Comment by tonyedgecombe

I'm working on a PostScript interpreter. This is a retirement project. I wanted something substantial to sink my teeth into without any commercial pressure. I wanted to see if I could get back that intrinsic motivation that I for had for programming before I started my career. Back in the eighties I worked for the QMS distributor in the UK, QMS were Adobe's second OEM after Apple and made a range of PostScript printers. I was working in support at the time and would never have thought of taking on a project like this.

I have an original Apple LaserWriter which I can use through the serial port (but it won't print). I've pulled the ROM's in it and got them working through the MAME game emulator. This is great as I can debug the 68000 code, for instance I was able to reverse engineer the random number generator and the password for internaldict. Ghostscript is handy as well although I try not to rely on it too much as there are some differences between the two implementations.

The plan is to keep it as close as possible to the LaserWriter so that means level 1. PostScript is quite interesting in that it starts executing PostScript code as soon as you power on the printer. That code is responsible for initialising the printer, handling errors, managing the serial ports then receiving and executing the incoming PostScript job. You can load and dump this internal code with a simple script.

The interpreter is complete along with the 125 programming operators, core types and error handlers. The next stage is the graphics operators. I'm going to target PDF for output as the drawing model is the same as PostScript. I'm assuming that handling the fonts is going to be the bulk of the work.

It's written in Rust, so far about 14,000 lines and 650 unit tests. In some ways it would have been easier in C as I could have followed the exact memory layout in the original interpreter however I really dislike C.