Interned strings

Important

The design and implementation chapter is outdated

Let’s ignore timestamps for now and also ignore how access to the global logger is synchronized. This is the simplest case: logging a string literal with no formatting.

#![allow(unused)]
fn main() {
extern crate defmt;
defmt::info!("Hello, world!");
}

As we saw in the previous section this string will get interned. Interning converts the string into a usize index. This usize index will be further compressed using LEB128. Some examples: (values on the right are u8 arrays)

• 1usize -> [1]
• 127usize -> [127]
• 128usize -> [128, 1]
• 255usize -> [255, 1]

Because string indices start at zero and it’s unlikely that a program will intern more than 2^14 strings string literals will be serialized as 1 or 2 bytes indices.