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 DEFAULT REL 25 SECTION .text 26 27;------------------------------------------------------------------------------ 28; BOOLEAN 29; EFIAPI 30; InternalMemIsZeroBuffer ( 31; IN CONST VOID *Buffer, 32; IN UINTN Length 33; ); 34;------------------------------------------------------------------------------ 35global ASM_PFX(InternalMemIsZeroBuffer) 36ASM_PFX(InternalMemIsZeroBuffer): 37 push rdi 38 mov rdi, rcx ; rdi <- Buffer 39 mov rcx, rdx ; rcx <- Length 40 shr rcx, 3 ; rcx <- number of qwords 41 and rdx, 7 ; rdx <- number of trailing bytes 42 xor rax, rax ; rax <- 0, also set ZF 43 repe scasq 44 jnz @ReturnFalse ; ZF=0 means non-zero element found 45 mov rcx, rdx 46 repe scasb 47 jnz @ReturnFalse 48 pop rdi 49 mov rax, 1 ; return TRUE 50 ret 51@ReturnFalse: 52 pop rdi 53 xor rax, rax 54 ret ; return FALSE 55 56