python-evrmorelib 0.3.0

Evrmore fork of python-ravencoinlib, a fork of python-bitcoinlib

python-evrmorelib

Evrmore fork of python-bitcoinlib intended to provide access to Evrmore data structures and protocol. WIP - Test before use

The RPC interface, evrmore.rpc, is designed to work with Evrmore Core v3.3.0+.

"The only Python library for Evrmore I've ever used" - Warren Buffett

Requirements

libssl
Debian/Ubuntu: sudo apt-get install libssl-dev
Windows/other: https://wiki.openssl.org/index.php/Binaries 

Python modules:
    x16r-hash, x16rv2-hash and kawpow
    plyvel (requires libleveldb - for parsing Raven core .dat files)

Structure

Everything consensus critical is found in the modules under evrmore.core. This rule is followed pretty strictly, for instance chain parameters are split into consensus critical and non-consensus-critical.

evrmore.core            - Basic core definitions, datastructures, and
                          (context-independent) validation
evrmore.core.assets     - OP_EVR_ASSET data structures
evrmore.core.key        - ECC pubkeys
evrmore.core.script     - Scripts and opcodes
evrmore.core.scripteval - Script evaluation/verification
evrmore.core.serialize  - Serialization

In the future the evrmore.core may use the Satoshi sourcecode directly as a library. Non-consensus critical modules include the following:

evrmore          - Chain selection
evrmore.assets   - Asset name and metadata related code
evrmore.base58   - Base58 encoding
evrmore.bloom    - Bloom filters (incomplete)
evrmore.net      - Network communication (in flux)
evrmore.messages - Network messages (in flux)
evrmore.rpc      - Evrmore Core RPC interface support
evrmore.wallet   - Wallet-related code, currently Evrmore address and
                   private key support

Effort has been made to follow the Satoshi source relatively closely, for instance Python code and classes that duplicate the functionality of corresponding Satoshi C++ code uses the same naming conventions: CTransaction, CBlockHeader, nValue etc. Otherwise Python naming conventions are followed.

Mutable vs. Immutable objects

Like the Evrmore Core codebase CTransaction is immutable and CMutableTransaction is mutable; unlike the Evrmore Core codebase this distinction also applies to COutPoint, CTxIn, CTxOut, and CBlock.

Endianness Gotchas

Rather confusingly Evrmore Core shows transaction and block hashes as little-endian hex rather than the big-endian the rest of the world uses for SHA256. python-evrmorelib provides the convenience functions x() and lx() in evrmore.core to convert from big-endian and little-endian hex to raw bytes to accomodate this. In addition see b2x() and b2lx() for conversion from bytes to big/little-endian hex.

Module import style

While not always good style, it's often convenient for quick scripts if import * can be used. To support that all the modules have __all__ defined appropriately.

Example Code

See examples/ directory. For instance this example creates a transaction spending a pay-to-script-hash transaction output:

$ PYTHONPATH=. examples/spend-pay-to-script-hash-txout.py
<hex-encoded transaction>

Selecting the chain to use

Do the following:

import evrmore
evrmore.SelectParams(NAME)

Where NAME is one of 'testnet', 'mainnet', or 'regtest'. The chain currently selected is a global variable that changes behavior everywhere, just like in the Satoshi codebase.

Unit tests

Under evrmore/tests using test data from Evrmore Core. To run them:

python3 -m unittest discover

Alternately, if Tox (see https://tox.readthedocs.org/) is available on your system, you can run unit tests for multiple Python versions:

./runtests.sh

HTML coverage reports can then be found in the htmlcov/ subdirectory.

Documentation

Sphinx documentation is in the "doc" subdirectory. Run "make help" from there to see how to build. You will need the Python "sphinx" package installed.

Currently this is just API documentation generated from the code and docstrings. Higher level written docs would be useful, perhaps starting with much of this README. Pages are written in reStructuredText and linked from index.rst.

Implementation Notes

Bitcoin & Evrmore Compatibility

This library has been updated from bitcoin-python to handle Evrmore specific features:

1. Asset Support: Functionality for creating, transferring, and managing Evrmore assets
2. Script Opcodes: Support for Evrmore-specific script opcodes including OP_EVR_ASSET

OP_CHECKSEQUENCEVERIFY Support

This library includes support for OP_CHECKSEQUENCEVERIFY (BIP112), which is required for certain smart contract patterns like payment channels. The implementation includes:

1. Definition of the opcode (0xb2, formerly OP_NOP3)
2. Verification flag support (SCRIPT_VERIFY_CHECKSEQUENCEVERIFY)
3. Basic opcode validation

Note: The current CSV implementation has limitations in fully verifying relative timelocks since it doesn't have access to the previous transaction's outputs during script evaluation. When the CSV verification flag is enabled, the opcode will throw an error explaining this limitation.

Use OP_CHECKSEQUENCEVERIFY in your scripts as follows:

from evrmore.core.script import OP_CHECKSEQUENCEVERIFY, OP_DROP

# To create a script with relative timelock of 10 blocks
script = CScript([10, OP_CHECKSEQUENCEVERIFY, OP_DROP, pubkey, OP_CHECKSIG])