Usefulness of bool* in C#

Question

Can I use bool* in any kind of meaningful way. How would I convert bool* to a byte for instance, or store bool* in a byte

My goal is to manage my own memory in a project of mine, the specifics aren't important, just something id like to do. Now I would like to be able to store my own variables, and i happen to need to store a boolean value. How can i, using unsafe and a byte*, store this boolean value, and utilize my space best? Ideally to store 4 bits in the byte.

Answer 1

You can only use it in an unchecked code block.

unchecked
{

}

Which means the code u write in there won't be safe.

Why do you need to use bool* anyway ? Maybe there's someway around it...

Answer 2

In C# you wouldn't normally use a bool*, which is something you can only use in unsafe code (which brings forth a whole lot of other stuff like pinning objects and so forth). A bool* would be a pointer to a boolean. A pointer is 4 bytes long and cannot be converted to a byte without loss.

Why would you want to do this and where do you encounter this? Normally, there's not easily a use case for using pointers in C# unless you have a very specific demand (i.e., an API call, but that you can solve using P/Invoke).

EDIT: (because you edited your q.)

The following code snippet shows you how to get the address of a boolean variable and how to convert that pointer to an int (converting to byte is not possible, we need four bytes).

unsafe
{
    // get pointer to boolean
    bool* boolptr = &mybool;                

    // get the int ptr (not necessary though, but makes following easier)
    int* intptr = (int*)boolptr;

    // get value the pointer is pointing at
    int myint = *intptr;

    // get the address as a normal integer
    int myptraddress = (int) intptr;
}

you say "ideally store 4 bits in a byte". Unless you have a 4-bits machine architecture, I'd strongly advice against it because it will make retrieving and storing the booleans very slow. But more importantly: you are talking C# here, not C++. C# is bound to the CLR which states that a boolean is stored as a byte and that each memory address is four bytes long in 32 bits architectures, which means pointers are four bytes long. Hence, your question, converting a bool* (pointer to a bool) to something else can only be converted into an integer or other datatype that is four bytes wide.

A tip: using flags you can utilize space best: this makes enum types take up a bit for each flag, which gives you eight booleans for each byte.

Answer 3

You can store a boolean in a char if you do some converting with simple if-else statements

        byte b = ConvertBoolToByte(true);
        Console.WriteLine(b);

where

        private byte ConvertBoolToByte(Boolean boolean)
        {
            if (boolean)
                return 1;
            else
                return 0;
        }