From a481c4a45ef60de22d6dacf83010542ce8c6e1bb Mon Sep 17 00:00:00 2001 From: Chris Lu Date: Sun, 3 Oct 2021 13:50:52 -0700 Subject: [PATCH] return previous element if visited --- weed/util/skiplist/skiplist.go | 15 ++++++++------- weed/util/skiplist/skiplist_test.go | 18 +++++++++--------- 2 files changed, 17 insertions(+), 16 deletions(-) diff --git a/weed/util/skiplist/skiplist.go b/weed/util/skiplist/skiplist.go index 498af085d..b48a05b4a 100644 --- a/weed/util/skiplist/skiplist.go +++ b/weed/util/skiplist/skiplist.go @@ -67,17 +67,17 @@ func (t *SkipList) generateLevel(maxLevel int) int { return level } -func (t *SkipList) findEntryIndex(key []byte, level int) int { +func (t *SkipList) findEntryIndex(key []byte, minLevel int) int { // Find good entry point so we don't accidentally skip half the list. for i := t.maxLevel; i >= 0; i-- { - if t.startLevels[i] != nil && bytes.Compare(t.startLevels[i].Key, key) < 0 || i <= level { + if t.startLevels[i] != nil && bytes.Compare(t.startLevels[i].Key, key) < 0 || i <= minLevel { return i } } return 0 } -func (t *SkipList) findExtended(key []byte, findGreaterOrEqual bool) (foundElem *SkipListElement, ok bool, err error) { +func (t *SkipList) findExtended(key []byte, findGreaterOrEqual bool) (prevElementIfVisited *SkipListElement, foundElem *SkipListElement, ok bool, err error) { foundElem = nil ok = false @@ -120,6 +120,7 @@ func (t *SkipList) findExtended(key []byte, findGreaterOrEqual bool) (foundElem // Early exit if currentNode.Next[0] != nil && bytes.Compare(currentNode.Next[0].Key, key) == 0 { + prevElementIfVisited = currentNode var currentNodeNext *SkipListElement currentNodeNext, err = t.loadElement(currentNode.Next[0]) if err != nil { @@ -150,26 +151,26 @@ func (t *SkipList) findExtended(key []byte, findGreaterOrEqual bool) (foundElem // Find tries to find an element in the skiplist based on the key from the given ListElement. // elem can be used, if ok is true. // Find runs in approx. O(log(n)) -func (t *SkipList) Find(key []byte) (elem *SkipListElement, ok bool, err error) { +func (t *SkipList) Find(key []byte) (prevIfVisited *SkipListElement, elem *SkipListElement, ok bool, err error) { if t == nil || key == nil { return } - elem, ok, err = t.findExtended(key, false) + prevIfVisited, elem, ok, err = t.findExtended(key, false) return } // FindGreaterOrEqual finds the first element, that is greater or equal to the given ListElement e. // The comparison is done on the keys (So on ExtractKey()). // FindGreaterOrEqual runs in approx. O(log(n)) -func (t *SkipList) FindGreaterOrEqual(key []byte) (elem *SkipListElement, ok bool, err error) { +func (t *SkipList) FindGreaterOrEqual(key []byte) (prevIfVisited *SkipListElement, elem *SkipListElement, ok bool, err error) { if t == nil || key == nil { return } - elem, ok, err = t.findExtended(key, true) + prevIfVisited, elem, ok, err = t.findExtended(key, true) return } diff --git a/weed/util/skiplist/skiplist_test.go b/weed/util/skiplist/skiplist_test.go index 75cbc6cfd..115656cd9 100644 --- a/weed/util/skiplist/skiplist_test.go +++ b/weed/util/skiplist/skiplist_test.go @@ -23,12 +23,12 @@ func TestInsertAndFind(t *testing.T) { var listPointer *SkipList listPointer.Insert(k0, k0) - if _, ok, _ := listPointer.Find(k0); ok { + if _, _, ok, _ := listPointer.Find(k0); ok { t.Fail() } list = New(memStore) - if _, ok, _ := list.Find(k0); ok { + if _, _, ok, _ := list.Find(k0); ok { t.Fail() } if !list.IsEmpty() { @@ -42,7 +42,7 @@ func TestInsertAndFind(t *testing.T) { } for i := 0; i < maxN; i++ { key := []byte(strconv.Itoa(maxN - i)) - if _, ok, _ := list.Find(key); !ok { + if _, _, ok, _ := list.Find(key); !ok { t.Fail() } } @@ -55,7 +55,7 @@ func TestInsertAndFind(t *testing.T) { } for i := 0; i < maxN; i++ { key := []byte(strconv.Itoa(i)) - if _, ok, _ := list.Find(key); !ok { + if _, _, ok, _ := list.Find(key); !ok { t.Fail() } } @@ -71,7 +71,7 @@ func TestInsertAndFind(t *testing.T) { for _, e := range rList { key := []byte(strconv.Itoa(e)) // println("find", e) - if _, ok, _ := list.Find(key); !ok { + if _, _, ok, _ := list.Find(key); !ok { t.Fail() } } @@ -215,7 +215,7 @@ func TestFindGreaterOrEqual(t *testing.T) { var listPointer *SkipList // Test on empty list. - if _, ok, _ := listPointer.FindGreaterOrEqual(Element(0)); ok { + if _, _, ok, _ := listPointer.FindGreaterOrEqual(Element(0)); ok { t.Fail() } @@ -227,7 +227,7 @@ func TestFindGreaterOrEqual(t *testing.T) { for i := 0; i < maxN; i++ { key := Element(rand.Intn(maxNumber)) - if v, ok, _ := list.FindGreaterOrEqual(key); ok { + if _, v, ok, _ := list.FindGreaterOrEqual(key); ok { // if f is v should be bigger than the element before if v.Prev != nil && bytes.Compare(v.Prev.Key, key) >= 0 { fmt.Printf("PrevV: %s\n key: %s\n\n", string(v.Prev.Key), string(key)) @@ -261,7 +261,7 @@ func TestChangeValue(t *testing.T) { for i := 0; i < maxN; i++ { // The key only looks at the int so the string doesn't matter here! - f1, ok, _ := list.Find(Element(i)) + _, f1, ok, _ := list.Find(Element(i)) if !ok { t.Fail() } @@ -269,7 +269,7 @@ func TestChangeValue(t *testing.T) { if err != nil { t.Fail() } - f2, ok, _ := list.Find(Element(i)) + _, f2, ok, _ := list.Find(Element(i)) if !ok { t.Fail() }