; Jade Yu Cheng
; ICS 312
; Assignment 6 Exercise 3
; April 9, 2009
; This program prompts the user to enter a signed 32-bit integer. The program
; prints out the binary representation of the integer. The user is prompted
; for a motif after the binary representation of the integer is printed.
; Program prints out the number of times the user specified motif occurs in the
; binary representation of the entered number.
%include "asm_io.inc"
segment .data
msg1 db "Enter an integer: ", 0 ; msg1
msg2 db "The binary representation is: ", 0 ; msg2
msg3 db "The number of motifs is: ", 0 ; msg3
msg4 db "Enter a binary motif: ", 0 ; msg4
msg5 db "Invalid input.", 0 ; msg5
counter dd 0 ; motif counter
len dd 0 ; size of motif
motif dd 0 ; space for a maximum of 32 bit motif number
bitmask dd 0 ; e.g., it's 0..011 for motif 00, 01, 10, or 11
segment .bss
binary resb 32 ; space to store binary representation
input resd 1 ; space for the 32 bit input number
iterations resd 1 ; number of loops needed to find motif
segment .text
global asm_main
asm_main:
enter 0,0 ; setup
pusha ; setup
;;; prompt the user the enter a number and treat it as a 32 bit number.
mov eax, msg1 ; print out the prompt message.
call print_string
call read_int ; read a number and store in eax
mov [input], eax ; store the input number into input
;;; convert the number to its binary and store it in binary..
convert:
mov ebx, binary ; ebx points to binary
add ebx, 31 ; ebx points to the last bit of binary
convert_loop:
cmp ebx, binary - 1 ; terminate when all 32 bits are written
je convert_loop_end
shr eax, 1 ; right shift by 1, equavilent as divide by 2
jc write_one ; if carry flag is set wirte 1 to ebx
mov [ebx], byte 0 ; otherwise wirte 0 to ebx
dec ebx ; decrement ebx to the next spot to write to
jmp convert_loop
write_one:
mov [ebx], byte 1 ; write 1 to ebx
dec ebx ; decrement ebx to the next spot to write
jmp convert_loop
convert_loop_end:
;;; print out binary
print:
mov eax, msg2 ; print out the second message
call print_string
mov ebx, binary ; let ebx points to binary
print_loop:
cmp ebx, binary + 32; terminate when it reaches the end
je print_loop_end
mov eax,0 ; clean up eax
mov al, [ebx] ; move the bit in eax
call print_int ; print it out
inc ebx ; increment the pointer to the next spot
jmp print_loop
print_loop_end:
call print_nl ; print a blank line
;;; prompt user to enter a binary motif and store it as a 32 bit number.
;;; Meanwhile create a 32 bit long mask to turn off bits in input that
;;; do not concern. E.g., motif 101's mask is 0..0111.
motif_block:
mov eax, msg4 ; print out the message to prompt user input
call print_string
call read_char ; absorb the enter key stroke left by read_int
mov bl, 0 ; get at most 32 bit long user input
motif_loop:
cmp bl, 33
je invalid_input ; input that's longer than 32 bits is invalid
inc bl
call read_char ; obtain the character
cmp eax, 10 ; terminiate if it's the enter key
je motif_loop_end
shl dword [motif], 1; left shift the old motif and old mask by 1
shl dword [bitmask], 1
inc dword [bitmask] ; increment mask by 1 to turn on the last bit
inc dword [len] ; increment length count
cmp eax, 48 ; do not increment motif if the input is 0
je motif_loop
cmp eax, 49 ; increment motif by 1 if the input is 1
jne invalid_input ; anything else is invalid
inc dword [motif] ; increment by 1 if the input is 1
jmp motif_loop ; read the next character
invalid_input:
mov eax, msg5 ; ortherwise print error message and try again
call print_string
call print_nl
jmp end
motif_loop_end:
;;; find out the incidence of the user specified motif.
mov eax, 33 ; compute the iterations number
sub eax, [len] ; there will be 32 - [len] + 1 times iterations
mov [iterations], eax
find_loop_start:
mov ecx, [input] ; let ecx contain the value of input number
mov ebx, [motif] ; let ebx contain the value of motif number
mov edx, 0 ; loop 32 - [len] + 1 times
find_loop:
cmp edx, [iterations]
je find_loop_end
mov eax, ecx ; eax hold temporary input number
and eax, [bitmask] ; turn off the first series bits
shr ecx, 1 ; right shift ecx to examine the next set
inc edx ; increment loop counter
cmp eax, ebx ; compare motif with modified input
jne find_loop
inc dword [counter] ; increment counter if it's a match
jmp find_loop
find_loop_end:
;;; print out the incidence of the user specified motif
mov eax, msg3 ; print out message 3
call print_string
mov eax, [counter]
call print_int ; print out the counter value
call print_nl
;;; clean up code
end:
popa ; cleanup
mov eax, 0 ; cleanup
leave ; cleanup
ret ; cleanup
