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Special Forums Hardware Filesystems, Disks and Memory How does memory mapping work? Post 302517269 by Corona688 on Tuesday 26th of April 2011 10:05:17 AM
Old 04-26-2011
One of those refuses to load, and the other is in some odd computing language I've never seen before.

How about this?

To start you off:

Code:
char *mem;
int fd=open("filename", O_RDWR|O_CREAT, 0666); // Create the file
ftruncate(fd, getpagesize()); // Extend it to the length of the page size, probably 4K

// Map the file(MAP_SHARED) into memory with read and write permissions, at any available address(i.e. NULL)
mem=mmap(NULL, getpagesize(), PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0L);
if(mem == MAP_FAILED) // Failure doesnot mean null!
{
        perror("Couldn't mmap");
        return(1);
}

// Fill file with Z's
memset(mem, 'Z', getpagesize());

This User Gave Thanks to Corona688 For This Post:
 

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getpagesize(3C)                                            Standard C Library Functions                                            getpagesize(3C)

NAME
getpagesize - get system page size SYNOPSIS
#include <unistd.h> int getpagesize(void); DESCRIPTION
The getpagesize() function returns the number of bytes in a page. Page granularity is the granularity of many of the memory management calls. The page size is a system page size and need not be the same as the underlying hardware page size. The getpagesize() function is equivalent to sysconf(_SC_PAGE_SIZE) and sysconf(_SC_PAGESIZE). See sysconf(3C). RETURN VALUES
The getpagesize() function returns the current page size. ERRORS
No errors are defined. USAGE
The value returned by getpagesize() need not be the minimum value that malloc(3C) can allocate. Moreover, the application cannot assume that an object of this size can be allocated with malloc(). ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ SEE ALSO
pagesize(1), brk(2), getrlimit(2), mmap(2), mprotect(2), munmap(2), malloc(3C), msync(3C), sysconf(3C), attributes(5) SunOS 5.10 27 Jun 2000 getpagesize(3C)
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