1 files changed, 220 insertions, 0 deletions
diff --git a/weed/filesys/dirty_page_interval.go b/weed/filesys/dirty_page_interval.go
new file mode 100644
index 000000000..ec94c6df1
--- /dev/null
+++ b/weed/filesys/dirty_page_interval.go
@@ -0,0 +1,220 @@
+package filesys
+
+import (
+	"bytes"
+	"io"
+	"math"
+)
+
+type IntervalNode struct {
+	Data   []byte
+	Offset int64
+	Size   int64
+	Next   *IntervalNode
+}
+
+type IntervalLinkedList struct {
+	Head *IntervalNode
+	Tail *IntervalNode
+}
+
+type ContinuousIntervals struct {
+	lists []*IntervalLinkedList
+}
+
+func (list *IntervalLinkedList) Offset() int64 {
+	return list.Head.Offset
+}
+func (list *IntervalLinkedList) Size() int64 {
+	return list.Tail.Offset + list.Tail.Size - list.Head.Offset
+}
+func (list *IntervalLinkedList) addNodeToTail(node *IntervalNode) {
+	// glog.V(4).Infof("add to tail [%d,%d) + [%d,%d) => [%d,%d)", list.Head.Offset, list.Tail.Offset+list.Tail.Size, node.Offset, node.Offset+node.Size, list.Head.Offset, node.Offset+node.Size)
+	list.Tail.Next = node
+	list.Tail = node
+}
+func (list *IntervalLinkedList) addNodeToHead(node *IntervalNode) {
+	// glog.V(4).Infof("add to head [%d,%d) + [%d,%d) => [%d,%d)", node.Offset, node.Offset+node.Size, list.Head.Offset, list.Tail.Offset+list.Tail.Size, node.Offset, list.Tail.Offset+list.Tail.Size)
+	node.Next = list.Head
+	list.Head = node
+}
+
+func (list *IntervalLinkedList) ReadData(buf []byte, start, stop int64) {
+	t := list.Head
+	for {
+
+		nodeStart, nodeStop := max(start, t.Offset), min(stop, t.Offset+t.Size)
+		if nodeStart < nodeStop {
+			// glog.V(0).Infof("copying start=%d stop=%d t=[%d,%d) t.data=%d => bufSize=%d nodeStart=%d, nodeStop=%d", start, stop, t.Offset, t.Offset+t.Size, len(t.Data), len(buf), nodeStart, nodeStop)
+			copy(buf[nodeStart-start:], t.Data[nodeStart-t.Offset:nodeStop-t.Offset])
+		}
+
+		if t.Next == nil {
+			break
+		}
+		t = t.Next
+	}
+}
+
+func (c *ContinuousIntervals) TotalSize() (total int64) {
+	for _, list := range c.lists {
+		total += list.Size()
+	}
+	return
+}
+
+func subList(list *IntervalLinkedList, start, stop int64) *IntervalLinkedList {
+	var nodes []*IntervalNode
+	for t := list.Head; t != nil; t = t.Next {
+		nodeStart, nodeStop := max(start, t.Offset), min(stop, t.Offset+t.Size)
+		if nodeStart >= nodeStop {
+			// skip non overlapping IntervalNode
+			continue
+		}
+		nodes = append(nodes, &IntervalNode{
+			Data:   t.Data[nodeStart-t.Offset : nodeStop-t.Offset],
+			Offset: nodeStart,
+			Size:   nodeStop - nodeStart,
+			Next:   nil,
+		})
+	}
+	for i := 1; i < len(nodes); i++ {
+		nodes[i-1].Next = nodes[i]
+	}
+	return &IntervalLinkedList{
+		Head: nodes[0],
+		Tail: nodes[len(nodes)-1],
+	}
+}
+
+func (c *ContinuousIntervals) AddInterval(data []byte, offset int64) {
+
+	interval := &IntervalNode{Data: data, Offset: offset, Size: int64(len(data))}
+
+	var newLists []*IntervalLinkedList
+	for _, list := range c.lists {
+		// if list is to the left of new interval, add to the new list
+		if list.Tail.Offset+list.Tail.Size <= interval.Offset {
+			newLists = append(newLists, list)
+		}
+		// if list is to the right of new interval, add to the new list
+		if interval.Offset+interval.Size <= list.Head.Offset {
+			newLists = append(newLists, list)
+		}
+		// if new interval overwrite the right part of the list
+		if list.Head.Offset < interval.Offset && interval.Offset < list.Tail.Offset+list.Tail.Size {
+			// create a new list of the left part of existing list
+			newLists = append(newLists, subList(list, list.Offset(), interval.Offset))
+		}
+		// if new interval overwrite the left part of the list
+		if list.Head.Offset < interval.Offset+interval.Size && interval.Offset+interval.Size < list.Tail.Offset+list.Tail.Size {
+			// create a new list of the right part of existing list
+			newLists = append(newLists, subList(list, interval.Offset+interval.Size, list.Tail.Offset+list.Tail.Size))
+		}
+		// skip anything that is fully overwritten by the new interval
+	}
+
+	c.lists = newLists
+	// add the new interval to the lists, connecting neighbor lists
+	var prevList, nextList *IntervalLinkedList
+
+	for _, list := range c.lists {
+		if list.Head.Offset == interval.Offset+interval.Size {
+			nextList = list
+			break
+		}
+	}
+
+	for _, list := range c.lists {
+		if list.Head.Offset+list.Size() == offset {
+			list.addNodeToTail(interval)
+			prevList = list
+			break
+		}
+	}
+
+	if prevList != nil && nextList != nil {
+		// glog.V(4).Infof("connecting [%d,%d) + [%d,%d) => [%d,%d)", prevList.Head.Offset, prevList.Tail.Offset+prevList.Tail.Size, nextList.Head.Offset, nextList.Tail.Offset+nextList.Tail.Size, prevList.Head.Offset, nextList.Tail.Offset+nextList.Tail.Size)
+		prevList.Tail.Next = nextList.Head
+		prevList.Tail = nextList.Tail
+		c.removeList(nextList)
+	} else if nextList != nil {
+		// add to head was not done when checking
+		nextList.addNodeToHead(interval)
+	}
+	if prevList == nil && nextList == nil {
+		c.lists = append(c.lists, &IntervalLinkedList{
+			Head: interval,
+			Tail: interval,
+		})
+	}
+
+	return
+}
+
+func (c *ContinuousIntervals) RemoveLargestIntervalLinkedList() *IntervalLinkedList {
+	var maxSize int64
+	maxIndex := -1
+	for k, list := range c.lists {
+		if maxSize <= list.Size() {
+			maxSize = list.Size()
+			maxIndex = k
+		}
+	}
+	if maxSize <= 0 {
+		return nil
+	}
+
+	t := c.lists[maxIndex]
+	c.lists = append(c.lists[0:maxIndex], c.lists[maxIndex+1:]...)
+	return t
+
+}
+
+func (c *ContinuousIntervals) removeList(target *IntervalLinkedList) {
+	index := -1
+	for k, list := range c.lists {
+		if list.Offset() == target.Offset() {
+			index = k
+		}
+	}
+	if index < 0 {
+		return
+	}
+
+	c.lists = append(c.lists[0:index], c.lists[index+1:]...)
+
+}
+
+func (c *ContinuousIntervals) ReadData(data []byte, startOffset int64) (offset int64, size int) {
+	var minOffset int64 = math.MaxInt64
+	var maxStop int64
+	for _, list := range c.lists {
+		start := max(startOffset, list.Offset())
+		stop := min(startOffset+int64(len(data)), list.Offset()+list.Size())
+		if start <= stop {
+			list.ReadData(data[start-startOffset:], start, stop)
+			minOffset = min(minOffset, start)
+			maxStop = max(maxStop, stop)
+		}
+	}
+
+	if minOffset == math.MaxInt64 {
+		return 0, 0
+	}
+
+	offset = minOffset
+	size = int(maxStop - offset)
+	return
+}
+
+func (l *IntervalLinkedList) ToReader() io.Reader {
+	var readers []io.Reader
+	t := l.Head
+	readers = append(readers, bytes.NewReader(t.Data))
+	for t.Next != nil {
+		t = t.Next
+		readers = append(readers, bytes.NewReader(t.Data))
+	}
+	return io.MultiReader(readers...)
+}