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core: add function description

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rjl493456442 2018-07-24 19:17:42 +08:00
parent dc894c1f4d
commit 7cf608f72c
1 changed files with 26 additions and 0 deletions
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26
core/vm/instructions.go
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@ -496,6 +496,32 @@ func opExtCodeCopy(pc *uint64, evm *EVM, contract *Contract, memory *Memory, sta
return nil, nil
}
// opExtCodeHash returns the code hash of a specified account.
// There are several cases when the function is called, while we can relay everything
// to `state.GetCodeHash` function to ensure the correctness.
// (1) Caller tries to get the code hash of a normal contract account, state
// should return the relative code hash and set it as the result.
//
// (2) Caller tries to get the code hash of a non-existent account, state should
// return common.Hash{} and zero will be set as the result.
//
// (3) Caller tries to get the code hash for an account without contract code,
// state should return emptyCodeHash(0xc5d246...) as the result.
//
// (4) Caller tries to get the code hash of a precompiled account, the result
// should be zero or emptyCodeHash.
//
// It is worth noting that in order to avoid unnecessary create and clean,
// all precompile accounts on mainnet have been transferred 1 wei, so the return
// here should be emptyCodeHash.
// If the precompile account is not transferred any amount on a private or
// customized chain, the return value will be zero.
//
// (5) Caller tries to get the code hash for an account which is marked as suicided
// in the current transaction, the code hash of this account should be returned.
//
// (6) Caller tries to get the code hash for an account which is marked as deleted,
// this account should be regarded as a non-existent account and zero should be returned.
func opExtCodeHash(pc *uint64, evm *EVM, contract *Contract, memory *Memory, stack *Stack) ([]byte, error) {
slot := stack.peek()
slot.SetBytes(evm.StateDB.GetCodeHash(common.BigToAddress(slot)).Bytes())