reading the file name from user input in MIPS assembly
Character 10 (0xa) is the Ascii code for linefeed, which many *nix operating systems use for line terminator. It should not be part of the filename. Just strip it off. Also, such operating systems use 0 for a string terminator. It should be at the end of the filename unless the open call takes a number of characters parameter.
The solution is to take the user's reply, find character 10 and replace it with zero. Use the result as the filename to open.
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Hassan Al-Jeshi almost 2 years
I'm writing a MIPS assembly code that will ask the user for the file name and it will produce some statistics about the content of the file.
However, when I hard code the file name into a variable from the beginning it works just fine, but when I ask the user to input the file name it does not work.
after some debugging, I have discovered that the program adds 0x00 char and 0x0a char (check asciitable.com) at the end of user input in the memory and that's why it does not open the file based on the user input.
anyone has any idea about how to get rid of those extra chars, or how to open the file after getting its name from the user??
here is my complete code (it is working fine except for the file name from user thing, and anybody is free to use it for any purpose he/she wants to):
.data fin: .ascii "" # filename for input msg0: .asciiz "aaaa" msg1: .asciiz "Please enter the input file name:" msg2: .asciiz "Number of Uppercase Char: " msg3: .asciiz "Number of Lowercase Char: " msg4: .asciiz "Number of Decimal Char: " msg5: .asciiz "Number of Words: " nline: .asciiz "\n" buffer: .asciiz "" .text #----------------------- li $v0, 4 la $a0, msg1 syscall li $v0, 8 la $a0, fin li $a1, 21 syscall jal fileRead #read from file move $s1, $v0 #$t0 = total number of bytes li $t0, 0 # Loop counter li $t1, 0 # Uppercase counter li $t2, 0 # Lowercase counter li $t3, 0 # Decimal counter li $t4, 0 # Words counter loop: bge $t0, $s1, end #if end of file reached OR if there is an error in the file lb $t5, buffer($t0) #load next byte from file jal checkUpper #check for upper case jal checkLower #check for lower case jal checkDecimal #check for decimal jal checkWord #check for words addi $t0, $t0, 1 #increment loop counter j loop end: jal output jal fileClose li $v0, 10 syscall fileRead: # Open file for reading li $v0, 13 # system call for open file la $a0, fin # input file name li $a1, 0 # flag for reading li $a2, 0 # mode is ignored syscall # open a file move $s0, $v0 # save the file descriptor # reading from file just opened li $v0, 14 # system call for reading from file move $a0, $s0 # file descriptor la $a1, buffer # address of buffer from which to read li $a2, 100000 # hardcoded buffer length syscall # read from file jr $ra output: li $v0, 4 la $a0, msg2 syscall li $v0, 1 move $a0, $t1 syscall li $v0, 4 la $a0, nline syscall li $v0, 4 la $a0, msg3 syscall li $v0, 1 move $a0, $t2 syscall li $v0, 4 la $a0, nline syscall li $v0, 4 la $a0, msg4 syscall li $v0, 1 move $a0, $t3 syscall li $v0, 4 la $a0, nline syscall li $v0, 4 la $a0, msg5 syscall addi $t4, $t4, 1 li $v0, 1 move $a0, $t4 syscall jr $ra checkUpper: blt $t5, 0x41, L1 #branch if less than 'A' bgt $t5, 0x5a, L1 #branch if greater than 'Z' addi $t1, $t1, 1 #increment Uppercase counter L1: jr $ra checkLower: blt $t5, 0x61, L2 #branch if less than 'a' bgt $t5, 0x7a, L2 #branch if greater than 'z' addi $t2, $t2, 1 #increment Lowercase counter L2: jr $ra checkDecimal: blt $t5, 0x30, L3 #branch if less than '0' bgt $t5, 0x39, L3 #branch if greater than '9' addi $t3, $t3, 1 #increment Decimal counter L3: jr $ra checkWord: bne $t5, 0x20, L4 #branch if 'space' addi $t4, $t4, 1 #increment words counter L4: jr $ra fileClose: # Close the file li $v0, 16 # system call for close file move $a0, $s0 # file descriptor to close syscall # close file jr $ra
Note: I'm using MARS Simulator, if that makes any different
Update: I have solved the problem by writing and calling the following procedure:
nameClean: li $t0, 0 #loop counter li $t1, 21 #loop end clean: beq $t0, $t1, L5 lb $t3, fin($t0) bne $t3, 0x0a, L6 sb $zero, fin($t0) L6: addi $t0, $t0, 1 j clean L5: jr $ra