string 在 MIPS 程序集中反转字符串
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原文地址: http://stackoverflow.com/questions/8198205/
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Reversing a string in MIPS Assembly
提问by Erdem E.
I'm trying to prompt the user for the length of a string, allocate space for that string, then print it out in reverse.
我试图提示用户输入字符串的长度，为该字符串分配空间，然后反向打印出来。
For the life of me, I can't figure out why this isn't working..
对于我的生活，我无法弄清楚为什么这不起作用..
Sample Output:
(spim) run
Please enter an integer:
7
string
(spim)
Now the length of "string" should be 6 right? + the null terminating character which should make it 7. Can anyone spot where I'm going wrong with my approach?
现在“字符串”的长度应该是 6 吧？+ 应为 7 的空终止字符。有人能发现我的方法哪里出了问题吗？
.data
nl: .asciiz "\n"
inputPrompt: .asciiz "Please enter an integer:\n"
theString: .space 32
theInteger: .word 1
.text
main:
la $a0, inputPrompt #load address a0 with prompt
li $v0, 4 #load system call, print string into v0
syscall
li $v0, 5 #load system call, read int into v0
syscall
sw $v0, theInteger #store saved int into $t0
li $v0, 8 #load system call, read string with mem address
la $a0, theString #load address of reserved string space
lw $a1, theInteger #load address of saved int length for string
syscall
lw $t0, theInteger
add $a1,$zero,$t0 #pass lenght of string
jal stringreverse #reverse the string
stringreverse:
add $t0,$a0,$zero #starting address
add $t1,$zero,$zero #i = 0
addi $t2,$a1,-1 #j = length-1
loop:
add $t3,$t0,$t1
lb $t4,0($t3) #the lb string[i]
add $t5,$t0,$t2
lb $t6,0($t5) #the lb string[j]
sb $t4,0($t5) #string[j] = string[i]
sb $t6,0($t3) #string[i] = string[j]
addi $t1,$t1,1 #i++
addi $t2,$t2,-1 #j--
slt $t6,$t2,$t1
beqz $t6,loop
exit:
li $v1, 4 #system call to print reversed string
la $a2, 0($a1)
syscall
li $v0, 10
syscall # Exit program
回答by Erdem E.
there was a small error in indexing...and instead of re writing on top of the old one i used new memory space called reverse...
索引中有一个小错误……我没有在旧的基础上重写，而是使用了称为反向的新内存空间……
stringreverse:
add $t0,$a0,$zero #starting address
add $t1,$zero,$zero
add $t3,$zero,$zero #i = 0
addi $t2,$a1,-2 #j = length-1
loop:
add $t5,$t0,$t2
lb $t6,0($t5) #the lb string[j]
sb $t6,reverse($t3)
addi $t2,$t2,-1 #j--
addi $t3,$t3,+1 #i++
slt $t7,$t2,$t1
beqz $t7,loop
