Interned strings

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.

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.