MdePkg/Library/BaseMemoryLibOptDxe/Ia32/IsZeroBuffer.nasm

   1 ;------------------------------------------------------------------------------
   2 ;
   3 ; Copyright (c) 2016, Intel Corporation. All rights reserved.<BR>
   4 ; SPDX-License-Identifier: BSD-2-Clause-Patent
   5 ;
   6 ; Module Name:
   7 ;
   8 ;   IsZeroBuffer.nasm
   9 ;
  10 ; Abstract:
  11 ;
  12 ;   IsZeroBuffer function
  13 ;
  14 ; Notes:
  15 ;
  16 ;------------------------------------------------------------------------------
  17
  18     SECTION .text
  19
  20 ;------------------------------------------------------------------------------
  21 ;  BOOLEAN
  22 ;  EFIAPI
  23 ;  InternalMemIsZeroBuffer (
  24 ;    IN CONST VOID  *Buffer,
  25 ;    IN UINTN       Length
  26 ;    );
  27 ;------------------------------------------------------------------------------
  28 global ASM_PFX(InternalMemIsZeroBuffer)
  29 ASM_PFX(InternalMemIsZeroBuffer):
  30     push    edi
  31     mov     edi, [esp + 8]             ; edi <- Buffer
  32     mov     ecx, [esp + 12]            ; ecx <- Length
  33     mov     edx, ecx                   ; edx <- ecx
  34     shr     ecx, 2                     ; ecx <- number of dwords
  35     and     edx, 3                     ; edx <- number of trailing bytes
  36     xor     eax, eax                   ; eax <- 0, also set ZF
  37     repe    scasd
  38     jnz     @ReturnFalse               ; ZF=0 means non-zero element found
  39     mov     ecx, edx
  40     repe    scasb
  41     jnz     @ReturnFalse
  42     pop     edi
  43     mov     eax, 1                     ; return TRUE
  44     ret
  45 @ReturnFalse:
  46     pop     edi
  47     xor     eax, eax
  48     ret                                ; return FALSE
  49