EIP1283 - Net gas metering

What is wrong?

ttps://eips.ethereum.org/EIPS/eip-1087 https://eips.ethereum.org/EIPS/eip-1283 is coming in Constantinople

How can it be fixed

Implement the changes to how SSTORE costs are computed.

[pipermerriam]

@veox just in case you read these in your email, I update my response with explicit answers to your questions.

[pipermerriam]

Looking at our JournalDB class, I believe 1283 is going to be easiest to implement. We’ll have to figure out how to expose the original/current values to the SSTORE opcode but that shouldn’t be too difficult.

To answer your specific questions.

Which of the two (if either) would more closely describe the situation in py-evm?

I believe that our architecture is closest to 1283 since we keep an in-memory map of current values.

Would implementing either require pushing the “cache for original values of storage items” deeper? Or is that already available at the point where gas-use metering is done?

Implementing 1283 will require exposing information about the cache (the journal) deeper as to make it available within the SSTORE opcode function. I suspect this will be best done as a combination of a formal API on the AccountDB for checking storage slot status. I believe this will involve simply querying the self._trie which should return the original value, and self._journaltrie which should return the current value.