Crate bitty_write_macro

Size-optimized versions of the standard library’s write! and writeln! macros

Why use these macros?

In code size-constrained systems that perform string formatting, using the write! or writeln! macro can generate larger code than writing the contents directly, even after linking and inlining.

The write! and writeln! macros provided by this crate detect when the write could be optimized as a direct write with write_str (for fmt::Write) or write (for io::Write) and calls that instead of format_args! and write_fmt.

The std feature

By default, this crate is #![no_std] and only supports fmt::Write. To write to io::Write sinks, enable the std feature.

Known drawbacks

These macros:

• Target a write_str method on the trait, using an internal adapter to expose write_str on io::Write.
• Do not currently accept concat! in the format string.
• Do not optimize nested format_args! like write!(w, "{}", format_args!("x")).

Macros

• branch_on_format_capture
  Accepts two macro specifications and a set of format_args! arguments and conditionally expands based on whether the format_args! specifies any arguments to format.
• write
  An optimizing version of core::write! that calls write_str/write when possible.
• writeln
  An optimizing version of core::writeln! that calls write_str/write when possible.