Win32 汇编[29] – 串指令: MOVS*、CMPS*、SCAS*、LODS*、REP、REPE、REPNE 等

这里的 “串” 并不单指字符串, 包括所有连续的数据(如数组); 串指令只用于内存操作.

移动串指令: MOVSB、MOVSW、MOVSD ;从 ESI -> EDI; 执行后, ESI 与 EDI 的地址移动相应的单位
比较串指令: CMPSB、CMPSW、CMPSD ;比较 ESI、EDI; 执行后, ESI 与 EDI 的地址移动相应的单位
扫描串指令: SCASB、SCASW、SCASD ;依据 AL/AX/EAX 中的数据扫描 EDI 指向的数据, 执行后 EDI 自动变化
储存串指令: STOSB、STOSW、STOSD ;将 AL/AX/EAX 中的数据储存到 EDI 给出的地址, 执行后 EDI 自动变化
载入串指令: LODSB、LODSW、LODSD ;将 ESI 指向的数据载入到 AL/AX/EAX, 执行后 ESI 自动变化

其中的 B、W、D 分别指 Byte、Word、DWord, 表示每次操作的数据的大小单位.

上述指令可以有重复前缀:
REP             ECX > 0 时
REPE (或 REPZ)  ECX > 0 且 ZF=1 时
REPNE(或 REPNZ) ECX > 0 且 ZF=0 时
;重复前缀可以自动按单位(1、2、4)递减 ECX

MOVSB: 移动字符串

; Test29_1.asm
.386
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

.data
    szSource db 'Delphi 2010', 0 
    len      equ $ - szSource - 1
    szDest   db len dup(?), 0
.code
main proc
    lea esi, szSource
    lea edi, szDest
    mov ecx, len
    cld ;复位标志寄存器的方向标志, 以让串地址由低到高
    rep movsb
    PrintString szDest ;Delphi 2010
    ret
main endp
end main

上面的例子, 假如不使用重复前缀…

; Test29_2.asm
.386
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

.data
    szSource db 'Delphi 2010', 0 
    len      equ $ - szSource - 1
    szDest   db len dup(?), 0
.code
main proc
    lea esi, szSource
    lea edi, szDest
    mov ecx, len
    cld
@@: movsb
    dec ecx
    jnz @B
    PrintString szDest
    ret
main endp
end main

MOVSD 例:

; Test29_3.asm
.386
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

.data
    ddSource dd 11h,22h,33h
    ddDest   dd lengthof ddSource dup(?)
.code
main proc
    lea esi, ddSource
    lea edi, ddDest
    mov ecx, lengthof ddSource
    cld
    rep movsd
    DumpMem offset ddDest, sizeof ddDest ;11 00 00 00 - 22 00 00 00 - 33 00 00 00
    ret
main endp
end main

MOVSW 例:

; Test29_4.asm
.386
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

.data
    ddSource dw 11h,22h,33h
    ddDest   dw lengthof ddSource dup(?)
.code
main proc
    lea esi, ddSource
    lea edi, ddDest
    mov ecx, lengthof ddSource
    cld
    rep movsw
    DumpMem offset ddDest, sizeof ddDest ;11 00 22 00 - 33 00 00 00
    ret
main endp
end main

CMPSD 例:

; Test29_5.asm
.386p
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

.data
    ddVal1 dd 1234h
    ddVal2 dd 5678h
.code
main proc
    lea esi, ddVal1
    lea edi, ddVal2
    cmpsd
    je L1
    PrintText '两数不等'
    jmp L2
L1: PrintText '两数相等'
L2: ret
main endp
end main

CMPSW 例:

; Test29_6.asm
.386p
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

.data
    dwArr1 dw 1,2,3,4,5
    dwArr2 dw 1,3,5,7,9
.code
main proc
    lea esi, dwArr1
    lea edi, dwArr2
    mov ecx, lengthof dwArr1
    cld
    repe cmpsw
    je L1
    PrintText '两数组不等'
    jmp L2
L1: PrintText '两数组相等'
L2: ret
main endp
end main

对比数组时, 假如数组长度不一致…

; Test29_7.asm
.386p
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

.data
    dwArr1 dw 1,2,3,4,5
    dwArr2 dw 1,2,3,4,5,6
.code
main proc
    lea esi, dwArr1
    lea edi, dwArr2
    mov ecx, lengthof dwArr1
    cmp ecx, lengthof dwArr2
    jne L1
    cld
    repe cmpsw
    jne L1
    PrintText '两数组相等'
    jmp L2
L1: PrintText '两数组不等'
L2: ret
main endp
end main

如果对比的是 0 结束的字符串, 长度不一致也不用考虑

; Test29_8.asm
.386p
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

.data
    szText1 db 'Delphi 2010', 0
    szText2 db 'Delphi 2011', 0
.code
main proc
    lea esi, szText1
    lea edi, szText2
    mov ecx, lengthof szText1
    cld
    repe cmpsb
    je L1
    PrintText '字符串不同'
    jmp L2
L1: PrintText '字符串相同'
L2: ret
main endp
end main

SCASB 例:

; Test29_9.asm
.386p
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

.data
    szText db 'ABCDEFGH', 0
.code
main proc
    lea edi, szText
    mov al, 'F'
    mov ecx, lengthof szText - 1
    cld
    repne scasb
    je L1
    PrintText '没找到'
    jmp L2
L1: sub ecx, lengthof szText - 1
    neg ecx
    PrintDec ecx ;如果找得到, 这里显示是第几个字符; 本例结果是 6
L2: ret
main endp
end main

STOSB 例:

; Test29_10.asm
.386p
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

.data
    len = 31
    szText db len dup(0), 0
.code
main proc
    lea edi, szText
    mov al, 'x'
    mov ecx, len
    cld
    rep stosb
    PrintString szText ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
    ret
main endp
end main

LODSW 例: 数组求和

; Test29_11.asm
.386p
.model flat, stdcall

include    windows.inc
include    kernel32.inc
include    masm32.inc
include    debug.inc
includelib kernel32.lib
includelib masm32.lib
includelib debug.lib

.data
    dwArr dw 1,2,3,4,5,6,7,8,9,10
.code
main proc
    lea esi, dwArr
    mov ecx, lengthof dwArr
    xor edx, edx
    xor eax, eax
@@: lodsw
    add edx, eax
    loop @B
    PrintDec edx ;55
    ret
main endp
end main