FastLED ↔ Asio Compatibility Layer

FastLED's networking types are designed to be portable to/from Boost.Asio code. This document maps Asio concepts to their FastLED equivalents.

Type Mapping

Asio	FastLED	Header
`boost::asio::ip::tcp::socket`	`fl::asio::ip::tcp::socket`	`fl/stl/asio/ip/tcp.h`
`boost::asio::ip::tcp::acceptor`	`fl::asio::ip::tcp::acceptor`	`fl/stl/asio/ip/tcp.h`
`boost::asio::ip::tcp::endpoint`	`fl::asio::ip::tcp::endpoint`	`fl/stl/asio/ip/tcp.h`
`boost::asio::mutable_buffer`	`fl::span<u8>`	`fl/stl/span.h`
`boost::asio::const_buffer`	`fl::span<const u8>`	`fl/stl/span.h`
`boost::system::error_code`	`fl::asio::error_code`	`fl/stl/asio/error_code.h`
`boost::system::errc`	`fl::asio::errc`	`fl/stl/asio/error_code.h`

Operation Mapping

Asio	FastLED
`io_context::run()`	`AsyncManager::update_all()`
`io_context::poll()`	`async_run()`
`socket.connect(ep)`	`socket.connect(ep)`
`socket.close()`	`socket.close()`
`socket.shutdown()`	`socket.shutdown()`
`read_some(buf, ec)`	`socket.read_some(buf, ec)`
`write_some(buf, ec)`	`socket.write_some(buf, ec)`
`async_read(s, buf, handler)`	`s.async_read_some(buf, handler)`
`async_write(s, buf, handler)`	`s.async_write_some(buf, handler)`
`async_connect(s, ep, handler)`	`s.async_connect(ep, handler)`
`acceptor.open(ep)`	`acceptor.open(port)`
`acceptor.listen(backlog)`	`acceptor.listen(backlog)`
`acceptor.accept(peer)`	`acceptor.accept(peer)`

Completion Handler Signatures

Asio Handler Concept	FastLED Equivalent
`void(error_code, size_t)` (ReadHandler/WriteHandler)	`fl::asio::io_handler`
`void(error_code)` (ConnectHandler/AcceptHandler)	`fl::asio::connect_handler`

Error Handling

cpp

// Asio style — works identically in FastLED
fl::asio::error_code ec;
size_t n = sock.read_some(buffer, ec);
if (ec) {
    // handle error
}

// Check specific errors
if (ec.code == fl::asio::errc::would_block) { ... }
if (ec.code == fl::asio::errc::eof) { ... }

// Convert to/from fl::Error
fl::Error err = ec.to_error();
fl::asio::error_code ec2 = fl::asio::error_code::from_error(err);

What's NOT Ported (By Design)

No io_context — FastLED's AsyncManager + Scheduler fill this role
No completion tokens — Template metaprogramming too heavy for embedded
No strand — FastLED is single-threaded per task
No SSL/TLS — Out of scope
No UDP — TCP only (for now)
No scatter/gather I/O — Single-buffer operations only