עבאדי

.data
	str1:.asciiz "\nInsert a number in hexadecimal: "
	str2:.asciiz "\nDecimal value: "
	newline:.asciiz "\n"
	hex: .space 33
	strsize: .word 0
.text
.globl main
main:	
	li $v0,4	#prints str1
	la $a0,str1
	syscall
 
	li $v0,8	#reads string
	la $a0,hex
	li $a1,32
	syscall
 
	li $v0,4	#prints str2
	la $a0,str2
	syscall
 
	jal fixstr	#replace \n with \0
 
	jal converthex	#converts to decimal
 
 
	move $a0,$v0
	li $v0,1
	syscall
 
	li $v0,4	#prints newline
	la $a0,newline
	syscall
 
	li $v0,10 #exit
	syscall
 
 
fixstr:
	la $t0,hex
	li $t1,0
	li $t3,10 # new line \n
	loop:
		lb $t2,($t0)
		beq $t2,$t3,foundnewline
		addi $t0,$t0,1
		addi $t1,$t1,1
		j loop
	foundnewline:
		sb $zero,($t0)
		sw $t1,strsize	
	jr $ra
 
 
hexchar2dec:
	li $t0,47
	blt $a0,$t0,terminate
	li $t0,70
	bgt $a0,$t0,terminate 
 
	li $t0,57
	ble $a0,$t0,ok
 
	li $t0,65
	blt $a0,$t0,terminate
 
ok: #between 48...57 or 65...70 = 0-9 or A-F
	li $t0,58
	blt $a0,$t0,number
	addi $v0,$a0,-55
	jr $ra
number:
	addi $v0,$a0,-48
	jr $ra
 
terminate:
	li $v0,-1
	jr $ra
 
power:	
	move $t0,$a0
	beqz $t0,ret1
	li $t1,1
	li $t2,16
	p_loop:
		mul $t1,$t1,$t2
		addi $t0,$t0,-1
		beqz $t0,done
		j p_loop
 
	done:
		move $v0,$t1
		jr $ra
	ret1:
		li $v0,1
		jr $ra	
 
converthex:
	la $t0,hex
	li $t1,0
	lw $t3,strsize
	addi $t3,$t3,-1
	li $t4,-1
	li $t6,0 	#sum
	c_loop:
		lb $t1,($t0)
		beqz $t1,finish
 
		move $a0,$t1
		addi $sp,$sp,-8 
		sw $ra,0($sp)
		sw $t0,4($sp)
		jal hexchar2dec
		lw $ra,0($sp)      
		lw $t0,4($sp)	
		addi $sp,$sp,8
 
		beq $v0,$t4,badstring
		move $t5,$v0		# save current char
		move $a0,$t3 		# pos
 
		addi $sp,$sp,-16 
		sw $ra,0($sp)
		sw $t0,4($sp)
		sw $t1,8($sp)
		sw $t2,12($sp)
 
		jal power		# 16^pos
 
		lw $ra,0($sp)      
		lw $t0,4($sp)
		lw $t1,8($sp)
		lw $t2,12($sp)	
		addi $sp,$sp,16
 
		mul $t5,$t5,$v0
		add  $t6,$t6,$t5 	# sum += currentchar^16^pos
		addi $t3,$t3,-1		# pos-1
		addi $t0,$t0,1		# next char
		j c_loop
	badstring:
		li $v0,-1
		jr $ra
 
	finish:
		move $v0,$t6
		jr $ra