package pilorama // nodeInfo couples parent and metadata. type nodeInfo struct { Parent Node Meta Meta Timestamp Timestamp } // state represents state being replicated. type state struct { operations []LogMove tree } // newState constructs new empty tree. func newState() *state { return &state{ tree: *newTree(), } } // undo un-does op and changes s in-place. func (s *state) undo(op *LogMove) { children := s.tree.childMap[op.Parent] for i := range children { if children[i] == op.Child { if len(children) > 1 { s.tree.childMap[op.Parent] = append(children[:i], children[i+1:]...) } else { delete(s.tree.childMap, op.Parent) } break } } if op.HasOld { s.tree.infoMap[op.Child] = op.Old oldChildren := s.tree.childMap[op.Old.Parent] for i := range oldChildren { if oldChildren[i] == op.Child { return } } s.tree.childMap[op.Old.Parent] = append(oldChildren, op.Child) } else { delete(s.tree.infoMap, op.Child) } } // Apply puts op in log at a proper position, re-applies all subsequent operations // from log and changes s in-place. func (s *state) Apply(op *Move) error { var index int for index = len(s.operations); index > 0; index-- { if s.operations[index-1].Time <= op.Time { break } } if index == len(s.operations) { s.operations = append(s.operations, s.do(op)) return nil } s.operations = append(s.operations[:index+1], s.operations[index:]...) for i := len(s.operations) - 1; i > index; i-- { s.undo(&s.operations[i]) } s.operations[index] = s.do(op) for i := index + 1; i < len(s.operations); i++ { s.operations[i] = s.do(&s.operations[i].Move) } return nil } // do performs a single move operation on a tree. func (s *state) do(op *Move) LogMove { lm := LogMove{ Move: Move{ Parent: op.Parent, Meta: op.Meta, Child: op.Child, }, } _, parentInTree := s.tree.infoMap[op.Parent] shouldPut := !s.tree.isAncestor(op.Child, op.Parent) && !(op.Parent != 0 && op.Parent != TrashID && !parentInTree) shouldRemove := op.Parent == TrashID p, ok := s.tree.infoMap[op.Child] if ok { lm.HasOld = true lm.Old = p } if !shouldPut { return lm } if shouldRemove { if ok { s.removeChild(op.Child, p.Parent) } delete(s.tree.infoMap, op.Child) return lm } if !ok { p.Timestamp = op.Time } else { s.removeChild(op.Child, p.Parent) } p.Meta = op.Meta p.Parent = op.Parent s.tree.infoMap[op.Child] = p s.tree.childMap[op.Parent] = append(s.tree.childMap[op.Parent], op.Child) return lm } func (s *state) removeChild(child, parent Node) { oldChildren := s.tree.childMap[parent] for i := range oldChildren { if oldChildren[i] == child { s.tree.childMap[parent] = append(oldChildren[:i], oldChildren[i+1:]...) break } } } func (s *state) timestamp() Timestamp { if len(s.operations) == 0 { return 0 } return s.operations[len(s.operations)-1].Time + 1 } func (s *state) findSpareID() Node { id := uint64(1) for _, ok := s.infoMap[id]; ok; _, ok = s.infoMap[id] { id++ } return id } // tree is a mapping from the child nodes to their parent and metadata. type tree struct { infoMap map[Node]nodeInfo childMap map[Node][]Node } func newTree() *tree { return &tree{ childMap: make(map[Node][]Node), infoMap: make(map[Node]nodeInfo), } } // isAncestor returns true if parent is an ancestor of a child. // For convenience, also return true if parent == child. func (t tree) isAncestor(parent, child Node) bool { for c := child; c != parent; { p, ok := t.infoMap[c] if !ok { return false } c = p.Parent } return true } // getPathPrefix descends by path constructed from values of attr until // there is no node corresponding to a path element. Returns the amount of nodes // processed and ID of the last node. func (t tree) getPathPrefix(attr string, path []string) (int, Node) { var curNode Node loop: for i := range path { children := t.childMap[curNode] for j := range children { f := t.infoMap[children[j]].Meta.GetAttr(attr) if string(f) == path[i] { curNode = children[j] continue loop } } return i, curNode } return len(path), curNode } // get returns list of nodes which have the specified path from root // descending by values of attr from meta. func (t tree) get(attr string, path []string, latest bool) []Node { if len(path) == 0 { return nil } i, curNode := t.getPathPrefix(attr, path[:len(path)-1]) if i < len(path)-1 { return nil } var nodes []Node var lastTs Timestamp children := t.childMap[curNode] for i := range children { info := t.infoMap[children[i]] fileName := string(info.Meta.GetAttr(attr)) if fileName == path[len(path)-1] { if latest { if info.Timestamp >= lastTs { nodes = append(nodes[:0], children[i]) } } else { nodes = append(nodes, children[i]) } } } return nodes } // getMeta returns meta information of node n. func (t tree) getMeta(n Node) Meta { return t.infoMap[n].Meta }