Chapter 20. Introduction

This document describes the filesystem infrastructure provided in eCos. This is implemented by the FILEIO package and provides POSIX compliant file and IO operations together with the BSD socket API. These APIs are described in the relevant standards and original documentation and will not be described here. See the Posix Standard Support documentation for details of which parts of the POSIX standard are supported.

This document is concerned with the interfaces presented to client filesystems and network protocol stacks.

The FILEIO infrastructure consist mainly of a set of tables containing pointers to the primary interface functions of a file system. This approach avoids problems of namespace pollution (for example several filesystems can have a function called read(), so long as they are static). The system is also structured to eliminate the need for dynamic memory allocation.

New filesystems can be written directly to the interfaces described here. Existing filesystems can be ported very easily by the introduction of a thin veneer porting layer that translates FILEIO calls into native filesystem calls.

The term filesystem should be read fairly loosely in this document. Object accessed through these interfaces could equally be network protocol sockets, device drivers, fifos, message queues or any other object that can present a file-like interface.