ContentHash for Python

Python implementation of EIP 1577 content hash.

Description

This is a simple package made for encoding and decoding content hashes has specified in the EIP 1577. This package will be useful for every Ethereum developer wanting to interact with EIP 1577 compliant ENS resolvers.

For JavaScript implementation, see pldespaigne/content-hash.

Installation

Requirements

ContentHash requires Python 3.5 or higher.

From PyPI

The recommended way to install ContentHash is from PyPI with PIP.

pip install content-hash

From Source

Alternatively, you can also install it from the source.

git clone https://github.com/filips123/ContentHashPy.git
cd ContentHashPy
python setup.py install

Usage

Supported Codecs

The following codecs are currently supported:

• swarm-ns
• ipfs-ns
• ipns-ns

Every other codec supported by multicodec will be encoded by default in utf-8. You can see the full list of the supported codecs here.

Getting Codec

You can use a get_codec function to get codec from the content hash.

It takes a content hash as a HEX string and returns the codec name. A content hash can be prefixed with a 0x, but it's not mandatory.

import content_hash

chash = 'bc037a716b746c776934666563766f367269'
codec = content_hash.get_codec(chash)

print(codec) # onion

Decoding

You can use a decode function to decode a content hash.

It takes a content hash as a HEX string and returns the decoded content as a string. A content hash can be prefixed with a 0x, but it's not mandatory.

import content_hash

chash = 'e3010170122029f2d17be6139079dc48696d1f582a8530eb9805b561eda517e22a892c7e3f1f'
value = content_hash.decode(chash)

print(value) # QmRAQB6YaCyidP37UdDnjFY5vQuiBrcqdyoW1CuDgwxkD4

Encoding

You can use an encode function to encode a content hash.

It takes a supported codec as a string and a value as a string and returns the corresponding content hash as a HEX string. The output will not be prefixed with a 0x.

import content_hash

codec = 'swarm-ns'
value = 'd1de9994b4d039f6548d191eb26786769f580809256b4685ef316805265ea162'
chash = content_hash.encode(codec, value)

print(chash) # e40101701b20d1de9994b4d039f6548d191eb26786769f580809256b4685ef316805265ea162

Creating Codecs

All supported codec profiles are available in content_hash/profiles/__init__.py, in PROFILES dictionary. You need to add a new profile there. You only need to add a new profile if your codec encoding and decoding are different from utf-8.

Each profile must have the same name as the corresponding codec in the multicodec library.

A profile must also have decode and encode function. They should be passed as a string containing the name of the module for required decode or encode. All such modules are available in content_hash/decodes and content_hash/encodes.

Each module name should describe it as much as possible. Its name can only contain valid characters for Python modules.

Each decode module must have a decode function. It must be a function that takes a bytes input and returns a str result.

Each encode module must have an encode function. It must be a function that takes a str input and returns a bytes result.

All inputs and outputs must be the same as in the JavaScript implementation. Multiple profiles can share the same decodes and encodes.

Versioning

This library uses SemVer for versioning. For the versions available, see the tags on this repository.

License

This library is licensed under the MIT license. See the LICENSE file for details.