abiparser - application binary interface (abi) parser machinery / helper for Ethereum & Co. (blockchain) contracts
- home :: github.com/rubycocos/blockchain
- bugs :: github.com/rubycocos/blockchain/issues
- gem :: rubygems.org/gems/abiparser
- rdoc :: rubydoc.info/gems/abiparser
You can calculate the function selectors (or "sighash",
that is, signature hash)
by hashing the function signature
e.g. supportsInterface(bytes4) with the Keccak 256-Bit algorithm
and than use the first 4 bytes, that is, 0x01ffc9a7 (out of 32 bytes),
that is, 0x01ffc9a7a5cef8baa21ed3c5c0d7e23accb804b619e9333b597f47a0d84076e2. Example:
require 'abiparser'
sig = 'supportsInterface(bytes4)'
pp keccak256( sig )[0,4].hexdigest
#=> "0x01ffc9a7"Note: The String#hexdigest (also known as String#bin_to_hex) helper
converts a binary string (with BINARY/ASCII-8BIT encoding)
into a hex(adecimal) string.
You can calcuate interface (type) ids
by xor-ing (^) together the sighashes.
If the interface only has one function than
the interface (type) id equals the function sighash (by definition).
interface ERC165 {
/// @notice Query if a contract implements an interface
/// @param interfaceID The interface identifier, as specified in ERC-165
/// @dev Interface identification is specified in ERC-165.
/// @return `true` if the contract implements `interfaceID` and
/// `interfaceID` is not 0xffffffff, `false` otherwise
function supportsInterface(bytes4 interfaceID) external view returns (bool);
}
// The interface identifier for this interface is 0x01ffc9a7.If you check the sighash for supportsInterface(bytes4),
that is, 0x01ffc9a7 (see above)
than - bingo! - the interface id for ERC165 matches up.
Let's try to calculate the ERC20 standard (fungible) token interface
where the official id is 0x36372b07 by xor-ing (^) together all function sighashes:
pp (keccak256('totalSupply()')[0,4] ^
keccak256('balanceOf(address)')[0,4] ^
keccak256('allowance(address,address)')[0,4] ^
keccak256('transfer(address,uint256)')[0,4] ^
keccak256('approve(address,uint256)')[0,4] ^
keccak256('transferFrom(address,address,uint256)')[0,4]).hexdigest
#=> "0x36372b07"
# or where def sig(bin) = keccak256(bin)[0,4])
pp (sig('totalSupply()') ^
sig('balanceOf(address)') ^
sig('allowance(address,address)') ^
sig('transfer(address,uint256)') ^
sig('approve(address,uint256)') ^
sig('transferFrom(address,address,uint256)')).hexdigest
#=> "0x36372b07"Voila! Or re(use) the builtin pre-defined interfaces. Example:
pp IERC165.inteface_id #=> "0x01ffc9a7"
pp IERC20.interface_id #=> "0x36372b07"
pp IERC721.interface_id #=> "0x80ac58cd"
pp IERC721_METADATA.interface_id #=> "0x5b5e139f"
pp IERC721_ENUMERABLE.interface_id #=> "0x780e9d63"Yes, you can. Define your own interface. Let's have a looksie at the built-ins. Example:
IERC165 = ABI::Interface.new(
'supportsInterface(bytes4)'
)
IERC20 = ABI::Interface.new(
'totalSupply()',
'balanceOf(address)',
'allowance(address,address)',
'transfer(address,uint256)',
'approve(address,uint256)',
'transferFrom(address,address,uint256)'
)
IERC721 = ABI::Interface.new(
'balanceOf(address)',
'ownerOf(uint256)',
'approve(address,uint256)',
'getApproved(uint256)',
'setApprovalForAll(address,bool)',
'isApprovedForAll(address,address)',
'transferFrom(address,address,uint256)',
'safeTransferFrom(address,address,uint256)',
'safeTransferFrom(address,address,uint256,bytes)' )
IERC721_METADATA = ABI::Interface.new(
'name()',
'symbol()',
'tokenURI(uint256)' )
IERC721_ENUMERABLE = ABI::Interface.new(
'tokenOfOwnerByIndex(address,uint256)',
'totalSupply()',
'tokenByIndex(uint256)' )
...To be continued...
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