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2018-10-05 07:02

JackAsser

Registered: Jun 2002
Posts: 2014

32bit Decimal convertion

Anybody got this shitz for 32-bit numbers? http://codebase64.org/doku.php?id=base:hexadecimal_to_decimal_c..

... 17 posts hidden. Click here to view all posts....

2018-10-05 10:33

JackAsser

Registered: Jun 2002
Posts: 2014

Quote: If he is, I could sort of sympathise with that, if it was part of a large project like Eye of the Beholder with zillions of lines of code and someone else had already implemented a 32-bit version of that routine.

I can't sympathise with the spelling of "Convertion" (Conversion) though. ;)

Also not zillions, but just 40688 at the moment (675kb).

2018-10-05 10:35

Krill

Registered: Apr 2002
Posts: 2980

Quoting JackAsser

nope, same there as on Codebase.

Indeed, Codebase has a straight 1:1 rip of the original 6502.org page, without giving proper credit. Not cool, Codebase, not cool.

Quoting JackAsser

Thinking of some simple shift+add with the 1/10 since that is a very simple bitpattern 110011001100110011...

Please elaborate. :)

2018-10-05 10:36

JackAsser

Registered: Jun 2002
Posts: 2014

Quote: You're too lazy to pick any of the 3 approaches and modify the routine for 32-bit numbers? :)

Actually I didn't even bother to look closer on that code posted there but I didn't now and it's meant to be extended.

"The principle should be pretty clear. You can take it out to as many digits as you want."

However it relies on decimal mode being set, something my interrupt handlers can't handle and I'm not willing to fuck timing all over the place.

2018-10-05 10:41

Krill

Registered: Apr 2002
Posts: 2980

You have shitloads of spare memory for lookup tables, right? :) That allows for a very simple and fast approach with 4 8-bit lookups and 3 adds, both times decimal places, or something, i think.

2018-10-05 10:42

JackAsser

Registered: Jun 2002
Posts: 2014

Quote: Quoting JackAsser
nope, same there as on Codebase.
Indeed, Codebase has a straight 1:1 rip of the original 6502.org page, without giving proper credit. Not cool, Codebase, not cool.

Quoting JackAsser
Thinking of some simple shift+add with the 1/10 since that is a very simple bitpattern 110011001100110011...
Please elaborate. :)

Basically you want to do:

int value = 0xdeadbeef;

int digit0 = value%10; value/=10;
int digit1 = value%10; value/=10;
int digit2 = value%10; value/=10;
int digit3 = value%10; value/=10;
int digit4 = value%10; value/=10;
int digit5 = value%10; value/=10;
.
.
.

When rolling your own division the remainder will pop out automatically. Doing a /10 is the same as doing a multiply by 1/10. Multiply by 1/10 is simply a shift+add multiplication with a %110011001100... bitpattern.

2018-10-05 10:43

JackAsser

Registered: Jun 2002
Posts: 2014

Quote: You have shitloads of spare memory for lookup tables, right? :) That allows for a very simple and fast approach with 4 8-bit lookups and 3 adds, both times decimal places, or something, i think.

I actually don't have shitloads of memory left and this code can be dead slow so I'd rather have it tight.

2018-10-05 10:45

Krill

Registered: Apr 2002
Posts: 2980

Then i'd go with the first algorithm, bitwise conversion without any tables or div/mul.

2018-10-05 10:47

JackAsser

Registered: Jun 2002
Posts: 2014

Quote: Then i'd go with the first algorithm, bitwise conversion without any tables or div/mul.

Need to digest it. Don't understand at all how it works atm. :D

2018-10-05 10:52

JackAsser

Registered: Jun 2002
Posts: 2014

Quote: Need to digest it. Don't understand at all how it works atm. :D

Or I just substract billions, and when underflowing, roll back one step and start substracting 100-millions, and then 10-millions etc.. down to ones. Should be resonably fast.

ldx #<-1
:
sec
lda TMP+0
sbc #<(1000000000>>0)
sta TMP+0
lda TMP+1
sbc #<(1000000000>>8)
sta TMP+1
lda TMP+2
sbc #<(1000000000>>16)
sta TMP+2
lda TMP+1
sbc #<(1000000000>>24)
sta TMP+1
inx
bvc :-

etc..

2018-10-05 11:12

JackAsser

Registered: Jun 2002
Posts: 2014

Enjoy:

.export htd32
.proc htd32
		HTD_IN = ARGS+0		; 32-bit input
		HTD_OUT = RESULT	; 10-digit output, one digit per ZP-loc

		ldy #0 ;digit position
		:
			; Count digits on position y
			ldx #<-1 ;digit value
			:
				inx
				sec
				lda HTD_IN+0
				sbc table0,y
				sta HTD_IN+0
				lda HTD_IN+1
				sbc table1,y
				sta HTD_IN+1
				lda HTD_IN+2
				sbc table2,y
				sta HTD_IN+2
				lda HTD_IN+3
				sbc table3,y
				sta HTD_IN+3
			bcs :-

			; Rollback underflowed result
			clc
			lda HTD_IN+0
			adc table0,y
			sta HTD_IN+0
			lda HTD_IN+1
			adc table1,y
			sta HTD_IN+1
			lda HTD_IN+2
			adc table2,y
			sta HTD_IN+2
			lda HTD_IN+3
			adc table3,y
			sta HTD_IN+3

			txa
			sta HTD_OUT,y
			iny
			cpy #10
		bne :--

		rts

table0:	.byte <(1000000000>> 0),<(100000000>> 0),<(10000000>> 0),<(1000000>> 0),<(100000>> 0),<(10000>> 0),<(1000>> 0),<(100>> 0),<(10>> 0),<(1>> 0)
table1:	.byte <(1000000000>> 8),<(100000000>> 8),<(10000000>> 8),<(1000000>> 8),<(100000>> 8),<(10000>> 8),<(1000>> 8),<(100>> 8),<(10>> 8),<(1>> 8)
table2:	.byte <(1000000000>>16),<(100000000>>16),<(10000000>>16),<(1000000>>16),<(100000>>16), <(10000>>16),<(1000>>16),<(100>>16),<(10>>16),<(1>>16)
table3:	.byte <(1000000000>>24),<(100000000>>24),<(10000000>>24),<(1000000>>24),<(100000>>24), <(10000>>24),<(1000>>24),<(100>>24),<(10>>24),<(1>>24)
.endproc

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