format pe console 4.0
include 'WIN32AX.INC'
entry main
.data
buf db 65,65,65
size dd ?
.code
mov ecx,-1
xor al,al
mov edi,buf
repne scasb
not ecx
dec ecx
mov [size],ecx
proc main
invoke CreateFile,'test.txt',GENERIC_WRITE,0,0,4,FILE_ATTRIBUTE_NORMAL,0
invoke WriteFile,eax,buf,size,0,0
invoke ExitProcess,0
endp
data import
library kernel32,'kernel32.dll'
include 'API\KERNEL32.INC'
end data    

format pe console 4.0
include 'WIN32AX.INC'

.data
      buf db 65,65,65
     bufsize = $ - buf
   byteswritten dd ?
.code
  main:
   invoke  CreateFile, 'test.txt', GENERIC_WRITE, 0, 0, 4, FILE_ATTRIBUTE_NORMAL, 0
  invoke  WriteFile, eax, buf, bufsize, byteswritten, 0
       invoke  ExitProcess, 0

.end main    

proc AppendToFile uses ecx ebx edx, lpFileName, lpBuffer

            local nBytes:DWORD

            mov [nBytes], INVALID_HANDLE_VALUE
            
            invoke CreateFile, [lpFileName], GENERIC_WRITE, 0, 0, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, 0
            cmp eax, INVALID_HANDLE_VALUE
            jz .finish
            
            mov ebx, eax

            invoke SetFilePointer, eax, 0, 0, FILE_END
            cmp eax, INVALID_HANDLE_VALUE
            jz .finish

            invoke lstrlen, [lpBuffer]
            invoke WriteFile, ebx, [lpBuffer], eax, addr nBytes, 0
            invoke CloseHandle, ebx

.finish:    mov eax, [nBytes]
            ret
endp