.

wcfs/δftail.go

@@ -48,7 +48,7 @@ import (
 //						  tracked set.
 //   .Update(δZ) -> δF				- update files δ tail given raw ZODB changes
 //   .ForgetPast(revCut)			- forget changes past revCut
-//   .SliceByRev(lo, hi) -> []δF		- query for all changes with rev ∈ (lo, hi]
+//   .SliceByRev(lo, hi) -> []δF		- query for all files changes with rev ∈ (lo, hi]
 //   .SliceByFileRev(file, lo, hi) -> []δfile	- query for changes of file with rev ∈ (lo, hi]
 //   .LastBlkRev(file, #blk, at)		- query for what is last revision that changed
 //						  file[#blk] as of @at database state.
@@ -58,6 +58,8 @@ import (
 //	[]blk
 //
 // XXX concurrent use
+//
+// XXX see also zodb.ΔTail
 type ΔFtail struct {
 	// ΔFtail merge btree.ΔTail with history of ZBlk
 	δBtail  *xbtree.ΔTail
@@ -66,11 +68,14 @@ type ΔFtail struct {
 
 // ΔF represents a change in files space.
 type ΔF struct {
-	Rev     zodb.Tid
-	Change	map[*BigFile]SetI64 // file -> δfile (= {}#blk)
+	Rev    zodb.Tid
+	Change map[*BigFile]SetI64 // file -> δfile (= {}#blk)
 }
 
-func NewΔFTail(at0 zodb.Tid) *ΔFtail {
+// NewΔFtail creates new ΔFtail object.
+//
+// Initial coverage of created ΔFtail is (at₀, at₀].
+func NewΔFtail(at0 zodb.Tid) *ΔFtail {
 	return &ΔFtail{
 		δBtail:  xbtree.NewΔTail(at0),
 		fileIdx: make(map[*btree.LOBTree]SetBigFile),
@@ -84,6 +89,8 @@ func (δFtail *ΔFtail) Tail() zodb.Tid { panic("TODO") }
 
 // Track adds tree path to tracked set and associates path root with file.
 //
+// XXX text
+//
 // A root can be associated with several files (each provided on different Track call).
 func (δFtail *ΔFtail) Track(file *BigFile, path []btree.LONode) {
 	δFtail.δBtail.Track(path)
@@ -95,6 +102,8 @@ func (δFtail *ΔFtail) Track(file *BigFile, path []btree.LONode) {
 	}
 	files.Add(file)
 
+	// XXX mark something dirty so that LastBlkRev and Slice* know what to rebuild?
+
 	// XXX debug
 /*
 	leaf := path[len(path)-1].(*btree.LOBucket)
@@ -106,7 +115,7 @@ func (δFtail *ΔFtail) Track(file *BigFile, path []btree.LONode) {
 
 // Update updates δFtail given raw ZODB changes.
 //
-// It returns corresponding change in files space.
+// It returns change in files space that corresponds to δZ.
 func (δFtail *ΔFtail) Update(δZ *zodb.EventCommit) ΔF {
 	δB := δFtail.δBtail.Update(δZ)
 	δF := ΔF{Rev: δB.Rev, Change: make(map[*BigFile]SetI64)}
@@ -132,7 +141,10 @@ func (δFtail *ΔFtail) Update(δZ *zodb.EventCommit) ΔF {
 	return δF
 }
 
-// XXX ForgetPast
+// ForgetPast discards all δFtail entries with rev ≤ revCut.
+func (δFtail *ΔFtail) ForgetPast(revCut zodb.Tid) {
+	panic("TODO")
+}
 
 // LastBlkRev returns last revision that changed file[blk] as of @at database state.
 //