Write an assembly program that defines the following array 10 25 56 80 3 , then create procedure reverse to display the array in reverse.
I can only get the size of the array. I tried to use push/pop.
Thank you!
.586
.MODEL FLAT
INCLUDE io.h
.stack 4096
.DATA
array1 DWORD 10,25,56,80,3 DUP (?)
size1 DWORD 5
outputLbl BYTE "The reverse is", 0
result BYTE 11 DUP (?), 0
.CODE
_MainProc PROC
mov eax,5
lea ebx,array1 ;get address
call reverse
dtoa result, eax
output outputLbl, result
_MainProc ENDP
reverse PROC
pushad
mov ecx, (5)/2
mov esi,0
mov edi,((5)-1)
L1:
mov eax, array1[esi*4]
mov ebx, array1[edi*4]
mov array1[esi*4], ebx
mov array1[edi*4], eax
loop L1
popad
ret
reverse ENDP
END
Related
I have elements loaded in stack and I need to move them to array. My code looks like this:
%include "asm_io.inc"
segment .data
array db 100 dup(0)
length db 0
segment .text
global _asm_main
extern getchar
_asm_main:
enter 0, 0
pusha
call getchar
char_loop:
mov ebx,10
sub eax, '0'
mul ebx
mov ebx, eax
call getchar
sub eax, '0'
add eax, ebx
push eax
inc BYTE[length]
call getchar
cmp eax, 10
je fill_array
cmp eax, 13
je fill_array
cmp eax, 32
je skip_spaces
jmp char_loop
skip_spaces:
call getchar
cmp eax, 32
je skip_spaces
jmp char_loop
fill_array:
mov ecx, [length]
mov ebx, array
l1:
pop eax
mov [ebx], eax ; should be al instead of eax
inc ebx
call print_int
call print_nl
loop l1
print_array:
mov ecx, [length]
mov ebx, array
l2:
mov eax, [ebx] ; should be al instead of eax
call print_int
call print_nl
inc ebx
loop l2
_asm_end:
call print_nl
popa
mov eax, 0
leave
ret
print_int in asm_io.asm is
print_int:
enter 0,0
pusha
pushf
push eax
push dword int_format
call _printf
pop ecx
pop ecx
popf
popa
leave
ret
Where int_format is int_format db "%i",0
Length and values in stack are correct, I had them printed but when I try to print array only last value is correct. Other values are random numbers. I tried combinations of registers of different sizes but it did not work. I think that error has to do something with size of registers or size of array.
Answer here:
As #xiver77 said in comments I was writing into array 4 bytes instead 1 byte. One element in array has 1 byte and I tried to write 4 bytes. That creates overflow of bites and change other elements in array. Instead mov [ebx], eax should be mov [ebx], al and mov eax, [ebx] for printing should be mov al [ebx].
Not sure if I need a third array to temporarily store values in order to swap contents of arrayA and arrayB. I am a student learning assembly for the first time so please keep it simple.
.386
.model flat,stdcall ; memory system
.stack 4096 ; declare stack memory size 4kb
ExitProcess proto,dwExitCode:dword
.data
arrayA byte 01d, 04d, 02d ; 8bits
arrayB word 02d, 05d, 05d ; 16bits
.code
main proc
mov EAX, 0
mov EBX, 0
mov ECX, 3
mov EDX, 0
L1:
movzx bx, arrayA[ebx]
mov ax, arrayB[ebx]
xchg arrayA[ebx], al
xchg arrayB[ebx], bx
inc ebx
loop L1
invoke ExitProcess,0
main endp
end main
I asked for help earlier and thought I was home free but I'm not. My logic was wrong and I've greatly altered it. This program is supposed to return the Max int in the array (which also happens to be the last element). After tracing it with GDB a few times, I see that I get to the 5th (2nd to last) element in the array, "20", when I hit a segmentation fault and the program halts. I set ECX to the array length and subtracted 1 from ECX to avoid this, but my logic is obviously wrong. Am I wrong in depending on the ECX counter to terminate the loop. Any ideas please?
***EDIT MAJOR EDITS TO CODE
SECTION .data ;data section
msg1: db "Here are the array elements:", 10, 0
msg1Len: equ $-msg1
msg2: db "Here is the sorted array:", 10, 0
msg2Len: equ $-msg2
arr: dd 12, 16, 6, 18, 10, 40, 30
arrLen: equ ($-arr)/4 ;number of elements = array length / 4
SECTION .bss
max resd 1 ;declare and reserve space for max
SECTION .text
global bsort
bsort:
push ebp ; save old ebp register
mov ebp, esp ; build a new stack
restart:
mov ebx, arr ; the base address argument is saved in ebx register
mov ecx, arrLen ; the size argument is saved in exc register
sub ecx, 1 ; Last member has no following element to compare with.
; So we need to reduce the counter by 1
top:
mov eax, [ebx] ;; access first array element. Move its value to eax
cmp eax, [ebx+4] ; compare the value of eax ([ebx]) with [ebx+4]
jle noswap ; if value at eax is less or equal to value of [ebx+4]
; no need to exchang values. Jump to noswap
xchg eax, [ebx+4] ; if value at eax > value [ebx+4], exchange
mov [ebx], eax ; store the new exchanged value at [ebx]
jmp restart ; reset the base address and counter. Start over
noswap:
add ebx, 4 ; move to the next array element
loop top ; loop back to the top if the register ecx > 0
leave
ret
global main
main:
push ebp
mov ebp, esp
mov ecx, msg1 ;print msg1
mov edx, msg1Len
call PString
;save array base address in ebx and save sizein in ecx
mov ebx, arr
mov ecx, arrLen; store num elements in ecx
;loop to print array
PrintArray:
mov eax, [ebx] ;move value [ebx] to eax
call PrintDec
call Println
add ebx, 4
loop PrintArray
;call bubblesort
call bsort
mov ecx, msg2
mov edx, msg2Len
call PString
;save arr base add in sbx and size in ecx
mov ebx, arr
mov ecx, arrLen
PrintSortedArray:
mov eax, [ebx]
call PrintDec
call Println
add ebx, 4
loop PrintSortedArray
;exit program and clean stack
mov esp, ebp
pop ebp
ret
PString:; save register values of the called function
pusha
mov eax,4 ; use 'write' system call = 4
mov ebx,1 ; file descriptor 1 = STDOUT
int 80h ; call the kernel
; restore the old register values of the called function
popa
ret
Println:
;will call PString func
;will change content of ecx and edx
;need to save registers used by the main program
section .data
nl db 10
section .text
pusha
mov ecx, nl
mov edx, 1
call PString
;return original register values
popa
ret
PrintDec:
;saves all registers so they return unmodified
;build the function to handle dword size
section .bss
decstr resb 10 ; 10 32-bit digits
ct1 resd 1 ;keep track of dec-string size
section .text
pusha; save registers
mov dword[ct1],0 ;initially assume 0
mov edi, decstr ; edi points to dec-string
add edi, 9 ; moved to the last element of string
xor edx, edx ; clear edx for 64-bit div
whileNotZero:
mov ebx, 10 ; get ready to divide by 10
div ebx ; divide by 10
add edx, '0' ; convert to ascii
mov byte[edi], dl ; put it in string
dec edi ; move to next char in str
inc dword[ct1] ; inc char counter
xor edx, edx ; clear edx
cmp eax, 0 ;is remainder 0?
jne whileNotZero ;if no, keep on looping
inc edi ; conversion finished, bring edi
mov ecx, edi ; back to start of string. make ecx
mov edx, [ct1] ; point to counterm edx gets # chars
mov eax, 4 ; print to stdout
mov ebx, 1
int 0x80 ; call kernel
popa ; restore registers
ret
My program works, but there is something wrong with my printMax function. The program terminates with a
Segmentation fault (core dumped).
I have tried building a stack for the function and just doing a pusha popa and both ways, I get the seg fault core dumped.
I've tried calling the function, but it just runs twice.
Any idea what I am doing wrong?
SECTION .data ;data section
msg1 : db "Here are the array elements:", 10, 0
msg1Len: equ $-msg1
msg2 : db "Here is the max value in the array:", 10, 0
msg2Len: equ $-msg2
arr : dd 2,4,6,8,10,20,40
arrLen : equ ($-arr)/4 ;number of elements = array length / 4
SECTION .bss
max resd 1 ;declare and reserve space for max
SECTION .text
global main
main:
push ebp
mov ebp, esp
mov ecx, msg1 ;print msg1
mov edx, msg1Len
call PString
;save array base address in ebx and save sizein in ecx
mov ebx, arr
mov ecx, arrLen; store num elements in ecx
;loop to print array
PrintArray:
mov eax, [ebx] ;move value [ebx] to eax
call PrintDec
call Println
add ebx, 4
loop PrintArray
printMax:
section .text
pusha
;reset array to find max
mov ebx, arr
mov ecx, arrLen
loopForMax:
mov eax, [ebx]
cmp eax, [ebx +4]
jle sameMax
mov [max], eax
sameMax:
add ebx, 4 ;move to next element
loop loopForMax
mov ecx, msg2
mov edx, msg2Len
call PString
mov eax, [max]
call PrintDec
call Println
popa
ret
;exit program and clean stack
mov esp, ebp
pop ebp
ret
PString:; save register values of the called function
pusha
mov eax,4 ; use 'write' system call = 4
mov ebx,1 ; file descriptor 1 = STDOUT
int 80h ; call the kernel
; restore the old register values of the called function
popa
ret
Println:
;will call PString func
;will change content of ecx and edx
;need to save registers used by the main program
section .data
nl db 10
section .text
pusha
mov ecx, nl
mov edx, 1
call PString
;return original register values
popa
ret
PrintDec:
;saves all registers so they return unmodified
;build the function to handle dword size
section .bss
decstr resb 10 ; 10 32-bit digits
ct1 resd 1 ;keep track of dec-string size
section .text
pusha; save registers
mov dword[ct1],0 ;initially assume 0
mov edi, decstr ; edi points to dec-string
add edi, 9 ; moved to the last element of string
xor edx, edx ; clear edx for 64-bit div
whileNotZero:
mov ebx, 10 ; get ready to divide by 10
div ebx ; divide by 10
add edx, '0' ; convert to ascii
mov byte[edi], dl ; put it in string
dec edi ; move to next char in str
inc dword[ct1] ; inc char counter
xor edx, edx ; clear edx
cmp eax, 0 ;is remainder 0?
jne whileNotZero ;if no, keep on looping
inc edi ; conversion finished, bring edi
mov ecx, edi ; back to start of string. make ecx
mov edx, [ct1] ; point to counterm edx gets # chars
mov eax, 4 ; print to stdout
mov ebx, 1
int 0x80 ; call kernel
popa ; restore registers
ret
I am using Masm with Irvine32 library. I am new to Assembly and I'm having trouble with converting the contents of a file into an array once I read it in. Once I read in the file and convert it, I should be able to sum up the array or whatever else I need to do with it but right now I'm having trouble with converting my array back to ascii after converting it to int, in order to print it out. I believe what I need to do is read in an input file that contains a list of numbers separated by spaces, convert ascii to int, store in an array, and finally, convert back to ascii and output the results. Is this correct?
My input looks something like this, with spaces to separate the numbers:
24 31 4 63 9 11 17 3 56 37
Here is my program so far:
INCLUDE Irvine32.inc
.data
TEN dword 10
BUFFER_SIZE = 5000
buffer dword BUFFER_SIZE dup (?)
bytesRead dword 0
inFilename byte "input.txt", 0
infileH dword 0
cnt dword 0
ary dword 20 dup (?) ; Array for storing converted ascii to int
bry dword 20 dup (?)
size dword 10
.code
main PROC
call zeroOut
; Open input file
mov edx, OFFSET inFilename
call OpenInputFile
mov infileH, eax
; Read file into buffer
mov edx, OFFSET buffer
mov ecx, BUFFER_SIZE
call ReadFromFile
mov bytesRead, eax
; Close input file
mov eax, infileH
call CloseFile
; Convert ascii to int and store in ary
call zeroOut
lea esi, OFFSET buffer
lea edi, OFFSET ary
mov edx, size
L1:
call convertasciitoint
mov [edi], eax
inc edi
inc esi
dec edx
call DumpRegs
cmp edx, 0
jne L1
call zeroOut
; Convert int to ascii for printing
lea esi, OFFSET ary
lea edi, OFFSET bry
mov ebx, size
L2:
call convertinttoascii
mov [edi], eax
inc esi
inc edi
dec ebx
cmp ebx, 0
jne L2
; Print output
lea esi, OFFSET bry
call myLine
exit
main ENDP
convertasciitoint PROC
mov ecx, 0
mov eax, 0
nextDigit:
mov bl, [esi]
cmp bl, '0'
jl outOfHere
cmp bl, '9'
jg outOfHere
add bl, -30h
imul eax, 10
add eax, ebx
;mov [esi], eax
;mov [edi], eax
inc ecx
inc esi
;inc edi
jmp nextDigit
outOfHere:
mov cnt, ecx
ret
convertasciitoint ENDP
convertinttoascii PROC
mov ecx, cnt
nextDigit:
mov al, [esi]
div TEN
mov eax, 0
mov al, dl
add al, 30h
;mov [edi], dl
;mov dl, [esi]
;inc esi
;inc edi
call DumpRegs
dec ecx
cmp ecx, 0
jne nextDigit
ret
convertinttoascii ENDP
myLine PROC
nextChar:
mov al, [esi]
inc esi
call WriteChar
cmp al, NULL
jne nextChar
ret
myLine ENDP
zeroOut PROC
mov eax, 0
mov ebx, 0
mov ecx, 0
mov edx, 0
ret
zeroOut ENDP
END main
Right now my program reads in the entire file correctly, if I print the buffer array everything is output correctly. I can convert my array to int but I can't convert it back to ascii correctly. Am I not looping or incrementing correctly? Using the input above, my output (after converting back to ascii) is 8589793965, which isn't correct. I can't figure out what I'm doing wrong. I'm trying to read in a number, divide by ten and add 30h to the remainder, is this correct? I can't seem to get to the second digit of the number correctly.
Any help would be much appreciated. Thanks