Byte Order and Byte Swapping

Include File(s): SDL_endian.h

Introduction

This category contains functions for handling endian-specific values.

Simple data types like integers and floats consist of several bytes. A 32bit integer (Sint32), for example, uses four bytes (as each byte has 8 bits). Endianness describes how the system orders the bytes of this value in memory.

Endianness comes in two forms - big and little.

• SDL_LIL_ENDIAN means byte order is 1234, where the least significant byte is stored first
• SDL_BIG_ENDIAN means byte order is 4321, where the most significant byte is stored first

Example: Imagine the 32bit integer number 16,909,060 in decimal.

• In hexadecimal that would be 0x01020304.
  0x01 is the most significant byte (the one that increases the value the most. 0x04 is the least significant byte (as it increases the value the least).
  When that is stored in memory on a little-endian system they are stored with the least significant byte first, producing the byte stream:

  • 0x04 0x03 0x02 0x01
    

  When that is stored in memory on a big-endian system they are stored with the most significant byte first, producing the byte stream:

  • 0x01 0x02 0x03 0x04
    

For further information about endianness read the Wikipedia article on the subject.

SDL_BYTEORDER is a macro that corresponds to the byte order used by the processor type it was compiled for.

• SDL_BYTEORDER is SDL_LIL_ENDIAN for x86, x64, and similar systems that use the little endian byte order.
• SDL_BYTEORDER is SDL_BIG_ENDIAN for PowerPC and similar systems that use the big endian byte order.

Functions

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