MIPS Assembly language.

Implement memset, strlen, strchr, strcat, and strcmp.

Use $a0 through $a3 as necessary for the standard C library's arguments to each function.

Return in $v0.

It is fine if a lot of your functions look a lot like each other. In fact, that's a good sign.

Don't worry about overruns or exception cases.

Implement strstr. Dont try this until youve finished the others (strstr is a lot more annoying to implement)

Testing program:

.data # The data segment.

welc1: .asciiz "Welcome to the test. "

welc2: .asciiz "First, strcpy. This should print 'Hello, world.' twice. "

welc3: .asciiz "Now, strlen. Should be 13: "

welc4: .asciiz "Now, memset. Should print 13 dots: "

welc5: .asciiz "Now, strchr. Should be a number, that +3, then zero. "

welc6: .asciiz "Now, strcat. Should be dots then 'Hello, world.'. "

welc7: .asciiz "Finally, strcmp. Should be 0, then 1, then -1. "

hello: .asciiz "Hello, world."

alice: .asciiz "alice"

bob: .asciiz "bob"

crlf: .asciiz " "

dot: .byte 46

stch: .byte 'l'

buf: .space 128

.text # The code segment.

main:

# --- WELCOME ---

li $v0, 4 # System call to print.

la $a0, welc1 # Load up our message.

syscall # Fire the system call.

# --- strcpy ---

li $v0, 4 # System call to print.

la $a0, welc2 # Load up our message.

syscall # Fire the system call.

li $v0, 4 # System call to print.

la $a0, hello # Load up our message.

syscall # Fire the system call.

li $v0, 4 # System call to print.

la $a0, crlf # Load up our message.

syscall # Fire the system call.

la $a0, buf

la $a1, hello

jal strcpy # strcpy(buf, hello)

move $a0, $v0 # Load up the returned message.

li $v0, 4 # System call to print.

syscall # Fire the system call.

li $v0, 4 # System call to print.

la $a0, crlf # Load up our message.

syscall # Fire the system call.

# --- strlen ---

li $v0, 4 # System call to print.

la $a0, welc3 # Load up our message.

syscall # Fire the system call.

la $a0, buf

jal strlen

move $s0, $v0

move $a0, $v0

li $v0, 1

syscall

li $v0, 4 # System call to print.

la $a0, crlf # Load up our message.

syscall # Fire the system call.

# --- memset ---

li $v0, 4 # System call to print.

la $a0, welc4 # Load up our message.

syscall # Fire the system call.

la $a0, buf

lb $a1, dot

move $a2, $s0

jal memset

move $a0, $v0 # Load up the returned message.

li $v0, 4 # System call to print.

syscall # Fire the system call.

li $v0, 4 # System call to print.

la $a0, crlf # Load up our message.

syscall # Fire the system call.

# --- strchr ---

li $v0, 4 # System call to print.

la $a0, welc5 # Load up our message.

syscall # Fire the system call.

la $a0, hello

li $v0, 1

syscall

li $v0, 4 # System call to print.

la $a0, crlf # Load up our message.

syscall # Fire the system call.

la $a0, hello

lb $a1, stch

jal strchr

move $a0, $v0

li $v0, 1

syscall

li $v0, 4 # System call to print.

la $a0, crlf # Load up our message.

syscall # Fire the system call.

la $a0, buf

lb $a1, stch

jal strchr

move $a0, $v0

li $v0, 1

syscall

li $v0, 4 # System call to print.

la $a0, crlf # Load up our message.

syscall # Fire the system call.

# --- strcat ---

li $v0, 4 # System call to print.

la $a0, welc6 # Load up our message.

syscall # Fire the system call.

la $a0, buf

la $a1, hello

jal strcat

move $a0, $v0 # Load up the returned message.

li $v0, 4 # System call to print.

syscall # Fire the system call.

li $v0, 4 # System call to print.

la $a0, crlf # Load up our message.

syscall # Fire the system call.

# --- strcmp ---

li $v0, 4 # System call to print.

la $a0, welc7 # Load up our message.

syscall # Fire the system call.

la $a0, alice

la $a1, alice

jal strcmp

move $a0, $v0

li $v0, 1

syscall

li $v0, 4 # System call to print.

la $a0, crlf # Load up our message.

syscall # Fire the system call.

la $a0, bob

la $a1, alice

jal strcmp

move $a0, $v0

li $v0, 1

syscall

li $v0, 4 # System call to print.

la $a0, crlf # Load up our message.

syscall # Fire the system call.

la $a0, alice

la $a1, bob

jal strcmp

move $a0, $v0

li $v0, 1

syscall

li $v0, 4 # System call to print.

la $a0, crlf # Load up our message.

syscall # Fire the system call.

# --- finished ---

li $v0, 10 # System call to exit.

syscall # Fire the system call.

strcpy:

# strcpy(dest, src) copies src into dest and returns dest.

# dest = $a0, src = $a1, return $a0 in $v0.

addi $sp, $sp, -4

sw $ra, 0($sp)

move $v0, $a0 # Do this now so we don't have to save $a0

strcpy_next:

lb $t0, 0($a1) # Load a byte

sb $t0, 0($a0) # Save a byte

addi $a0, $a0, 1 # Increment dest

addi $a1, $a1, 1 # Increment src

bne $t0, $zero, strcpy_next # Done?

lw $ra, 0($sp)

addi $sp, $sp, 4

jr $ra

# Copy new code here.