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96 lines
3.3 KiB
Go
96 lines
3.3 KiB
Go
// Copyright 2026 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package vm
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import "fmt"
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// GasCosts denotes a vector of gas costs in the multidimensional metering
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// paradigm. It represents the cost charged by an individual operation.
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//
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// StateGas is signed so an operation can express a state-gas refund
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// (negative cost) — e.g. an SSTORE that undoes an in-tx state creation.
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// Such a refund flows back into the StateGas reservoir of the GasBudget,
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// not into RegularGas.
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type GasCosts struct {
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RegularGas uint64
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StateGas int64
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}
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// String returns a visual representation of the gas vector.
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func (g GasCosts) String() string {
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return fmt.Sprintf("<%v,%v>", g.RegularGas, g.StateGas)
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}
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// GasBudget denotes a vector of remaining gas allowances available
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// for EVM execution in the multidimensional metering paradigm.
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// Unlike GasCosts which represents the price of an operation,
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// GasBudget tracks how much gas is left to spend.
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type GasBudget struct {
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RegularGas uint64 // The leftover gas for execution and state gas usage
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StateGas uint64 // The state gas reservoir
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}
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// NewGasBudget creates a GasBudget with the given initial regular gas allowance.
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func NewGasBudget(gas uint64) GasBudget {
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return GasBudget{RegularGas: gas}
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}
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// Used returns the amount of regular gas consumed so far.
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func (g GasBudget) Used(initial GasBudget) uint64 {
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return initial.RegularGas - g.RegularGas
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}
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// Exhaust sets all remaining gas to zero, preserving the initial amount
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// for usage tracking.
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func (g *GasBudget) Exhaust() {
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g.RegularGas = 0
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g.StateGas = 0
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}
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func (g *GasBudget) Copy() GasBudget {
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return GasBudget{RegularGas: g.RegularGas, StateGas: g.StateGas}
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}
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// String returns a visual representation of the gas budget vector.
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func (g GasBudget) String() string {
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return fmt.Sprintf("<%v,%v>", g.RegularGas, g.StateGas)
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}
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// CanAfford reports whether the budget has sufficient gas to cover the cost.
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func (g GasBudget) CanAfford(cost GasCosts) bool {
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return g.RegularGas >= cost.RegularGas
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}
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// Charge deducts the given gas cost from the budget. It returns the
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// pre-charge gas value and false if the budget does not have sufficient
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// gas to cover the cost.
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func (g *GasBudget) Charge(cost GasCosts) (uint64, bool) {
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prior := g.RegularGas
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if prior < cost.RegularGas {
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return prior, false
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}
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g.RegularGas -= cost.RegularGas
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return prior, true
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}
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// Refund adds the given gas budget back. It returns the pre-refund gas
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// value and whether the budget was actually changed.
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func (g *GasBudget) Refund(other GasBudget) (uint64, bool) {
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prior := g.RegularGas
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g.RegularGas += other.RegularGas
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return prior, g.RegularGas != prior
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}
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