What is memory-mapped file in C#?
A memory-mapped file is a feature of the Windows operating system which allows memory to be shared between two or more processes running on the same machine. It requires much less overhead than other methods of inter-process communication such as remoting or WCF.
How does MMAP file work?
mmap works by manipulating your process’s page table, a data structure your CPU uses to map address spaces. The CPU will translate “virtual” addresses to “physical” ones, and does so according to the page table set up by your kernel. When you access the mapped memory for the first time, your CPU generates a page fault.
Which of the following is a suitable use case for memory mapped files?
Another common use for memory-mapped files is to share memory between multiple processes. In modern protected mode operating systems, processes are generally not permitted to access memory space that is allocated for use by another process.
What is memory-mapped IO technique?
Memory mapped I/O is an interfacing technique in which memory related instructions are used for data transfer and the device is identified by a 16-bit address. In this type, the I/O devices are treated as memory locations. The control signals used are MEMR and MEMW.
How is memory-mapped?
Memory-mapping is a mechanism that maps a portion of a file, or an entire file, on disk to a range of addresses within an application’s address space. The application can then access files on disk in the same way it accesses dynamic memory.
How to read a memory mapped file as a stream?
Think to a memory mapped file as a “file” that -instead been stored outside the processing unit- is stored in-sync in memory. It has the advantage to be visible as a raw memory buffer being a file. If you want to read it as a stream, the simplest way is probably using a istringstream that has that raw buffer as the place to read from.
What is a memory-mapped file?
This mapping between a file and memory space enables an application, including multiple processes, to modify the file by reading and writing directly to the memory. You can use managed code to access memory-mapped files in the same way that native Windows functions access memory-mapped files, as described in Managing Memory-Mapped Files.
How do I map multiple processes to the same memory-mapped file?
Processes can map to the same memory-mapped file by using a common name that is assigned by the process that created the file. To work with a memory-mapped file, you must create a view of the entire memory-mapped file or a part of it. You can also create multiple views to the same part of the memory-mapped file, thereby creating concurrent memory.
What happens when a process writes to a memory-mapped file?
Process C opens the memory-mapped file and writes a value to it. Process A reads and displays the values from the memory-mapped file. After Process A is finished with the memory-mapped file, the file is immediately reclaimed by garbage collection. Compile the applications and open three Command Prompt windows.