BeRoPNG - A very tiny but complete PNG loader

[BeRo]

word and $FFFF0000 === 0 -- ALWAYS
word shl 16 === 0 -- ALWAYS.

Sorry, you're wrong. See my code again:

function Swap32(x:word):word;
begin
 result:=(Swap16(x and $ffff) shl 16) or Swap16((x and $ffff0000) shr 16);
end;

The first swap16 call gets "x and $ffff", and the result of it will shifted 16 bits to left, which's correct.
The second swap16 call gets "(x and $ffff0000) shr 16" or short "x shr 16", and the result of it will not shifted because it was already shifted 16 bits to right, which's also correct.

I guess, you had simply overlook the correct nested levels of the (...) blocks in my code.

[deathshadow]

Forgot about this thread... but:

function Swap32(x:word):word;

word is 16 bit unsigned... can only contain 0..$FFFF -- therein:

x and $ffff returns X

x and $ffff0000 returns 0, always...

since $FFFF is the highest number WORD can contain, $0000FFFF and $FFFF0000 == 0, ALWAYS. X in your function CANNOT hold a value that would return anything but zero on that second AND.... EVER.

See what I'm saying? for that function to work X would have to be DWORD and/or Longint... 32 bit... not 16 bit which is what WORD is.

[BeRo]

See what I'm saying? for that function to work X would have to be DWORD and/or Longint... 32 bit... not 16 bit which is what WORD is.

Yeah, I know (see the rest of the code), but this is unimportant, since this is 1. just a typo error in the typedef in the functiondef paramdef header (which's quick fixable) and 2. unused on little-endian systems