Hello,
I have problems when trying to read files with MapViewOfFile API function. Actually I only have problems when I try to read very large file. Here is what I am doing;
long offsetHight = 0;
long offsetLow = 0;
long positionAdjustment = 0;
int startpointer;
NativeMethods.SYSTEM_INFO syInfo = new NativeMethods.SYSTEM_INFO(
NativeMethods.GetSystemInf
offSettemp = (100000);
positionAdjustment = (offSettemp % syInfo.dwAllocationGranula
if (positionAdjustment != 0)
offSettemp = offSettemp - positionAdjustment;
offsetHight = ((offSettemp >> 32) & 0xFFFFFFFF);
offsetLow = (offSettemp & 0xFFFFFFFF);
IntPtr mapFile = NativeMethods.CreateFileMa
IntPtr viewFile = NativeMethods.MapViewOfFil
Above code returns the value for "viewFile" handle only when I map up to 1.9 GB but when I try to set the offset at (i.e 10 milion) the file handle always return zero and GetLastError is 8 ERROR_NOT_ENOUGH_MEMORY
Please advice....
Please advice.....
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As far as I know you can't buy a PC with memory > 4GB. That might be different on main frames or clusters but in any case you would need a 64bit operation system and - tell me if I am wrong - even 64bit Windows only runs on x86 hardware (PC).
So, as memory mapped files are loaded to the memory, I see no way to load a file > 4GB.
Regards, Alex
In your call to 'CresteFileMapping()', specify that small segment (or multiples of it) as the mapping object size. Using '0' here means a mapping object of the size of the whole fuile. E.g. like
IntPtr mapFile = NativeMethods.CreateFileMa
Hello jrk,
It does not work result is agian 0 (zero).....This is what I did;
IntPtr mapFile = NativeMethods.CreateFileMa
IntPtr viewFile = NativeMethods.MapViewOfFil
here offsetLow and offsetHight points to the size above 2^32 and if I multiply 8 kb with desirable address then again error(8) is thrown. Simply I want to read last 8KB of file that sizes 45 GB....
Thank you
>>>> Simply I want to read last 8KB of file that sizes 45 GB....
You could try the following though you would need to translate it to managed C++.
- open the file using fstream
- set position to file end - 8kb
#include <iostream>
#include <fstream>
using namespace std;
int main ( )
{
fstream file;
file.open( "huge.dat", ios_base::in);
// set read position
file.seekg( -8192, ios_base::end );
char buffer[8192];
if (file.read(buffer, 8192))
{
// ok
}
Regards, Alex
Several things, in a 32bit system 4gb is the largest addressing range - period. On NT the upper 2gb are reserved for kernal address and the lower for user space. The boundary can only be breached by kernel code running in the context of a user space app. Usermode can not reach into the upper 2 gig..... The VMM will not allow this unless you enable the PAE swith in your boot ini file that will enable 36bit addressing, thus allowing your usermode apps 3gb of virtual addressing. This is why it's returning not enough memory.
Otherwise, migrate too 64bit windows.... Also, IA64 is not based on x86 architecture.
Found this just now:
http://www.brianmadden.com
Just don't map the file.
Ok here is what I am doing;
I have application that is in the process with another running process. The other process open some files exclusively and my application needs to read some data from these files. What I do is; first duplicate the file handle and then map it to the file view and then read the buffer. I can do this until I need to map huge files and then the error is shown. CreateFileMapping function always gives me some handle(IntPtr) but MapViewOfFile does not. Can anybody advice if there is any other way to handle and exctract the buffer from these duplicated file handles?
After some more research it comes that Alex and mugman21 are right about MapViewOfFile? So I will need to accept their advices....
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by: itsmeandnobodyelsePosted on 2007-01-24 at 07:49:48ID: 18386727
>>>> file handle always return zero and GetLastError is 8 ERROR_NOT_ENOUGH_MEMORY
MapViewOfFile creates shared memory which is limited to physical memory as far as I know. Even if it would be virtual memory it is limited to 4GB or the size of the page file - memory already used by Windows, other processes and the current process.
Regards, Alex