MdePkg/Library/BaseMemoryLibOptPei/Ia32/IsZeroBuffer.nasm

   1 ;------------------------------------------------------------------------------
   2 ;
   3 ; Copyright (c) 2016, Intel Corporation. All rights reserved.<BR>
   4 ; This program and the accompanying materials
   5 ; are licensed and made available under the terms and conditions of the BSD License
   6 ; which accompanies this distribution.  The full text of the license may be found at
   7 ; http://opensource.org/licenses/bsd-license.php.
   8 ;
   9 ; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  10 ; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  11 ;
  12 ; Module Name:
  13 ;
  14 ;   IsZeroBuffer.nasm
  15 ;
  16 ; Abstract:
  17 ;
  18 ;   IsZeroBuffer function
  19 ;
  20 ; Notes:
  21 ;
  22 ;------------------------------------------------------------------------------
  23
  24     SECTION .text
  25
  26 ;------------------------------------------------------------------------------
  27 ;  BOOLEAN
  28 ;  EFIAPI
  29 ;  InternalMemIsZeroBuffer (
  30 ;    IN CONST VOID  *Buffer,
  31 ;    IN UINTN       Length
  32 ;    );
  33 ;------------------------------------------------------------------------------
  34 global ASM_PFX(InternalMemIsZeroBuffer)
  35 ASM_PFX(InternalMemIsZeroBuffer):
  36     push    edi
  37     mov     edi, [esp + 8]             ; edi <- Buffer
  38     mov     ecx, [esp + 12]            ; ecx <- Length
  39     mov     edx, ecx                   ; edx <- ecx
  40     shr     ecx, 2                     ; ecx <- number of dwords
  41     and     edx, 3                     ; edx <- number of trailing bytes
  42     xor     eax, eax                   ; eax <- 0, also set ZF
  43     repe    scasd
  44     jnz     @ReturnFalse               ; ZF=0 means non-zero element found
  45     mov     ecx, edx
  46     repe    scasb
  47     jnz     @ReturnFalse
  48     pop     edi
  49     mov     eax, 1                     ; return TRUE
  50     ret
  51 @ReturnFalse:
  52     pop     edi
  53     xor     eax, eax
  54     ret                                ; return FALSE
  55