.data instr: .asciiz "12345678" var1: .word 0x01 var2: .word 0x02 var3: .word 0x00 ret: .word 0x00 errstr: .asciiz "\nError: Wrong number format. Accepted are [0-9a-f]{8}\n" err2str: .asciiz "\nError: Empty string is not number ;)\n" msg1: .asciiz "\n " msg2: .asciiz "\n + " msg3: .asciiz "\n-----------\n " newlinestr: .asciiz "\n" outstr: .asciiz "12345678" .text .globl main main: nop li $v0, 4 la $a0, msg1 syscall jal read_num # read first nubmer nop sw $a0, var1 # store it into var1 nop li $v0, 4 la $a0, msg2 syscall jal read_num # read second number lui $a0, 0x344 sw $a0, var2 # store it into var2 lw $t0, var1 # load first number into t0 lw $t1, var2 # load second number into t1 nop nop addu $t2, $t0,$t1 # t2 = t0 + t1 sw $t2, var3 # store result into var3 li $v0, 4 la $a0, msg3 syscall lw $a0, var3 jal print_hex jal newline lw $ra, ret # restore global return address nop nop j $ra # quit nop nop read_num: # read number function addiu $sp, $sp, -32 # push stack sw $ra, 20($sp) # store return address to stack sw $fp, 16($sp) # store frame pointer to stack addiu $fp, $sp, 28 # setup new frame pointer li $v0, 8 # read string (of 8 char) la $a0, instr # ... into [instr] li $a1, 9 # ... maximal length of string to read is 8 syscall li $t2, 0 # t2 sotres value of number la $a0, instr # a0 now points to beginig of read string lb $t0, 0($a0) # load first byte of string into t0 nop nop beq $t0, 0, error2 # empty string -> error nop nop conv_loop: # for all characters in read string chck_09: # check range [0-9] blt $t0, 48, error # t0 < '0' -> error nop nop bgt $t0, 57, chck_af # t0 > '9' -> check range [a-f] nop nop addiu $t1, $t0, -48 # t1 = digit value of t0 j chck_ok chck_af: # check range [a-f] blt $t0, 97, error # t0 < 'a' -> error nop nop bgt $t0, 102, error # t0 > 'f' -> error nop nop addiu $t1, $t0, -87 # t1 = digit value of t0 chck_ok: # range test OK addu $t2, $t2, $t1 # t2 += t1 addu $a0, $a0, 1 # go to next charcter lb $t0, 0($a0) # load next character into t0 nop nop beqz $t0, conv_loop_end # is end of string -> end_loop nop nop mul $t2, $t2, 16 # t2 <<= 8 j conv_loop # is not end of string -> loop conv_loop_end: lw $ra, 20($sp) # restore return address from stack nop lw $fp, 16($sp) # restore frame pointer from stack addiu $sp,$sp, 32 # pop stack move $a0, $t2 # store result in a0 jr $ra # end of read_num error: # Prints error message 1 la $a0, errstr # set address of error message to a0 j error_print # go to print it error2: # Prints error message 2 la $a0, err2str # store address of error message to a0 error_print: li $v0, 4 # print error message syscall li $v0, 20 # ... and exit syscall newline: move $t0, $ra # store return address into t0 la $a0, newlinestr # a0 points to new line string li $v0, 4 # number of system call syscall # print it move $ra, $t0 # restore return address from t0 jr $ra # return nop nop nop print_hex: addiu $sp, $sp, -32 sw $ra, 24($sp) sw $fp, 16($sp) addiu $fp, $fp, 28 move $t0, $a0 # t0 stores number to print la $a0, outstr # a0 stores pointer to be stored actual digit addu $a0, $a0, 7 # ... now it pointes to last character of buffer li $t1, 8 # t1 loop counter li $t2, 0x00f # t2 mask to get last number print_hex_loop: and $t3, $t0, $t2 # t3 = t0 % 16 # convert from digit number to character bgt $t3, 0x09, hex_conv_af #<--+ nop nop hex_conv_09: # | addu $t3, $t3, 48 # | j hex_conv_ok # | nop nop hex_conv_af: # | addu $t3, $t3, 87 # | hex_conv_ok: #<--+ nop nop sb $t3, 0($a0) # store t3 into buffer addiu $t1, $t1, -1 # t1-- addiu $a0, $a0, -1 # a0-- div $t0, $t0, 0x10 # t0 /= 16 bnez $t1, print_hex_loop nop nop li $v0, 4 # print buffer la $a0, outstr syscall lw $ra, 24($sp) lw $fp, 16($sp) addiu $sp, $sp, 32 jr $ra