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我正在尝试编写使用 MARS（我的 MIPS 模拟器）伪随机数生成器的代码，以在字符串中选择一个随机字符，将其从内存中取出并放入寄存器，然后用星号 '*' 替换内存中的那个字符.

到目前为止，它只打乱了这个词的一部分，这让我发疯了。我找不到此代码中的哪些内容不起作用。我什至不需要直接的答案，只是提示/提示会很有帮助。

这是代码：

#this loop extracts a char at random from a string in memory, stores it in a register, and replaces the char in the string with an asterisk '*'

.data

.align 2
string0: .ascii "Tyler\n"

.align 2
endString: .asciiz "Loop completed!\n"
.align 2
scrambleString: .asciiz


.text

#counter
li $t0, 5

#pointer to string0
la $s0, string0




loop2:

#is counter = 0? go to loop3 if so
beq $t0, $0, loop3

#seed & prepare randomized number generator
li $v0, 30 
syscall

li $v0, 40 #sets seed
syscall

#generates random number in $a0, with the coUnter $t0 being the upper bound
addi $a1, $t0, 1
li $v0, 42
syscall


#add STRING POINTER by random number in $a0, store this new address in $t1
#addi $a0, $a0, 1
add $t1, $s0, $a0
#srlv $t1, $s0, $a0

#isolates that bytesized char, puts it into $t2
lbu $t2, ($t1)
#beq $t2, 0x5c, loop2

#replaces char in original string with "*"
li $t3, 0x2a
sb $t3, ($t1)

beq $t1, $t3, loop2
#decrement counter
addi $t0, $t0, -1

#loop return
j loop2


loop3:
la $a0, string0
li $v0, 4
syscall

li $v0, 10
syscall
4

1 回答 1

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  1. You are resetting the random number seed on every iteration of your loop (loop2:).
  2. Syscalls 40 and 42 each take 2 parameters which should be in $a0 and $a1. See here.
  3. The temporary registers $t0,...,$t9 get altered by each syscall. You should be using the callee saved registers $s0,...$s8 instead.
于 2012-10-15T22:09:11.573 回答