aleksey-nikolaev / endianness

Endianness is very simple, light, header-only library designed to reduce conversions between big-endian and little-endian data

Endianness

Endianness is very simple, light, header-only library designed to reduce conversions between big-endian and little-endian data.

• Requires STL C++17

Build and Install

Usage after install

Endianness library can be built and installed as any other cmake project. After that add to your CMake project file CMakeLists.txt:

find_package(Endianness)

And link to your target imported target ENDIAN::Endian

target_link_libraries(<target> ENDIAN::Endian)

Usage as submodule

If you prefer submodule instead of install add to your CMakeLists.txt

add_subdirectory(<Endianness source realative path>)
target_link_libraries(<target> ENDIAN::Endian)

Debug Visualisation

With happy debugging on MSVS you can use Endian.natvis This natvis file can swap bytes of big-endian data for better view.

Usage

• You can use the Endian in constexpr
• It is possible to use the Endian as a key in unordered associative containers. Avoid to use with containers that need the less operator for comparision - only == and != operators have no byte swap.
• Not necessary, but useful aliases:

#include <endianness.h>
#include <stdint.h>

using int16le = endianness::LittleEndian<int16_t>;
using uint16le = endianness::LittleEndian<uint16_t>;
using int32le = endianness::LittleEndian<int32_t>;
using uint32le = endianness::LittleEndian<uint32_t>;
using int64le = endianness::LittleEndian<int64_t>;
using uint64le = endianness::LittleEndian<uint64_t>;

using int16be = endianness::BigEndian<int16_t>;
using uint16be = endianness::BigEndian<uint16_t>;
using int32be = endianness::BigEndian<int32_t>;
using uint32be = endianness::BigEndian<uint32_t>;
using int64be = endianness::BigEndian<int64_t>;
using uint64be = endianness::BigEndian<uint64_t>;

Example

• No byte swap type conversion:

constexpr uint32be MASK = 0xF0F01234; //Compile-time expressions
#pragma pack(push, 1)
struct FileHeader
{
    static constexpr uint32be SIGNATURE = 'A123'; //Compile-time expressions
    uint32be signature;
    uint32be tag; 
};
#pragma pop()
...
std::unordered_set<uint32be> tags{'qwer','tyui','opas','dfgh'};
std::unordered_map<uint32be, int> hashmap;
auto fileHeader = reinterpret_cast<const FileHeader*>(pointer);
if (fileHeader && fileHeader->signature == FileHeader::SIGNATURE){
  uint32be tag = fileHeader->tag;
  if(tags.count(tag)){
    tag &= MASK;
    ++hashmap[tag];
  }
}

• With byte swap:

// no byte swap on big-endian platform
uint16be a = 7;
uint32be b = a;// uint16be -> uint16_t -> uint32_t -> uint32be
int c = a + b;
bool d = (a < 32) // ok: uint16be -> uint16_t : d = true
//bool e = (a != 3) // error: need explicitly cast a to int or 3 to uint16be
bool e = (a != (uint16be)3) // ok: e = true