A simple binary tree program -- in assembler
I believe every programmer must learn assembly programming. It brings the programmer and the machine closer and strengthens the bond between them. I learned the term GIGO (Garbage In Garbage Out) when I got first introduced to computer programming. Nothing has changed since. The languages and their environments have become better beyond doubt. Still, a computer and its resources are as good as its programmer.
Assembly language makes you understand how the machine is working beyond all that glittery higher level languages. If you are a system programmer, learning assembly becomes a must because there are things that C can't handle. I will leave more discussion on "Why learning assembly is important" for later post.
Every new architecture that I learn, I learn its assembler first. When I got first introduced to MIPS, I learned its assembly language. Below is a program that I wrote to achieve that.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 | # # This program takes 10 integer values from user, # inserts them into a binary tree and then prints # the tree "inorder" # # # The tree_node is like this: # struct tree_node { # int value; # struct tree_node *left; # struct tree_node *right; # } .text #----------------------------------------------------------- # # This function prints a given node. # The nodes pointer is provided in $a0. # print_node: subu $sp, $sp, 32 # space on stack sw $ra, 28($sp) # store the return address sw $fp, 24($sp) # store the current frame pointer. addiu $fp, $sp, 32 # $fp to start of stack. move $t0, $a0 # save the nodes pointer to $t0 lw $a0, ($t0) # move the integer value to $a0. jal print_int_with_newline # print the integer. nop lw $ra, 28($sp) lw $fp, 24($sp) addiu $sp, $sp, 32 # reclaim the stack. jr $ra #---------------------------------------------------------- # This function prints the given integer and # then prints a new line after it. # $a0 - Integer to be printed. print_int_with_newline: subu $sp, $sp, 32 #minium stack frame sw $ra, 28($sp) #store the return address. sw $fp, 24($sp) #store the frame pointer. sw $a0, 20($sp) #store the argument. addiu $fp, $sp, 32 #base of the frame. #print the integer first. li $v0, 1 syscall #print the new line. la $a0, newline li $v0, 4 syscall #regenerate the previous frame. lw $ra, 28($sp) lw $fp, 24($sp) lw $a0, 20($sp) addiu $sp, $sp, 32 #reclaim the stack frame. jr $ra #return to caller. #------------------------------------------------------------ # This function creates a new tree node, assigns a given # value to it. Initializes it properly and returns the # pointer to it. # $a0 -> Integer to be assigned in value. # $v0 -> on success, returns with node pointer here else zero. # create_tree_node: subu $sp, $sp, 32 sw $ra, 28($sp) sw $fp, 24($sp) addiu $fp, $sp, 32 move $t0, $a0 li $a0, 12 li $v0, 9 syscall beqz $v0, out_of_memory sw $t0, ($v0) sw $zero, 4($v0) sw $zero, 8($v0) out_of_memory: lw $ra, 28($sp) lw $fp, 24($sp) addiu $sp, $sp, 32 jr $ra #--------------------------------------------------------------- # # This function gets number of specified integers in the # given buffer. # # $a0 -> Pointer to the destination buffer. # $a1 -> number of integers to be read out. # get_num_integers: addiu $sp, $sp, -32 # min stack. sw $ra, 28($sp) # store ra sw $fp, 24($sp) # store callers frame pointer. addiu $fp, $sp, 32 # point to our frame. move $t0, $a0 # destination buffer move $t1, $a1 # number of integers. read_loop: beqz $t1, read_loop_exit addiu $t1, $t1, -1 # decrement the count li $v0, 5 syscall sw $v0, ($t0) addiu $t0, $t0, 4 # point to next number(int are 4 bytes) b read_loop nop read_loop_exit: lw $ra, 28($sp) lw $fp, 24($sp) addiu $sp, $sp, 32 jr $ra #--------------------------------------------------------------- # This function adds a node to the given node. If it cannot be # added to the current node, it calls itself recursively until # it finds a node where it can add the given number. # # $a0 -> The starting node # $a1 -> The node to add. .globl add_node_to_tree add_node_to_tree: addiu $sp, $sp, -32 sw $ra, 28($sp) sw $fp, 24($sp) sw $a0, 20($sp) sw $a1, 16($sp) addiu $fp, $sp, 32 lw $t0, ($a0) # value of the starting current node. lw $t1, ($a1) # value of the node to add. bgt $t1, $t0, is_greater lw $t2, 4($a0) #load the left pointer. beqz $t2, null_left move $a0, $t2 # take this left pointer start loc now. jal add_node_to_tree nop b __return_add_node_to_tree nop is_greater: lw $t2, 8($a0) #load the right pointer. beqz $t2, null_right move $a0, $t2 # take this right pointer start loc now. jal add_node_to_tree nop b __return_add_node_to_tree nop null_left: # null left means that we can add the pointer here. sw $a1, 4($a0) b __return_add_node_to_tree nop null_right: sw $a1, 8($a0) b __return_add_node_to_tree nop __return_add_node_to_tree: lw $ra, 28($sp) lw $fp, 24($sp) lw $a0, 20($sp) lw $a1, 16($sp) addiu $sp, $sp, 32 jr $ra #---------------------------------------------------------------- # # This function prints the tree in order. # # $a0 -> root node. .globl print_inorder print_inorder: addiu $sp, $sp, -32 sw $ra, 28($sp) sw $fp, 24($sp) sw $a0, 20($sp) addiu $fp, $sp, 32 lw $t1, 4($a0) beqz $t1, print_curr move $a0, $t1 jal print_inorder nop print_curr: lw $a0, 20($sp) lw $t0, ($a0) move $a0, $t0 jal print_int_with_newline nop lw $a0, 20($sp) lw $t1, 8($a0) beqz $t1, __return_print_inorder move $a0, $t1 jal print_inorder nop __return_print_inorder: lw $ra, 28($sp) lw $fp, 24($sp) lw $a0, 20($sp) addiu $sp, $sp, 32 jr $ra #------------------------------------------------------------------ main: # readout 10 integers in buffer. la $a0, buffer li $a1, 10 jal get_num_integers nop li $t6, 10 la $t8, buffer li $t7, 0 tree_create_loop: beqz $t6, tree_create_done addiu $t6, $t6, -1 lw $a0, ($t8) jal create_tree_node addiu $t8, $t8, 4 #point to next number beqz $v0, alloc_failed nop beqz $t7, init_root move $a1, $v0 move $a0, $t7 jal add_node_to_tree nop b tree_create_loop nop init_root: move $t7, $v0 b tree_create_loop nop tree_create_done: move $a0, $t7 jal print_inorder nop b exit nop alloc_failed: la $a0, OOM_Error li $v0, 4 syscall exit: li $v0, 10 syscall .data buffer: .space 1024 OOM_Error: .asciiz "Out of memory!\n" newline: .asciiz "\n" |
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