TryTrunc

gistfile1.pas

function TryTrunc(x: Extended; out Val: Int64): boolean;
var
  oldcw, cw, sw: word;
asm
    fld      x
    fwait

    fnstcw   oldcw
    fnstcw   cw
    fwait
    or       cw, $0f00             // towards zero, full precision
    fldcw    cw
    mov      eax, dword ptr val
    fistp    qword ptr [eax]

    fnstsw   sw
    mov      ax, sw
    not      ax
    and      ax, 1                 // IE = 1
    mov      Result, al
    test     al,al
    jnz      @noexception
    fnclex                         // if IE, eat exception
@noexception:
    fwait                          // raise all others

    FLDCW    oldcw
end;