MicroStr

A lightweight, stack-allocated string with fixed capacity and UTF-8 support.
Ideal for no_std environments, embedded systems, and performance-critical code.

[dependencies]
microstr = "0.3"

What is MicroStr?

• ✅ No heap allocations — fully stack-based.
• ✅ UTF-8 safe — always valid string content.
• ✅ no_std by default — works without std.
• ✅ Const generic capacity — size known at compile time.
• ✅ Truncation-aware — safely appends strings without overflow.
• ✅ Seamless std integration — supports Display, Debug, From<String>, etc.
• ✅ Optional serde support — JSON (de)serialization with length checking.

Usage

use microstr::MicroStr;

// Create a string with capacity of 16 bytes
let mut s: MicroStr<16> = MicroStr::new();

s.push_str("Hello");
s.push('!');

assert_eq!(s.as_str(), "Hello!");
assert_eq!(s.len(), 6);           // 6 Unicode chars
assert_eq!(s.bytes_len(), 6);     // 6 bytes
assert_eq!(s.push_str(" this won't fit entirely"), Err(10)); // Truncated safely

You can also use it like a regular &str thanks to Deref:

if s.starts_with("Hello") {
    println!("Greeting: {}", s);
}

Cargo Features

Enable optional features in Cargo.toml:

[dependencies]
microstr = { version = "0.3", features = ["std", "serde"] }

Example with serde

#[cfg(feature = "serde")]
{
    let s = microstr!("Hello", 11);
    let json = s.to_json().unwrap();
    assert_eq!(json, r#""hello""#);

    let s2 = MicroStr::from_json(r#""world""#).unwrap();
    assert_eq!(s2, "world");
}

Why MicroStr?

• Predictable performance: No allocations, no heap usage.
• Memory safety: Always valid UTF-8, no buffer overflows.
• Great for constrained environments: Embedded, kernels, WASM.
• Easy migration: Drop-in replacement for String in many cases.
• Macro: Creation via the convenient macro microstr!

Comparison with heapless::String

microstr prioritizes zero-cost truncation and ease of use in embedded contexts.

API Documentation

📚 Full documentation: https://docs.rs/microstr

License

MIT License

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you shall be dual licensed as above, without any additional terms or conditions.