From: Robert Lee <rhlee@nwu.edu>
Subject: Re: Converting SUN number to Intel
Date: 25 Aug 1999 00:00:00 GMT
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Rene Tschaggelar wrote:
>
> for storing the numbers, there is the big endian/little endian issue.

I suspected that this was the issue but I wasn't sure.  The underlying
tidbit you need is an assembler instruction called 'bswap' that reverses
the bytes in a 32bit quantity.  Here's a collection of Swap routines.
You'll note that many are the same except for the typing of the
params/result.  Also I assume that you pass the backwards version
essentially as untyped DWords.

type
  TData8=double;

function Swap2(a:cardinal):word;
asm
  bswap eax
  shr eax,16
end;

function Swap4(a:cardinal):cardinal;
asm
  bswap eax
end;

function Swap4Signed(a:cardinal):longint;
asm
  bswap eax
end;

procedure SwapDoubleTo8(const a:double; var b:TData8);
asm
  mov edx,dword ptr[a]
  mov ecx,dword ptr[a+4]
  bswap edx
  bswap ecx
  mov dword ptr [eax],ecx
  mov dword ptr [eax+4],edx
end;

function Swap8ToDouble(var a:TData8):double;
var
  hold:double;
asm
  mov edx,dword ptr[eax]
  mov ecx,dword ptr[eax+4]
  bswap edx
  bswap ecx
  mov dword ptr [hold],ecx
  mov dword ptr [hold+4],edx
  fld hold;
end;

--
Bob Lee
High Performance Delphi - http://www.econos.com/optimize/