Embedded targets and I/O

This page summarizes how the Rust workspace supports no_std, bare-metal style builds, and transport integration.

Feature flags (all library crates)

Feature	Meaning
std (default)	Full standard library; file helpers and std::error::Error impls where applicable.
alloc (default)	Heap types (Vec, String) for cryptographic and protocol buffers.

Disable defaults for bare-metal style builds:

cargo check -p noxtls --no-default-features --features alloc

std-only APIs

When std is disabled, the following are unavailable (use in-memory / slice APIs instead):

Crate	API
noxtls-core	LibraryConfig::from_mbedtls_style_file — use from_mbedtls_style_str with bytes you loaded.
noxtls-x509	pem_file_to_der, pem_file_to_der_blocks, der_to_pem_file, der_to_file.
noxtls	TicketStore::save_to_file, TicketStore::load_from_file.

TLS transport (noxtls)

The transport module defines:

• transport::blocking::BlockingStream — synchronous read/write.
• transport::stream_async::AsyncByteStream — async read/write (uses async_trait(?Send) for embedded-io-async compatibility).

Optional Cargo features on noxtls (forwarded to noxtls-io):

Feature	Purpose
adapter-embedded-io	EmbeddedIoTransport wrapping embedded-io Read + Write.
adapter-embedded-io-async	EmbeddedIoAsyncTransport wrapping embedded-io-async.
adapter-tokio	TokioAsyncTransport for tokio types with AsyncReadExt + AsyncWriteExt (implies std).

Example checks:

cargo check -p noxtls --features adapter-embedded-io
cargo check -p noxtls --features adapter-embedded-io-async
cargo check -p noxtls --features adapter-tokio

Handshake helpers

transport::drive::read_exact_blocking reads a fixed number of bytes through a BlockingStream for framing layers built on top of the protocol state machine.