零出裝配

Question

記憶，我會用代碼首先啓動：

.equ SWI_Open, 0x66  @ open a file 
.equ SWI_Close, 0x68  @ close a file 
.equ SWI_PrStr, 0x69  @ Write a null-ending string 
.equ SWI_RdStr, 0x6a  @ Read a string 
.equ Stdout, 1   @ Set output target to be Stdout 
.equ SWI_Exit, 0x11  @ Stop execution 
.global _start 
.text 

_start: 
    ldr r0,=InFileName 
    mov r1,#0 
    swi SWI_Open 
    bcs InFileError 
    ldr r1,=InFileHandle 
    str r0,[r1] 
    mov r8, r0  @ r8 will hold the address of the file handle 
ReadLoop: 
    mov r0, r8 
    ldr r1, =LineArray 
    mov r2, #256 
    swi SWI_RdStr 
    bcs EndReached 
    @ r1 now has address of the read line 
    mov r9, r1  @ r9 will hold the memory address of the read line 
    mov r4, #0  @ r4 = START 
    mov r5, #1  @ r5 = END 
    bl PerLineFunc  @ r0/r1 args passed to PerLineFunc 
    @ ShuffleWord within PerLineFunc should change the words around, so now we just need to print the new line of words 
    mov r0, #Stdout 
    mov r1, r9 
    swi SWI_PrStr 
    ldr r1, =NL 
    swi SWI_PrStr 
    bal ReadLoop 

SWI_RdStr讀取指定的文件，並將其存儲線與存儲到R1的地址位置記憶。我的問題是，我不知道如何將行讀入的內存清零。如果第一行是20個字符，並且下一行是15，那麼在讀取第二行之後，第一行的最後5個字符仍然在內存中。

我想這會是這樣的：

ldr r1, =LineArray 
str #0, [r1] 

但返回一個語法錯誤......我只是想再次運行ReadLoop之前重置內存。

編輯：在OP中發佈答案。需要被添加到ReadLoop

mov r0, #0 
ldr r1, =LineArray 
mov r2, #0 
bl EraseMemory @ r0, r1, and r2 passed into EraseMemory 

這裏結束 這第一部分是在EraseMemory功能

EraseMemory: 
    str r0, [r1] 
    add r1, r1, #4 
    add r2, r2, #1 
    cmp r2, #64   @ 256/4 = 64 
    bxeq lr    @ This loop should run 64 times to erase all 256 bytes of memory that were used 
    bal EraseMemory 

Answer 1

首先，您需要立即值寫入寄存器：

ldr r1, =LineArray 
mov r0, #0 
str r0, [r1]