Add example using std::io::Write

[RandomInsano]

Help users learn how to directly write data to an object implementing std::io::Write.

Doing some tests with 1,000 counters:

• Directly to a String: 454KB of RAM
• Directly to a file: 305KB of RAM

Closes out #258

[RandomInsano]

For the testing, I used heaptrack on Linux and read the "peak heap memory consumption" value. One one test of each was done.

[mxinden]

Great. Small comment. Otherwise looks good to me. Thanks for the help!

[mxinden]

Suggested change

	pub struct IoWriterWrapper<W>(W)
	where
	W: Write;
	pub struct IoWriterWrapper<W>(W);

Is the bound needed in the struct definition? It should only be needed in the std::fmt::Write implementation below.

[mxinden]

I would assume a module comment would be more appropriate. Feel free to ignore.

Suggested change

	/// Example showing how one could write to a file or socket instead of a string.
	/// For large metrics registries this will be more memory efficient
	//! Example showing how one could write to a file or socket instead of a string.
	//! For large metrics registries this will be more memory efficient.

[mxinden]

Please address the CI failures.

[RandomInsano]

Thanks all! I’m happy with whatever changes were needed.

[mxinden]

@RandomInsano just to avoid any confusion, you would need to make the above changes and then push another commit or amend your existing commit. Of course, there is no rush.

[RandomInsano]

Thanks for the clarification! Code is pushed now. Verified the code still compiles and the assert still passes.

[RandomInsano]

Missed the DCO failure. Decided to squash and force a new commit.

[mxinden]

Well done. Thanks.