package mpt import "github.com/nspcc-dev/neo-go/pkg/util" // lcp returns longest common prefix of a and b. // Note: it does no allocations. func lcp(a, b []byte) []byte { if len(a) < len(b) { return lcp(b, a) } var i int for i = 0; i < len(b); i++ { if a[i] != b[i] { break } } return a[:i] } func lcpMany(kv []keyValue) []byte { if len(kv) == 1 { return kv[0].key } p := lcp(kv[0].key, kv[1].key) if len(p) == 0 { return p } for i := range kv[2:] { p = lcp(p, kv[2+i].key) } return p } // toNibbles mangles path by splitting every byte into 2 containing low- and high- 4-byte part. func toNibbles(path []byte) []byte { result := make([]byte, len(path)*2) for i := range path { result[i*2] = path[i] >> 4 result[i*2+1] = path[i] & 0x0F } return result } // strToNibbles mangles path by splitting every byte into 2 containing low- and high- 4-byte part, // ignoring the first byte (prefix). func strToNibbles(path string) []byte { result := make([]byte, (len(path)-1)*2) for i := 0; i < len(path)-1; i++ { result[i*2] = path[i+1] >> 4 result[i*2+1] = path[i+1] & 0x0F } return result } // fromNibbles performs operation opposite to toNibbles and does no path validity checks. func fromNibbles(path []byte) []byte { result := make([]byte, len(path)/2) for i := range result { result[i] = path[2*i]<<4 + path[2*i+1] } return result } // GetChildrenPaths returns a set of paths to node's children who are non-empty HashNodes // based on the node's path. func GetChildrenPaths(path []byte, node Node) map[util.Uint256][][]byte { res := make(map[util.Uint256][][]byte) switch n := node.(type) { case *LeafNode, *HashNode, EmptyNode: return nil case *BranchNode: for i, child := range n.Children { if child.Type() == HashT { cPath := make([]byte, len(path), len(path)+1) copy(cPath, path) if i != lastChild { cPath = append(cPath, byte(i)) } paths := res[child.Hash()] paths = append(paths, cPath) res[child.Hash()] = paths } } case *ExtensionNode: if n.next.Type() == HashT { cPath := make([]byte, len(path)+len(n.key)) copy(cPath, path) copy(cPath[len(path):], n.key) res[n.next.Hash()] = [][]byte{cPath} } default: panic("unknown Node type") } return res }