I am using WriteFile function for writting some data to harddisk.
Is there any limit in size of data it can write.
Basically this function is writting imcomplete data.
I checked the contents of file. ( Writs encoded data to file then
decode the data using Winzip ( MIME data )
no of Bytes are at boundries like : fff, 9fff, ffff ...
Any idea why this is hapening ?
I'm not sure if there is a limit, or how to find out.
Are you checking the parameter that tells the number of bytes written to see
if it equals the number of bytes to write? Perhaps you can just keep calling
WriteFile...WriteFile and ERROR_INSUFFICIENT_BUFFER
I'm using the WriteFileEx function to write a file asynchronously.
However I sometimes get the error code ERROR_INSUFFICIENT_BUFFER (with
GetLastError), although the function still returns a success and the
data gets written ok. However I don't think it is actually doing an
I open the file with a call to CreateFile, with the flags:
FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED | FILE_FLAG_NO_BUFFERING
To satisfy the No buffering, I use VirtualAlloc and make sure
source/dest and size values are all aligned to sector sizes. That bit
Also, if I try...WriteFile need help,
Can some one explaint to me why is my output file print out garbage string,
event I print BOM at the begining of the file? Did I miss something?
Tue Feb 07 15:22:02 2006 Testing log file 1.
hFile = CreateFile(szDirectory, GENERIC_WRITE, FILE_SHARE_WRITE, NULL,
CREATE_NEW, FILE_ATTRIBUTE_NORMAL, NULL);
if (NULL != hFile && INVALID_HANDLE_VALUE != hFile)
SetFilePointer(hFile, 0, NULL, FILE_BEGIN);
WriteFile(hFile, &BOM, sizeof(BOM), &cBytes, NULL);
void WriteToFile(wchar_t* p_...Is there a solution for writefile fails in vista
I was trying to write from starting sector of the harddisk through writefile
function, In vista WriteFile() function fails(Access denied) due to security
methods in vista and server 2008. Is there a solution for this ???
There are better Vista programmers here than me, but I think you either need
Elevate your program to a status that allows this function
Have your user run as an administrator account to do this kind of advanced
Some things to try anyway.
"StudioX" <StudioX@discussions.microsoft.com> wrote in message
news:3837A5AB-2FF...ReadFile & WriteFile Problem?
I need to read/write on raw disk drive and it works.
After many trials, I found a little bit strange thing.
The API ReadFile and WriteFlle read/write datas only from sector size
I don't know why it should do like that.
Following is my code.
void readBytes ( void *readBuf, long bytesToMove, long bytesToRead)
int ret = SetFilePointer (diskHandle, bytesToMove, NULL, FILE_BEGIN);
unsigned long bytesRead;
BOOL result = ReadFile ( diskHandle, readBuf, bytesToRead, &bytesRead
printf("read %d bytes!!\n", bytesRead);
long by...WriteFile(), LPT, and spooler
I can open an LPT port with CreateFile() and then write data to that port
with WriteFile(). However, one of my test ports has a spooler attached to
it so sometimes when I write data to it the spooler holds the data and
doesn't squirt the data out of the port. So this brings up 2 questions:
1) When I open a parallel port with CreateFile() is there a reliable way to
determine if a spooler is attached to the LPT? BTW, I tried using
"\\\\.\\NONSPOOLED_LPT1" as the port name and GetLastError() gave me an
error code 2 ("The system cannot find the file specified.").
2) ...serial WriteFile hangs
I need to get an old Win98 program running on WinXP.
The program works on Win98, but hangs in WriteFile to COM port on Windows-XP.
The Visual-C++ program remote controls an embedded board through serial port.
> I need to get an old Win98 program running on WinXP.
> The program works on Win98, but hangs in WriteFile to COM port on Windows-XP.
> The Visual-C++ program remote controls an embedded board through serial port.
> Any ideas?
There is something wrong with the program. Done properly, the same code
should work on Win98 and XP. ...WriteFile function hangs!
I am printing something through the LPT using the API WriteFile. This is
working fine when the printer is connected to the system.But if the printer
is not connected then it hangs!! When debugged it found that the program
hangs in WriteFile function. Its not coming out from that function!! How to
solve it? Pls help...
It may just be trying to write all of the characters and waiting for each to
time out since the printer is not there. You may want to check for access
to the printer perhaps by trying to write a single innocuous control
character to the printer first (ba...printing to parallel port with writefile
I was wondering if someone might be able to tell me how to use writefile
to send a string of text to a parallel printer. The text is special IPL
printer codes for a barcode printer so it has to be sent directly to a
printer. I have used the system command() though with mixed results in
Visual C++ and windows. I am used to programming in DOS where all I had
to do was send a file to a printer using the copy command like: "copy
227-029.fmt lpt1" or "copy 227-029.fmt com1" (after setting up the com
port with another system command.
Even so I would like to know how to...CString UNICODE WriteFile problem...
I am trying to send command to a manchine via serial port.
I have created a serial port class called as CSerPort,and it has a function
SendString() as below. My problem is here that when i try to send a string
,such as "AT+X", via this function,the machine does not respond. If i write
the command directly to the WriteFile function as a parameter;
if( (WriteFile(hCOMx,"AT+X",sCommand.GetLength(),&wWrittenBytes, NULL)) ==
then it responds properly.
I have an ASCII version of this class and it works very well. I tried to
assign the sComma...WriteFile, insert data in the middle of the file.
What I want to do is to insert data (not overwrite existing data) in the
middle of a big file. Does WriteFile( ) have this option?
If there's no way to insert data in the middle, I guess I have to read out
all the data from the insertion point, and append my new data, and write them
back to the file? Isn't this too inefficient? Anybody knows how OS handles
this kind of "insert in the middle" scenario?
Thank you, I appreciate your opinion.
Well you answered your own question. There is no way to write to the middle
of the file without overwriting what's ...Question on how to monitor spool status with WriteFile
I'm sending a file to the parallel port using CreateFile() and WriteFile().
The whole file is immediately being sent to the spooler however it takes
some time for the data to be completely sent to the printer. Is there a way
to monitor the status on this spool job from my program so that I can take
some action when the job is complete?
Take a look at EnumJobs and GetJob function. Using these two functions you
can get the status of the print jobs for a particular printer.
"mao" <NoSpam> wrote in message
> ...how to work writefile function with Microsoft Word
If we write any DOC file using MS Word i think we need
above functions.... Can anyone tell me what happned between WriteFile
& closefile functions.
if i hook WriteFile function & im using it like::::
BOOL WINAPI _WriteFile(
HANDLE hFile, // handle to file to write
LPCVOID lpBuffer, // pointer to
data to write to file
DWORD nNumberOfBytesToWrite, // number of bytes to write
LPDWORD lpNumberOfBytesWritten, // pointer to number of bytes..."ERROR_INVALID_PARAMETER": ReadFile() and WriteFile()
I am writing a program that connects to a serial port and writes data. I
follow the guides from MSDN and I use ReadFile() and WriteFile() to do data
I/O. The port is opened in non-overlapped I/O mode. But whenever I call
ReadFile() or WriteFile(), it returns error number 87, and when I look that
up, it is the ERROR_INVALID_PARAMETER.
So I made sure that everything was okay. The buffer I pass to those
functions is actually allocated and okay, and the variables for how many
bytes to read/write, and the lpdword for how bytes were actually read/written
are okay as well. And the over...ReadFile then WriteFile to Console without the line breaks,...
well, this sound a little strange to ask such a "simple" question,
but i would like tho hear someone with a good recommendation
on this. I integrated a little "dum file content as hex" into my console
application but whever the console output finds a line break it does
what a line break is meant to do: goes to teh next line. But how do i
i have two columns(10:10): One for the Hex Data and the other for
the plain file content. You can imagine what happens, when the console
reaches a line break inside a file a prints it out to the std output, which
the breaks the line t...WriteFile access error on UMDF USB driver
I am creating a driver based on the UMDF FX2_driver sample. My device
differs in that it has one input and one output interrupt endpoint. Also am
providing a symbolic name. I have a test application I would like to use
with this driver/device that uses WriteFile to send data to the driver. I am
able to verify thru tracing and a line trace that the data from the WriteFile
is being received by the driver and passed on to the usb device. However,
the WriteFile fails with a GetLastError() of 1117 (ERROR_IO_DEVICE). Need to
determine why I am getting this error.
ricobandito &l...Calling Response to WriteFile and also update page problem
I have a VB.net app the sends an Excel file to the browser and it also need
to hide some fields on the form at the same time. But the form is not hiding
the controlls. The "Open/Save/Cancel" diaolog opens on the browser but the
page stays the same, the controls are not hidden. Below is a sample of the
code I'm using to send the file to the browser and hide the controls. What
am I doing wrong?
Sub SendReport(ByRef SaveFile As String)
tblMessage.Visible = False
lblMessage.Text = ""
'Response.Clos...WriteFile doesn't send data to LPT1 until CloseHandle is called
Please, forgive me for posting twice, didn't really know where this
question should really go to, nor where could I get an answer.
My program tries to send data directly to the parallel port to a
printer, code lies at the end. In short it does this:
First opens with CreateFile the device "\\.\\LPT1" as read/write in a
non-overlapped mode, next sends a string to the printer on the other
side, finally waits for the user to enter any string to close handle
I've noted with the aid of sniffers (http://www.sysinternals.com) that
WriteFile doesn't ...