推一根绳子的每一个字符到堆栈MIPS [英] Push Each Character of a String Into a Stack MIPS

问题描述

所以，我的工作在MIPS的一个项目，以检查是否由用户输入的字符串是回文与否。我卡上读取字符串，并以一个（code的PushLoop一部分）推弦的每个字符入堆栈中一个组成部分。当我调试它，程序似乎觉得我还没有输入任何东西。这是我到目前为止有：

So I'm working on a project in MIPS to check if a string input by the user is a palindrome or not. The part I'm stuck on is reading the string and pushing each character of the string into the stack one by one (the PushLoop part of the code). When I debug it, the program seems to think I haven't entered anything at all. Here's what I have so far:

.text

main:

li $v0, 4                       # Prints str1
la $a0, str1
syscall

jal Init                        # Sets $s0 equal to $sp to compare if the stack is empty later

li $v0, 8                       # Read String
la $a0, buffer                  # Loads memory buffer (100)
li $a1, 100                     # Defines length of buffer
syscall

la $t0, buffer                  # Moves base register to $t0

PushLoop:   
    lb $a2, ($t0)               # Loads current character into $a2
    beqz $a2, fin               # if $a2 is equal to zero, the loop is terminated
    jal Push                    # Pushes what is stored in $a0 to the stack
    add $t0, $t0, -8            # Subtracts from buffer 
    j PushLoop

fin:
    la $t0, buffer              # Resets the memory buffer (I think)

PopLoop:
    jal IsEmpty                 # Checks if the stack is empty
    lb $a2, ($t0)               # Loads current character into $a2
    beq $v0, 1, isPal           # If stack is empty, jump to isPal
    jal Pop                     # Pops what is stored in the stack to $t1
    add $t0, $t0, -8            # Subtracts from buffer
    bne $a2, $t1, notPal
    j PopLoop


notPal:
    li $v0, 4                   # Prints str3
    la $a0, str3
    syscall

    li $v0, 0                   # loads 0 into $v0
    j end

isPal:
    li $v0, 4                   # Prints str2
    la $a0, str2
    syscall

    li $v0, 1                   # loads 1 into $v0
    j end

#EXIT
end: 
    li $v0, 10                  # ends the program
    syscall

Push:
    addi $sp, $sp, -8           # Move stack pointer
    sb $a2, ($sp)               # Store contents of $a2 at ($sp)
    jr $ra


Pop:
    lw $t1, ($sp)               # Pop char from stack and store in $t1
    addi $sp, $sp, 8            # Move stack pointer
    jr $ra

Init:
    add $s0, $sp, $zero         # Sets $s0 equal to $sp
    jr $ra


IsEmpty:
    beq $sp, $s0, Yes           # If $s0 is equal to the initial value of $sp, then stack is empty
    li $v0, 0                   # Loads 0 into $v0
    jr $ra

    Yes:
    li $v0, 1                   # Loads 1 into $v0
    jr $ra



 .data # Data declaration section
 str1: .asciiz "Please enter a String:  "
 str2: .asciiz "Is a palindrome!"
 str3: .asciiz "Is NOT a palindrome"

 buffer: .space 100

我敢肯定有更多的东西错的code，但我只是想在一个时间壁球一个bug被纠正。非常感谢帮助我！

I'm sure there are more things wrong with the code, but I'm just trying to squash one bug at a time. Thanks so much for helping me out!

推荐答案

您在不使用的系统调用8正确：

You're not using syscall 8 properly:

li $v0, 8                       # Read String
la $t0, buffer                  # Loads memory buffer (100)
syscall

如果您阅读系统调用8 的说明，它说的参数 $ A0 =缓冲，$ A1 =长度的。因此，这些三线code应改为类似：

If you read the description of syscall 8, it says "Arguments $a0 = buffer, $a1 = length". So those three lines of code should be changed into something like:

li $v0, 8                       # Read String
la $a0, buffer
li $a1, 100                  
syscall

然后，你可以做拉$ T0，缓冲如果你仍然想使用系统调用后 $ T0 作为对于内存基址寄存器中的 PushLoop 读。

Then you can do la $t0, buffer after the syscall if you still want to use $t0 as the base register for the memory reads in PushLoop.

这篇关于推一根绳子的每一个字符到堆栈MIPS的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！