rebind(CryptoPP::AllocatorWithCleanup<_Tp1>& __a, const _Tp2*)
{
        return (CryptoPP::AllocatorWithCleanup<_Tp2>&)(__a);
}
#endif

NAMESPACE_END

#if CRYPTOPP_MSC_VERSION
# pragma warning(pop)
#endif

#endif