this is an example of creating a swap asset (ERC20) contract with required Swapin and Swapout methods for cross chain bridge.

please ref. to CrossChain-Bridge.

npm install

This has been already done. Mention here only for re-flatten if modified later.

mpm install -g truffle-flattener
truffle-flattener internal/BtcSwapAsset.sol | sed '/SPDX-License-Identifier:/d' | sed 1i'// SPDX-License-Identifier: MIT' > contracts/BtcSwapAsset.sol
truffle-flattener internal/EthSwapAsset.sol | sed '/SPDX-License-Identifier:/d' | sed 1i'// SPDX-License-Identifier: MIT' > contracts/EthSwapAsset.sol
truffle-flattener internal/UsdtSwapAsset.sol | sed '/SPDX-License-Identifier:/d' | sed 1i'// SPDX-License-Identifier: MIT' > contracts/UsdtSwapAsset.sol
truffle-flattener internal/Erc20SwapAsset.sol | sed '/SPDX-License-Identifier:/d' | sed 1i'// SPDX-License-Identifier: MIT' > contracts/Erc20SwapAsset.sol

truffle-config.js

Normally, you may meed to modify the following items:

host: the rpc host of the node
port: the rpc port of the node
network_id: the chain id

Add and modify contracts in contracts directory.

like our example: BtcSwapAsset.sol.

Add an js file to depoly contract in migrations directory.

like our example: 2_deploy_contracts.js.

Use the following command to compile contracts:

truffle compile

or re-compile all contracts:

truffle compile --all

Use the following command to deploy contract:

truffle migrate

or re-deploy contract:

truffle migrate --reset

We may want to perform a test or 'dry run' migration firstly:

truffle migrate --dry-run

Because we need to build a raw contract creation transaction and sign this raw transaction using DCRM technology,

So we need the bytecode as the transaction input data to build a raw contract cteation transaction.

bytecode can be found in ./build/contracts/BtcSwapAsset.json

The bytecode files in bytecode/solc directory are generated by the following command, with solc version of 0.5.4+commit.9549d8ff.Emscripten.clang

solcjs --bin --output-dir solc --evm-version byzantium --optimize --runs=1500 contracts/*.sol

use remix: https://remix.ethereum.org/#optimize=true&evmVersion=null&version=soljson-v0.5.4+commit.9549d8ff.js&runs=200

the bytecode in truffle built contracts is runtime bytecode which has not the constructor argument info.

we should append the packed constructor arguments data (like abi encoding) to the end of the runtime bytecode to generage the creation bytecode which is used as contract creation transaction's input data.

the following is a way by attaching to full node:

abi = ...
runtime_bytecode = ...
creation_bytecode = eth.contract(abi).getData(param1,param2,...lastparam,{from:eth.coinbase,data:runtime_bytecode})

We can access the above deployed contract in truffle console terminal.

Firstly log into truffle console terminal:

truffle console

Then assign an variable app to the deployed contract instance:

BtcSwapAsset.deployed().then(function(instance){ app = instance; })

For convenience, we can also assign all local accounts to accounts variable:

web3.eth.getAccounts().then(function(result){ accounts = result })

Now we can access the methods and attributes of the deployed contract.

For example,

app.Swapout("45678","2MxQaHFhqKgYyTgcJj8foYHbPJQLQxvXQjp",{from:accounts[1]})

after attached to the running node, we can access the contract by the following infos:

app = eth.contract(abi).at(contractAddress)

abi can be found in ./build/contracts/BtcSwapAsset.json (after building)