在此函数中，我应该输入用户输入（4个字符串）并将其转换为27，无论左侧或右侧的空格如何，该字符串都应仍为有效字符串，并且我认为这样做不会对于右边的空格，但也请看看我对左边空格所做的操作。
字符串不能为空，太长或超出范围。因此，我的数字s应该为0-9，并且字母（无论大写还是小写）都是A-R和a-r。
我还必须编写一个子程序（ConvertString）将有效的用户输入转换为数字。它必须是递归的，因此子程序应自行调用。然后，当调用函数时，输入必须通过堆栈传递到函数中，并且当子程序返回转换结果（一个数字）时，应将其存储在堆栈中，然后由调用者从堆栈中读取。 / p>
主程序应打印基数。这是我第三次使用MIPS汇编语言，我感到困惑，因为我不知道我是否正确实现了递归函数或如何解决纠结。该代码将于明天到期，因此将不胜感激。谢谢
.data
str: .space 1000
msgempty: .asciiz "Input is empty."
msginvalid: .asciiz "Invalid base-28 number."
msglong: .asciiz "Input is too long."
.text
main:
#tells program to expect userinput
li $v0, 8
la $a0, str
li $a1, 1000
syscall
LeftSpaces:
#deletes the left spaces if any in user input
li $t8, 32 #ascii code for space
lb $t9, 0($a0) #stores 0 into $t9
beq $t8, $t9, CharacterSpaces
move $t9, $a0
j Length
CharacterSpaces:
#deletes spaces if there are any
addi $a0, $a0, 1
j LeftSpaces
Length:
addi $t0, $t0, 0
addi $t1, $t1, 10
add $t4, $t4, $a0 #add can add registers and with addi you have to have a immediate number
FindLength:
#Finds the length of the string
lb $t2, 0($a0)
beqz $t2, CheckLength #if t2 equal to 0 go to CheckLength function
beq $t2, $t1, CheckLength #if t1 and t1 are equal go to CheckLength function
addi $a0, $a0, 1
addi $t0, $t0, 1
j FindLength
CheckLength:
#Checks if the string is empty or too long
beqz $t0, EmptyInput
slti $t3, $t0, 5 #if string is of appropriate length
beqz $t3, LongInput
move $a0, $t4
j ConvertString
exit:
#tell the system the end of main
li $v0, 10
syscall
ConvertString:
#Allocating space in the stack
subu $sp, $sp, 16
sw $ra, 0($sp) #starting at first element
sw $s0, 4($sp) #starting at second element
sw $s1, 8($sp) #starting at third element
sw $s2, 12($sp) #starting at third element
#base case
li $v0, 1
beq $a0, 0, InvalidInput
move $s0, $a0
addi $a0, $a0, 1
jal ConvertString
#makes sure that character is in range
lb $t5, 0($a0)
beqz $t5, Conversion
beq $t5, $t1, Conversion
slti $t6, $t5, 48 #if the character is less than 0 than invalid
bne $t6, $zero, InvalidInput
slti $t6, $t5, 58 # if character is less than 9 then valid
bne $t6, $zero, FindingChar
slti $t6, $t5, 65 # if character less than A then invalid
bne $t6, $zero, InvalidInput
slti $t6, $t5, 82 # if character less than R then valid
bne $t6, $zero, FindingChar
slti $t6, $t5, 97 # if character less than a then invalid
bne $t6, $zero, InvalidInput
slti $t6, $t5, 115 # if character less than s then valid
bne $t6, $zero, FindingChar
bgt $t5, 114, InvalidInput # if character greater than r then invalid
lw $ra, 0($sp) #starting at first element
lw $s0, 4($sp) #starting at second element
lw $s1, 8($sp) #starting at third element
lw $s2, 12($sp) #starting at third element
addi $sp, $sp, 16
jr $ra
FindingChar:
#checks character individually for string
addi $a0, $a0, 1
j ConvertString
Conversion:
move $a0, $t4
addi $t7, $t7, 0 #intializes t7
add $s0, $s0, $t0
addi $s0, $s0, -1 #sets s0 to s0 plus 16-bit immediate for overflow
li $s3, 3 #will be stored at first character
li $s2, 2 #will be stored at 2nd character
li $s1, 1 #will be stored at 3rd character
li $s5, 0 #will be stored at 4th character
ConvertBase:
lb $s4, 0($a0)
beqz $s4, BaseResult #if s4 equal to 0 go to BaseResult function
beq $s4, $t1, BaseResult #if equal go to BaseResult function
slti $t6, $s4, 58
bne $t6, $zero, Base10 #if not equal go to Base10 function
slti $t6, $s4, 82
bne $t6, $zero, Base28UP #based on ascii number
slti $t6, $s4, 115
bne $t6, $zero, Base28LO #based on ascii number
Base10:
addi $s4, $s4, -48 #need 10 for base converter so 58-48 =10 and stored into s4
j Arrange
Base28UP:
addi $s4, $s4, -54 #need 28 so subtract 82-54 to get 28 and does upper conversion
j Arrange
Base28LO:
addi $s4, $s4, -87
Arrange:
#Have to arrange characters so they can be converted in the right place by the right number
beq $s0, $s3, Char1
beq $s0, $s2, Char2
beq $s0, $s1, Char3
beq $s0, $s5, Char4
#converts characters to base 28 based on hi or lo
Char1:
li $s6, 21952
mult $s4, $s6
mflo $s7
add $t7, $t7, $s7
addi $s0, $s0, -1
addi $a0, $a0, 1
j ConvertBase
Char2:
li $s6, 784
mult $s4, $s6
mflo $s7
add $t7, $t7, $s7
addi $s0, $s0, -1
addi $a0, $a0, 1
j ConvertBase
Char3:
li $s6, 28
mult $s4, $s6
mflo $s7
add $t7, $t7, $s7
addi $s0, $s0, -1
addi $a0, $a0, 1
j ConvertBase
Char4:
li $s6, 1
mult $s4, $s6
mflo $s7
add $t7, $t7, $s7
BaseResult:
li $v0, 1
move $a0, $t7
syscall
EmptyInput:
#checks to see if the input is empty
la $a0, msgempty #loading message
li $v0, 4 #prints string
syscall
j exit
InvalidInput:
#checks to see if the input is invlalid
la $a0, msginvalid
li $v0, 4
syscall
j exit
LongInput:
#checks to see if the input is longer than 4 characters
la $a0, msglong
li $v0, 4
syscall
j exit