Thread: File Acess under Windows (Using MSVC++ 6)

If you are using VC++, you can use the file mapping apis......they map a filoe into a contiguous area of memory (just like when loading an exe or dll)

Create a file called MyFile.txt, Write "Hello World" into it and save it....the run this prog in the same directory...it will map the file.....copy its contents from 1 memory loaction to another, and then change the mapped memory - this change will be reflected in the file when you quit the program

Code:

#include <windows.h>

int main()
{
	HANDLE hFile = CreateFile("MyFile.txt",
		GENERIC_READ  | GENERIC_WRITE,0,0,
		OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,0);
	if(hFile != INVALID_HANDLE_VALUE)
	{
		HANDLE hMap = CreateFileMapping(hFile,0,PAGE_READWRITE,0,0,0);
		if(hMap != 0)
		{
			char* Buff = static_cast<char*>(MapViewOfFile(hMap,
				FILE_MAP_ALL_ACCESS,0,0,0));
			if(Buff != 0)
			{
				DWORD Size = GetFileSize(hFile,0);
				if(Size != 0xFFFFFFFF)
				{
					char* String = new char[Size+1];
					if(String != 0)
					{
						CopyMemory(String,Buff,Size);
						String[Size] = '\0';
						MessageBox(0,String,"Result",MB_OK);
						Buff[0] = 'M';
						CopyMemory(String,Buff,Size);
						MessageBox(0,String,"On Change",MB_OK);
						delete [] String;
					}
					else
					{
						MessageBox(0,"Unable to alloc space",0,MB_OK);
					}
				}
				else
				{
					MessageBox(0,"Unable to size file",0,MB_OK);
				}

			}
			else
			{
				MessageBox(0,"Unable to map file",0,MB_OK);
			}
			CloseHandle(hMap);
		}
		else
		{
			MessageBox(0,"Unable to open map",0,MB_OK);
		}
		CloseHandle(hFile);
	}
	else
	{
		MessageBox(0,"Unable to open file",0,MB_OK);
	}
	
	return 0;
}

Originally posted by Codeplug
Once you've impressed all your friends with knowledge of memory mapped files under Win32 - you can just read the file into memory using operators/methods like >>, get(), getline(), and read().
Write some code and come back and ask for help if you are still stuck.

gg

He asked a question how to address a file as memory, and I gave an example....what's the problem?

Originally posted by Codeplug
Settle down Fordy....just keying off of

Sorry.....I was a bit snappy.....more coffee needed

fordy is alwsys snappy