2020-12-09 19:11:15 +00:00
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order: 2
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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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2021-06-22 10:49:18 +00:00
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+++ https://github.com/tharsis/ethermint/blob/v0.3.1/x/evm/types/statedb.go#L33-L85
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2020-12-09 19:11:15 +00:00
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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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