;------------------------------------------------------------------------------ | |
; | |
; Copyright (c) 2016, Intel Corporation. All rights reserved.<BR> | |
; SPDX-License-Identifier: BSD-2-Clause-Patent | |
; | |
; Module Name: | |
; | |
; IsZeroBuffer.nasm | |
; | |
; Abstract: | |
; | |
; IsZeroBuffer function | |
; | |
; Notes: | |
; | |
;------------------------------------------------------------------------------ | |
DEFAULT REL | |
SECTION .text | |
;------------------------------------------------------------------------------ | |
; BOOLEAN | |
; EFIAPI | |
; InternalMemIsZeroBuffer ( | |
; IN CONST VOID *Buffer, | |
; IN UINTN Length | |
; ); | |
;------------------------------------------------------------------------------ | |
global ASM_PFX(InternalMemIsZeroBuffer) | |
ASM_PFX(InternalMemIsZeroBuffer): | |
push rdi | |
mov rdi, rcx ; rdi <- Buffer | |
mov rcx, rdx ; rcx <- Length | |
shr rcx, 3 ; rcx <- number of qwords | |
and rdx, 7 ; rdx <- number of trailing bytes | |
xor rax, rax ; rax <- 0, also set ZF | |
repe scasq | |
jnz @ReturnFalse ; ZF=0 means non-zero element found | |
mov rcx, rdx | |
repe scasb | |
jnz @ReturnFalse | |
pop rdi | |
mov rax, 1 ; return TRUE | |
ret | |
@ReturnFalse: | |
pop rdi | |
xor rax, rax | |
ret ; return FALSE | |