71 lines
2.6 KiB
Rust
71 lines
2.6 KiB
Rust
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use ethers::{
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prelude::*,
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providers::call_raw::RawCall,
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utils::{parse_ether, Geth},
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};
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use std::sync::Arc;
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abigen!(Greeter, "ethers-contract/tests/solidity-contracts/greeter.json",);
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#[tokio::main]
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async fn main() -> eyre::Result<()> {
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let geth = Geth::new().spawn();
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let provider = Provider::<Http>::try_from(geth.endpoint()).unwrap();
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let client = Arc::new(provider);
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// Both empty accounts
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let target: Address = "0x6fC21092DA55B392b045eD78F4732bff3C580e2c".parse()?;
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let from: Address = "0x295a70b2de5e3953354a6a8344e616ed314d7251".parse()?;
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// Override the sender's balance for the call
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let pay_amt = parse_ether(1u64)?;
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let tx = TransactionRequest::pay(target, pay_amt).from(from);
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let state = call_raw::balance(from, pay_amt * 2);
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// The call succeeds as if the sender had sufficient balance
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client.call_raw(&tx.into()).state(&state).await.expect("balance override");
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// Get the runtime bytecode for the Greeter contract using eth_call to
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// simulate the deploy transaction
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let deploy = Greeter::deploy(client.clone(), "Hi".to_string())?;
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let runtime_bytecode = deploy.call_raw().await?;
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// Instantiate a Greeter, though no bytecode exists at the target address
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let greeter = Greeter::new(target, client.clone());
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// Override the target account's code, simulating a call to Greeter.greet()
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// as if the Greeter contract was deployed at the target address
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let state = call_raw::code(target, runtime_bytecode.clone());
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let res = greeter.greet().call_raw().state(&state).await?;
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// greet() returns the empty string, because the target account's storage is empty
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assert_eq!(&res, "");
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// Encode the greeting string as solidity expects it to be stored
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let greeting = "Hello, world";
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let greet_slot = H256::zero();
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let greet_val = encode_string_for_storage(greeting);
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// Override the target account's code and storage
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let mut state = call_raw::state();
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state.account(target).code(runtime_bytecode.clone()).store(greet_slot, greet_val);
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let res = greeter.greet().call_raw().state(&state).await?;
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// The call returns "Hello, world"
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assert_eq!(&res, greeting);
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Ok(())
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}
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// Solidity stores strings shorter than 32 bytes in a single storage slot,
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// with the lowest order byte storing 2 * length and the higher order
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// bytes storing the string data (left aligned)
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fn encode_string_for_storage(s: &str) -> H256 {
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let mut bytes = s.as_bytes().to_vec();
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let len = bytes.len();
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assert!(len < 32, "longer strings aren't stored in a single slot");
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bytes.resize(31, 0);
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bytes.push(len as u8 * 2);
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H256::from_slice(&bytes)
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}
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