BACnet ASN.1 Parser

A lightweight Node.js parser for ASN.1 notation of BACnet data types.

Features

• ✅ Parse ASN.1 definitions of BACnet data types
• ✅ Support for ENUMERATED, SEQUENCE, CHOICE, BIT STRING, OCTET STRING
• ✅ Handle APPLICATION tags and context-specific tags
• ✅ Range and size constraints
• ✅ OPTIONAL fields and extensibility markers
• ✅ Production-ready with comprehensive error handling

Installation

npm install

Usage

Parse ASN.1 Content

import { parse, ParserError } from './src/index.js';

const asn1 = `
BAClibTriState ::= ENUMERATED {
    off (0),
    on (1),
    auto (2)
}
`;

try {
    const definitions = parse(asn1);
    console.log(definitions);
} catch (error) {
    if (error instanceof ParserError) {
        console.error(`Parse error at line ${error.line}: ${error.message}`);
    }
}

Parse ASN.1 File

import { parse } from './src/index.js';
import fs from 'fs';

// Parse ASN.1 content
const asn1Content = fs.readFileSync('input.asn1', 'utf8');
const definitions = parse(asn1Content);

console.log(definitions);

Project Structure

bacnet-asn1-parser/
├── src/
│   └── index.js           # ASN.1 parser implementation
├── tests/
│   ├── invalid-data/      # Invalid ASN.1 test files
│   ├── valid-data/        # Valid ASN.1 test files
│   └── test-suite.js      # Comprehensive test suite
└── README.md

ASN.1 Support

Supported constructs:

• ✅ ENUMERATED types with named values
• ✅ SEQUENCE types with ordered fields
• ✅ CHOICE types with alternative fields
• ✅ BIT STRING with named bits
• ✅ OCTET STRING
• ✅ Type references
• ✅ SEQUENCE OF and SEQUENCE SIZE OF
• ✅ APPLICATION tags
• ✅ Context-specific tags
• ✅ Range constraints (MIN..MAX)
• ✅ Size constraints
• ✅ OPTIONAL fields
• ✅ Extensibility markers (...)

Example input:

BAClibTriState ::= ENUMERATED {
    off (0),
    on (1),
    auto (2)
}

BACnetObjectIdentifier ::= [APPLICATION 12] SEQUENCE {
    object-type [0] BACnetObjectType,
    instance-number [1] Unsigned (0..4194303)
}

Output Format

The parser returns an array of definition objects:

[
  {
    name: 'BAClibTriState',
    type: 'Enumerated',
    items: [
      { name: 'off', number: 0 },
      { name: 'on', number: 1 },
      { name: 'auto', number: 2 }
    ]
  },
  {
    name: 'BACnetObjectIdentifier',
    primitive: 12,
    type: 'SEQUENCE',
    items: [
      { name: 'object-type', number: 0, type: 'BACnetObjectType' },
      { 
        name: 'instance-number', 
        number: 1, 
        type: 'Unsigned',
        range: { min: 0, max: 4194303 }
      }
    ]
  }
]

API Reference

parse(content)

Parse ASN.1 content string and return definitions.

Parameters:

• content (string): ASN.1 notation to parse

Returns: Array of definition objects

Throws: ParserError if parsing fails

ParserError

Custom error class for parsing errors.

Properties:

• message: Error description
• name: 'ParserError'
• line: Line number where error occurred

Testing

Run the comprehensive test suite:

npm test

The test suite includes:

• 26 valid ASN.1 test cases
• 19 invalid ASN.1 test cases
• Detailed HTML test report generation

Use Cases

1. BACnet Protocol Development: Parse standard ASN.1 definitions into structured format
2. Code Generation: Use parsed definitions to generate code in various languages
3. Protocol Analysis: Extract and analyze BACnet type definitions
4. Documentation: Generate documentation from ASN.1 specifications
5. Validation: Verify ASN.1 syntax correctness

License

BSD-2-Clause