armaniferrante / pure-evm Goto Github PK

When returning memory types, the returndatasize payload is prepended to the return value. In such cases, one must chop it off before returning from pure_evm.exec().

I'll get to this soon, but the workaround for now is to just chop it off the first 64 bytes of the return data for such types. For example, see https://github.com/armaniferrante/pure-evm/blob/master/wasm/examples/node/ttt.js#L14.

This shouldn't affect fixed-sized (not in memory) primitive types like u256, for example, https://github.com/armaniferrante/pure-evm/blob/master/wasm/examples/node/index.js#L16.

All javascript tests are just ad hoc js scripts with assertions. Use something proper like mocha/jest.

Currently only running node examples.

Builtin functions like sha256 and recover execute as cross contract calls to fixed account addresses on Ethereum.

Currently, pure-evm doesn't allow any cross contract calls whatsoever.

It might be desireable to special case "builtin" functions as requested by #6.

Trying to use this package to run view functions, and running into some strange issues.

When I try to call execute with the bytecode retrieved from eth_getCode (the runtime/deployed bytecode), I get a rust panic error:

RuntimeError: unreachable
        at __rust_start_panic (wasm-function[330]:0x3a810)
        at rust_panic (wasm-function[213]:0x39f81)

      313 |
      314 |       // Execute on the raw bytes.
    > 315 |       const output = pure_evm.exec(
          |                               ^
      316 |         Uint8Array.from(Buffer.from(bytecode.replace("0x", ""), "hex")),
      317 |         encodedData,
      318 |       );

      at std::panicking::rust_panic_with_hook::h5e7c2dc110ae79d4 (wasm-function[95]:0x36e5a)
      at std::panicking::begin_panic::h6da1813f9eea9b6a (wasm-function[200]:0x39c59)
      at <pure_evm::pure_ext::PureExt as vm::ext::Ext>::depth::he3b3a85b57bdb8e8 (wasm-function[273]:0x3a540)
      at evm::interpreter::Interpreter<Cost>::exec_instruction::h8137cbc088506585 (wasm-function[1]:0xc988)
      at <evm::interpreter::Interpreter<Cost> as vm::Exec>::exec::h41e00997af783aac (wasm-function[5]:0x1df67)
      at pure_evm::exec::h1eb45dc630e9c525 (wasm-function[10]:0x24982)
          at exec (wasm-function[92]:0x36a29)
      at Object.module.exports.exec (../../node_modules/pure-evm/pure-evm_main.js:38:22)
      at AppInstance.computeStateTransition (src/models/app-instance.ts:315:31)
          at runMicrotasks (<anonymous>)

Interestingly enough, when using the init/creation bytecode, the error disappears and the output of the execute function once converted to a hex string is the same as the deployed bytecode returned from eth_getCode. Any idea on what might be causing these errors?

Here is a code snippet (running in node env, not browser):

const appArtifact = require(`@connext/contracts/artifacts/${pureAppName}.json`);
const iface = new Interface(appArtifact.abi);

// applyAction is a view function, using solidity 0.6
const data = iface.encodeFunctionData("applyAction", [
        this.encodedLatestState,
        this.encodeAction(action),
]);
const encodedData = Uint8Array.from(Buffer.from(data.replace("0x", ""), "hex"));

const bytecode = await provider.send("eth_getCode", [this.appDefinition, "latest"]);

// Works IFF using init bytecode, but returns deployed bytecode hex string. Fails otherwise.
const output = pure_evm.exec(
        Uint8Array.from(Buffer.from(bytecode.replace("0x", ""), "hex")),
        encodedData,
);

// Taken from the ttt test
const bytes = defaultAbiCoder.decode(["bytes"], output)[0];
const computedNextState = defaultAbiCoder.decode([this.abiEncodings.stateEncoding], bytes)[0];