StateManager Should be public

[wanderer]

It would be nice to expose the StateManager publically. And split it into its own module. What should the API be?

[wanderer]

currently the API is

• getAccount
• exists // checks if an account exists
• _putAccount
• getAccountBalance
• putAccountBalance
• putContractCode
• getContractCode
• _lookupStorageTrie
• _getStorageTrie
• getContractStorage
• putContractStorage
• commitContracts
• revertContracts
• getBlockHash
• checkpoint
• commit
• revert
• getStateRoot
• warmCache
• dumpStorage
• hasGenesisState
• generateCanonicalGenesis
• generateGenesis

Also It would be nice to inculde the following from https://github.com/ethereumjs/ethereumjs-account

• account.getCode(trie, cb)
• account.setCode(trie, code, cb)
• account.getStorage(trie, key, cb)
• account.setStorage(trie, key, val, cb)

[kumavis]

the stateManager is the semantic layer over the merkle-patricia-tree.

two things to consider in terms of api design:

• how to get data from the blockchain (e.g. balance for account x)
• how to provide data from the blockchain (e.g. lazily from a remote node)

on the data-providing side:

for the provider engine I wanted to be able to override contract code set/gets and storage set/gets
It was possible but it would be nice if this was a little easier
https://github.com/MetaMask/provider-engine/blob/bcc101b75212fc19175d827112f369d225573230/subproviders/vm.js#L94-L98
I used:

• _lookupStorageTrie
• cache._lookupAccount
• getContractCode
• setContractCode

EDIT: update link to point to correct lines and be locked to commit

[kumavis]

Here is an example of how providing a custom StateManager could be very useful:

Creating a vm backed by an arbitrary data source (here as eth rpc data lookups)
https://github.com/ethereumjs/ethereumjs-vm/blob/master/lib/hooked.js#L79-L84

[kumavis]

here is an example of a module consumer overwriting StateManager https://github.com/ethereum/browser-solidity/pull/345/files