Trunc / Frac -> Wie funktionieren die intern?

[sakura]

Einfach mal als Beispiel an Trunc:

Delphi-Quellcode:

{ *********************************************************************** }
{                                                                         }
{ Delphi / Kylix Cross-Platform Runtime Library                           }
{ System Unit                                                             }
{                                                                         }
{ Copyright (c) 1988-2004 Borland Software Corporation                    }
{                                                                         }
{ Copyright and license exceptions noted in source                        }
{                                                                         }
{ *********************************************************************** }

procedure       _TRUNC;
asm
       { ->    FST(0)   Extended argument       }
       { <-    EDX:EAX  Result                  }

        SUB     ESP,12
        FNSTCW  [ESP].Word          // save
        FNSTCW  [ESP+2].Word        // scratch
        FWAIT
        OR      [ESP+2].Word, $0F00  // trunc toward zero, full precision
        FLDCW   [ESP+2].Word
        FISTP   qword ptr [ESP+4]
        FWAIT
        FLDCW   [ESP].Word
        POP     ECX
        POP     EAX
        POP     EDX
end;

......