Extend memory gadgets to handle dynamic offset and length#279
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| /// to integer. It handles the "no expansion" feature when length is zero. | ||
| #[derive(Clone, Debug)] | ||
| pub(crate) struct MemoryAddressGadget<F> { | ||
| memory_offset: Cell<F>, |
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memory_offset is starting point of address for expansion ?
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Yes, more precisely, the starting point of address for call_data or return_data specified by caller.
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My understanding of this gadget is that it aims to provide the max used address after a memory access by an opcode that takes offset and length like CALLDATACOPY, CODECOPY, EXTCODECOPY, RETURNDATACOPY. And I think this max address would then be used in the MemoryExpansionGadget to calculate the gas_cost of the possible expansion.
And MemoryAddressGadget returns max_address = 0 when the length = 0 so that no memory expansion is performed in such case, even if the offset is past the current max used address.
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Exactly, thanks for explanation!
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This PR is part of #278, which extends memory gadgets to add/extend
MemoryAddressGadget- To handle dynamic offset and length expansion. It's also useful for memory expansion opcode likeCALLDATACOPY.MemoryExpansionGadget- To support multiple expansion size. It's useful for*CALL*which assign 2 memory chunks as expansion targets.It also refactors some frequently used constant and methods. For main changes, please refer to
memory_gadget.rs