func (t *MerkleTree) getChildPointer(n *node, isRight bool) (**node, error) {
ix := coname.BitToIndex(isRight)
if n.childIds[ix] != 0 && n.children[ix] == nil {
// lazy-load the child. *don't* append to n.prefixBits!
childIndex := append(append([]bool{}, n.prefixBits...), isRight)
child, err := t.loadNode(n.childIds[ix], childIndex)
if err != nil {
return nil, err
}
n.children[ix] = child
}
return &n.children[ix], nil
}
// Set updates the leaf value at the index (or inserts it if it did not exist).
// In-memory: doesn't actually touch the disk yet.
func (snapshot *NewSnapshot) Set(indexBytes []byte, value []byte) (err error) {
if len(indexBytes) != coname.IndexBytes {
return fmt.Errorf("Wrong index length")
}
if len(value) != coname.HashBytes {
return fmt.Errorf("Wrong value length")
}
value = append([]byte(nil), value...) // Make a copy of value
indexBits := coname.ToBits(coname.IndexBits, indexBytes)
nodePointer := &snapshot.root
position := 0
// Traverse down the tree, following either the left or right child depending on the next bit.
for *nodePointer != nil && !(*nodePointer).isLeaf {
nodePointer, err = snapshot.tree.getChildPointer(*nodePointer, indexBits[position])
if err != nil {
return
}
position++
}
if *nodePointer == nil {
// We've hit an empty branch where this leaf belongs -- put it there.
*nodePointer = &node{
diskNode: diskNode{
isLeaf: true,
indexBytes: append([]byte{}, indexBytes...), // Make a copy of indexBytes
value: value,
},
prefixBits: indexBits[:position],
}
} else if bytes.Equal((*nodePointer).indexBytes, indexBytes) {
// We have an existing leaf at this index; just replace the value
(*nodePointer).value = value
} else {
// We have a different leaf with a matching prefix. We'll have to create new intermediate nodes.
oldLeaf := *nodePointer
oldLeafIndexBits := coname.ToBits(coname.IndexBits, oldLeaf.indexBytes)
// Create a new intermediate node for each bit that has now become shared.
for oldLeafIndexBits[position] == indexBits[position] {
newNode := &node{
diskNode: diskNode{
isLeaf: false,
},
prefixBits: indexBits[:position],
}
*nodePointer, nodePointer = newNode, &newNode.children[coname.BitToIndex(indexBits[position])]
position++
}
// Create a new node at which the tree now branches.
splitNode := &node{
diskNode: diskNode{
isLeaf: false,
},
prefixBits: indexBits[:position],
}
// Create the new leaf under the splitNode
newLeaf := &node{
diskNode: diskNode{
isLeaf: true,
indexBytes: append([]byte{}, indexBytes...), // Make a copy of the index
value: value,
},
prefixBits: indexBits[:position+1],
}
// Move the old leaf's index down
oldLeaf.prefixBits = oldLeafIndexBits[:position+1]
splitNode.children[coname.BitToIndex(indexBits[position])] = newLeaf
splitNode.children[coname.BitToIndex(oldLeafIndexBits[position])] = oldLeaf
*nodePointer = splitNode
}
return nil
}
func (n *LookupTracingNode) ChildHash(rightChild bool) []byte {
return n.node.childHashes[coname.BitToIndex(rightChild)][:]
}