asn1tools

This benchmark compares the C source code generated by asn1tools against asn1scc and asn1c.

Key differences noted in the benchmark:

• Executable Size: asn1tools produces significantly smaller executables than asn1c. This is because asn1c includes encode/decode functions for all codecs and supports more ASN.1 constructs using dynamic memory, whereas asn1tools is optimized for UPER.
• Execution Time: asn1tools demonstrates faster encoding and decoding times compared to asn1scc and asn1c under similar optimization levels (e.g., -O3).
• Code Complexity: asn1tools has the smallest codebase (832 lines of code), followed by asn1scc (3549 lines), and asn1c (10159 lines).
• Memory Usage: asn1tools and asn1scc show stable runtime memory usage, while asn1c exhibits more significant heap usage fluctuations during execution.

Install the asn1tools package using pip to enable ASN.1 parsing, encoding, and decoding in Python.

pip install asn1tools

Use asn1tools.compile_files to compile one or more ASN.1 specification files into a Specification object. This object is then used for encoding and decoding data according to the compiled specification.

import asn1tools
spec = asn1tools.compile_files(['path/to/spec.asn'])

To decode ASN.1 encoded data, use the following functions depending on your input format:

• asn1tools.parse_files(files, type_name, ...): Parses encoded data from files.
• asn1tools.parse_string(string, type_name, ...): Parses encoded data from a string.
• asn1tools.parse_dict(dict, type_name, ...): Parses encoded data from a dictionary.

Note: These functions typically require the name of the ASN.1 type you are parsing.

Use asn1tools.compile_files() to compile an ASN.1 specification file. This returns a module object used to encode and decode messages using a specified codec.

Supported codecs include:

• Basic Encoding Rules (BER)
• Distinguished Encoding Rules (DER)
• Generic String Encoding Rules (GSER)
• JSON Encoding Rules (JER)
• Basic Octet Encoding Rules (OER)
• Aligned Packed Encoding Rules (PER)
• Unaligned Packed Encoding Rules (UPER)
• XML Encoding Rules (XER)

If no codec is specified during compilation, it defaults to BER.

import asn1tools
# Compile the specification
foo = asn1tools.compile_files('tests/files/foo.asn')

# Encode a message (defaulting to BER)
encoded = foo.encode('Question', {'id': 1, 'question': 'Is 1+1=3?'})

# Decode the message
decoded = foo.decode('Question', encoded)
print(decoded)  # {'id': 1, 'question': 'Is 1+1=3?'}

For scenarios where the specification is not in a file, use these functions to create a Specification object:

• asn1tools.compile_string(string, ...): Compiles an ASN.1 specification provided as a string.
• asn1tools.compile_dict(dict, ...): Compiles an ASN.1 specification provided as a dictionary.

asn1tools supports several ASN.1 encoding rules as specified by ITU-T and IETF standards, including:

• BER, CER, DER: Basic Encoding Rules, Canonical Encoding Rules, and Distinguished Encoding Rules (X.690).
• PER: Packed Encoding Rules (X.691).
• XER: XML Encoding Rules (X.693).
• OER: Octet Encoding Rules (X.696).
• GSER: Generic String Encoding Rules (RFC 3641).
• JER: JSON Encoding Rules.

The asn1tools shell subcommand provides an interactive environment to compile specifications and convert encoded data between formats.

By default, the shell uses BER as the input codec and GSER as the output codec (producing human-readable text).

> asn1tools shell
$ help
$ compile tests/files/foo.asn
$ convert Question <hex_encoded_data>