Diff methods that use tracked and node sinking ForEach methods

Author: i-norden

diff.go

@@ -24,10 +24,11 @@ const (
 // Change represents a change to a DAG and contains a reference to the old and
 // new CIDs.
 type Change struct {
-	Type   ChangeType
-	Key    string
-	Before *cbg.Deferred
-	After  *cbg.Deferred
+	Type           ChangeType
+	Key            string
+	Before         *cbg.Deferred
+	After          *cbg.Deferred
+	SelectorSuffix []int
 }
 
 func (ch Change) String() string {
@@ -57,6 +58,29 @@ func Diff(ctx context.Context, prevBs, curBs cbor.IpldStore, prev, cur cid.Cid,
 	return diffNode(ctx, prevHamt, curHamt, 0)
 }
 
+// DiffTrackedWithNodeSink returns a set of changes that transform node 'prev' into node 'cur'. opts are applied to both prev and cur.
+// it associates selector suffixes with the emitted Change set and sinks all unique nodes encountered under the current CID to the provided CBORUnmarshaler
+func DiffTrackedWithNodeSink(ctx context.Context, prevBs, curBs cbor.IpldStore, prev, cur cid.Cid, b *bytes.Buffer, sink cbg.CBORUnmarshaler, trail []int, opts ...Option) ([]*Change, error) {
+	if prev.Equals(cur) {
+		return nil, nil
+	}
+
+	prevHamt, err := LoadNode(ctx, prevBs, prev, opts...)
+	if err != nil {
+		return nil, err
+	}
+
+	curHamt, err := LoadNode(ctx, curBs, cur, opts...)
+	if err != nil {
+		return nil, err
+	}
+
+	if curHamt.bitWidth != prevHamt.bitWidth {
+		return nil, xerrors.Errorf("diffing HAMTs with differing bitWidths not supported (prev=%d, cur=%d)", prevHamt.bitWidth, curHamt.bitWidth)
+	}
+	return diffNodeTrackedWithNodeSink(ctx, prevHamt, curHamt, 0, b, sink, trail)
+}
+
 func diffNode(ctx context.Context, pre, cur *Node, depth int) ([]*Change, error) {
 	// which Bitfield contains the most bits. We will start a loop from this index, calling Bitfield.Bit(idx)
 	// on an out of range index will return zero.
@@ -176,6 +200,144 @@ func diffNode(ctx context.Context, pre, cur *Node, depth int) ([]*Change, error)
 	return changes, nil
 }
 
+func diffNodeTrackedWithNodeSink(ctx context.Context, pre, cur *Node, depth int, b *bytes.Buffer, sink cbg.CBORUnmarshaler, trail []int) ([]*Change, error) {
+	// which Bitfield contains the most bits. We will start a loop from this index, calling Bitfield.Bit(idx)
+	// on an out of range index will return zero.
+	bp := cur.Bitfield.BitLen()
+	if pre.Bitfield.BitLen() > bp {
+		bp = pre.Bitfield.BitLen()
+	}
+
+	if sink != nil {
+		if b == nil {
+			b = bytes.NewBuffer(nil)
+		}
+		b.Reset()
+		if err := cur.MarshalCBOR(b); err != nil {
+			return nil, err
+		}
+		if err := sink.UnmarshalCBOR(b); err != nil {
+			return nil, err
+		}
+	}
+
+	// the changes between cur and prev
+	var changes []*Change
+	l := len(trail)
+	// loop over each bit in the bitfields
+	for idx := bp; idx >= 0; idx-- {
+		preBit := pre.Bitfield.Bit(idx)
+		curBit := cur.Bitfield.Bit(idx)
+
+		subTrail := make([]int, l, l+1)
+		copy(subTrail, trail)
+		subTrail = append(subTrail, idx)
+
+		if preBit == 1 && curBit == 1 {
+			// index for pre and cur will be unique to each, calculate it here.
+			prePointer := pre.getPointer(byte(pre.indexForBitPos(idx)))
+			curPointer := cur.getPointer(byte(cur.indexForBitPos(idx)))
+
+			// both pointers are shards, recurse down the tree.
+			if prePointer.isShard() && curPointer.isShard() {
+				if prePointer.Link == curPointer.Link {
+					continue
+				}
+				preChild, err := prePointer.loadChild(ctx, pre.store, pre.bitWidth, pre.hash)
+				if err != nil {
+					return nil, err
+				}
+				curChild, err := curPointer.loadChild(ctx, cur.store, cur.bitWidth, cur.hash)
+				if err != nil {
+					return nil, err
+				}
+
+				change, err := diffNodeTrackedWithNodeSink(ctx, preChild, curChild, depth+1, b, sink, subTrail)
+				if err != nil {
+					return nil, err
+				}
+				changes = append(changes, change...)
+			}
+
+			// check if KV's from cur exists in any children of pre's child.
+			if prePointer.isShard() && !curPointer.isShard() {
+				childKV, err := prePointer.loadChildKVs(ctx, pre.store, pre.bitWidth, pre.hash)
+				if err != nil {
+					return nil, err
+				}
+				changes = append(changes, diffKVsTracked(childKV, curPointer.KVs, idx, subTrail)...)
+
+			}
+
+			// check if KV's from pre exists in any children of cur's child.
+			if !prePointer.isShard() && curPointer.isShard() {
+				childKV, err := curPointer.loadChildKVs(ctx, cur.store, cur.bitWidth, cur.hash)
+				if err != nil {
+					return nil, err
+				}
+				changes = append(changes, diffKVsTracked(prePointer.KVs, childKV, idx, subTrail)...)
+			}
+
+			// both contain KVs, compare.
+			if !prePointer.isShard() && !curPointer.isShard() {
+				changes = append(changes, diffKVsTracked(prePointer.KVs, curPointer.KVs, idx, subTrail)...)
+			}
+		} else if preBit == 1 && curBit == 0 {
+			// there exists a value in previous not found in current - it was removed
+			pointer := pre.getPointer(byte(pre.indexForBitPos(idx)))
+
+			if pointer.isShard() {
+				child, err := pointer.loadChild(ctx, pre.store, pre.bitWidth, pre.hash)
+				if err != nil {
+					return nil, err
+				}
+				rm, err := removeAllTracked(ctx, child, idx, subTrail)
+				if err != nil {
+					return nil, err
+				}
+				changes = append(changes, rm...)
+			} else {
+				for _, p := range pointer.KVs {
+					changes = append(changes, &Change{
+						Type:           Remove,
+						Key:            string(p.Key),
+						Before:         p.Value,
+						After:          nil,
+						SelectorSuffix: subTrail,
+					})
+				}
+			}
+		} else if curBit == 1 && preBit == 0 {
+			// there exists a value in current not found in previous - it was added
+			pointer := cur.getPointer(byte(cur.indexForBitPos(idx)))
+
+			if pointer.isShard() {
+				child, err := pointer.loadChild(ctx, pre.store, pre.bitWidth, pre.hash)
+				if err != nil {
+					return nil, err
+				}
+				add, err := addAllTrackWithNodeSink(ctx, child, idx, b, sink, subTrail)
+				if err != nil {
+					return nil, err
+				}
+				changes = append(changes, add...)
+			} else {
+				for _, p := range pointer.KVs {
+					changes = append(changes, &Change{
+						Type:           Add,
+						Key:            string(p.Key),
+						Before:         nil,
+						After:          p.Value,
+						SelectorSuffix: subTrail,
+					})
+				}
+			}
+		}
+	}
+
+	return changes, nil
+}
+
 func diffKVs(pre, cur []*KV, idx int) []*Change {
 	preMap := make(map[string]*cbg.Deferred, len(pre))
 	curMap := make(map[string]*cbg.Deferred, len(cur))
@@ -222,6 +384,55 @@ func diffKVs(pre, cur []*KV, idx int) []*Change {
 	return changes
 }
 
+func diffKVsTracked(pre, cur []*KV, idx int, trail []int) []*Change {
+	preMap := make(map[string]*cbg.Deferred, len(pre))
+	curMap := make(map[string]*cbg.Deferred, len(cur))
+	var changes []*Change
+
+	for _, kv := range pre {
+		preMap[string(kv.Key)] = kv.Value
+	}
+	for _, kv := range cur {
+		curMap[string(kv.Key)] = kv.Value
+	}
+	// find removed keys: keys in pre and not in cur
+	for key, value := range preMap {
+		if _, ok := curMap[key]; !ok {
+			changes = append(changes, &Change{
+				Type:           Remove,
+				Key:            key,
+				Before:         value,
+				After:          nil,
+				SelectorSuffix: trail,
+			})
+		}
+	}
+	// find added keys: keys in cur and not in pre
+	// find modified values: keys in cur and pre with different values
+	for key, curVal := range curMap {
+		if preVal, ok := preMap[key]; !ok {
+			changes = append(changes, &Change{
+				Type:           Add,
+				Key:            key,
+				Before:         nil,
+				After:          curVal,
+				SelectorSuffix: trail,
+			})
+		} else {
+			if !bytes.Equal(preVal.Raw, curVal.Raw) {
+				changes = append(changes, &Change{
+					Type:           Modify,
+					Key:            key,
+					Before:         preVal,
+					After:          curVal,
+					SelectorSuffix: trail,
+				})
+			}
+		}
+	}
+	return changes
+}
+
 func addAll(ctx context.Context, node *Node, idx int) ([]*Change, error) {
 	var changes []*Change
 	if err := node.ForEach(ctx, func(k string, val *cbg.Deferred) error {
@@ -239,6 +450,24 @@ func addAll(ctx context.Context, node *Node, idx int) ([]*Change, error) {
 	return changes, nil
 }
 
+func addAllTrackWithNodeSink(ctx context.Context, node *Node, idx int, b *bytes.Buffer, sink cbg.CBORUnmarshaler, trail []int) ([]*Change, error) {
+	var changes []*Change
+	if err := node.ForEachTrackedWithNodeSink(ctx, trail, b, sink, func(k string, val *cbg.Deferred, selectorSuffix []int) error {
+		changes = append(changes, &Change{
+			Type:           Add,
+			Key:            k,
+			Before:         nil,
+			After:          val,
+			SelectorSuffix: selectorSuffix,
+		})
+
+		return nil
+	}); err != nil {
+		return nil, err
+	}
+	return changes, nil
+}
+
 func removeAll(ctx context.Context, node *Node, idx int) ([]*Change, error) {
 	var changes []*Change
 	if err := node.ForEach(ctx, func(k string, val *cbg.Deferred) error {
@@ -255,3 +484,21 @@ func removeAll(ctx context.Context, node *Node, idx int) ([]*Change, error) {
 	}
 	return changes, nil
 }
+
+func removeAllTracked(ctx context.Context, node *Node, idx int, trail []int) ([]*Change, error) {
+	var changes []*Change
+	if err := node.ForEachTracked(ctx, trail, func(k string, val *cbg.Deferred, selectorSuffix []int) error {
+		changes = append(changes, &Change{
+			Type:           Remove,
+			Key:            k,
+			Before:         val,
+			After:          nil,
+			SelectorSuffix: selectorSuffix,
+		})
+
+		return nil
+	}); err != nil {
+		return nil, err
+	}
+	return changes, nil
+}

hamt.go

@@ -885,24 +885,29 @@ func (n *Node) ForEach(ctx context.Context, f func(k string, val *cbg.Deferred)
 // This method also provides the trail of indices to the current node, which can be used to formulate a selector suffix
 func (n *Node) ForEachTracked(ctx context.Context, trail []int, f func(k string, val *cbg.Deferred, selectorSuffix []int) error) error {
 	idx := 0
+	l := len(trail)
 	for _, p := range n.Pointers {
 		// Seek the next set bit in the bitfield to find the actual index for this pointer
 		for n.Bitfield.Bit(idx) == 0 {
 			idx++
 		}
-		trail = append(trail, idx)
+
+		subTrail := make([]int, l, l+1)
+		copy(subTrail, trail)
+		subTrail = append(subTrail, idx)
+
 		if p.isShard() {
 			chnd, err := p.loadChild(ctx, n.store, n.bitWidth, n.hash)
 			if err != nil {
 				return err
 			}
 
-			if err := chnd.ForEachTracked(ctx, trail, f); err != nil {
+			if err := chnd.ForEachTracked(ctx, subTrail, f); err != nil {
 				return err
 			}
 		} else {
 			for _, kv := range p.KVs {
-				if err := f(string(kv.Key), kv.Value, trail); err != nil {
+				if err := f(string(kv.Key), kv.Value, subTrail); err != nil {
 					return err
 				}
 			}
@@ -932,24 +937,29 @@ func (n *Node) ForEachTrackedWithNodeSink(ctx context.Context, trail []int, b *b
 		}
 	}
 	idx := 0
+	l := len(trail)
 	for _, p := range n.Pointers {
 		// Seek the next set bit in the bitfield to find the actual index for this pointer
 		for n.Bitfield.Bit(idx) == 0 {
 			idx++
 		}
-		trail = append(trail, idx)
+
+		subTrail := make([]int, l, l+1)
+		copy(subTrail, trail)
+		subTrail = append(subTrail, idx)
+
 		if p.isShard() {
 			chnd, err := p.loadChild(ctx, n.store, n.bitWidth, n.hash)
 			if err != nil {
 				return err
 			}
 
-			if err := chnd.ForEachTrackedWithNodeSink(ctx, trail, b, sink, f); err != nil {
+			if err := chnd.ForEachTrackedWithNodeSink(ctx, subTrail, b, sink, f); err != nil {
 				return err
 			}
 		} else {
 			for _, kv := range p.KVs {
-				if err := f(string(kv.Key), kv.Value, trail); err != nil {
+				if err := f(string(kv.Key), kv.Value, subTrail); err != nil {
 					return err
 				}
 			}