Crate clasp_embedded 

CLASP Embedded

Minimal no_std implementation of the standard CLASP binary protocol.

This crate provides both client AND server (mini-router) capabilities for embedded devices like ESP32, Raspberry Pi Pico, etc.

Protocol Compatibility

Uses the same compact binary protocol as the full CLASP implementation. Messages from embedded devices are fully compatible with desktop/cloud routers.

Memory Budget

Component	ESP32 (320KB)	RP2040 (264KB)	Notes
Client	~2KB	~2KB	State cache, subscriptions
Server	~4KB	~4KB	+ session management
Buffers	~1KB	~1KB	TX/RX configurable

Features

• alloc - Enable heap allocation for dynamic strings (recommended for ESP32)
• server - Enable mini-router/server mode
• client - Enable client mode (default)

Modules

msg

Message type codes (standard CLASP binary format)

val

Value type codes (standard CLASP binary format)

Structs

CacheEntry

A cached parameter entry

Client

Embedded CLASP client (compact binary protocol)

StateCache

Fixed-size parameter cache

Enums

ClientState

Client state

Message

Decoded message (zero-copy where possible)

Value

Simple value type for embedded (core types, no allocation needed)

Constants

FLAGS_BINARY

Frame flags for compact binary encoding Bits: [qos:2][has_ts:1][enc:1][cmp:1][rsv:1][version:2]

HEADER_SIZE

Frame header size (without timestamp)

MAGIC

Protocol magic byte

MAX_ADDRESS_LEN

Maximum address length

MAX_CACHE_ENTRIES

Maximum cached parameters

MAX_PAYLOAD

Maximum payload for embedded (configurable, smaller than full 65535)

RX_BUF_SIZE

TX_BUF_SIZE

Buffer size for messages

VERSION

Protocol version (used in HELLO messages)

Functions

decode_header

Decode frame header, returns (flags, payload_len) or None

decode_message

Decode a message from a frame payload

decode_string

Decode a string, returns (str slice, bytes consumed)

decode_value

Decode a value, returns (value, bytes_consumed) Note: For String/Bytes types, use decode_value_ext with alloc feature

encode_header

Encode frame header with binary encoding flags

encode_hello

Encode a HELLO message (binary format) Format: msg_type(1) + version(1) + features(1) + name + token

encode_hello_frame

Encode a HELLO frame

encode_ping_frame

Encode a PING frame

encode_pong_frame

Encode a PONG frame

encode_set

Encode a SET message payload (without frame header) Format: msg_type(1) + flags(1) + addr_len(2) + addr + value_data Flags: [has_rev:1][lock:1][unlock:1][has_ttl:1][vtype:4]

encode_set_frame

Encode a complete SET frame (header + payload)

encode_string

Encode a string (u16 length prefix)

encode_subscribe

Encode a SUBSCRIBE message Format: msg_type(1) + id(4) + pattern + type_mask(1) + opt_flags(1)

encode_subscribe_frame

Encode a SUBSCRIBE frame

encode_value

Encode a value, returns bytes written