First post

[Derry]

Hi,

For some inexplicable reason, I've decided to learn Win32 assembly language - MASM. At the moment I'm working my way through Icezelion's tutorials and reading various posts to the forum.
Playing with file i/o I have 4 buttons on a dialog box, a checkbox, an edit box and a static.
Button 1 sets the check box
Button 2 clears the checkbox
Button 3 writes 'checked' or 'unchecked' to a file along with carriage returns/linefeeds

so the file may now contain for example:

Checked
Unchecked
Unchecked
Checked
etc

see code below:

.elseif eax==IDC_BTN1
invoke SendDlgItemMessage,hWin,IDC_CHK1,BM_SETCHECK,1,0

.elseif eax==IDC_BTN2
invoke SendDlgItemMessage,hWin,IDC_CHK1,BM_SETCHECK,0,0   
   
.elseif eax==IDC_BTN3         
         
invoke IsDlgButtonChecked,hWin,IDC_CHK1   
         
mov ChkState,eax
         
.if ChkState==BST_CHECKED
            
invoke   CreateFile,addr p2FileName,GENERIC_WRITE,NULL,NULL,OPEN_ALWAYS,FILE_ATTRIBUTE_ARCHIVE,NULL
            
mov   hFile, eax   
            
invoke SetFilePointer,hFile,0,0,FILE_END
            
invoke WriteFile,hFile,addr IsItChecked,LENGTHOF IsItChecked,addr pwritten,NULL
                        
invoke CloseHandle,hFile
         
         
.elseif ChkState==BST_UNCHECKED
                           
invoke   CreateFile,addr p2FileName,GENERIC_WRITE,NULL,NULL,OPEN_ALWAYS,FILE_ATTRIBUTE_ARCHIVE,NULL
            
mov   hFile, eax   
            
invoke SetFilePointer,hFile,0,0,FILE_END
            
invoke WriteFile,hFile,addr IsItNotChecked,LENGTHOF IsItNotChecked,addr pwritten,NULL
                        
invoke CloseHandle,hFile
               
.endif

Let's say I want to read the first line from the file into the edit box and/or static control

The third parameter of readfile is confusing me, how do I specify the number of bytes to read?

BOOL ReadFile(

    HANDLE hFile,   // handle of file to read
    LPVOID lpBuffer,   // address of buffer that receives data 
    DWORD nNumberOfBytesToRead,   // number of bytes to read
    LPDWORD lpNumberOfBytesRead,   // address of number of bytes read
    LPOVERLAPPED lpOverlapped    // address of structure for data
   );



I've tried this piece of code which I know is rubbish

.elseif eax==IDC_BTN4
      
invoke CreateFile,ADDR GetFile,GENERIC_READ,NULL,NULL,OPEN_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL
mov hGetFile,eax
invoke SetFilePointer,hGetFile,0,0,FILE_BEGIN
invoke ReadFile,hGetFile,pMem,hMem,SizeRW,NULL
invoke SendDlgItemMessage,hWin,IDC_EDT1,ADDR pMem,0,0
         
invoke CloseHandle,hGetFile

How would I read say the read first line into the static control?

I took the code below from a post, it loops through a variable until NULL and writes the string out to a messagebox.

.data
SomeString db 'zebra stripes',0

.code
begin:

mov ecx, offset SomeString

@@:
inc ecx
mov dl, byte ptr [ecx]
test dl,dl
jnz @B

invoke MessageBox,0,ADDR SomeString,0,MB_OK

end begin


I assume this may be a possible solution but needing to specify the number of bytes to read from the file has me stumped. Apologies for being so long-winded

Any help gratefully received and thanks in advance

Derry

[anon]

What I usually do is use GetFileSize and use the results for nNumberOfBytesToRead (the third parameter)
that way you will be able to read the entire file. You can of course use a smaller number if you know how
many bytes you want to read.

[Derry]

Thanks Anon,

I have looked at filesize now and think i understand how I can read an entite file, but what do I do if I only want to read a line of text into a static control when I don't know the size of that line?
Sorry if I was not clear with the first post

Derry

[jojo]

For getting the first string only, you need something like this:

   invoke ReadFile, hFile, BufStart, dwFileSize, ADDR dwBytesRead, 0
   mov   bSuccess,eax
   invoke   CloseHandle, hFile
   mov   ecx,dwBytesRead
   mov   edi,BufStart

; edi will point to CRLF-terminated strings. We scan for the CRLF.
   dec   edi   ;edi=BufStart-1, for compensation of first inc after Get_CR

Get_Next:
   mov   edx,ecx   ;ACD free - edx is our counter
   mov   eax,2573   ;CrLF=13,10
Get_CR:
   inc   edi
   dec   ecx
   jle   CrFound
   cmp   word ptr[edi],ax
   jne   Get_CR
CrFound:
   sub   edx,ecx   ;len of string

... now here you need to copy the edx bytes into a buffer, then add a zero byte, and pass the address of the buffer to the edit control

[Mark Jones]

Jojo, should you preserve EDI?

Hi Derry, try searching above in the little search box. Just the other day someone else was asking the same thing and there were a couple more interesting methods posted. :)

[jojo]

Jojo, should you preserve EDI?

Yes indeed. In my actual code, I use

MyProc   proc...
   pushad         ;save all registers
   ...
   popad         ;restore all registers
   mov   eax,whatever
   ret
pushad+popad is lazy but pretty safe :toothy

[Vortex]

Hi Derry,

Welcome to the forum :U