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// Copyright (C) 2006 Davis E. King (davis@dlib.net)
// License: Boost Software License See LICENSE.txt for the full license.
#ifndef DLIB_BYTE_ORDEREr_KERNEL_1_
#define DLIB_BYTE_ORDEREr_KERNEL_1_
#include "byte_orderer_kernel_abstract.h"
#include "../algs.h"
#include "../assert.h"
namespace dlib
{
class byte_orderer
{
/*!
INITIAL VALUE
- if (this machine is little endian) then
- little_endian == true
- else
- little_endian == false
CONVENTION
- host_is_big_endian() == !little_endian
- host_is_little_endian() == little_endian
- if (this machine is little endian) then
- little_endian == true
- else
- little_endian == false
!*/
public:
// this is here for backwards compatibility with older versions of dlib.
typedef byte_orderer kernel_1a;
byte_orderer (
)
{
// This will probably never be false but if it is then it means chars are not 8bits
// on this system. Which is a problem for this object.
COMPILE_TIME_ASSERT(sizeof(short) >= 2);
unsigned long temp = 1;
unsigned char* ptr = reinterpret_cast<unsigned char*>(&temp);
if (*ptr == 1)
little_endian = true;
else
little_endian = false;
}
virtual ~byte_orderer (
){}
bool host_is_big_endian (
) const { return !little_endian; }
bool host_is_little_endian (
) const { return little_endian; }
template <
typename T
>
inline void host_to_network (
T& item
) const
{ if (little_endian) flip(item); }
template <
typename T
>
inline void network_to_host (
T& item
) const { if (little_endian) flip(item); }
template <
typename T
>
void host_to_big (
T& item
) const { if (little_endian) flip(item); }
template <
typename T
>
void big_to_host (
T& item
) const { if (little_endian) flip(item); }
template <
typename T
>
void host_to_little (
T& item
) const { if (!little_endian) flip(item); }
template <
typename T
>
void little_to_host (
T& item
) const { if (!little_endian) flip(item); }
private:
template <
typename T,
size_t size
>
inline void flip (
T (&array)[size]
) const
/*!
ensures
- flips the bytes in every element of this array
!*/
{
for (size_t i = 0; i < size; ++i)
{
flip(array[i]);
}
}
template <
typename T
>
inline void flip (
T& item
) const
/*!
ensures
- reverses the byte ordering in item
!*/
{
DLIB_ASSERT_HAS_STANDARD_LAYOUT(T);
T value;
// If you are getting this as an error then you are probably using
// this object wrong. If you think you aren't then send me (Davis) an
// email and I'll either set you straight or change/remove this check so
// your stuff works :)
COMPILE_TIME_ASSERT(sizeof(T) <= sizeof(long double));
// If you are getting a compile error on this line then it means T is
// a pointer type. It doesn't make any sense to byte swap pointers
// since they have no meaning outside the context of their own process.
// So you probably just forgot to dereference that pointer before passing
// it to this function :)
COMPILE_TIME_ASSERT(is_pointer_type<T>::value == false);
const size_t size = sizeof(T);
unsigned char* const ptr = reinterpret_cast<unsigned char*>(&item);
unsigned char* const ptr_temp = reinterpret_cast<unsigned char*>(&value);
for (size_t i = 0; i < size; ++i)
ptr_temp[size-i-1] = ptr[i];
item = value;
}
bool little_endian;
};
// make flip not do anything at all for chars
template <> inline void byte_orderer::flip<char> ( char& ) const {}
template <> inline void byte_orderer::flip<unsigned char> ( unsigned char& ) const {}
template <> inline void byte_orderer::flip<signed char> ( signed char& ) const {}
}
#endif // DLIB_BYTE_ORDEREr_KERNEL_1_
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