bswap.pas

{$ifdef CPUX64}
function bswap32(a: cardinal): cardinal;
{$ifdef FPC}nostackframe; assembler; asm {$else} asm .noframe {$endif FPC}
  mov eax, a
  bswap eax
end;

function bswap64(const a: QWord): QWord; {$ifdef FPC}nostackframe; assembler; asm {$else}
asm .noframe // rcx=a (Linux: rdi)
{$endif FPC}
  mov rax, a
  bswap rax
end;
{$else}
{$ifdef CPUX86}
function bswap32(a: cardinal): cardinal;
asm
  bswap eax
end;

function bswap64({$ifdef FPC_X86}constref{$else}const{$endif} a: QWord): QWord;
asm
  {$ifdef FPC_X86}
  mov edx, dword ptr[eax]
  mov eax, dword ptr[eax + 4]
  {$else}
  mov edx, a.TQWordRec.L
  mov eax, a.TQWordRec.H
  {$endif FPC_X86}
  bswap edx
  bswap eax
end;
{$else}
{$ifdef FPC}
function bswap32(a: cardinal): cardinal;
begin
  result := SwapEndian(a); // use fast platform-specific function
end;

function bswap64(const a: QWord): QWord;
begin
  result := SwapEndian(a); // use fast platform-specific function
end;
{$else}
function bswap32(a: cardinal): cardinal;
begin
  result := ((a and $ff)shl 24)or((a and $ff00)shl 8)or
            ((a and $ff0000)shr 8)or((a and $ff000000)shr 24);
end;

function bswap64(const a: QWord): QWord;
begin
  TQWordRec(result).L := bswap32(TQWordRec(a).H);
  TQWordRec(result).H := bswap32(TQWordRec(a).L);
end;
{$endif FPC}
{$endif CPUX86}
{$endif CPUX64}