Embedded Programming with Modern C++ Cookbook

Detecting the endianness of the platform

Endianness defines the order in which bytes that represent large numerical values are stored in memory.

There are two types of endianness:

• Big-endian: The most significant byte is stored first. A 32-bit value, 0x01020304, is stored at the ptr address, as follows: 

  Offset in memory (byte)	Value
  ptr	0x01
  ptr + 1	0x02
  ptr + 2	ox03
  ptr + 3	0x04

  Examples of big-endian architectures include AVR32 and Motorola 68000.

• Little-endian: The least significant byte is stored first. A 32-bit value, 0x01020304, is stored at the ptr address, as follows:

  Offset in memory (byte)	Value
  ptr	0x04
  ptr + 1	0x03
  ptr + 2	0x02
  ptr + 3	0x01

  The x86 architecture is little-endian.

Taking care ...