beacon/light: new Range methods, simplified deleteFrom

beacon/light/canonical.go

@@ -102,23 +102,13 @@ func (cs *canonicalStore[T]) add(backend ethdb.KeyValueWriter, period uint64, va
 
 // deleteFrom removes items starting from the given period.
 func (cs *canonicalStore[T]) deleteFrom(batch ethdb.Batch, fromPeriod uint64) (deleted Range) {
-	if fromPeriod >= cs.periods.End {
-		return
-	}
-	if fromPeriod < cs.periods.Start {
-		fromPeriod = cs.periods.Start
-	}
-	deleted = Range{Start: fromPeriod, End: cs.periods.End}
-	for period := fromPeriod; period < cs.periods.End; period++ {
+	keepRange, deleteRange := cs.periods.Split(fromPeriod)
+	deleteRange.Each(func(period uint64) {
 		batch.Delete(cs.databaseKey(period))
 		cs.cache.Remove(period)
-	}
-	if fromPeriod > cs.periods.Start {
-		cs.periods.End = fromPeriod
-	} else {
-		cs.periods = Range{}
-	}
-	return
+	})
+	cs.periods = keepRange
+	return deleteRange
 }
 
 // get returns the item at the given period or the null value of the given type

beacon/light/range.go

@@ -52,3 +52,27 @@ func (a *Range) Expand(period uint64) {
 		a.End++
 	}
 }
+
+// Split splits the range into two ranges. The 'fromPeriod' will be the first
+// element in the second range (if present).
+// The original range is unchanged by this operation
+func (a *Range) Split(fromPeriod uint64) (Range, Range) {
+	if fromPeriod <= a.Start {
+		// First range empty, everything in second range,
+		return Range{}, *a
+	}
+	if fromPeriod >= a.End {
+		// Second range empty, everything in first range,
+		return *a, Range{}
+	}
+	x := Range{a.Start, fromPeriod}
+	y := Range{fromPeriod, a.End}
+	return x, y
+}
+
+// Each invokes the supplied function fn once per period in range
+func (a *Range) Each(fn func(uint64)) {
+	for p := a.Start; p < a.End; p++ {
+		fn(p)
+	}
+}