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snake.s
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snake.s
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# This program was written by Mahi Rahman
# v1.0.0
#
# Requires:
# - [no external symbols]
#
# Provides:
# - Global variables:
.globl symbols
.globl grid
.globl snake_body_row
.globl snake_body_col
.globl snake_body_len
.globl snake_growth
.globl snake_tail
# - Utility global variables:
.globl last_direction
.globl rand_seed
.globl input_direction__buf
# - Functions for you to implement
.globl main
.globl init_snake
.globl update_apple
.globl move_snake_in_grid
.globl move_snake_in_array
# - Utility functions provided for you
.globl set_snake
.globl set_snake_grid
.globl set_snake_array
.globl print_grid
.globl input_direction
.globl get_d_row
.globl get_d_col
.globl seed_rng
.globl rand_value
########################################################################
# Constant definitions.
N_COLS = 15
N_ROWS = 15
MAX_SNAKE_LEN = N_COLS * N_ROWS
EMPTY = 0
SNAKE_HEAD = 1
SNAKE_BODY = 2
APPLE = 3
NORTH = 0
EAST = 1
SOUTH = 2
WEST = 3
########################################################################
# .DATA
.data
# const char symbols[4] = {'.', '#', 'o', '@'}
symbols:
.byte '.', '#', 'o', '@'
.align 2
# int8_t grid[N_ROWS][N_COLS] = { EMPTY }
grid:
.space N_ROWS * N_COLS
.align 2
# int8_t snake_body_row[MAX_SNAKE_LEN] = { EMPTY }
snake_body_row:
.space MAX_SNAKE_LEN
.align 2
# int8_t snake_body_col[MAX_SNAKE_LEN] = { EMPTY }
snake_body_col:
.space MAX_SNAKE_LEN
# int snake_body_len = 0
snake_body_len:
.word 0
# int snake_growth = 0
snake_growth:
.word 0
# int snake_tail = 0
snake_tail:
.word 0
# Game over prompt, for your convenience...
main__game_over:
.asciiz "Game over! Your score was "
########################################################################
# .TEXT <main>
.text
main:
# Args: void
# Returns:
# - $v0: int
#
# Frame: $ra
# Uses: $a0, $t0, $v0, $t1, $t2, $t3
# Clobbers: $a0
#
# Locals:
# - 'int direction' in $a0
# - ' int score' in $t3
#
# Structure:
# main
# -> [prologue]
# -> body
# -> loop
# -> [epilogue]
# Code:
main__prologue:
# set up stack frame
addiu $sp, $sp, -4
sw $ra, ($sp)
main__body:
jal init_snake # initialise the snake
jal update_apple # intialise the apple position
main__body_loop:
jal print_grid # prints the grid
jal input_direction # returns the current int direction into $v0
move $a0, $v0 # copy $v0 (int direction) into $a0
jal update_snake # update_snake(direction)
# returns $v0 (boolean value)
# if update_snake(direction) == true then main__body_loop
beq $v0, 1, main__body_loop
lw $t1, snake_body_len # load snake_body_len into $t1
li $t2, 3 # load 3 into $t2
div $t1, $t2 # snake_body_len / 3 ($t1 / $t2)
mflo $t3 # current score ($t3)
# printf("Game over! Your score was %d\n", score)
# "Game over! Your score was "
li $v0, 4
la $a0, main__game_over
syscall
# "%d"
li $v0, 1
move $a0, $t3
syscall
# "\n"
li $a0, '\n'
li $v0, 11
syscall
main__epilogue:
# tear down stack frame
lw $ra, ($sp)
addiu $sp, $sp, 4
# return 0
li $v0, 0
jr $ra
########################################################################
# .TEXT <init_snake>
.text
init_snake:
# Args: void
# Returns: void
#
# Frame: $ra
# Uses: $a0, $a1, $a2
# Clobbers: $a0, $a1, $a2
#
# Locals:
# - void
#
# Structure:
# init_snake
# -> [prologue]
# -> body
# -> [epilogue]
# Code:
init_snake__prologue:
# set up stack frame
addiu $sp, $sp, -4
sw $ra, ($sp)
init_snake__body:
li $a0, 7 # int row = 7
li $a1, 7 # int col = 7
li $a2, SNAKE_HEAD # int body_piece = SNAKE_HEAD
jal set_snake # set_snake(7, 7, SNAKE_HEAD)
li $a0, 7 # int row = 7
li $a1, 6 # int col = 6
li $a2, SNAKE_BODY # int body_piece = SNAKE_BODY
jal set_snake # set_snake(7, 6, SNAKE_BODY)
li $a0, 7 # int row = 7
li $a1, 5 # int col = 5
li $a2, SNAKE_BODY # int body_piece = SNAKE_BODY
jal set_snake # set_snake(7, 5, SNAKE_BODY)
li $a0, 7 # int row = 7
li $a1, 4 # int col = 4
li $a2, SNAKE_BODY # int body_piece = SNAKE_BODY
jal set_snake # set_snake(7, 4, SNAKE_BODY)
init_snake__epilogue:
# tear down stack frame
lw $ra, ($sp)
addiu $sp, $sp, 4
# return
jr $ra
########################################################################
# .TEXT <update_apple>
.text
update_apple:
# Args: void
# Returns: void
#
# Frame: $ra
# Uses: $a0, $s0, $s1, $t0, $t1, $t2, $t3, $t4, $t4, $t5
# Clobbers: $a0
#
# Locals:
# - 'int apple_row' in $s0
# - 'int apple_col' in $s1
#
# Structure:
# update_apple
# -> [prologue]
# -> body
# -> [epilogue]
# Code:
update_apple__prologue:
# set up stack frame
addiu $sp, $sp, -4
sw $ra, ($sp)
update_apple__body:
li $a0, N_ROWS
jal rand_value # rand_value(N_ROWS)
move $s0, $v0 # apple_row = rand_value(N_ROWS)
li $a0, N_COLS
jal rand_value # rand_value(N_COLS)
move $s1, $v0 # apple_col = rand_value(N_COLS)
la $t0, grid
mul $t1, $s0, N_COLS
add $t2, $t1, $s1
add $t3, $t2, $t0
lb $t4, ($t3) # grid[apple_row][apple_col]
# if grid[apple_row][apple_col] != EMPTY then update_apple__body
bne $t4, EMPTY, update_apple__body
li $t5, APPLE # load APPLE into $t5
sb $t5, ($t3) # grid[apple_row][apple_col] = APPLE
update_apple__epilogue:
# tear down stack frame
lw $ra, ($sp)
addiu $sp, $sp, 4
# return
jr $ra
########################################################################
# .TEXT <update_snake>
.text
update_snake:
# Args:
# - $a0: int direction
# Returns:
# - $v0: bool
#
# Frame: $ra, $s0, $s1, $s2, $s3, $s4
# Uses: $s0, $s1, $s2, $s3, $s4, $t0, $t1, $t2, $t3, $t4, $t5,
# $t6, $t7, $a0, $a1
# Clobbers: $t0, $t1, $t2, $t3, $a0, $a1
#
# Locals:
# - 'int d_row' in $s0
# - 'int d_col' in $s1
# - 'int head_row' in $t4
# - 'int head_col' in $t5
# - 'int new_head_row ' in $s0
# - 'int new_head_col' in $s1
# - 'bool apple' in $s3
#
# Structure:
# update_snake
# -> [prologue]
# -> body
# -> continue
# -> true
# -> end
# -> [epilogue]
# Code:
update_snake__prologue:
# set up stack frame
addiu $sp, $sp, -20
sw $s0, ($sp)
sw $s1, 4($sp)
sw $s2, 8($sp)
sw $s3, 12($sp)
sw $ra, 16($sp)
update_snake__body:
jal get_d_row # get_d_row(direction)
move $s0, $v0 # copy the return into $s0 (int d_row)
jal get_d_col # get_d_col(direction)
move $s1, $v0 # copy the return into $s1 (int d_col)
la $t1, snake_body_row
lb $t4, 0($t1) # int head_row = snake_body_row[0]
la $t1, snake_body_col
lb $t5, 0($t1) # int head_col = snake_body_col[0]
la $t0, grid
mul $t1, $t4, N_COLS
add $t2, $t1, $t5
add $t3, $t2, $t0
li $t1, SNAKE_BODY # load SNAKE_BODY into $t1
sb $t1, 0($t3) # grid[head_row][head_col] = SNAKE_BODY
add $s0, $t4, $s0 # int new_head_row = head_row + d_row
add $s1, $t5, $s1 # int new_head_col = head_col + d_col
blt $s0, 0, update_snake__end # if (new_head_row < 0) return false
bge $s0, N_ROWS, update_snake__end # if (new_head_row >= N_ROWS) return false
blt $s1, 0, update_snake__end # if (new_head_col < 0) return false
bge $s1, N_COLS, update_snake__end # if (new_head_col >= N_COLS) return false
la $t2, grid
mul $t3, $s0, N_COLS
add $t4, $t3, $s1
add $t5, $t4, $t2
lb $t6, 0($t5) # grid[new_head_row][new_head_col]
li $t7, APPLE # load APPLE into $t8
li $s3, 0 # bool apple = False
# if grid[new_head_row][new_head_col] != APPLE then update_snake__continue
bne $t6, $t7, update_snake__continue
li $s3, 1 # bool apple = True
update_snake__continue:
lw $s2, snake_body_len
addi $s2, $s2, -1 # snake_tail = snake_body_len - 1
sw $s2, snake_tail
move $a0, $s0 # copy $s0 into $a0 as argument new_head_row
move $a1, $s1 # copy $s1 into $a1 as argument new_head_col
jal move_snake_in_grid # move_snake_in_grid(new_head_row, new_head_col)
li $t3, 0 # false
beq $v0, $t3, update_snake__end # if (! move_snake_in_grid(new_head_row, new_head_col))
# return false
move $a0, $s0 # copy $s0 into $a0 as argument new_head_row
move $a1, $s1 # copy $s1 into $a1 as argument new_head_col
jal move_snake_in_array # move_snake_in_array(new_head_row, new_head_col)
# if apple != true then update_snake__true
bne $s3, 1, update_snake__true
lw $t0, snake_growth
addiu $t0, $t0, 3
sw $t0, snake_growth # snake_growth += 3
jal update_apple
update_snake__true:
# return true
li $v0, 1
j update_snake__epilogue
update_snake__end:
# return false
li $v0, 0
update_snake__epilogue:
# tear down stack frame
lw $s0, ($sp)
lw $s1, 4($sp)
lw $s2, 8($sp)
lw $s3, 12($sp)
lw $ra, 16($sp)
addiu $sp, $sp, 20
# return
jr $ra
########################################################################
# .TEXT <move_snake_in_grid>
.text
move_snake_in_grid:
# Args:
# - $a0: new_head_row
# - $a1: new_head_col
# Returns:
# - $v0: bool
#
# Frame: $ra
# Uses: $t0, $t1, $t2, $t3, $t4, $t5, $v0
# Clobbers: $t0, $t1, $t2, $t3
#
# Locals:
# - 'int tail' in $t0
# - 'int tail_row' in $t4
# - 'int tail_col' in $t5
#
# Structure:
# move_snake_in_grid
# -> [prologue]
# -> body
# -> growth
# -> continue_growth
# -> false
# -> [epilogue]
# Code:
move_snake_in_grid__prologue:
# set up stack frame
addiu $sp, $sp, -4
sw $ra, ($sp)
move_snake_in_grid__body:
lw $t0, snake_growth # load snake_growth into $t0
# if (snake_growth > 0)
bgt $t0, 0, move_snake_in_grid_growth
lw $t0, snake_tail # ($t0) int tail = snake_tail
la $t1, snake_body_row
mul $t2, $t0, 1
add $t3, $t2, $t1
lb $t4, 0($t3) # int tail_row = snake_body_row[tail]
la $t1, snake_body_col
mul $t2, $t0, 1
add $t3, $t2, $t1
lb $t5, 0($t3) # int tail_col = snake_body_col[tail]
la $t0, grid
mul $t1, $t4, N_COLS
add $t2, $t1, $t5
add $t3, $t2, $t0
li $t0, EMPTY
sb $t0, 0($t3) # grid[tail_row][tail_col] = EMPTY
move_snake_in_grid_continue_growth:
la $t0, grid
mul $t1, $a0, N_COLS
add $t2, $t1, $a1
add $t3, $t2, $t0
lb $t4, 0($t3) # grid[new_head_row][new_head_col]
# if grid[new_head_row][new_head_col] == SNAKE_BODY then move_snake_in_grid_false
beq $t4, SNAKE_BODY, move_snake_in_grid_false
li $t0, SNAKE_HEAD # load SNAKE_HEAD into $t0
sb $t0, 0($t3) # grid[new_head_row][new_head_col] = SNAKE_HEAD
# return true
li $v0, 1
j move_snake_in_grid__epilogue
move_snake_in_grid_growth:
lw $t0, snake_tail
addi $t0, $t0, 1 # #snake_tail++
sw $t0, snake_tail
lw $t1, snake_body_len
addiu $t1, $t1, 1
sw $t1, snake_body_len # snake_body_len++
lw $t2, snake_growth
addiu $t2, $t2, -1
sw $t2, snake_growth # snake_growth--
j move_snake_in_grid_continue_growth
move_snake_in_grid_false:
# return false
li $v0, 0
move_snake_in_grid__epilogue:
# tear down stack frame
lw $ra, ($sp)
addiu $sp, $sp, 4
# return true
jr $ra
########################################################################
# .TEXT <move_snake_in_array>
.text
move_snake_in_array:
# Arguments:
# - $a0: int new_head_row
# - $a1: int new_head_col
# Returns: void
#
# Frame: $ra, $s0, $s1, $s2
# Uses: $s0, $s1, $s2, $t0, $t1, $t2, $t3, $t4, $t5, $a0, $a1, $a2
# Clobbers: $a0, $a1, $a2, $t0, $t1, $t2, $t3, $t4, $t5
#
# Locals:
# - 'int i' in $s0
#
# Structure:
# move_snake_in_array
# -> [prologue]
# -> body
# -> move_snake_in_array__loop01
# -> move_snake_in_array__end01
# -> [epilogue]
# Code:
move_snake_in_array__prologue:
# set up stack frame
addiu $sp, $sp, -16
sw $s0, ($sp)
sw $s1, 4($sp)
sw $s2, 8($sp)
sw $ra, 12($sp)
move_snake_in_array__body:
lw $s0, snake_tail # ($s0) int i = snake_tail
move $s1, $a0 # ($s1) int new_head_row
move $s2, $a1 # ($s2) int new_head_col
move_snake_in_array__loop01:
# if i < 1 then move_snake_in_array__end01
blt $s0, 1, move_snake_in_array__end01
addiu $t0, $s0, -1 # index = i - 1
la $t1, snake_body_row
mul $t2, $t0, 1
add $t3, $t2, $t1
lb $t4, 0($t3) # x = snake_body_row[index]
la $t1, snake_body_col
mul $t2, $t0, 1
add $t3, $t2, $t1
lb $t5, 0($t3) # y = snake_body_col[index]
# move x, y and i as arguments
move $a0, $t4
move $a1, $t5
move $a2, $s0
jal set_snake_array # set_snake_array(x, y, i)
addiu $s0, $s0, -1 # i--
j move_snake_in_array__loop01
move_snake_in_array__end01:
# move new_head_row and new_head_col as arguments
move $a0, $s1
move $a1, $s2
li $a2, 0 # load 0 into $a2 as third argument to set_snake_array
jal set_snake_array # set_snake_array(new_head_row, new_head_col, 0)
move_snake_in_array__epilogue:
# tear down stack frame
lw $s0, ($sp)
lw $s1, 4($sp)
lw $s2, 8($sp)
lw $ra, 12($sp)
addiu $sp, $sp, 16
jr $ra # return
########################################################################
.data
last_direction:
.word EAST
rand_seed:
.word 0
input_direction__invalid_direction:
.asciiz "invalid direction: "
input_direction__bonk:
.asciiz "bonk! cannot turn around 180 degrees\n"
.align 2
input_direction__buf:
.space 2
########################################################################
# .TEXT <set_snake>
.text
set_snake:
# Args:
# - $a0: int row
# - $a1: int col
# - $a2: int body_piece
# Returns: void
#
# Frame: $ra, $s0, $s1
# Uses: $a0, $a1, $a2, $t0, $s0, $s1
# Clobbers: $t0
#
# Locals:
# - `int row` in $s0
# - `int col` in $s1
#
# Structure:
# set_snake
# -> [prologue]
# -> body
# -> [epilogue]
# Code:
set_snake__prologue:
# set up stack frame
addiu $sp, $sp, -12
sw $ra, 8($sp)
sw $s0, 4($sp)
sw $s1, ($sp)
set_snake__body:
move $s0, $a0 # $s0 = row
move $s1, $a1 # $s1 = col
jal set_snake_grid # set_snake_grid(row, col, body_piece)
move $a0, $s0
move $a1, $s1
lw $a2, snake_body_len
jal set_snake_array # set_snake_array(row, col, snake_body_len)
lw $t0, snake_body_len
addiu $t0, $t0, 1
sw $t0, snake_body_len # snake_body_len++
set_snake__epilogue:
# tear down stack frame
lw $s1, ($sp)
lw $s0, 4($sp)
lw $ra, 8($sp)
addiu $sp, $sp, 12
# return
jr $ra
########################################################################
# .TEXT <set_snake_grid>
.text
set_snake_grid:
# Args:
# - $a0: int row
# - $a1: int col
# - $a2: int body_piece
# Returns: void
#
# Frame: None
# Uses: $a0, $a1, $a2, $t0
# Clobbers: $t0
#
# Locals: None
#
# Structure:
# set_snake
# -> body
# Code:
li $t0, N_COLS
mul $t0, $t0, $a0 # 15 * row
add $t0, $t0, $a1 # (15 * row) + col
sb $a2, grid($t0) # grid[row][col] = body_piece
jr $ra # return
########################################################################
# .TEXT <set_snake_array>
.text
set_snake_array:
# Args:
# - $a0: int row
# - $a1: int col
# - $a2: int nth_body_piece
# Returns: void
#
# Frame: None
# Uses: $a0, $a1, $a2
# Clobbers: None
#
# Locals: None
#
# Structure:
# set_snake_array
# -> body
# Code:
sb $a0, snake_body_row($a2) # snake_body_row[nth_body_piece] = row
sb $a1, snake_body_col($a2) # snake_body_col[nth_body_piece] = col
# return
jr $ra
########################################################################
# .TEXT <print_grid>
.text
print_grid:
# Args: void
# Returns: void
#
# Frame: None
# Uses: $v0, $a0, $t0, $t1, $t2
# Clobbers: $v0, $a0, $t0, $t1, $t2
#
# Locals:
# - `int i` in $t0
# - `int j` in $t1
# - `char symbol` in $t2
#
# Structure:
# print_grid
# -> for_i_cond
# -> for_j_cond
# -> for_j_end
# -> for_i_end
# Code:
li $v0, 11
li $a0, '\n'
syscall # putchar('\n')
li $t0, 0 # int i = 0
print_grid__for_i_cond:
bge $t0, N_ROWS, print_grid__for_i_end # while (i < N_ROWS)
li $t1, 0 # int j = 0
print_grid__for_j_cond:
bge $t1, N_COLS, print_grid__for_j_end # while (j < N_COLS)
li $t2, N_COLS
mul $t2, $t2, $t0 # 15 * i
add $t2, $t2, $t1 # (15 * i) + j
lb $t2, grid($t2) # grid[(15 * i) + j]
lb $t2, symbols($t2) # char symbol = symbols[grid[(15 * i) + j]]
li $v0, 11 # syscall 11: print_character
move $a0, $t2
syscall # putchar(symbol)
addiu $t1, $t1, 1 # j++
j print_grid__for_j_cond
print_grid__for_j_end:
li $v0, 11 # syscall 11: print_character
li $a0, '\n'
syscall # putchar('\n')
addiu $t0, $t0, 1 # i++
j print_grid__for_i_cond
print_grid__for_i_end:
# return
jr $ra
########################################################################
# .TEXT <input_direction>
.text
input_direction:
# Args: void
# Returns:
# - $v0: int
#
# Frame: None
# Uses: $v0, $a0, $a1, $t0, $t1
# Clobbers: $v0, $a0, $a1, $t0, $t1
#
# Locals:
# - `int direction` in $t0
#
# Structure:
# input_direction
# -> input_direction__do
# -> input_direction__switch
# -> input_direction__switch_w
# -> input_direction__switch_a
# -> input_direction__switch_s
# -> input_direction__switch_d
# -> input_direction__switch_newline
# -> input_direction__switch_null
# -> input_direction__switch_eot
# -> input_direction__switch_default
# -> input_direction__switch_post
# -> input_direction__bonk_branch
# -> input_direction__while
# Code:
input_direction__do:
li $v0, 8 # syscall 8: read_string
la $a0, input_direction__buf
li $a1, 2
syscall # direction = getchar()
lb $t0, input_direction__buf
input_direction__switch:
beq $t0, 'w', input_direction__switch_w # case 'w':
beq $t0, 'a', input_direction__switch_a # case 'a':
beq $t0, 's', input_direction__switch_s # case 's':
beq $t0, 'd', input_direction__switch_d # case 'd':
beq $t0, '\n', input_direction__switch_newline # case '\n':
beq $t0, 0, input_direction__switch_null # case '\0':
beq $t0, 4, input_direction__switch_eot # case '\004':
j input_direction__switch_default # default:
input_direction__switch_w:
li $t0, NORTH # direction = NORTH
j input_direction__switch_post # break
input_direction__switch_a:
li $t0, WEST # direction = WEST
j input_direction__switch_post # break
input_direction__switch_s:
li $t0, SOUTH # direction = SOUTH
j input_direction__switch_post # break
input_direction__switch_d:
li $t0, EAST # direction = EAST
j input_direction__switch_post # break
input_direction__switch_newline:
j input_direction__do # continue
input_direction__switch_null:
input_direction__switch_eot:
li $v0, 17 # syscall 17: exit2
li $a0, 0
syscall # exit(0)
input_direction__switch_default:
li $v0, 4 # syscall 4: print_string
la $a0, input_direction__invalid_direction
syscall # printf("invalid direction: ")
li $v0, 11 # syscall 11: print_character
move $a0, $t0
syscall # printf("%c", direction)
li $v0, 11 # syscall 11: print_character
li $a0, '\n'
syscall # printf("\n")
j input_direction__do # continue
input_direction__switch_post:
blt $t0, 0, input_direction__bonk_branch # if (0 <= direction ...
bgt $t0, 3, input_direction__bonk_branch # ... && direction <= 3 ...
lw $t1, last_direction # last_direction
sub $t1, $t1, $t0 # last_direction - direction
abs $t1, $t1 # abs(last_direction - direction)
beq $t1, 2, input_direction__bonk_branch # ... && abs(last_direction - direction) != 2)
sw $t0, last_direction # last_direction = direction
move $v0, $t0
jr $ra # return direction
input_direction__bonk_branch:
li $v0, 4 # syscall 4: print_string
la $a0, input_direction__bonk
syscall # printf("bonk! cannot turn around 180 degrees\n")
input_direction__while:
j input_direction__do # while (true)
########################################################################
# .TEXT <get_d_row>
.text
get_d_row:
# Args:
# - $a0: int direction
# Returns:
# - $v0: int
#
# Frame: None
# Uses: $v0, $a0
# Clobbers: $v0
#
# Locals: None
#
# Structure:
# get_d_row
# -> get_d_row__south:
# -> get_d_row__north:
# -> get_d_row__else:
# Code:
beq $a0, SOUTH, get_d_row__south # if (direction == SOUTH)
beq $a0, NORTH, get_d_row__north # else if (direction == NORTH)
j get_d_row__else # else
get_d_row__south:
li $v0, 1
# return 1
jr $ra
get_d_row__north:
li $v0, -1
# return -1
jr $ra
get_d_row__else:
li $v0, 0
# return 0
jr $ra
########################################################################
# .TEXT <get_d_col>
.text
get_d_col:
# Args:
# - $a0: int direction
# Returns:
# - $v0: int
#
# Frame: None
# Uses: $v0, $a0
# Clobbers: $v0
#
# Locals: None