Crate rustyasn

RustyASN - ASN.1 Encoding for FIX Protocol

This crate provides Abstract Syntax Notation One (ASN.1) encoding support for the FIX protocol. It supports multiple encoding rules:

• BER (Basic Encoding Rules) - Self-describing, flexible
• DER (Distinguished Encoding Rules) - Canonical subset of BER
• OER (Octet Encoding Rules) - Byte-aligned, efficient

Features

• Zero-copy decoding where possible
• Streaming support for continuous message processing
• Type-safe ASN.1 schema compilation
• Integration with RustyFix field types
• High-performance implementation optimized for low-latency trading

ASN.1 Schema Compilation

This crate uses a custom ASN.1 parser implementation in its build script rather than the standard rasn-compiler crate. This architectural decision was made due to version compatibility issues:

Why Custom Parser?

• Version Incompatibility: The rasn-compiler crate has compatibility issues with rasn 0.18.x, which is used throughout the RustyFix project. Using rasn-compiler would require either downgrading rasn or dealing with breaking API changes.

• FIX-Specific Optimizations: The custom parser is tailored for FIX protocol message structures and generates code that integrates seamlessly with RustyFix’s type system and performance requirements.

• Build Stability: The custom implementation is immune to breaking changes in rasn-compiler updates, ensuring consistent builds across environments.

• Reduced Dependencies: Eliminates rasn-compiler and its transitive dependencies, reducing build complexity and potential security surface.

Supported ASN.1 Features

The custom parser supports the ASN.1 constructs commonly used in FIX protocol extensions:

• SEQUENCE types with optional fields and explicit tags
• ENUMERATED types with explicit discriminant values
• CHOICE types with context-specific tags
• INTEGER types with constraint annotations
• String types (UTF8String, PrintableString, VisibleString, etc.)

Migration Path

Future migration to rasn-compiler will be considered when:

• rasn-compiler achieves stable compatibility with rasn 0.18.x+
• The RustyFix project upgrades to a newer rasn version
• The maintenance burden of the custom parser becomes significant

For complex ASN.1 schemas requiring advanced features not implemented in the custom parser, the build script provides fallback mechanisms and clear error messages.

Usage

use rustyasn::{Config, Encoder, Decoder, EncodingRule};
use rustyfix::Dictionary;
use std::sync::Arc;

fn example() -> Result<(), Box<dyn std::error::Error>> {
    // Configure encoding
    let config = Config::new(EncodingRule::OER);
    let dictionary = Arc::new(Dictionary::fix44()?);

    // Create encoder and decoder
    let encoder = Encoder::new(config.clone(), dictionary.clone());
    let decoder = Decoder::new(config, dictionary);

    // Start encoding a message
    let mut handle = encoder.start_message(
        "D",         // MsgType: NewOrderSingle
        "SENDER",    // SenderCompID
        "TARGET",    // TargetCompID
        1,           // MsgSeqNum
    );

    // Add fields and encode
    handle.add_string(11, "ORDER001");  // ClOrdID
    let encoded = handle.encode()?;

    // Decode the message
    let message = decoder.decode(&encoded)?;
    println!("Decoded message type: {}", message.msg_type());
     
    Ok(())
}

Re-exports

pub use config::Config;

pub use config::EncodingRule;

pub use decoder::Decoder;

pub use decoder::DecoderStreaming;

pub use encoder::Encoder;

pub use encoder::EncoderHandle;

pub use error::DecodeError;

pub use error::EncodeError;

pub use error::Error;

pub use error::Result;

pub use field_types::Asn1Boolean;

pub use field_types::Asn1Bytes;

pub use field_types::Asn1FieldError;

pub use field_types::Asn1Integer;

pub use field_types::Asn1String;

pub use field_types::Asn1UInteger;

pub use generated::Asn1Field;

pub use generated::Asn1FixMessage;

pub use generated::FixFieldTag;

pub use generated::FixMessageType;

pub use message::Message;

pub use message::MessageGroup;

Modules

buffers

Const generic buffer types for optimal performance.

config

Configuration options for ASN.1 encoding and decoding.

decoder

ASN.1 decoder implementation for FIX messages.

encoder

ASN.1 encoder implementation for FIX messages.

error

Error types for ASN.1 encoding and decoding operations.

field_types

ASN.1 field type implementations that integrate with RustyFix FieldType trait.

generated

Generated ASN.1 definitions from FIX dictionaries.

message

ASN.1 message implementation with FieldMap trait support.

schema

ASN.1 schema definitions and FIX message type mappings.

types

ASN.1 type definitions and FIX field mappings.

Constants

FIELD_BUFFER_SIZE

Default buffer size for field serialization (64 bytes)

MAX_HEADER_FIELDS

Maximum number of standard header fields

MEDIUM_FIELD_COLLECTION_SIZE

Size for medium field collections (16 fields)

SMALL_FIELD_COLLECTION_SIZE

Size for small field collections (8 fields)

VERSION

Version information for the ASN.1 encoding implementation

Traits

AsnType

A trait representing any type that can represented in ASN.1.

Decode

A data type that can decoded from any ASN.1 format.

Encode

A data type that can be encoded to a ASN.1 data format.

Derive Macros

AsnType

An automatic derive of the AsnType trait.

Decode

An automatic derive of the Decode trait.

Encode

An automatic derive of the Encode trait.