Eth(ereum) Lite
ethlite - light-weight machinery to query / call ethereum (blockchain contract) services via json-rpc (incl. tuple support)
- home :: github.com/rubycocos/blockchain
- bugs :: github.com/rubycocos/blockchain/issues
- gem :: rubygems.org/gems/ethlite
- rdoc :: rubydoc.info/gems/ethlite
Usage
Step 0: Setup JSON RPC Client
Let's use the simple (built-in) JSON RPC client.
Get the eth node uri via the INFURA_URI enviroment variable / key e.g. https://mainnet.infura.io/v3/<YOUR_KEY_HERE>
:
ETH_NODE = JsonRpc.new( ENV['INFURA_URI'] )
Do-It-Yourself (DIY) JSON RPC eth_call With "Hand-Coded" To-The-Metal ABI Encoding/Decoding
Let's try to build a JSON-RPC request from scratch calling
a (constant/read-only/view) blockchain contract method via eth_call
.
Let's try function tokenURI(uint256 tokenId) returns (string)
that lets you request the metdata uri for a (non-fungible) token.
Let's try the Moonbirds contract @ 0x23581767a106ae21c074b2276d25e5c3e136a68b:
## contract address - let's try moonbirds
contract_address = '0x23581767a106ae21c074b2276d25e5c3e136a68b'
token_ids = (0..9)
token_ids.each do |token_id|
puts "==> calling tokenURI(#{token_id})..."
tokenURI = eth_call( ETH_NODE, contract_address,
'tokenURI', ['uint256'], ['string'],
[token_id] )
puts " ...returns: #{tokenURI}"
end
And the "magic" hand-coded to-the-metal eth_call
machinery:
## construct a json-rpc call from scratch
def eth_call( rpc,
contract_address,
name, inputs, outputs,
args )
## binary encode method sig(nature)
signature = "#{name}(#{inputs.join(',')})"
signature_hash = Ethlite::Utils.encode_hex(
Ethlite::Utils.keccak256(signature))[0..7]
pp signature
# => "tokenURI(uint256)"
pp signature_hash
# => "c87b56dd"
## binary encode method arg(ument)s
args_encoded = Ethlite::Utils.encode_hex(
Ethlite::Abi.encode_abi( inputs, args) )
data = '0x' + signature_hash + args_encoded
## json-rpc method and params
method = 'eth_call'
params = [{ to: contract_address,
data: data},
'latest'
]
## do the json-rpc request
response = rpc.request( method, params )
puts "response:"
pp response
## decode binary result
string_data = Ethlite::Utils.decode_hex(
Ethlite::Utils.remove_0x_head(response))
result = Ethlite::Abi.decode_abi( outputs, string_data )
result.length == 1 ? result[0] : result
end
resulting in (with debug json rpc request/reponse output):
calling tokenURI(0)
... json_rpc POST payload request:
{"jsonrpc":"2.0",
"method":"eth_call",
"params":[
{"to":"0x23581767a106ae21c074b2276d25e5c3e136a68b",
"data":"0xc87b56dd0000000000000000000000000000000000000000000000000000000000000000"},
"latest"],
"id":1
}
json_rpc response:
{"jsonrpc":"2.0",
"id":1,"result":"0x0000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000003a68747470733a2f2f6c6976652d2d2d6d657461646174612d35636f767071696a61612d75632e612e72756e2e6170702f6d657461646174612f30000000000000"
}
...returns: https://live---metadata-5covpqijaa-uc.a.run.app/metadata/0
calling tokenURI(1)...
json_rpc POST payload request:
{"jsonrpc":"2.0",
"method":"eth_call",
"params":[
{"to":"0x23581767a106ae21c074b2276d25e5c3e136a68b",
"data":"0xc87b56dd0000000000000000000000000000000000000000000000000000000000000001"},
"latest"],
"id":2
}
json_rpc response:
{"jsonrpc":"2.0",
"id":2,"result":"0x0000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000003a68747470733a2f2f6c6976652d2d2d6d657461646174612d35636f767071696a61612d75632e612e72756e2e6170702f6d657461646174612f31000000000000"
}
...returns: https://live---metadata-5covpqijaa-uc.a.run.app/metadata/1
JSON RPC eth_call With ContractMethod Helper
Let's retry using the convenience builtin
ContractMethod
helper:
## contract address - let's try moonbirds
contract_address = '0x23581767a106ae21c074b2276d25e5c3e136a68b'
ETH_tokenURI = Ethlite::ContractMethod.new( 'tokenURI',
inputs: ['uint256'],
outputs: ['string'] )
token_ids = (0..9)
token_ids.each do |token_id|
puts "==> tokenURI(#{token_id}) returns:"
pp ETH_tokenURI.do_call( ETH_NODE, contract_address, [token_id] )
end
resulting in:
==> tokenURI(0) returns:
"https://live---metadata-5covpqijaa-uc.a.run.app/metadata/0"
==> tokenURI(1) returns:
"https://live---metadata-5covpqijaa-uc.a.run.app/metadata/1"
==> tokenURI(2) returns:
"https://live---metadata-5covpqijaa-uc.a.run.app/metadata/3"
...
And so on and so forth.
License
The scripts are dedicated to the public domain. Use it as you please with no restrictions whatsoever.
Questions? Comments?
Post them on the D.I.Y. Punk (Pixel) Art reddit. Thanks.