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| // Copyright 2023 The go-ethereum Authors | ||
| // This file is part of the go-ethereum library. | ||
| // | ||
| // The go-ethereum library is free software: you can redistribute it and/or modify | ||
| // it under the terms of the GNU Lesser General Public License as published by | ||
| // the Free Software Foundation, either version 3 of the License, or | ||
| // (at your option) any later version. | ||
| // | ||
| // The go-ethereum library is distributed in the hope that it will be useful, | ||
| // but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| // GNU Lesser General Public License for more details. | ||
| // | ||
| // You should have received a copy of the GNU Lesser General Public License | ||
| // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>. | ||
|
|
||
| package gasestimator | ||
|
|
||
| import ( | ||
| "context" | ||
| "errors" | ||
| "fmt" | ||
| "math" | ||
| "math/big" | ||
|
|
||
| "github.com/unicornultrafoundation/go-u2u/common" | ||
| "github.com/unicornultrafoundation/go-u2u/core/state" | ||
| "github.com/unicornultrafoundation/go-u2u/core/types" | ||
| "github.com/unicornultrafoundation/go-u2u/core/vm" | ||
| "github.com/unicornultrafoundation/go-u2u/evmcore" | ||
| "github.com/unicornultrafoundation/go-u2u/log" | ||
| "github.com/unicornultrafoundation/go-u2u/params" | ||
| ) | ||
|
|
||
| // Options are the contextual parameters to execute the requested call. | ||
| // | ||
| // Whilst it would be possible to pass a blockchain object that aggregates all | ||
| // these together, it would be excessively hard to test. Splitting the parts out | ||
| // allows testing without needing a proper live chain. | ||
| type Options struct { | ||
| Config *params.ChainConfig // Chain configuration for hard fork selection | ||
| Chain evmcore.DummyChain // Chain context to access past block hashes | ||
| Header *evmcore.EvmHeader // Header defining the block context to execute in | ||
| State *state.StateDB // Pre-state on top of which to estimate the gas | ||
|
|
||
| ErrorRatio float64 // Allowed an overestimation ratio for faster estimation termination | ||
| } | ||
|
|
||
| // Estimate returns the lowest possible gas limit that allows the transaction to | ||
| // run successfully with the provided context options. It returns an error if the | ||
| // transaction always reverts, or if there are unexpected failures. | ||
| func Estimate(ctx context.Context, call *types.Message, opts *Options, gasCap uint64) (uint64, []byte, error) { | ||
| // Binary search the gas limit, as it may need to be higher than the amount used | ||
| var ( | ||
| lo uint64 // lowest-known gas limit where tx execution fails | ||
| hi uint64 // lowest-known gas limit where tx execution succeeds | ||
| ) | ||
| // Determine the highest gas limit can be used during the estimation. | ||
| hi = opts.Header.GasLimit | ||
| if call.Gas() >= params.TxGas { | ||
| hi = call.Gas() | ||
| } | ||
| // Normalize the max fee per gas the call is willing to spend. | ||
| var feeCap *big.Int | ||
| if call.GasFeeCap() != nil { | ||
| feeCap = call.GasFeeCap() | ||
| } else if call.GasPrice() != nil { | ||
| feeCap = call.GasPrice() | ||
| } else { | ||
| feeCap = common.Big0 | ||
| } | ||
| // Recap the highest gas limit with account's available balance. | ||
| if feeCap.BitLen() != 0 { | ||
| balance := opts.State.GetBalance(call.From()) | ||
|
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||
| available := balance | ||
| if call.Value() != nil { | ||
| if call.Value().Cmp(available) >= 0 { | ||
| return 0, nil, evmcore.ErrInsufficientFundsForTransfer | ||
| } | ||
| available.Sub(available, call.Value()) | ||
| } | ||
| allowance := new(big.Int).Div(available, feeCap) | ||
|
|
||
| // If the allowance is larger than maximum uint64, skip checking | ||
| if allowance.IsUint64() && hi > allowance.Uint64() { | ||
| transfer := call.Value() | ||
| if transfer == nil { | ||
| transfer = new(big.Int) | ||
| } | ||
| log.Debug("Gas estimation capped by limited funds", "original", hi, "balance", balance, | ||
| "sent", transfer, "maxFeePerGas", feeCap, "fundable", allowance) | ||
| hi = allowance.Uint64() | ||
| } | ||
| } | ||
| // Recap the highest gas allowance with specified gas cap. | ||
| if gasCap != 0 && hi > gasCap { | ||
| log.Debug("Caller gas above allowance, capping", "requested", hi, "cap", gasCap) | ||
| hi = gasCap | ||
| } | ||
| // If the transaction is a plain value transfer, short circuit estimation and | ||
| // directly try 21000. Returning 21000 without any execution is dangerous as | ||
| // some tx field combos might bump the price up even for plain transfers (e.g. | ||
| // unused access list items). Ever so slightly wasteful, but safer overall. | ||
| if len(call.Data()) == 0 { | ||
| if call.To() != nil && opts.State.GetCodeSize(*call.To()) == 0 { | ||
| failed, _, err := execute(ctx, call, opts, params.TxGas) | ||
| if !failed && err == nil { | ||
| return params.TxGas, nil, nil | ||
| } | ||
| } | ||
| } | ||
| // We first execute the transaction at the highest allowable gas limit, since if this fails we | ||
| // can return error immediately. | ||
| failed, result, err := execute(ctx, call, opts, hi) | ||
| if err != nil { | ||
| return 0, nil, err | ||
| } | ||
| if failed { | ||
| if result != nil && !errors.Is(result.Err, vm.ErrOutOfGas) { | ||
| return 0, result.Revert(), result.Err | ||
| } | ||
| return 0, nil, fmt.Errorf("gas required exceeds allowance (%d)", hi) | ||
| } | ||
| // For almost any transaction, the gas consumed by the unconstrained execution | ||
| // above lower-bounds the gas limit required for it to succeed. One exception | ||
| // is those that explicitly check gas remaining in order to execute within a | ||
| // given limit, but we probably don't want to return the lowest possible gas | ||
| // limit for these cases anyway. | ||
| lo = result.UsedGas - 1 | ||
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| // There's a fairly high chance for the transaction to execute successfully | ||
| // with gasLimit set to the first execution's usedGas + gasRefund. Explicitly | ||
| // check that gas amount and use as a limit for the binary search. | ||
| optimisticGasLimit := (result.UsedGas + result.RefundedGas + params.CallStipend) * 64 / 63 | ||
| if optimisticGasLimit < hi { | ||
| failed, _, err = execute(ctx, call, opts, optimisticGasLimit) | ||
| if err != nil { | ||
| // This should not happen under normal conditions since if we make it this far the | ||
| // transaction had run without an error at least once before. | ||
| log.Error("Execution error in estimate gas", "err", err) | ||
| return 0, nil, err | ||
| } | ||
| if failed { | ||
| lo = optimisticGasLimit | ||
| } else { | ||
| hi = optimisticGasLimit | ||
| } | ||
| } | ||
| // Binary search for the smallest gas limit that allows the tx to execute successfully. | ||
| for lo+1 < hi { | ||
| if opts.ErrorRatio > 0 { | ||
| // It is a bit pointless to return a perfect estimation, as changing | ||
| // network conditions require the caller to bump it up anyway. Since | ||
| // wallets tend to use 20-25% bump, allowing a small approximation | ||
| // error is fine (as long as it's upwards). | ||
| if float64(hi-lo)/float64(hi) < opts.ErrorRatio { | ||
| break | ||
| } | ||
| } | ||
| mid := (hi + lo) / 2 | ||
| if mid > lo*2 { | ||
| // Most txs don't need that much higher gas limit than their gas used. Most txs don't | ||
| // require near the full block limit of gas, so the selection of where to bisect the | ||
| // range here is skewed to favor the low side. | ||
| mid = lo * 2 | ||
| } | ||
| failed, _, err = execute(ctx, call, opts, mid) | ||
| if err != nil { | ||
| // This should not happen under normal conditions since if we make it this far the | ||
| // transaction had run without an error at least once before. | ||
| log.Error("Execution error in estimate gas", "err", err) | ||
| return 0, nil, err | ||
| } | ||
| if failed { | ||
| lo = mid | ||
| } else { | ||
| hi = mid | ||
| } | ||
| } | ||
| return hi, nil, nil | ||
| } | ||
|
|
||
| // execute is a helper that executes the transaction under a given gas limit and | ||
| // returns true if the transaction fails for a reason that might be related to | ||
| // not enough gas. A non-nil error means execution failed due to reasons unrelated | ||
| // to the gas limit. | ||
| func execute(ctx context.Context, call *types.Message, opts *Options, gasLimit uint64) (bool, *evmcore.ExecutionResult, error) { | ||
| // Configure the call for this specific execution (and revert the change after) | ||
| defer func(gas uint64) { call.SetGasLimit(gas) }(call.Gas()) | ||
| call.SetGasLimit(gasLimit) | ||
|
|
||
| // Execute the call and separate execution faults caused by a lack of gas or | ||
| // other non-fixable conditions | ||
| result, err := run(ctx, call, opts) | ||
| if err != nil { | ||
| if errors.Is(err, evmcore.ErrIntrinsicGas) { | ||
| return true, nil, nil // Special case, raise gas limit | ||
| } | ||
| return true, nil, err // Bail out | ||
| } | ||
| return result.Failed(), result, nil | ||
| } | ||
|
|
||
| // run assembles the EVM as defined by the consensus rules and runs the requested | ||
| // call invocation. | ||
| func run(ctx context.Context, call *types.Message, opts *Options) (*evmcore.ExecutionResult, error) { | ||
| // Assemble the call and the call context | ||
| var ( | ||
| msgContext = evmcore.NewEVMTxContext(call) | ||
| evmContext = evmcore.NewEVMBlockContext(opts.Header, opts.Chain, nil) | ||
|
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||
| dirtyState = opts.State.Copy() | ||
| ) | ||
| // Lower the base fee to 0 to avoid breaking EVM | ||
| // invariants (basefee < feecap). | ||
| if msgContext.GasPrice.Sign() == 0 { | ||
| evmContext.BaseFee = new(big.Int) | ||
| } | ||
| evm := vm.NewEVM(evmContext, msgContext, dirtyState, opts.Config, vm.Config{NoBaseFee: true}) | ||
| // Monitor the outer context and interrupt the EVM upon cancellation. To avoid | ||
| // a dangling goroutine until the outer estimation finishes, create an internal | ||
| // context for the lifetime of this method call. | ||
| ctx, cancel := context.WithCancel(ctx) | ||
| defer cancel() | ||
|
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||
| go func() { | ||
| <-ctx.Done() | ||
| evm.Cancel() | ||
| }() | ||
| // Execute the call, returning a wrapped error or the result | ||
| result, err := evmcore.ApplyMessage(evm, call, new(evmcore.GasPool).AddGas(math.MaxUint64)) | ||
| if vmerr := dirtyState.Error(); vmerr != nil { | ||
| return nil, vmerr | ||
| } | ||
| if err != nil { | ||
| return result, fmt.Errorf("failed with %d gas: %w", call.Gas(), err) | ||
| } | ||
| return result, nil | ||
| } |
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