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