I have been working on an assembly program that sorts a list of dates and then prints out the dates sorted oldest to newest. The dates are in the format of DD- MMM-YYYY, e.g. “23-JUL-2010”.
I have made steady progress, but now my program crashes right away, and I'm having difficulty finding out why. I'm using the MASM32 editor.
Here's my program...
include \masm32\include\masm32rt.inc
.data?
number dd ?
.data
dates BYTE "23-JUL-2010", 0, "22-JUL-2010", 0, "23-JUL-2009", 0, "31-JUL-2012", 0, "05-MAR-2010", 0, "12-MAR-1010", 0
values dd 5 DUP(0, 0, 0, 0, 0)
nDates DWORD 6
counter DD 0
temp dd 0
years dd 0
months BYTE "JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC",0
.code
DateToNumber MACRO items, mons, result
LOCAL loop_top
PUSHAD
lea EDI, [items]
MOV AL, [EDI]
AAA
MOV BL, 10
MUL BL
MOV DL, AL
ADD EDI, 1
SUB EAX, EAX
MOV AL, [EDI]
AAA
ADD DL, AL
MOV result, EDX
SUB EDX, EDX
SUB ESI, ESI
SUB EDI, EDI
mov EAX, 0 ; EAX is the month number
loop_top:
lea ESI, [items+3] ; ESI will be a ptr into the date string we are trying to convert to a number
lea EDI, [mons + EAX * 4] ; EDI will be a ptr into the months array
inc EAX
mov ECX, 3 ; length of a month string
cld
repe cmpsb ; compare mystring and months for 3 characters
jne loop_top ; keep looping until we find the month
mov EBX, result
mov BH,AL
SUB EBX, EBX
MOV years, EBX
lea EDI, [items]
ADD EDI,7
MOV AL, [EDI]
AAA
MOV BX, 1000
MUL BX
MOV years, EAX
SUB BX, BX
SUB EAX, EAX
ADD EDI, 1
MOV AL, [EDI]
AAA
MOV BX, 100
MUL BX
SUB BX, BX
ADD years, EAX
SUB EAX, EAX
ADD EDI, 1
MOV AL, [EDI]
AAA
MOV BX, 10
MUL BX
SUB BX, BX
ADD years, EAX
SUB EAX, EAX
ADD EDI, 1
MOV AL, [EDI]
AAA
SHL EAX, 16
ADD result, EAX
POPAD
ENDM
start:
MOV ECX, 1
SUB EDX, EDX
SUB EAX, EAX
DateToNumber dates, months, number
MOV EAX, number
MOV values, EAX
DateToNumber [dates+12], months, number
MOV EAX, number
MOV [values+4], EAX
DateToNumber [dates+24], months, number
MOV EAX, number
MOV [values+8], EAX
DateToNumber [dates+48], months, number
MOV EAX, number
MOV [values+16], EAX
DateToNumber [dates+36], months, number
MOV EAX, number
MOV [values+12], EAX
DateToNumber [dates+60], months, number
MOV EAX, number
MOV [values+20], EAX
print chr$("[ ",)
;lea EDI, [values]
;push EDI
;Call BubbleSort
;Call NumberToDate
out_top:
mov eax, [values+esi*4]
mov temp, eax
print str$(temp)
print chr$(", ")
inc esi
cmp esi, 5
jne out_top
; Formatting the last character
mov eax, [values+esi*4]
mov temp, eax
print str$(temp)
print chr$(" ]", 13, 10)
exit
;NumberToDate-
; Parameter is a 32-bit unsigned number.
; Turns the number back into its corresponding date string.
; Returns the address of the string.
;
NumberToDate :
enter 0, 0
print "NumberToDate called"
leave
ret 0
;BubbleSort-
; Parameters are the address of an array of 32-bit unsigned numbers and the length of the array.
; Sorts the array in place from smallest to largest.
; No return value.
;
BubbleSort:
enter 0, 0
PUSHAD
mov ecx, 0
mov edx, 0
print "BubbleSort called"
MOV ESI, [EBP + 8]
top:
cmp edx, 5
je inc_loop
inc edx
mov eax, [esi+ecx*4] ; moves array index 0 into eax
cmp [esi+edx*4], eax ; compares index 1 to index 2
jl top ; jumps to top if index1 is less than or equal to index 2
; swaps the values edx and ecx are pointing to
mov ebx, [esi+edx*4]
mov [esi+ecx*4], ebx
mov [esi+edx*4], eax
jmp top
inc_loop:
mov edx, -1
inc ecx
cmp ecx, 5
jl top
POPAD
leave
ret 4
END start
If any of you could help me understand where I'm going wrong, or help me debug this I would greatly appreciate it. Thanks in advance!
out_top: mov eax, [values+esi*4] mov temp, eax print str$(temp) print chr$(", ") inc esi cmp esi, 5 jne out_top
In this part of your program you depend on the correct value in ESI, but you forgot to initialize it!
XOR ESI, ESI <<<< Add this line
out_top:
mov eax, [values+esi*4]
mov temp, eax
print str$(temp)
print chr$(", ")
inc esi
cmp esi, 5
jne out_top
values dd 5 DUP(0, 0, 0, 0, 0)
Seeing this I suspect you don't understand the DUP operator very well!
Your code needs to reserve space for 6 dwords, but this line reserves 25 such dwords. Write one of the following:
values dd 0,0,0,0,0,0
or else
values dd 6 dup(0)
Having your DateToNumber code as a macro wastes a lot of bytes. This should have been written as a subroutine.
Remember that each time you use the macro, the entire code snippet is substituted. In your program this happens 6 times.