学 Win32 汇编[21]

汇编指令的一般性要求: 1、两个操作数的尺寸必须一致; 2、操作数不能同为内存.

MOV(Move): 最常用的数据传送指令

---

;该指令不影响 EFlags
;指令格式: (其中的 r、m、i 分别表示: 寄存器、内存、立即数)
MOV r/m, r/m/i

---

; Test21_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?
    val dd ?
.code
main proc
    mov val, 123
    mov edx, val
    mov eax, edx
    PrintDec eax ;123
    ret
main endp
end main

---

LEA(Load Effective Address): 有效地址传送指令

---

;该指令不影响 EFlags
;指令格式:
LEA r, m

---

; Test21_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
    szText db 'ABCDEFG', 0
.code
main proc
    lea eax, offset szText
    lea ebx, szText
    PrintHex eax ;00403000
    PrintHex ebx ;00403000
    ret
main endp
end main

---

XCHG(Exchange): 交换指令

---

;该指令不影响 EFlags
;指令格式:
XCHG r/m, r/m

---

; Test21_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
    val1 dd 111
    val2 dd 222
.code
main proc
    mov eax, val1
    xchg eax, val2
    mov val1, eax
    PrintDec val1 ;222
    PrintDec val2 ;111
    ret
main endp
end main

---

XLATB(Translate Byte)、XLAT(Translate): 换码指令

---

;XLATB 可简化为 XLAT
;该指令不影响 EFlags

;XLAT 无参数, 操作和 EBX、AL 相关
;执行 XLAT 前, 先把源地址放入 EBX, 把字节序号放入 AL
;执行后, 指定字节被读入 AL

---

; Test21_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
    szText db 'ABCDEFG', 0
.code
main proc
    lea ebx, szText
    mov al, 1
    xlat
    PrintHex al ;42 - 这是 'B' 的 ASSII 编码
    
    mov al, 2
    xlatb
    PrintHex al ;43 - 这是 'C' 的 ASSII 编码
    ret
main endp
end main

---

MOVZX(Move With Zero-Extend): 零扩展传送

---

;该指令不影响 EFlags
;指令格式:
MOVZX r32, r16/m16
MOVZX r16, r8/m8

---

;示例同 MOVSX

---

MOVSX(Move With Sign-Extend): 符号扩展传送

---

;该指令不影响 EFlags
;指令格式:
MOVZX r32, r16/m16
MOVZX r16, r8/m8

;MOVZX 和 MOVSX 的区别是:
;1、MOVZX 会将目标寄存器中高出的位补 0
;2、如果源操作数的最高位是 1, MOVSX 会将目标寄存器中高出的位补 1; 反之补 0

---

; Test21_5.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
    bVal   db 90h
    dwVal1 dw 7FFFh
    dwVal2 dw 8000h
.code
main proc
    movzx eax, dwVal1
    movsx edx, dwVal1
    PrintHex eax ;00007FFF
    PrintHex edx ;00007FFF
    
    movzx eax, dwVal2
    movsx edx, dwVal2
    PrintHex eax ;00008000
    PrintHex edx ;FFFF8000
    
    mov cl, bVal
    movzx ax, cl
    movsx dx, cl
    PrintHex ax  ;0090
    PrintHex dx  ;FF90
    ret
main endp
end main