feat(core): add gas meter

core/gas/meter.go

@@ -0,0 +1,40 @@
+// Package gas provides a basic API for app modules to track gas usage.
+package gas
+
+import "context"
+
+type Gas = uint64
+
+// Service represents a gas service which can retrieve and set a gas meter in a context.
+// gas.Service is a core API type that should be provided by the runtime module being used to
+// build an app via depinject.
+type Service interface {
+	// GetGasMeter returns the current transaction-level gas meter. A non-nil meter
+	// is always returned. When one is unavailable in the context an infinite gas meter
+	// will be returned.
+	GetGasMeter(context.Context) Meter
+
+	// GetBlockGasMeter returns the current block-level gas meter. A non-nil meter
+	// is always returned. When one is unavailable in the context an infinite gas meter
+	// will be returned.
+	GetBlockGasMeter(context.Context) Meter
+
+	// WithGasMeter returns a new context with the provided transaction-level gas meter.
+	WithGasMeter(ctx context.Context, meter Meter) context.Context
+
+	// WithBlockGasMeter returns a new context with the provided block-level gas meter.
+	WithBlockGasMeter(ctx context.Context, meter Meter) context.Context
+}
+
+// Meter represents a gas meter.
+type Meter interface {
+	GasConsumed() Gas
+	GasConsumedToLimit() Gas
+	GasRemaining() Gas
+	Limit() Gas
+	ConsumeGas(amount Gas, descriptor string)
+	RefundGas(amount Gas, descriptor string)
+	IsPastLimit() bool
+	IsOutOfGas() bool
+	String() string
+}