X ΔFtail.SliceByFileRoot tests started to work draftly after "on-the-fly" rework

wcfs/internal/zdata/δftail.go

@@ -393,6 +393,7 @@ func (δFtail *ΔFtail) ForgetPast(revCut zodb.Tid) {
 //
 // Note: contrary to regular go slicing, low is exclusive while high is inclusive.
 func (δFtail *ΔFtail) SliceByFileRev(zfile *ZBigFile, lo, hi zodb.Tid) /*readonly*/[]*ΔFile {
+	//fmt.Printf("\n")
 	xtail.AssertSlice(δFtail, lo, hi)
 
 	// XXX locking
@@ -456,7 +457,10 @@ func (δFtail *ΔFtail) SliceByFileRev(zfile *ZBigFile, lo, hi zodb.Tid) /*reado
 	} else {
 		ZinblkAt = lo
 	}
-//	it--
+	// XXX hack - should be in ΔBtail.SliceByRevRoot
+	if ZinblkAt <= lo {
+		it = -1 // don't go down beyond that
+	}
 
 	iz := len(vδZ) - 1
 	for (iz >= 0 || it >= 0) {
@@ -465,6 +469,7 @@ func (δFtail *ΔFtail) SliceByFileRev(zfile *ZBigFile, lo, hi zodb.Tid) /*reado
 		if iz >= 0 {
 			δZ := vδZ[iz]
 			if ZinblkAt <= δZ.Rev {
+				//fmt.Printf("δZ @%s\n", δZ.Rev)
 				for _, oid := range δZ.Changev {
 					inblk, ok := Zinblk[oid]
 					if ok && len(inblk) != 0 {
@@ -480,6 +485,7 @@ func (δFtail *ΔFtail) SliceByFileRev(zfile *ZBigFile, lo, hi zodb.Tid) /*reado
 		// δT -> adjust Zinblk + update δf
 		if it >= 0 {
 			δT := vδT[it]
+			//fmt.Printf("δT @%s\n", δT.Rev)
 			for blk, δzblk := range δT.ΔKV {
 				// apply in reverse as we go ←
 				if δzblk.New != xbtree.VDEL {

wcfs/internal/zdata/δftail_test.go

@@ -308,8 +308,18 @@ func TestΔFtail(t *testing.T) {
 
 		// XXX more
 
-		// found by TestΔFtailRandom
+		// ---- found by TestΔFtailRandom ----
+
 		{δT{1:a,6:i,7:d,8:e},   δD(a,c,e,f,g,h,i,j)},
+
+		// was including <= lo entries in SliceByFileRev
+		{δT{0:b,2:j,3:i,5:f,6:b,7:i,8:d},	δD(a,b,c,d,e,g,i,j)},
+		{δT{0:e,2:h,4:d,9:b},			δD(a,h,i)},
+		{δT{0:j,1:i,3:g,5:a,6:e,7:j,8:f,9:d},	δD()},
+		{δT{0:b,1:f,2:h,4:b,8:b},		δD(b,d,i)},
+		{δT{1:a,3:d,6:j},			δD(b,c,d,f,g,h,i,j)},
+		{δT{0:i,1:f,4:e,5:e,7:d,8:h},		δD(d,j)},
+		{δT{},					δD(a,b,c,e,f,g,h,i,j)},
 	}
 
 	testq := make(chan ΔFTestEntry)