by Lori Matassa
Endianess describes how multi-byte data is represented by a computer system and is dictated by the CPU architecture of the system. Unfortunately not all computer systems are designed with the same Endian-architecture. The difference in Endian-architecture is an issue when software or data is shared between computer systems. An analysis of the computer system and its interfaces will determine the requirements of the Endian implementation of the software.
Software is sometimes designed with one specific Endian-architecture in mind, limiting the portability of the code to other processor architectures. This type of implementation is considered to be Endian-specific. However, Endian-neutral software can be developed, allowing the code to be ported easily between processors of different Endian-architectures, and without rewriting any code. Endian-neutral software is developed by identifying system memory and external data interfaces, and using Endian-neutral coding practices to implement the interfaces.
Platform migration requires consideration of the Endian-architecture of the current and target platforms, as well as the Endian-architecture of the code. Best known methods describe the software interface information that should be considered and how to convert Endian-specific code to Endian-neutral code.
This white paper establishes a set of fundamental guidelines for software developers who wish to develop Endian-neutral code or convert Endian-specific code through the use of some or all of the coding techniques documented in this paper.
Note: The examples in this paper are based on 32-bit processor architecture.