Stacker4x compression driver

Stacker4x is also hosted on HPCalc.org

Stacker4x allows HP48/49/50 owners to use compressed data as if they were normal. It is a compression driver, that will automatically compress / decompress all data transparently.

Stacker4x is inspired by Stacker for DOS, a 1990 PC software from Stac Electronics,
which compressed data on Hard Disk and allowed users to access them as if they were normal. Nowadays, the same can be achieved on Windows by checking the "compress" checkbox.

Stacker4x compress and decompress very fast to ensure smooth operation.
It is based on FastLZD v0.4c, which is about 10 times faster than other compressors.
Typical compression ratio is about 1.5, which means you can store approximately 50% more data in the same memory space.


Features available :
- Transparently compress & store any object (trapping STO, RCL and Shift-menu keys)
- Display memory savings
- Can stop compression anytime by pressing any key
- Save & extract from/to extension ports (SD Card port :3: intentionnally filtered out)
- Mass compression/decompression utilities provided (zDIR, uDIR), with automatic recursive compression on directories
- Transparently deliver objects in original format
- Programs are automatically decompressed & run
- Default to normal STO when not enough memory to compress


Current Version : Stacker4x v1.2

What's new : update FastLZD to v0.4c : Faster and better compression ratio


How to use it ?

Install the library on any port and reset the calculator (ON+C).
Note : the library can be installed into any extension port, no restriction (example : 1 STO).

At calculator initialization, Stacker4x automatically install and activate itself.

Quickest way to start Stacker4x is to run 'zDIR' from HOME directory.
All your data will be converted into compressed format, and you will be informed of how much memory is saved in the process.

You can stop the compression process at any time. You can also start 'zDIR' from any sub-directory, and it will just compress this part of memory.

You can de-activate Stacker4x by using zMODE, or disabling the User Keyboard (LeftShift+Alpha).
When stacker4x is activated, data is stored in compressed format.
When it is deactivated, data is stored in original format.
Compressed data will still work properly even when Stacker4x is deactivated !

If you want to uninstall Stacker4x,
first run 'uDIR' from HOME directory.
All your data will be converted into uncompressed format.

Version History :

Stacker4x v1.1
compressor update to FastLZD v0.4b

Stacker4x v1.0
initial release

zSTO : Proof of concept version (HP48)
Note : zSTO PoC is a program, not a library, and remap only STO/RCL keys.

Candidate features for future Stacker4x version :

- Detect when an object is already compressed to avoid another useless attempt at compressing it again (for example when using zDIR)
- Use less memory to create objects (currently uses Compressed-Size x 2, which is a problem for large objects)
- Faster auto-evaluation routine in assembler

Potential :
- Filter-out "Large" objects in main memory, to avoid running out of memory (no problem for expansion ports however)