Write string data to MemoryMappedFile
Solution 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));
Solution 2
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));
Solution 3
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.
Comments
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kevp almost 2 years
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 out on the other side. The tutorial says to use byte array. Forgive me I am new to this and trying on my own first.
Thanks, Kevin
##Write to mapped file using System; using System.IO.MemoryMappedFiles; class Program1 { static void Main() { // create a memory-mapped file of length 1000 bytes and give it a 'map name' of 'test' MemoryMappedFile mmf = MemoryMappedFile.CreateNew("test", 1000); // write an integer value of 42 to this file at position 500 MemoryMappedViewAccessor accessor = mmf.CreateViewAccessor(); accessor.Write(500, 42); Console.WriteLine("Memory-mapped file created!"); Console.ReadLine(); // pause till enter key is pressed // dispose of the memory-mapped file object and its accessor accessor.Dispose(); mmf.Dispose(); } } ##read from mapped file using System; using System.IO.MemoryMappedFiles; class Program2 { static void Main() { // open the memory-mapped with a 'map name' of 'test' MemoryMappedFile mmf = MemoryMappedFile.OpenExisting("test"); // read the integer value at position 500 MemoryMappedViewAccessor accessor = mmf.CreateViewAccessor(); int value = accessor.ReadInt32(500); // print it to the console Console.WriteLine("The answer is {0}", value); // dispose of the memory-mapped file object and its accessor accessor.Dispose(); mmf.Dispose(); } }