;------------------------------------------------------------------------------ ; ; Copyright (c) 2016, 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: ; ; IsZeroBuffer.nasm ; ; Abstract: ; ; IsZeroBuffer function ; ; Notes: ; ;------------------------------------------------------------------------------ SECTION .text ;------------------------------------------------------------------------------ ; BOOLEAN ; EFIAPI ; InternalMemIsZeroBuffer ( ; IN CONST VOID *Buffer, ; IN UINTN Length ; ); ;------------------------------------------------------------------------------ global ASM_PFX(InternalMemIsZeroBuffer) ASM_PFX(InternalMemIsZeroBuffer): push edi mov edi, [esp + 8] ; edi <- Buffer mov edx, [esp + 12] ; edx <- Length xor ecx, ecx ; ecx <- 0 sub ecx, edi and ecx, 15 ; ecx + edi aligns on 16-byte boundary jz @Is16BytesZero cmp ecx, edx cmova ecx, edx ; bytes before the 16-byte boundary sub edx, ecx xor eax, eax ; eax <- 0, also set ZF repe scasb jnz @ReturnFalse ; ZF=0 means non-zero element found @Is16BytesZero: mov ecx, edx and edx, 15 shr ecx, 4 jz @IsBytesZero .0: pxor xmm0, xmm0 ; xmm0 <- 0 pcmpeqb xmm0, [edi] ; check zero for 16 bytes pmovmskb eax, xmm0 ; eax <- compare results cmp eax, 0xffff jnz @ReturnFalse add edi, 16 loop .0 @IsBytesZero: mov ecx, edx xor eax, eax ; eax <- 0, also set ZF repe scasb jnz @ReturnFalse ; ZF=0 means non-zero element found pop edi mov eax, 1 ; return TRUE ret @ReturnFalse: pop edi xor eax, eax ret ; return FALSE