I'm actually looking to be pointed in the right direction on an issue.
I'm looking to convert a date in x86 Assembly from the format "DD-MMM-YYYY" to a unique number so that it can be bubble sorted later and eventually converted back.
So, when I have a string input ie: .data inDate dw "08-SEP-1993"
And I want to split it up to
day = "08"
month = "SEP"
year = "1993"
So that I can process it further (I'll be converting SEP to "7", ect.)
So my question is what is a simple, efficient way to break the date down (code-wise)? I know I'll need to convert the date format to allow for sorting, but I'm new to Assembly so I'm not positive how to break the string up so I can convert it.
Also, as a second question, how would you convert a number from the string to an actual numerical value?
Thanks!
NOTE: I suppose it should be noted I'm using masm32
Next little program was made with EMU8086 (16 bits), it captures numbers from keyboard as strings, convert them to numeric to compare, and finally it converts a number to string to display. Notice the numbers are captured with 0AH, which requieres a 3-level variable "str". The conversion procedures that you need are at the bottom of the code (string2number and number2string).
.model small
.stack 100h
.data
counter dw ?
msj1 db 'Enter a number: $'
msj2 db 'The highest number is: $'
break db 13,10,'$'
str db 6 ;MAX NUMBER OF CHARACTERS ALLOWED (4).
db ? ;NUMBER OF CHARACTERS ENTERED BY USER.
db 6 dup (?) ;CHARACTERS ENTERED BY USER.
highest dw 0
buffer db 6 dup(?)
.code
;INITIALIZE DATA SEGMENT.
mov ax, @data
mov ds, ax
;-----------------------------------------
;CAPTURE 5 NUMBERS AND DETERMINE THE HIGHEST.
mov counter, 5 ;HOW MANY NUMBERS TO CAPTURE.
enter_numbers:
;DISPLAY MESSAGE.
mov dx, offset msj1
call printf
;CAPTURE NUMBER AS STRING.
mov dx, offset str
call scanf
;DISPLAY LINE BREAK.
mov dx, offset break
call printf
;CONVERT CAPTURED NUMBER FROM STRING TO NUMERIC.
mov si, offset str ;PARAMETER (STRING TO CONVERT).
call string2number ;NUMBER RETURNS IN BX.
;CHECK IF CAPTURED NUMBER IS THE HIGHEST.
cmp highest, bx
jae ignore ;IF (HIGHEST >= BX) IGNORE NUMBER.
;IF NO JUMP TO "IGNORE", CURRENT NUMBER IS HIGHER THAN "HIGHEST".
mov highest, bx ;CURRENT NUMBER IS THE HIGHEST.
ignore:
;CHECK IF WE HAVE CAPTURED 5 NUMBERS ALREADY.
dec counter
jnz enter_numbers
;-----------------------------------------
;DISPLAY HIGHEST NUMBER.
;FIRST, FILL BUFFER WITH '$' (NECESSARY TO DISPLAY).
mov si, offset buffer
call dollars
;SECOND, CONVERT HIGHEST NUMBER TO STRING.
mov ax, highest
mov si, offset buffer
call number2string
;THIRD, DISPLAY STRING.
mov dx, offset msj2
call printf
mov dx, offset buffer
call printf
;FINISH PROGRAM.
mov ax, 4c00h
int 21h
;-----------------------------------------
;PARAMETER : DX POINTING TO '$' FINISHED STRING.
proc printf
mov ah, 9
int 21h
ret
endp
;-----------------------------------------
;PARAMETER : DX POINTING TO BUFFER TO STORE STRING.
proc scanf
mov ah, 0Ah
int 21h
ret
endp
;------------------------------------------
;CONVERT STRING TO NUMBER.
;PARAMETER : SI POINTING TO CAPTURED STRING.
;RETURN : NUMBER IN BX.
proc string2number
;MAKE SI TO POINT TO THE LEAST SIGNIFICANT DIGIT.
inc si ;POINTS TO THE NUMBER OF CHARACTERS ENTERED.
mov cl, [ si ] ;NUMBER OF CHARACTERS ENTERED.
mov ch, 0 ;CLEAR CH, NOW CX==CL.
add si, cx ;NOW SI POINTS TO LEAST SIGNIFICANT DIGIT.
;CONVERT STRING.
mov bx, 0
mov bp, 1 ;MULTIPLE OF 10 TO MULTIPLY EVERY DIGIT.
repeat:
;CONVERT CHARACTER.
mov al, [ si ] ;CHARACTER TO PROCESS.
sub al, 48 ;CONVERT ASCII CHARACTER TO DIGIT.
mov ah, 0 ;CLEAR AH, NOW AX==AL.
mul bp ;AX*BP = DX:AX.
add bx, ax ;ADD RESULT TO BX.
;INCREASE MULTIPLE OF 10 (1, 10, 100...).
mov ax, bp
mov bp, 10
mul bp ;AX*10 = DX:AX.
mov bp, ax ;NEW MULTIPLE OF 10.
;CHECK IF WE HAVE FINISHED.
dec si ;NEXT DIGIT TO PROCESS.
loop repeat ;COUNTER CX-1, IF NOT ZERO, REPEAT.
ret
endp
;------------------------------------------
;FILLS VARIABLE WITH '$'.
;USED BEFORE CONVERT NUMBERS TO STRING, BECAUSE
;THE STRING WILL BE DISPLAYED.
;PARAMETER : SI = POINTING TO STRING TO FILL.
proc dollars
mov cx, 6
six_dollars:
mov bl, '$'
mov [ si ], bl
inc si
loop six_dollars
ret
endp
;------------------------------------------
;CONVERT A NUMBER IN STRING.
;ALGORITHM : EXTRACT DIGITS ONE BY ONE, STORE
;THEM IN STACK, THEN EXTRACT THEM IN REVERSE
;ORDER TO CONSTRUCT STRING (STR).
;PARAMETERS : AX = NUMBER TO CONVERT.
; SI = POINTING WHERE TO STORE STRING.
proc number2string
mov bx, 10 ;DIGITS ARE EXTRACTED DIVIDING BY 10.
mov cx, 0 ;COUNTER FOR EXTRACTED DIGITS.
cycle1:
mov dx, 0 ;NECESSARY TO DIVIDE BY BX.
div bx ;DX:AX / 10 = AX:QUOTIENT DX:REMAINDER.
push dx ;PRESERVE DIGIT EXTRACTED FOR LATER.
inc cx ;INCREASE COUNTER FOR EVERY DIGIT EXTRACTED.
cmp ax, 0 ;IF NUMBER IS
jne cycle1 ;NOT ZERO, LOOP.
;NOW RETRIEVE PUSHED DIGITS.
cycle2:
pop dx
add dl, 48 ;CONVERT DIGIT TO CHARACTER.
mov [ si ], dl
inc si
loop cycle2
ret
endp
Now the 32 bits version. Next is a little program that assigns to EAX a big number, convert it to string and convert it back to numeric, here it is:
.model small
.586
.stack 100h
.data
msj1 db 13,10,'Original EAX = $'
msj2 db 13,10,'Flipped EAX = $'
msj3 db 13,10,'New EAX = $'
buf db 11
db ?
db 11 dup (?)
.code
start:
;INITIALIZE DATA SEGMENT.
mov ax, @data
mov ds, ax
;CONVERT EAX TO STRING TO DISPLAY IT.
call dollars ;NECESSARY TO DISPLAY.
mov eax, 1234567890
call number2string ;PARAMETER:AX. RETURN:VARIABLE BUF.
;DISPLAY 'ORIGINAL EAX'.
mov ah, 9
mov dx, offset msj1
int 21h
;DISPLAY BUF (EAX CONVERTED TO STRING).
mov ah, 9
mov dx, offset buf
int 21h
;FLIP EAX.
call dollars ;NECESSARY TO DISPLAY.
mov eax, 1234567890
call flip_eax ;PARAMETER:AX. RETURN:VARIABLE BUF.
;DISPLAY 'FLIPPED EAX'.
mov ah, 9
mov dx, offset msj2
int 21h
;DISPLAY BUF (EAX FLIPPED CONVERTED TO STRING).
mov ah, 9
mov dx, offset buf
int 21h
;CONVERT STRING TO NUMBER (FLIPPED EAX TO EAX).
mov si, offset buf ;STRING TO REVERSE.
call string2number ;RETURN IN EBX.
mov eax, ebx ;THIS IS THE NEW EAX FLIPPED.
;CONVERT EAX TO STRING TO DISPLAY IT.
call dollars ;NECESSARY TO DISPLAY.
call number2string ;PARAMETER:EAX. RETURN:VARIABLE BUF.
;DISPLAY 'NEW EAX'.
mov ah, 9
mov dx, offset msj3
int 21h
;DISPLAY BUF (EAX CONVERTED TO STRING).
mov ah, 9
mov dx, offset buf
int 21h
;WAIT UNTIL USER PRESS ANY KEY.
mov ah, 7
int 21h
;FINISH PROGRAM.
mov ax, 4c00h
int 21h
;------------------------------------------
flip_eax proc
mov si, offset buf ;DIGITS WILL BE STORED IN BUF.
mov bx, 10 ;DIGITS ARE EXTRACTED DIVIDING BY 10.
mov cx, 0 ;COUNTER FOR EXTRACTED DIGITS.
extracting:
;EXTRACT ONE DIGIT.
mov edx, 0 ;NECESSARY TO DIVIDE BY EBX.
div ebx ;EDX:EAX / 10 = EAX:QUOTIENT EDX:REMAINDER.
;INSERT DIGIT IN STRING.
add dl, 48 ;CONVERT DIGIT TO CHARACTER.
mov [ si ], dl
inc si
;NEXT DIGIT.
cmp eax, 0 ;IF NUMBER IS
jne extracting ;NOT ZERO, REPEAT.
ret
flip_eax endp
;------------------------------------------
;CONVERT STRING TO NUMBER IN EBX.
;SI MUST ENTER POINTING TO THE STRING.
string2number proc
;COUNT DIGITS IN STRING.
mov cx, 0
find_dollar:
inc cx ;DIGIT COUNTER.
inc si ;NEXT CHARACTER.
mov bl, [ si ]
cmp bl, '$'
jne find_dollar ;IF BL != '$' JUMP.
dec si ;BECAUSE IT WAS OVER '$', NOT OVER THE LAST DIGIT.
;CONVERT STRING.
mov ebx, 0
mov ebp, 1 ;MULTIPLE OF 10 TO MULTIPLY EVERY DIGIT.
repeat:
;CONVERT CHARACTER.
mov eax, 0 ;NOW EAX==AL.
mov al, [ si ] ;CHARACTER TO PROCESS.
sub al, 48 ;CONVERT ASCII CHARACTER TO DIGIT.
mul ebp ;EAX*EBP = EDX:EAX.
add ebx, eax ;ADD RESULT TO BX.
;INCREASE MULTIPLE OF 10 (1, 10, 100...).
mov eax, ebp
mov ebp, 10
mul ebp ;AX*10 = EDX:EAX.
mov ebp, eax ;NEW MULTIPLE OF 10.
;CHECK IF WE HAVE FINISHED.
dec si ;NEXT DIGIT TO PROCESS.
loop repeat ;CX-1, IF NOT ZERO, REPEAT.
ret
string2number endp
;------------------------------------------
;FILLS VARIABLE STR WITH '$'.
;USED BEFORE CONVERT NUMBERS TO STRING, BECAUSE
;THE STRING WILL BE DISPLAYED.
dollars proc
mov si, offset buf
mov cx, 11
six_dollars:
mov bl, '$'
mov [ si ], bl
inc si
loop six_dollars
ret
dollars endp
;------------------------------------------
;NUMBER TO CONVERT MUST ENTER IN EAX.
;ALGORITHM : EXTRACT DIGITS ONE BY ONE, STORE
;THEM IN STACK, THEN EXTRACT THEM IN REVERSE
;ORDER TO CONSTRUCT STRING (BUF).
number2string proc
mov ebx, 10 ;DIGITS ARE EXTRACTED DIVIDING BY 10.
mov cx, 0 ;COUNTER FOR EXTRACTED DIGITS.
cycle1:
mov edx, 0 ;NECESSARY TO DIVIDE BY EBX.
div ebx ;EDX:EAX / 10 = EAX:QUOTIENT EDX:REMAINDER.
push dx ;PRESERVE DIGIT EXTRACTED (DL) FOR LATER.
inc cx ;INCREASE COUNTER FOR EVERY DIGIT EXTRACTED.
cmp eax, 0 ;IF NUMBER IS
jne cycle1 ;NOT ZERO, LOOP.
;NOW RETRIEVE PUSHED DIGITS.
mov si, offset buf
cycle2:
pop dx
add dl, 48 ;CONVERT DIGIT TO CHARACTER.
mov [ si ], dl
inc si
loop cycle2
ret
number2string endp
end start