汇编-LENGTHOF返回数组中元素的个数

 LENGTH OF操作符计算数组中元素的个数

.386
.model flat,stdcall
.stack 4096
ExitProcess PROTO,dwExitCode:DWORD

.data
byte1 BYTE 10,20,30
arrayl WORD 30 DUP(?) ,0,0 
array2 WORD 5 DUP(3 DUP(?) )   ;二维数组
;如果在数组定义中出现了嵌套的DUP操作符， 则LENGTHOF返回的是两个计数值的乘积

array3 DWORD 1, 2, 3, 4
digitStr BYTE "12345678",0


.code
main PROC
        
        mov eax,LENGTHOF byte1
        mov ebx,LENGTHOF arrayl
        mov ecx,LENGTHOF array2
        mov edx,LENGTHOF array3
        mov esi,LENGTHOF digitStr

        ;EAX = 00000003h EBX = 00000020h ECX = 0000000Fh EDX = 00000004h ESI = 00000009h

    INVOKE ExitProcess,0
main ENDP
END  main

 

 

如果数组定义占据了多个程序行， 则LENGTHOF只针对第一行定义的数据

.386
.model flat,stdcall
.stack 4096
ExitProcess PROTO,dwExitCode:DWORD

.data
myArray BYTE 10, 20, 30, 40, 50
    BYTE 60, 70, 80, 90, 100


.code
main PROC
        
        mov eax,LENGTHOF myArray   ;EAX = 00000005
        
    INVOKE ExitProcess,0
main ENDP
END  main

 

也可以在第一行结尾处用逗号，并在下一行继续进行数组初始化

.386
.model flat,stdcall
.stack 4096
ExitProcess PROTO,dwExitCode:DWORD

.data
myArray BYTE 10, 20, 30, 40, 50,
            60, 70, 80, 90, 100


.code
main PROC
        
        mov eax,LENGTHOF myArray   ;EAX = 0000000Ah
        
    INVOKE ExitProcess,0
main ENDP
END  main