82 lines
3.6 KiB
Markdown
82 lines
3.6 KiB
Markdown
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# State
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The `x/evm` module keeps the following objects in state:
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| | Key | Value |
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|-----------------|---------------------------------------------------|---------------------------|
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| Block Height | `[]byte{1} + []byte(block.Hash)` | `BigEndian(block.Height)` |
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| Bloom | `[]byte{2} + []byte(block.Height)` | `[]byte(Bloom)` |
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| Tx Logs | `[]byte{3} + []byte(tx.Hash)` | `amino([]Log)` |
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| Account Code | `[]byte{4} + []byte(code.Hash)` | `[]byte(Code)` |
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| Account Storage | `[]byte{5} + []byte(address) + []byte(state.Key)` | `[]byte(state.Value)` |
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| Chain Config | `[]byte{6}` | `amino(ChainConfig)` |
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## `CommitStateDB`
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`StateDB`s within the ethereum protocol are used to store anything within the IAVL tree. `StateDB`s
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take care of caching and storing nested states. It's the general query interface to retrieve
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contracts and accounts
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The Ethermint `CommitStateDB` is a concrete type that implements the EVM `StateDB` interface.
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Instead of using a trie and database for querying and persistence, the `CommitStateDB` uses
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`KVStores` (key-value stores) and Cosmos SDK `Keeper`s to facilitate state transitions.
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The `CommitStateDB` contains a store key that allows the DB to write to a concrete subtree of the
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multistore that is only accessible to the EVM module.
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+++ https://github.com/cosmos/ethermint/blob/v0.3.1/x/evm/types/statedb.go#L33-L85
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The functionalities provided by the Ethermint `StateDB` are:
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* CRUD of `stateObject`s and accounts:
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* Balance
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* Code
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* Nonce
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* State
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* EVM module parameter getter and setter
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* State transition logic
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* Preparation: transaction index and hash, block hash
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* CRUD of transaction logs
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* Aggregate queries
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* Snapshot state
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* Identify current state with a revision
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* Revert state to a given revision
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* State transition and persistence
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* Preparation: tx and block context
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* Commit state objects
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* Finalise state objects
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* Export state for upgrades
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* Auxiliary functions
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* Copy state
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* Reset state
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## State Objects
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State objects are used by the VM which is unable to deal with database-level errors. Any error that occurs during a database read is memoized here and will eventually be returned by `StateDB.Commit`.
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The Ethermint `stateObject` is a concrete type that mimics the functionality from the `go-ethereum`
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private `stateObject` type. It keeps track of the interim values for the contract bytecode, storage
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state and balance of an `EthAccount`.
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The storage entries (original and "dirty") for each state object are represented as slices instead
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of maps since latter can cause non-deterministic block app hashes, which result in the chain
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halting.
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When a `stateObject` is committed during `EndBlock`. It sets sets the account contract code to store, as well as the dirty storage state. The account's nonce and the account balance are updated by calling the `auth` and `bank` module setter functions, respectively.
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+++ https://github.com/cosmos/ethermint/blob/v0.3.1/x/evm/types/state_object.go#L49-L81
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The functionalities provided by the Ethermint `stateObject` are:
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* Storage state getter and setter (temporary)
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* Contract bytecode getter and setter (temporary)
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* Balance getter and setter (temporary)
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* Balance accounting (temporary)
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* Account nonce and address getter and setter (temporary)
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* Auxiliary functions: copy, RLP encoding, empty
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* Commit state object (final)
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