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String manipulation - from C++ to Assembly, I've reached a point in my education where I need to translate how to manipulate strings in ASM.
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| admiral27 |
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Member
Group: Members
Posts: 33
Member No.: 7931
Joined: 17-May 08
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I've reached a point in my education when I need to translate how to manipulate strings in ASM.
For example, lets say I have this in C++
| CODE | hMemory = GlobalAlloc( GMEM_MOVEABLE | GMEM_ZEROINIT), MEMSIZE );
pMemory = GlobalLock( hMemory );
SendMessage( hEdit, WM_GETTEXT, MEMSIZE-1, pMemory );
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This should fill an area of memory located by pMemory from the control hEdit. What I want to do is to pull out chunks of text, 80 characters at a time. How would you manipulate text in ASM?
Any type of example will be greatly appreciated, even if it uses a different method than this. Thank you.
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| admiral27 |
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Member
Group: Members
Posts: 33
Member No.: 7931
Joined: 17-May 08
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I'm sorry... I've never been very good at posting to forums. I seem to either put too much or too little.
I'm trying to understand how to deal with string manipulation in ASM. I know how to do the global alloc to get a handle to string, but I want to do a bit more.
Lets just assume I've successfully pulled the text from a EDIT control (through a "save to file" function) and I want to do other things with the string.
I have a pointer to the text that was in the "EDIT" control. I would like to take that pointer and copy it in 80 character chunks and send it to the printer. What I'm not sure of is how to do it, especially with GlobalAlloc; I'm used to using Alloc or Malloc. My thinking is that I should use pointer incrementing or push the values on the stack... Honestly, I'm THAT new to all of this, so thats why I supplied so little and I'm hoping for different ideas, since I'm sure there's lots of ways to accomplish the same thing.
Since I first posted, I found a list of instructions I have never seen before
| CODE | rep movsb;copies a string
repe cmpsb;compares a string
repne scasb;scans a string for a character
rep stosb;sets a character in a string
cld;sets the direction flag to forward
mov esi, source;move the source address in to esi
mov edi, dest;move the destination address in to edi
mov ecx, length;move the length to copy in to ecx
rep movsb;copy length bytes from esi to edi |
I'm wondering if this is the first step.
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| shoorick |
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Extremely Active Member
Group: Admins
Posts: 2303
Member No.: 160
Joined: 22-June 04
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here is my ready code (FASM) for saving and loading UNICODE text from/to MULTILINE edit control - no comments at all, if there any question - ask
====================
(failed to upload nor zip, neigther inc)
====================
| CODE | ;=======================================================================
proc load_file _name
;-----------------------------------------------------------------------
local cnt dd ?
local mem dd ?
;-----------------------------------------------------------------------
push edi
push esi
invoke CreateFile,[_name],GENERIC_READ,FILE_SHARE_READ,0,\
OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,0
cmp eax,INVALID_HANDLE_VALUE
mov esi,eax
je .done
invoke GetFileSize,esi,0
or eax,eax
mov edi,eax
je .done_close
add eax,2
invoke LocalAlloc,LMEM_MOVEABLE,eax
mov [mem],eax
invoke LocalLock,eax
push eax
lea ecx,[cnt]
mov word [eax + edi],0
invoke ReadFile,esi,eax,edi,ecx,0
invoke LocalUnlock
cmp edi,[cnt]
je .done_close
invoke LocalFree,[mem]
mov [mem],INVALID_HANDLE_VALUE
.done_close:
invoke CloseHandle,esi
mov eax,[mem]
.done:
pop esi
pop edi
ret
;-----------------------------------------------------------------------
endp
;=======================================================================
;
;=======================================================================
proc save_file _name,_buff,_size,_bom
;-----------------------------------------------------------------------
push edi
push esi
xor eax,eax
mov esi,[_buff]
cmp word [esi],BOM
jne @F
mov [_bom],0
@@:
mov edi,[_size]
add edi,edi
jnz @F
mov edi,esi
mov ecx,-1
repne scasw
sub edi,[_buff]
sub edi,2
@@:
invoke CreateFile,[_name],GENERIC_WRITE,0,0,CREATE_ALWAYS,\
FILE_ATTRIBUTE_NORMAL,0
cmp eax,INVALID_HANDLE_VALUE
je .done
mov esi,eax
cmp [_bom],0
je @F
lea ecx,[_name]
invoke WriteFile,esi,bom,2,ecx,0
cmp [_name],2
je @F
mov edi,-1
jmp .close
@@:
lea ecx,[_name]
invoke WriteFile,esi,[_buff],edi,ecx,0
invoke SetEndOfFile,esi
sub edi,[_name]
.close:
invoke CloseHandle,esi
mov eax,edi
.done:
pop esi
pop edi
ret
;-----------------------------------------------------------------------
endp
;=======================================================================
;
;=======================================================================
proc append_file _name,_buff,_size
;-----------------------------------------------------------------------
push edi
push esi
mov esi,[_buff]
mov edi,[_size]
cmp word [esi],BOM
jne @F
add esi,2
sub edi,2
@@:
add edi,edi
jnz @F
mov edi,esi
mov ecx,-1
repne scasw
sub edi,[_buff]
sub edi,2
@@:
invoke CreateFile,[_name],GENERIC_WRITE,FILE_SHARE_READ,0,\
OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,0
cmp eax,INVALID_HANDLE_VALUE
je .done
mov esi,eax
invoke SetFilePointer,eax,0,0,FILE_END
lea ecx,[_name]
invoke WriteFile,esi,[_buff],edi,ecx,0
sub edi,[_name]
.close:
invoke CloseHandle,esi
mov eax,edi
.done:
pop esi
pop edi
ret
;-----------------------------------------------------------------------
endp
;=======================================================================
;
;=======================================================================
proc SaveEdit _edit,_file
;-----------------------------------------------------------------------
invoke SendMessage,[_edit],WM_GETTEXTLENGTH,0,0
push eax
invoke SendMessage,[_edit],EM_GETHANDLE,0,0
invoke LocalLock,eax
or eax,eax
pop edx
jz @F
push eax
stdcall save_file,[_file],eax,edx,1
pop edx
push eax
invoke LocalUnlock,edx
pop eax
ret
;-----------------------------------------------------------------------
endp
;=======================================================================
;
;=======================================================================
proc AppendToFile _edit,_file
;-----------------------------------------------------------------------
invoke SendMessage,[_edit],WM_GETTEXTLENGTH,0,0
push eax
invoke SendMessage,[_edit],EM_GETHANDLE,0,0
invoke LocalLock,eax
or eax,eax
pop edx
jz @F
push eax
stdcall append_file,[_file],eax,edx,1
pop edx
push eax
invoke LocalUnlock,edx
pop eax
ret
;-----------------------------------------------------------------------
endp
;=======================================================================
;
;=======================================================================
proc LoadEdit _edit,_file
;-----------------------------------------------------------------------
stdcall load_file,[_file]
cmp eax,INVALID_HANDLE_VALUE
je @F
push 0
push eax
invoke SendMessage,[_edit],EM_GETHANDLE,0,0
mov [_file],eax
invoke SendMessage,[_edit],EM_SETHANDLE
invoke LocalFree,[_file]
xor eax,eax
@@:
ret
;-----------------------------------------------------------------------
endp
;=======================================================================
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