From Retrosoftware

17/12/2010: More additions and code reduction

This covers the past few days where I've being doing dribs and drabs when I have had time. First off, some new stuff. I added a pseudo-random number generator as just grabbing a value from &FE44 didn't turn out to be random (interestingly enough Brian Howarth's code just gets the low byte of the system clock for this). I also added the print counter routine, one vital step on getting SCORE working properly.

The other area of work was code reduction, which I saved some notes on byte reductions. The first step was turning JSR xyz:RTS into JMP xyz; this saved about 5 bytes. Next I added a couple of functions to perform 16-bit addition to the most commonly used pointers. Some moving pointers around so I could could use common code also saved some bytes. Finally I found a whole chunk of code that I had duplicated, so this went.

The final savings were around 56 bytes, with details shown below:

Because I'm using two pointers (bufptr and foundptr) I have a duplication of code which I should probably try and remove:

.skipstringbp
{
               ldy #0
               lda (bufptr),y
               jmp addtobufptr
}

; simple routine to add A to bufptr and save a few bytes
.addtobufptr
{
               clc
               adc bufptr
               sta bufptr
               bcc nooverflow
               inc bufptr+1
.nooverflow    rts
}

This could save another 17 bytes; I need to think it out better though...

Edit: As I posted this, I realised that I can remove the jmp statement as the code will fall through anyway. So another 6 bytes down - size at the moment is &C3E; with about &200 of this being the system engine messages.

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