EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/DivU64x32.c

/*++

Copyright (c) 2006, Intel Corporation. All rights reserved.<BR>
This program and the accompanying materials                          
are licensed and made available under the terms and conditions of the BSD License         
which accompanies this distribution.  The full text of the license may be found at        
http://opensource.org/licenses/bsd-license.php                                            
                                                                                          
THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,                     
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.             

Module Name:

  DivU64x32.c

Abstract:

  64-bit division function for IA-32

--*/

#include "Tiano.h"

UINT64
DivU64x32 (
  IN UINT64   Dividend,
  IN UINTN    Divisor,
  OUT UINTN   *Remainder OPTIONAL
  )
/*++

Routine Description:

  This routine allows a 64 bit value to be divided with a 32 bit value returns 
  64bit result and the Remainder.

Arguments:

  Dividend  - dividend
  Divisor   - divisor
  Remainder - buffer for remainder
  
Returns:

  Dividend  / Divisor
  Remainder = Dividend mod Divisor
  
N.B. only works for 31bit divisors!!

--*/
{
  __asm {
    xor edx, edx                    ; Clear EDX

    mov eax, dword ptr Dividend[4]  ; Put high 32 bits of 64-bit dividend in EAX
    mov ecx, Divisor                ; Put 32 bits divisor in ECX
    div ecx                         ; Dividend   Divisor  Quoitent...Remainder
                                    ;  0:EAX  /  ECX   =  EAX      EDX   

    push eax                        ; Push quoitent in stack

    mov eax, dword ptr Dividend[0]  ; Put low 32 bits of 64-bit dividend in EAX              
    div ecx                         ; Leave the REMAINDER in EDX as High 32-bit of new dividend
                                    ; Dividend   Divisor  Quoitent...Remainder              
                                    ;  EDX:EAX  /  ECX   =  EAX      EDX               

    mov ecx, Remainder              ; Put &REMAINDER to ecx

    jecxz Label1                    ; If ecx == 0, no remainder exist, return with quoitent in EDX directly 
    mov dword ptr [ecx], edx        ; Put EDX through REMAINDER pointer in ECX 

Label1:
    pop edx                         ; Pop High 32-bit QUOITENT to EDX
  }
}