"Stretching" a byte variable into two byte variables?

[richard]

sample the msb of your byte
if its set add three to your word var
shift left the byte var 1 bit the word 2 bits
repeat for all 8 bits

[CuriousOne]

and if it not?

[richard]

don't add 3

[tumbleweed]

If you start off with B=0 and C=0 you can skip half those statements and only do the ones where A.x = 1

[CuriousOne]

I wanted it to be shorter, by using loop and

X.Y=Z
but as I can see, you can't use another variable as bit reference, only static values.

[CuriousOne]

uint16_t enlargeYourByte(uint8_t input)

2

{

3	uint16_t x = input;

4	x = (x ^ (x << 4)) & 0x0f0f;

5	x = (x ^ (x << 2)) & 0x3333;

6	x = (x ^ (x << 1)) & 0x5555;

7	return x | (x << 1));

8

}

This is how they do it in C. Can we port this to PBP ?

[mpgmike]

I think this does it:

Input VAR BYTE
Wide VAR WORD
X VAR WORD
Y VAR WORD

EnlargeYourByte:
X = Input
Y = Input << 4
X = X ^ Y
X = X & $0F0F
Y = X << 2
X = X ^ Y
X = X & $3333
Y = X << 1
X = X ^ Y
X = X & $5555
Wide = X << 1
RETURN