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From: Lars Erdmann
If you want to implement the "L" variants of the various filesystem APIs, you
basically have to rewrite FAT32.IFS.
It's not just adding an additional entry point.
The "L" variants are called as 32-bit entry points whereas the old filesystem
APIs are called as 16-bit entry points.
There are a bunch of other implications where most of these deal with
improving throughput (for example using the
flat 32-bit strat3 entry point of OS2DASD.DMD/OS2LVM.DMD instead of the old
16-bit strat2 entry point).
On the other hand, while the kernel splits DosRead/DosWrite transfer into
chunks of 64k for the old 16-bit filesystems
the new entry points can swallow up to 4 GB passed on one invocation of
DosRead/DosWrite.
The bottom line is: the "> 2 GB extension" is a messy addon which is at best
documented in JFS.IFS source code.
The design is horrible and you have to introduce a thunking layer to properly
handle the mixture of 32-bit and
16-bit entry points. What's more, you can no longer use the (16-bit)
filesystem helpers or if you want to use them,
you need to thunk from 32-bit to 16-bit, call them and thunk back to 32-bit.
Have a look at the OS/2 OpenJFS source code and you will see what I mean.
The OpenJFS source code used to be available as a Netlabs CVS archive, Adrian
Gschwend from Netlabs has zipped it up
directly from the CVS source tree:
ftp://ftp.netlabs.org/pub/openjfs/openjfs-20070128203903.zip
If you want to step forward, ask Adrian Gschwend to convert this thing into an
SVN repository (and with Trac view
support).
Lars
--- Internet Rex 2.31
* Origin: Arcor (1:261/20.999)
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