Thread: How can I get const from a variable?

What the error message means is that the way you declare your array the compiler needs to know the size at compile time. You need to declare and use what I know as a dynamic array, something along the lines of (code from an other language in an other era so any input is welcome)

Code:

  byte* piBuf;
  piBuf = malloc(pcbNeeded+1);//just in case.
  long cbBuf = pcbNeeded;

As far as I can understand (and please keep in mind my C/C++ skills are probably worst that yours) lpbyte is pointer type variable and the code above should fit perfectly in it use.

Thanks, this worked - but not.
That is, it compiled fine this time but when I ran it, it failed again.
I've tried everything I could think of, verified that size is the size they required (even tried 10000 higher).
I verified all the parameters as best I can and I'm pretty sure they're right.

I get a 0 for a response and can't find a readable error anywhere, including the event log.


The le_printer parameter is a legitimate handle to a printer. I use it in other functions and it works fine. Also, this function does return a number for pcbNeeded.

Code:

typedef unsigned char byte;

byte bufEmpty[2];
long cbBufEmpty = sizeof(bufEmpty);
unsigned long pcbNeeded;
byte *piBuf;
long cbBuf;

GetPrinter((HANDLE *)le_printer, 2, (LPBYTE)bufEmpty, (DWORD)cbBufEmpty, (LPDWORD)pcbNeeded);			
piBuf = malloc(pcbNeeded+10000);//just in case.
cbBuf = pcbNeeded+10000;
			
if(GetPrinter((HANDLE *)le_printer, 2, (LPBYTE)piBuf, (DWORD)cbBuf, (LPDWORD)pcbNeeded) == 0)
{
    //Returns: pi2 failed! Required = 3435973836, Given: 3435973836
    sprintf(sRtn, "pi2 failed! Required = %lu, Given: %lu", pcbNeeded, cbBuf);			
    
}
PRINTER_INFO_2 *pi2 = (PRINTER_INFO_2 *) piBuf;

Don't use HANDLE*. It's just HANDLE, which I assume is what le_printer is anyway. And it looks like the structure is a fixed size, so try this simplification:

Code:

PRINTER_INFO_2 pi2;
DWORD cb;
if (GetPrinter(le_printer, 2, (LPBYTE)&pi2, sizeof pi2, &cb) == 0) {
    // does control reach here???
}

try this function to see what really goes wrong.

Code:

#include <windows.h>

TCHAR* GetLastErrorMessage(){
  DWORD   dwLastError = GetLastError();
  TCHAR*   lpBuffer =  (TCHAR*) malloc(sizeof(TCHAR)*1024);
  if(dwLastError != 0)    // Don't want to see a "operation done successfully" error ;-)
      FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM,                 // It/s a system error
                       NULL,                                      // No string to be formatted needed
                       dwLastError,                               // Hey Windows: Please explain this error!
                       MAKELANGID(LANG_NEUTRAL,SUBLANG_DEFAULT),  // Do it in the standard language
                       lpBuffer,              // Put the message here
                       sizeof(TChar)*1020,                     // Number of bytes to store the message
                       NULL);
  return lpBuffer;
}

I have not tested it yet, my current projects are windows agnostic and I can't test it fast I based the code at Retrieving the Last-Error Code (Windows) So I'm guessing that it should work unless I did something wrong.

Thanks guys but neither answer worked.
Both compiled but the first just returned that it failed.
YES - the control ends up inside the if that checks for 0.

The GetLastErrorMessage just threw the browser into the Web servers 'there's a problem' page.

Originally Posted by MAtkins

Thanks guys but neither answer worked.
Both compiled but the first just returned that it failed.
YES - the control ends up inside the if that checks for 0.

The GetLastErrorMessage just threw the browser into the Web servers 'there's a problem' page.

What type is le_printer? Where did you get it? Are you sure it's correct?

You've sprint'ed something into the variable sRtn. Can you view it's contents somewhere? Try putting the value of GetLastError into it as well. What's the value?

Code:

sprintf(sRtn, "error code: %u", GetLastError());

Look up the error code here: System Error Codes (Windows)

le_printer is an int. It's declared above all the functions used.
static int le_printer;

le_printer definitely equates to a valid printer handle, it's used throughout the app successfully.

I tried this and it still just pulls up the "HTTP Error 500.0 - Internal Server Error" and won't give me any valid information about the error.

Code:

PRINTER_INFO_2 pi2;
DWORD cb;
if (GetPrinter(le_printer, 2, (LPBYTE)&pi2, sizeof pi2, &cb) == 0) 
{
    // does control reach here???
    sprintf(sRtn, "error code: %u", GetLastError());
    RETURN_STRING(sRtn); //zend (php7) code that returns the error to the Web page
}

Try printing to a file:

Code:

FILE *f = fopen("somefile.txt", "w");  // put a full file path to some place you can write to and find
fprintf(f, "error code: %u\n", GetLastError());
fclose(f);

Originally Posted by Salem

So why is it so hard to make it a HANDLE* ?
Have you verified that HANDLE* and int are indeed the same size on your machine.

It should just be HANDLE, not HANDLE*. A HANDLE is actually a void* (or in windows terminology, a PVOID).
I'd like to know where le_printer came from and why it's an int.

OK, this much works fine.
As you can see the le_printer is filled from a Zend 'resource'.
It comes from an argument in the function call and le_printer is set to the argument.
If it doesn't work this function fails when trying to retrieve the printer. It doesn't fail and I use it to open a printer and to list printer fonts with no problem.

It returns
"Got printer"

Code:

zval *arg1;			
printer *resource;

byte bufEmpty[2];
long cbBufEmpty = sizeof(bufEmpty);
unsigned long pcbNeeded;
byte *piBuf;
long cbBuf;
long nNumRtnBytes;
char arCapabilities[2500];
char sErr;
char sRtn;

if( zend_get_parameters_ex(1, &arg1) == FAILURE )
{
    WRONG_PARAM_COUNT;
}

if ((resource = (printer *)zend_fetch_resource_ex(arg1, "Printer Handle", le_printer)) == NULL) 
{
    RETURN_STRING("Didn't get printer");
}

//sprintf(sRtn, "le_printer: %u", le_printer);
RETURN_STRING("Got printer");

sRtn needs to be a char array, not just a single char. Try char sRtn[250]. You should've received a compiler warning about that. And the return should be RETURN_STRING(sRtn, 1). The 1 means to make a copy of the string.

You still haven't explained where le_printer comes from. Nothing in the code you've shown is setting it. If it's just an int then you probably can't cast it to a HANDLE and expect it to work.

In your post #3, if you initialized pcbNeeded to 0 you probably wouldn't see such a ridiculous number. I.e., the function is probably failing because of a bad HANDLE and not setting pcbNeeded at all, so you're just seeing the random uninitialized value it contained.

Originally Posted by algorism

You still haven't explained where le_printer comes from.

OK, this is lengthy.
Here's the func that opens the printer based on its name and returns the handle to php:

Code:

PHP_FUNCTION(printer_open)
{
zval *arg1;
printer *resource;

int argc = ZEND_NUM_ARGS();

resource = (printer *)emalloc(sizeof(printer));
resource->dmModifiedFields = 0;

if( argc == 1 && zend_get_parameters_ex(1, &arg1) != FAILURE ) {
	convert_to_string_ex(arg1);
	resource->name = Z_STRVAL_P(arg1);
}
else if( argc == 0 ) {
	resource->name = PRINTER7_G(default_printer);
}
else {
	WRONG_PARAM_COUNT;
}

if (OpenPrinter(resource->name, &resource->handle, NULL) != 0) {
	resource->pi2 = (PRINTER_INFO_2 *)emalloc(sizeof(PRINTER_INFO_2));
	resource->pi2->pDevMode = (DEVMODE *)emalloc(DocumentProperties(NULL, NULL, resource->name, NULL, NULL, 0));
	if (DocumentProperties(NULL, resource->handle, resource->name, resource->pi2->pDevMode, NULL, DM_OUT_BUFFER) == IDOK) {
		resource->info.lpszDocName	= estrdup("PHP generated Document");
		resource->info.lpszOutput	= NULL;
		resource->info.lpszDatatype = estrdup("TEXT");
		resource->info.fwType		= 0;
		resource->info.cbSize		= sizeof(resource->info);
		resource->dc = CreateDC(NULL, resource->name, NULL, resource->pi2->pDevMode);
		RETURN_RES(zend_register_resource(resource, le_printer));
	}
}
else {
	php_error_docref(NULL TSRMLS_CC, E_WARNING, "couldn't connect to the printer [%s]", resource->name);
	RETURN_FALSE;
}
}

Here's the php that retrieves the handle from the above function and then uses the handle returned to call printer_get_papersources which is the function we've been working on:

Code:

$hndlPrinter = printer_open($PrinterName);
$sRtn = printer_get_papersources($hndlPrinter);

I use the printer_open with success to print basic text and (as you know) to list the printer's fonts.

Originally Posted by Salem

>Have you verified that HANDLE* and int are indeed the same size on your machine.

The type is provided above, in my original post. The HANDLE type is actually a void & Microsoft claims that it is 'A handle to an object.' typed from Microsoft's PVOID which is typed as VOID.
This has to work on any machine 2013+.