The x/erc20 module keeps the following objects in state:
State Object
Description
Key
Value
Store
TokenPair
Token Pair bytecode
[]byte{1} + []byte(id)
[]byte{tokenPair}
KV
TokenPairByERC20
Token Pair id bytecode by erc20 contract bytes
[]byte{2} + []byte(erc20)
[]byte(id)
KV
TokenPairByDenom
Token Pair id bytecode by denom string
[]byte{3} + []byte(denom)
[]byte(id)
KV
Token Pair
One-to-one mapping of native Cosmos coin denomination to ERC20 token contract addresses (i.e sdk.Coin ←→ ERC20).
type TokenPair struct {
// address of ERC20 contract token
Erc20Address string `protobuf:"bytes,1,opt,name=erc20_address,json=erc20Address,proto3" json:"erc20_address,omitempty"`
// cosmos base denomination to be mapped to
Denom string `protobuf:"bytes,2,opt,name=denom,proto3" json:"denom,omitempty"`
// shows token mapping enable status
Enabled bool `protobuf:"varint,3,opt,name=enabled,proto3" json:"enabled,omitempty"`
// ERC20 owner address ENUM (0 invalid, 1 ModuleAccount, 2 external address
ContractOwner Owner `protobuf:"varint,4,opt,name=contract_owner,json=contractOwner,proto3,enum=blockx.erc20.v1.Owner" json:"contract_owner,omitempty"`
}
Token pair ID
The unique identifier of a TokenPair is obtained by obtaining the SHA256 hash of the ERC20 hex contract address and the Coin denomination using the following function:
tokenPairId = sha256(erc20 + "|" + denom)
Token Origin
The ConvertCoin and ConvertERC20 functionalities use the owner field to check whether the token being used is a native Coin or a native ERC20. The field is based on the token registration proposal type (RegisterCoinProposal = 1, RegisterERC20Proposal = 2).
The Owner enumerates the ownership of a ERC20 contract.
type Owner int32
const (
// OWNER_UNSPECIFIED defines an invalid/undefined owner.
OWNER_UNSPECIFIED Owner = 0
// OWNER_MODULE erc20 is owned by the erc20 module account.
OWNER_MODULE Owner = 1
// EXTERNAL erc20 is owned by an external account.
OWNER_EXTERNAL Owner = 2
)
The Owner can be checked with the following helper functions:
// IsNativeCoin returns true if the owner of the ERC20 contract is the
// erc20 module account
func (tp TokenPair) IsNativeCoin() bool {
return tp.ContractOwner == OWNER_MODULE
}
// IsNativeERC20 returns true if the owner of the ERC20 contract not the
// erc20 module account
func (tp TokenPair) IsNativeERC20() bool {
return tp.ContractOwner == OWNER_EXTERNAL
}
Token Pair by ERC20 and by Denom
TokenPairByERC20 and TokenPairByDenom are additional state objects for querying a token pair id.
Genesis State
The x/erc20 module's GenesisState defines the state necessary for initializing the chain from a previous exported height. It contains the module parameters and the registered token pairs :
