VirualAlloc and ReadFile
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Yep, you are right. But here with this stuff i got more and more problems. For example, i cannot return bytes from function, (this code is a function, which should read a file into BYTE array and return this array among with nr of bytes read).
BYTE *ReadBytes(HANDLE hDevice, LPDWORD lpdwBytesRead)
{
SIZE_T BASE_BUFFER_SIZE = 512;BYTE \* bInitialBuffer = NULL; bInitialBuffer = (BYTE \*)VirtualAlloc(0, BASE\_BUFFER\_SIZE, MEM\_COMMIT | MEM\_RESERVE, PAGE\_READWRITE); if(bInitialBuffer == NULL) { // handle this shit TRACE("VirtualAlloc failed!"); return NULL; } DWORD dwReadBytes; while (FALSE != ReadFile(hDevice, bInitialBuffer, BASE\_BUFFER\_SIZE, (LPDWORD)&dwReadBytes, 0) && dwReadBytes > 0) { TRACE1("got some buffer! %d", dwReadBytes); lpdwBytesRead += dwReadBytes; } return bInitialBuffer;}
and if i call it:
DWORD read = 0;
BYTE *DataBuffer = ReadBytes(hFile, &read);read is always zero, and i got no bytes returned from function... And i cannot use just defined size (skip memory allocation). Help ;(
011011010110000101100011011010000110100101101110 0110010101110011
One step at a time. Have you progressed from your previous error, or not? With the
MEM_RESERVEflag, do you still get an invalid access error while callingReadFile?"Real men drive manual transmission" - Rajesh.
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Yep, you are right. But here with this stuff i got more and more problems. For example, i cannot return bytes from function, (this code is a function, which should read a file into BYTE array and return this array among with nr of bytes read).
BYTE *ReadBytes(HANDLE hDevice, LPDWORD lpdwBytesRead)
{
SIZE_T BASE_BUFFER_SIZE = 512;BYTE \* bInitialBuffer = NULL; bInitialBuffer = (BYTE \*)VirtualAlloc(0, BASE\_BUFFER\_SIZE, MEM\_COMMIT | MEM\_RESERVE, PAGE\_READWRITE); if(bInitialBuffer == NULL) { // handle this shit TRACE("VirtualAlloc failed!"); return NULL; } DWORD dwReadBytes; while (FALSE != ReadFile(hDevice, bInitialBuffer, BASE\_BUFFER\_SIZE, (LPDWORD)&dwReadBytes, 0) && dwReadBytes > 0) { TRACE1("got some buffer! %d", dwReadBytes); lpdwBytesRead += dwReadBytes; } return bInitialBuffer;}
and if i call it:
DWORD read = 0;
BYTE *DataBuffer = ReadBytes(hFile, &read);read is always zero, and i got no bytes returned from function... And i cannot use just defined size (skip memory allocation). Help ;(
011011010110000101100011011010000110100101101110 0110010101110011
csrss wrote:
i cannot return bytes from function, (this code is a function, which should read a file into BYTE array and return this array among with nr of bytes read).
This has nothing to do with
VirtualAlloc."Real men drive manual transmission" - Rajesh.
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One step at a time. Have you progressed from your previous error, or not? With the
MEM_RESERVEflag, do you still get an invalid access error while callingReadFile?"Real men drive manual transmission" - Rajesh.
At this moment:
while (FALSE != ReadFile(hDevice, bInitialBuffer, BASE_BUFFER_SIZE,
(LPDWORD)&dwReadBytes, 0) && dwReadBytes > 0)
{
TRACE1("got some buffer! %d", dwReadBytes);dwReadBytes contains right value, which is 106 bytes, that is exactly the size of my file (just a text file). Here :
lpdwBytesRead += dwReadBytes;
It tries to append them, but lpdwBytesRead contain some trash, even if it has been initialized outside the function to zero:
DWORD read = 0;
BYTE *DataBuffer = ReadBytes(hFile, &read);When function returns, read is zero and there is no buffer returned :(
011011010110000101100011011010000110100101101110 0110010101110011
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csrss wrote:
i cannot return bytes from function, (this code is a function, which should read a file into BYTE array and return this array among with nr of bytes read).
This has nothing to do with
VirtualAlloc."Real men drive manual transmission" - Rajesh.
I know it is not perfect :P (the code) I have never worked with unsigned type allocation before. (the only proper way for returning unsigned type from function i know is to declare buffer size and make this, BYTE, static) If i pass a pointer to BYTE to this function from calling function, it still returns empty BYTE buffer. I am out of ideas. Somebody, help? :P
011011010110000101100011011010000110100101101110 0110010101110011
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I know it is not perfect :P (the code) I have never worked with unsigned type allocation before. (the only proper way for returning unsigned type from function i know is to declare buffer size and make this, BYTE, static) If i pass a pointer to BYTE to this function from calling function, it still returns empty BYTE buffer. I am out of ideas. Somebody, help? :P
011011010110000101100011011010000110100101101110 0110010101110011
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Yep, you are right. But here with this stuff i got more and more problems. For example, i cannot return bytes from function, (this code is a function, which should read a file into BYTE array and return this array among with nr of bytes read).
BYTE *ReadBytes(HANDLE hDevice, LPDWORD lpdwBytesRead)
{
SIZE_T BASE_BUFFER_SIZE = 512;BYTE \* bInitialBuffer = NULL; bInitialBuffer = (BYTE \*)VirtualAlloc(0, BASE\_BUFFER\_SIZE, MEM\_COMMIT | MEM\_RESERVE, PAGE\_READWRITE); if(bInitialBuffer == NULL) { // handle this shit TRACE("VirtualAlloc failed!"); return NULL; } DWORD dwReadBytes; while (FALSE != ReadFile(hDevice, bInitialBuffer, BASE\_BUFFER\_SIZE, (LPDWORD)&dwReadBytes, 0) && dwReadBytes > 0) { TRACE1("got some buffer! %d", dwReadBytes); lpdwBytesRead += dwReadBytes; } return bInitialBuffer;}
and if i call it:
DWORD read = 0;
BYTE *DataBuffer = ReadBytes(hFile, &read);read is always zero, and i got no bytes returned from function... And i cannot use just defined size (skip memory allocation). Help ;(
011011010110000101100011011010000110100101101110 0110010101110011
csrss wrote:
lpdwBytesRead += dwReadBytes;
This looks suspect. You are incrementing the pointer instead of what the pointer points to. Is that your intent?
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"Some people are making such thorough preparation for rainy days that they aren't enjoying today's sunshine." - William Feather
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At this moment:
while (FALSE != ReadFile(hDevice, bInitialBuffer, BASE_BUFFER_SIZE,
(LPDWORD)&dwReadBytes, 0) && dwReadBytes > 0)
{
TRACE1("got some buffer! %d", dwReadBytes);dwReadBytes contains right value, which is 106 bytes, that is exactly the size of my file (just a text file). Here :
lpdwBytesRead += dwReadBytes;
It tries to append them, but lpdwBytesRead contain some trash, even if it has been initialized outside the function to zero:
DWORD read = 0;
BYTE *DataBuffer = ReadBytes(hFile, &read);When function returns, read is zero and there is no buffer returned :(
011011010110000101100011011010000110100101101110 0110010101110011
This piece of code works (you had trouble bringing the buffer to the calling function, which is resolved here)
#define BASE_BUFFER_SIZE 512
BOOL ReadBytes(HANDLE hFile, PBYTE bInitialBuffer)
{
DWORD dwReadBytes;
while (FALSE != ReadFile(hFile, bInitialBuffer, BASE_BUFFER_SIZE,
(LPDWORD)&dwReadBytes, 0) && dwReadBytes > 0)
{
/*CString str;
str.Format(L"got buffer! %d",dwReadBytes);
AfxMessageBox(str);*/
}
if(dwReadBytes <= 0)
{
return FALSE;
}
return TRUE;
}void CMTest1Dlg::OnBnClickedOk()
{
HANDLE hFile = NULL;hFile = CreateFile(L"C:\\\\temp\\\\myfile.txt", GENERIC\_READ, 0, 0, OPEN\_EXISTING, 0, 0); if(INVALID\_HANDLE\_VALUE == hFile){ AfxMessageBox(L"CreateFile failed"); return; } BYTE \*buffer = NULL; buffer = (BYTE \*)VirtualAlloc(0, BASE\_BUFFER\_SIZE, MEM\_COMMIT | MEM\_RESERVE, PAGE\_READWRITE); if(NULL == buffer) { AfxMessageBox(L"VirtualAlloc failed!"); return; } BOOL bRead = ReadBytes(hFile, buffer); //use buffer here}
"Real men drive manual transmission" - Rajesh.
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I got it!!! YEah!
*lpdwBytesRead += dwReadBytes;
Its just too much on my head, too much...
011011010110000101100011011010000110100101101110 0110010101110011
Everything's good now? :) The piece of code I've given above in my other reply doesn't involve any pointer arithmetic.
"Real men drive manual transmission" - Rajesh.
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Everything's good now? :) The piece of code I've given above in my other reply doesn't involve any pointer arithmetic.
"Real men drive manual transmission" - Rajesh.
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csrss wrote:
lpdwBytesRead += dwReadBytes;
This looks suspect. You are incrementing the pointer instead of what the pointer points to. Is that your intent?
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"Some people are making such thorough preparation for rainy days that they aren't enjoying today's sunshine." - William Feather