[17.09] Serializing bitseq alloc

bitseq/sequence.go

@@ -41,6 +41,7 @@ type Handle struct {
 	id         string
 	dbIndex    uint64
 	dbExists   bool
+	curr       uint64
 	store      datastore.DataStore
 	sync.Mutex
 }
@@ -193,34 +194,35 @@ func (h *Handle) getCopy() *Handle {
 		dbIndex:    h.dbIndex,
 		dbExists:   h.dbExists,
 		store:      h.store,
+		curr:       h.curr,
 	}
 }
 
 // SetAnyInRange atomically sets the first unset bit in the specified range in the sequence and returns the corresponding ordinal
-func (h *Handle) SetAnyInRange(start, end uint64) (uint64, error) {
+func (h *Handle) SetAnyInRange(start, end uint64, serial bool) (uint64, error) {
 	if end < start || end >= h.bits {
 		return invalidPos, fmt.Errorf("invalid bit range [%d, %d]", start, end)
 	}
 	if h.Unselected() == 0 {
 		return invalidPos, ErrNoBitAvailable
 	}
-	return h.set(0, start, end, true, false)
+	return h.set(0, start, end, true, false, serial)
 }
 
 // SetAny atomically sets the first unset bit in the sequence and returns the corresponding ordinal
-func (h *Handle) SetAny() (uint64, error) {
+func (h *Handle) SetAny(serial bool) (uint64, error) {
 	if h.Unselected() == 0 {
 		return invalidPos, ErrNoBitAvailable
 	}
-	return h.set(0, 0, h.bits-1, true, false)
+	return h.set(0, 0, h.bits-1, true, false, serial)
 }
 
 // Set atomically sets the corresponding bit in the sequence
 func (h *Handle) Set(ordinal uint64) error {
 	if err := h.validateOrdinal(ordinal); err != nil {
 		return err
 	}
-	_, err := h.set(ordinal, 0, 0, false, false)
+	_, err := h.set(ordinal, 0, 0, false, false, false)
 	return err
 }
 
@@ -229,7 +231,7 @@ func (h *Handle) Unset(ordinal uint64) error {
 	if err := h.validateOrdinal(ordinal); err != nil {
 		return err
 	}
-	_, err := h.set(ordinal, 0, 0, false, true)
+	_, err := h.set(ordinal, 0, 0, false, true, false)
 	return err
 }
 
@@ -298,7 +300,7 @@ func (h *Handle) CheckConsistency() error {
 }
 
 // set/reset the bit
-func (h *Handle) set(ordinal, start, end uint64, any bool, release bool) (uint64, error) {
+func (h *Handle) set(ordinal, start, end uint64, any bool, release bool, serial bool) (uint64, error) {
 	var (
 		bitPos  uint64
 		bytePos uint64
@@ -308,6 +310,7 @@ func (h *Handle) set(ordinal, start, end uint64, any bool, release bool) (uint64
 
 	for {
 		var store datastore.DataStore
+		curr := uint64(0)
 		h.Lock()
 		store = h.store
 		h.Unlock()
@@ -318,15 +321,18 @@ func (h *Handle) set(ordinal, start, end uint64, any bool, release bool) (uint64
 		}
 
 		h.Lock()
+		if serial {
+			curr = h.curr
+		}
 		// Get position if available
 		if release {
 			bytePos, bitPos = ordinalToPos(ordinal)
 		} else {
 			if any {
-				bytePos, bitPos, err = getFirstAvailable(h.head, start)
+				bytePos, bitPos, err = getAvailableFromCurrent(h.head, start, curr, end)
 				ret = posToOrdinal(bytePos, bitPos)
-				if end < ret {
-					err = ErrNoBitAvailable
+				if err == nil {
+					h.curr = ret + 1
 				}
 			} else {
 				bytePos, bitPos, err = checkIfAvailable(h.head, ordinal)
@@ -515,6 +521,29 @@ func getFirstAvailable(head *sequence, start uint64) (uint64, uint64, error) {
 	return invalidPos, invalidPos, ErrNoBitAvailable
 }
 
+// getAvailableFromCurrent will look for available ordinal from the current ordinal.
+// If none found then it will loop back to the start to check of the available bit.
+// This can be further optimized to check from start till curr in case of a rollover
+func getAvailableFromCurrent(head *sequence, start, curr, end uint64) (uint64, uint64, error) {
+	var bytePos, bitPos uint64
+	if curr != 0 && curr > start {
+		bytePos, bitPos, _ = getFirstAvailable(head, curr)
+		ret := posToOrdinal(bytePos, bitPos)
+		if end < ret {
+			goto begin
+		}
+		return bytePos, bitPos, nil
+	}
+
+begin:
+	bytePos, bitPos, _ = getFirstAvailable(head, start)
+	ret := posToOrdinal(bytePos, bitPos)
+	if end < ret {
+		return invalidPos, invalidPos, ErrNoBitAvailable
+	}
+	return bytePos, bitPos, nil
+}
+
 // checkIfAvailable checks if the bit correspondent to the specified ordinal is unset
 // If the ordinal is beyond the sequence limits, a negative response is returned
 func checkIfAvailable(head *sequence, ordinal uint64) (uint64, uint64, error) {