.

wcfs/δftail.go

@@ -112,15 +112,32 @@ func (δf *ΔFTail) LastRevOf(file *BigFile, blk int64, at zodb.Tid) (_ zodb.Tid
 	panic("TODO")
 }
 
+// XXX δB.GetAt(root, key, at)	at ∈ (tail, head]
+
 // LastBlkRev returns last revision that changed file[blk] as of @at database state.
 //
 // if exact=False - what is returned is only an upper bound for last block revision.
+//
+// at must ∈ (tail, head]	XXX [tail ?
 func (f *BigFile) LastBlkRev(blk int64, at zodb.Tid) (_ zodb.Tid, exact bool) {
 	δf := f.head.bfdir.δFtail
 
 	// revision of when blktab[blk] entry changed last.
-	treeKeyRev, exact := δf.ΔTail.LastRevOf(f.zfile.blktab, blk, at)	// XXX activate?
-	_ = treeKeyRev
+	//treeKeyRev, exact := δf.ΔTail.LastRevOf(f.zfile.blktab, blk, at)	// XXX activate?
 
-	panic("TODO")
+	zblkOid, ok, tabRev, tabRevExact := δf.ΔTail.GetAt(f.zfile.blktab, blk, at)
+
+	// block was removed
+	if !ok {
+		return tabTev, tabRevExact
+	}
+
+	// blktab[blk] was changed to point to a zblk @rev.
+	// blk revision is max rev and when zblk changed last in (rev, at] range.
+	zblkRev, zblkExact := δZ.LastRevOf(zblkOid, at)
+	if zblkRev > rev {
+		return zblkRev, zblkRevExact
+	} else {
+		return tabRev, tabRevExact
+	}
 }