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assembly - 使用 mips 替换字符串的特定字符

问题描述

我试图使用 mips 替换字符串的特定字符。该程序就像用户需要输入限制为 40 个字符的字符串，程序需要询问用户是否要替换字符串中的任何字符。在我的代码中，我只能打印一个字符，这是我的代码：

.data
prompt0: .asciiz " Please Enter any String :"
prompt:.asciiz "\n Your current string is: "
prompt1:.asciiz "\n Do you want to make any changes to the string? (y/n): " 
prompt2: .asciiz "\n Please Enter the Character that you want to Search for :"
prompt3: .asciiz "\n Please Enter the New Character :  "
prompt4: .asciiz "\n Your Final string is: "
 yes: .asciiz "y"
 No :.asciiz "n"
 Buffer: .space 40
.text
 li $v0, 4
 la $a0, prompt0
 syscall 

 li $v0,8        # take in input
 la $a0, Buffer      # load byte space into address
 li $a1, 40          # allot the byte space for string
 move $t0,$a0        # save string to t0
 syscall

li $v0,4
la $a0,prompt        # load and print "you wrote" string
syscall

la $a0, Buffer       # reload byte space to primary address
move $a0,$t0         # primary address = t0 address (load pointer)
li $v0,4         # print string
syscall



Loop:
    # Ask if user want to chnge rthe string or not
li $v0, 4     # syscall 4 (print_str)
la $a0, prompt1  # argument: string
syscall

     # GET INPUT FROM USER
li   $v0, 8   # get input
la   $a0, Buffer    # load byte space into address
li   $a1, 2         # allot the byte space for string
 move $t0,$a0        # save string to t0
syscall
#EDIT
lb $t1, yes  
lb $t0, 0($t0)   

#END EDIT

bne $t0, $t1, Exit

#IF YES, PRINT MESSAGE
li $v0,4
la $a0,prompt2
syscall


li $v0, 8   #get input
la $a0, Buffer  #load byte space into address
li $a1, 2      # allot the byte space for string
sw $t0,($a0)    #save string to t0
syscall

li $v0,4
la $a0,prompt3
syscall

li $v0, 8   #get input
la $a0, Buffer  #load byte space into address
li $a1, 2      # allot the byte space for string
move $t0,$a0    #save string to t0
syscall


la $a0,prompt     #load and print "you wrote" string
li $v0,4
syscall


la $a0, Buffer  #reload byte space to primary address
move $a0,$t0    # primary address = t0 address (load pointer)
li $v0,4        # print string
syscall
j Loop


 Exit:

li $v0,10       #end program
syscall 
     jr $ra

这是我想转换为 mips 的 C 程序：

#include <stdio.h>
#include <string.h>

int main()
{
    char str[40], ch, Newch;
    int i;

    printf("\n Please Enter any String :  ");
    gets(str);

    printf("\n Please Enter the Character that you want to Search for :  ");
    scanf("%c", &ch);

    getchar();

    printf("\n Please Enter the New Character :  ");
    scanf("%c", &Newch);

    for(i = 0; i <= strlen(str); i++)
    {
        if(str[i] == ch)  
        {
            str[i] = Newch;
        }
    }

    printf("\n The Final String after Replacing All Occurrences of '%c' with '%c' = %s ", ch, Newch, str);

    return 0;
}

标签： assemblymips

解决方案

一个 for 循环被翻译成汇编如下：

for ( initializer; condition; increment ) {
    body
}

首先，将其转换为 C 中的 while 循环：

initializer;
while ( condition ) {
    body
    increment
}

接下来，将 while 翻译成汇编，如下所示：

LoopTop:
    if ( ! condition ) goto ExitTheLoop;
    body
    increment
    goto LoopTop;
ExitTheLoop:

打印部分很简单，只需打印每个单独的组件，每个组件都有自己的系统调用。您的打印语句将分解为打印一个常量字符串，然后是一个变量字符，然后是一个常量字符串，另一个变量字符，一个常量字符串，您的翻译字符串，最后是一个空格或包含空格的常量字符串：7 个单独的系统调用。

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