2.5 KiB
lib9660 - a simple implementation of the ISO 9660 file system
lib9660 is a simple implementation of the ISO 9660 file system, as used on CD. It does not perform any dynamic memory allocations or depend upon any complicated standard library routines (actually all it requires is memcmp and memcpy). It provides a reasonable facsimilie of the standard POSIX file descriptor I/O API.
lib9660 is re-entrant; it is safe to use it from multiple threads, provided you do not access the same file from multiple threads (note that for these purposes the openat and opendirat functions count as accessing the passed parent file)
Usage notes
l9660_dir is simply a wrapper for l9660_file. You may use them interchangably if necessary to save memory (note that this will require casting). The distinct types are provided purely for type checking.
You can pass the same file/directory pointer for both child and parent parameters of l9660_open(dir)at. This can be useful in memory constrained environments.
l9660_read will not perform a read from the underlying device as long as the request can be answered from its' internal buffer. Be prepared for short reads.
lib9660_open(dir)at use lib9660_readdir internally. Remember to save and restore your seek position if that will be necessary.
Tuning parameters
L9660_SINGLEBUFFER
By default, lib9660 maintains a buffer per open file. This means each file (and directory) consumes just over 2kB of RAM for the buffer and state information.
If you are memory constrained, you can build with L9660_SINGLEBUFFER (make sure it is also defined in any files which include lib9660.h), which causes lib9660 to instead use a single common buffer. lib9660 will now consume a constant 2kB of RAM for this buffer, instead of 2kB per file.
The cost of this is slightly reduced performance; if you alternate between reading multiple files, then each time you change file that file's buffer must be reloaded. Additionally, this makes lib9660 no longer thread safe.
L9660_HAVE_STDIO
If your system has stdio.h and it defines SEEK_[SET,CUR,END], then lib9660 will use those definitions for l9660_seek. Otherwise, it will use its' own definitions of L9660_SEEK_[SET,CUR,END].
DEBUG
If you build l9660.c with DEBUG defined, then this will enable some library debugging features. Most notably, if L9660_DEBUG is set in the environment, then all directory entries processed (by the open[dir]at functions) will be dumped to stdout.
This requires a functioning printf and getenv. You probably don't need it