PTR: 指定要操作的数据尺寸 ; Test12_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 db 11h, 22h, 33h, 44h, 55h, 66h, 77h, 88h
.code
main proc
xor eax, eax ;清空 EAX, 同 mov eax, 0
mov eax, dword ptr val ;
PrintHex eax ;44332211
xor eax, eax ;
mov eax, dword ptr val+1 ;
PrintHex eax ;55443322
xor eax, eax ;
mov ax, word ptr val ;
PrintHex eax ;00002211
xor eax, eax ;
mov al, byte ptr val ;
PrintHex eax ;00000011
ret
main endp
end main
OFFSET: 获取全局变量或标号的偏移地址 ; Test12_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
v1 db ''abcdefg'', 0
v2 dd 11223344h
.code
main proc
PrintHex offset v1 ;00403000
PrintHex offset v2 ;00403008
PrintHex offset main ;00401000 - 这里的 main 是个标号
ret
;本例中的 offset 不能用 addr 代替
main endp
end main
ADDR: 类似 offset 也是获取变量的地址... ; Test12_3.asm
.386
.model flat, stdcall
;include windows.inc
include kernel32.inc
includelib kernel32.lib
include user32.inc
includelib user32.lib
.data
v1 dd 00434241h ;ABC
v2 dd 00636261h ;abc
.code
main proc
invoke MessageBox, 0, offset v1, offset v2, 0 ;现在 v1、v2 是全局变量
invoke MessageBox, 0, addr v2, addr v1, 0 ;使用 offset 和 addr 均可
invoke ExitProcess, 0
main endp
end main
获取局部变量的地址只能使用 ADDR: ; Test12_4.asm
.386
.model flat, stdcall
;include windows.inc
include kernel32.inc
includelib kernel32.lib
include user32.inc
includelib user32.lib
.code
main proc
LOCAL v1,v2
mov v1, 00434241h
mov v2, 00636261h
;invoke MessageBox, 0, offset v1, offset v2, 0 ;offset 不能获取局部变量的地址
invoke MessageBox, 0, addr v2, addr v1, 0
invoke ExitProcess, 0
main endp
end main
OFFSET 和 ADDR 的异同: 1、offset 不能获取局部变量的地址; 2、addr 只能用于调用函数(invoke)时, 不能用于赋值操作; 3、addr 面对局部变量时会转换为 lea 等指令, addr 面对全局变量时则直接调用 offset; 4、在 invoke 中应尽量使用 addr, 其他只用 offset.(责任编辑：admin) |
