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memory mapped files

Started by Austrian Coder Sep 4, 2003 at 4:55 AM 1 replies 1k views

Original Post

Sep 4, 2003 at 4:55 AM

Hi! I am tring to do the following: Open a file, map it to memory and print the content to the console. Sounds easy.... Here my try:

m_hFile = CreateFile(Archivname, GENERIC_READ | GENERIC_WRITE, 0, NULL,  OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);

// could not open file

if (m_hFile == INVALID_HANDLE_VALUE)
{
	return false;
}

	
// create file mapping

m_hMapFile = CreateFileMapping(m_hFile, NULL, PAGE_READWRITE, 0, 0, NULL);

if (m_hMapFile == NULL) 
{
	return false;
}  

// create view of file

m_lpMapAddress = MapViewOfFile(m_hMapFile, FILE_MAP_ALL_ACCESS, 0, 0, 0);

if (m_lpMapAddress == NULL) 
{
	return false;
}

// write the content of the file

cout << (char*)m_lpMapAddress << endl;

HANDLE		m_hMapFile;           // handle for the test file''s memory-mapped region

HANDLE		m_hFile;              // the file handle

LPVOID		m_lpMapAddress;       // pointer to the base address of the memory-mapped region

Whats wrong? Is there a good tutorial out in the net? I have found this one: http://www.flipcode.com/tutorials/tut_filemapping.shtml But i only discuss how to open, map and clode files... Thanks, Christian

Kippesoep

Sep 4, 2003 at 5:13 AM

That should work fine. However, since the file will most likely not have a trailing 0 byte, it won''t know when to stop writing the contents to the screen.

Austrian Coder

Author

Austrian Coder

Sep 4, 2003 at 5:36 AM

Ok... i have fixed that now, i hope.


m_hFile = CreateFile(Archivname, GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);

// could not open file

if (m_hFile == INVALID_HANDLE_VALUE)
{
	return false;
}

DWORD maxLen = GetFileSize(m_hFile, NULL);

// create file mapping

m_hMapFile = CreateFileMapping(m_hFile, NULL, PAGE_READWRITE, 0, maxLen, NULL);

if (m_hMapFile == NULL) 
{
	return false;
}  

// create view of file

m_lpMapAddress = MapViewOfFile(m_hMapFile, FILE_MAP_ALL_ACCESS, 0, 0, 0);

if (m_lpMapAddress == NULL) 
{
	return false;
}

cout << (char*)m_lpMapAddress << endl;

And it works... it prints test into the console

[edited by - Austrian Coder on September 4, 2003 6:44:38 AM]

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