Write string data to MemoryMappedFile

Question

I am following this tutorial here

I am having a hard time figuring out how to get a string \"THIS IS A TEST MESSAGE\" to store in the memory mapped file and then pull it

Answer 1

You can consider writing the length of the string and then the byte[] form of your string.
For example if I would like to write "Hello" then I convert it into bytes:

byte[] Buffer = ASCIIEncoding.ASCII.GetBytes("Hello");

then do following while writing into the memory mapped file.

MemoryMappedFile mmf = MemoryMappedFile.CreateNew("test", 1000);
MemoryMappedViewAccessor accessor = mmf.CreateViewAccessor();
accessor.Write(54, (ushort)Buffer.Length);
accessor.WriteArray(54 + 2, Buffer, 0, Buffer.Length);

While reading first go to position 54 and read 2 bytes holding length of your string. Then you can read an array of that length and convert it into string.

MemoryMappedFile mmf = MemoryMappedFile.CreateNew("test", 1000);
MemoryMappedViewAccessor accessor = mmf.CreateViewAccessor();
ushort Size = accessor.ReadUInt16(54);
byte[] Buffer = new byte[Size];
accessor.ReadArray(54 + 2, Buffer, 0, Buffer.Length); 
MessageBox.Show(ASCIIEncoding.ASCII.GetString(Buffer));

Answer 2

I used this to write the characters of a string:

string contentString = "Hello";
char[] charsToWrite = contentString.ToCharArray();
accessor.WriteArray(0, charsToWrite, 0, charsToWrite.Length);

This wrote wide characters. Both C# and C++ programs were able to read the data as wide characters.

Answer 3

It Works fine with CreateOrOpen instead of CreateNew! With the same code

MemoryMappedFile mmf = MemoryMappedFile.CreateOrOpen("test", 1000);
MemoryMappedViewAccessor accessor = mmf.CreateViewAccessor();
accessor.Write(54, (ushort)Buffer.Length);
accessor.WriteArray(54 + 2, Buffer, 0, Buffer.Length);

and

MemoryMappedFile mmf = MemoryMappedFile.CreateOrOpen("test", 1000);
MemoryMappedViewAccessor accessor = mmf.CreateViewAccessor();
ushort Size = accessor.ReadUInt16(54);
byte[] Buffer = new byte[Size];
accessor.ReadArray(54 + 2, Buffer, 0, Buffer.Length); 
MessageBox.Show(ASCIIEncoding.ASCII.GetString(Buffer));