TLV-for-Everyone

A small, Python-based BER-TLV (Tag-Length-Value) parser and encoder, designed for EMV and smartcard-style data structures.
It supports:

• Parsing TLV streams into a tree structure
• Constructed vs primitive tags
• Long-form and short-form lengths
• Nested TLVs inside constructed tags
• Round-trip encode/decode
• Case-insensitive tag lookup with simple path syntax (find("9F02"), find("A0/5F2A"))
• Dummy-root wrapper (FF) for multiple top-level siblings

Installation

pip install tlv-for-everyone

Usage

from TlvParser.TlvParser import BerTlvParser, BerTlvElement

# Parse an EMV-like TLV string
data = "9F02060000000001009F1A0208405F2A020978"
parser = BerTlvParser()
tlv = parser.parse_tlv(data)

# Pretty-print as dict
print(tlv.get_as_dict())

# Find a tag
val = tlv.find("9F02").get_value_as_hex_str()
print("Amount:", val)

Creating TLVs

# Construct a TLV structure programmatically
parent = BerTlvElement(0xA0, {})
child1 = BerTlvElement(0x9A, bytes.fromhex("250826"))
child2 = BerTlvElement(0x5F2A, bytes.fromhex("0124"))
parent.add_child(child1)
parent.add_child(child2)

# Encode to bytes
encoded = parent.encode().hex().upper()
print("Encoded:", encoded)

Running Tests

This project uses pytest and hypothesis.

pip install -r requirements-dev.txt

Run all tests:

pytest -v

Development Roadmap

• Improve XML/JSON exporters
• Add support for indefinite-length encoding
• More robust error handling and diagnostics
• PyPI packaging

Contributing

Pull requests are welcome! For major changes, please open an issue first to discuss what you’d like to change.

License

MIT License. See LICENSE for details.