aboutsummaryrefslogtreecommitdiffstats
path: root/MdePkg/Library/BaseMemoryLibOptDxe/Ia32/IsZeroBuffer.nasm
blob: cfd41a62500bc37068e48f79ea3f2f76b8f49537 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
;------------------------------------------------------------------------------
;
; 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     ecx, [esp + 12]            ; ecx <- Length
    mov     edx, ecx                   ; edx <- ecx
    shr     ecx, 2                     ; ecx <- number of dwords
    and     edx, 3                     ; edx <- number of trailing bytes
    xor     eax, eax                   ; eax <- 0, also set ZF
    repe    scasd
    jnz     @ReturnFalse               ; ZF=0 means non-zero element found
    mov     ecx, edx
    repe    scasb
    jnz     @ReturnFalse
    pop     edi
    mov     eax, 1                     ; return TRUE
    ret
@ReturnFalse:
    pop     edi
    xor     eax, eax
    ret                                ; return FALSE