plugeth/ethutil/trie.go

package ethutil

import (
	"fmt"
	"reflect"
)

// TODO
// A StateObject is an object that has a state root
// This is goig to be the object for the second level caching (the caching of object which have a state such as contracts)
type StateObject interface {
	State() *Trie
	Sync()
	Undo()
}

type Node struct {
	Key   []byte
	Value *Value
	Dirty bool
}

func NewNode(key []byte, val *Value, dirty bool) *Node {
	return &Node{Key: key, Value: val, Dirty: dirty}
}

func (n *Node) Copy() *Node {
	return NewNode(n.Key, n.Value, n.Dirty)
}

type Cache struct {
	nodes   map[string]*Node
	db      Database
	IsDirty bool
}

func NewCache(db Database) *Cache {
	return &Cache{db: db, nodes: make(map[string]*Node)}
}

func (cache *Cache) Put(v interface{}) interface{} {
	value := NewValue(v)

	enc := value.Encode()
	if len(enc) >= 32 {
		sha := Sha3Bin(enc)

		cache.nodes[string(sha)] = NewNode(sha, value, true)
		cache.IsDirty = true

		return sha
	}

	return v
}

func (cache *Cache) Get(key []byte) *Value {
	// First check if the key is the cache
	if cache.nodes[string(key)] != nil {
		return cache.nodes[string(key)].Value
	}

	// Get the key of the database instead and cache it
	data, _ := cache.db.Get(key)
	// Create the cached value
	value := NewValueFromBytes(data)
	// Create caching node
	cache.nodes[string(key)] = NewNode(key, value, false)

	return value
}

func (cache *Cache) Delete(key []byte) {
	delete(cache.nodes, string(key))

	cache.db.Delete(key)
}

func (cache *Cache) Commit() {
	// Don't try to commit if it isn't dirty
	if !cache.IsDirty {
		return
	}

	for key, node := range cache.nodes {
		if node.Dirty {
			cache.db.Put([]byte(key), node.Value.Encode())
			node.Dirty = false
		}
	}
	cache.IsDirty = false

	// If the nodes grows beyond the 200 entries we simple empty it
	// FIXME come up with something better
	if len(cache.nodes) > 200 {
		cache.nodes = make(map[string]*Node)
	}
}

func (cache *Cache) Undo() {
	for key, node := range cache.nodes {
		if node.Dirty {
			delete(cache.nodes, key)
		}
	}
	cache.IsDirty = false
}

// A (modified) Radix Trie implementation. The Trie implements
// a caching mechanism and will used cached values if they are
// present. If a node is not present in the cache it will try to
// fetch it from the database and store the cached value.
// Please note that the data isn't persisted unless `Sync` is
// explicitly called.
type Trie struct {
	prevRoot interface{}
	Root     interface{}
	//db   Database
	cache *Cache
}

func copyRoot(root interface{}) interface{} {
	var prevRootCopy interface{}
	if b, ok := root.([]byte); ok {
		prevRootCopy = CopyBytes(b)
	} else {
		prevRootCopy = root
	}

	return prevRootCopy
}

func NewTrie(db Database, Root interface{}) *Trie {
	// Make absolute sure the root is copied
	r := copyRoot(Root)
	p := copyRoot(Root)

	return &Trie{cache: NewCache(db), Root: r, prevRoot: p}
}

// Save the cached value to the database.
func (t *Trie) Sync() {
	t.cache.Commit()
	t.prevRoot = copyRoot(t.Root)
}

func (t *Trie) Undo() {
	t.cache.Undo()
	t.Root = t.prevRoot
}

func (t *Trie) Cache() *Cache {
	return t.cache
}

/*
 * Public (query) interface functions
 */
func (t *Trie) Update(key string, value string) {
	k := CompactHexDecode(key)

	t.Root = t.UpdateState(t.Root, k, value)
}

func (t *Trie) Get(key string) string {
	k := CompactHexDecode(key)
	c := NewValue(t.GetState(t.Root, k))

	return c.Str()
}

func (t *Trie) Delete(key string) {
	t.Update(key, "")
}

func (t *Trie) GetState(node interface{}, key []int) interface{} {
	n := NewValue(node)
	// Return the node if key is empty (= found)
	if len(key) == 0 || n.IsNil() || n.Len() == 0 {
		return node
	}

	currentNode := t.GetNode(node)
	length := currentNode.Len()

	if length == 0 {
		return ""
	} else if length == 2 {
		// Decode the key
		k := CompactDecode(currentNode.Get(0).Str())
		v := currentNode.Get(1).Raw()

		if len(key) >= len(k) && CompareIntSlice(k, key[:len(k)]) {
			return t.GetState(v, key[len(k):])
		} else {
			return ""
		}
	} else if length == 17 {
		return t.GetState(currentNode.Get(key[0]).Raw(), key[1:])
	}

	// It shouldn't come this far
	fmt.Println("GetState unexpected return")
	return ""
}

func (t *Trie) GetNode(node interface{}) *Value {
	n := NewValue(node)

	if !n.Get(0).IsNil() {
		return n
	}

	str := n.Str()
	if len(str) == 0 {
		return n
	} else if len(str) < 32 {
		return NewValueFromBytes([]byte(str))
	}

	return t.cache.Get(n.Bytes())
}

func (t *Trie) UpdateState(node interface{}, key []int, value string) interface{} {

	if value != "" {
		return t.InsertState(node, key, value)
	} else {
		// delete it
		return t.DeleteState(node, key)
	}

	return t.Root
}

func (t *Trie) Put(node interface{}) interface{} {
	/*
		TODO?
			c := Conv(t.Root)
			fmt.Println(c.Type(), c.Length())
			if c.Type() == reflect.String && c.AsString() == "" {
				return enc
			}
	*/

	return t.cache.Put(node)

}

func EmptyStringSlice(l int) []interface{} {
	slice := make([]interface{}, l)
	for i := 0; i < l; i++ {
		slice[i] = ""
	}
	return slice
}

func (t *Trie) InsertState(node interface{}, key []int, value interface{}) interface{} {
	if len(key) == 0 {
		return value
	}

	// New node
	n := NewValue(node)
	if node == nil || (n.Type() == reflect.String && (n.Str() == "" || n.Get(0).IsNil())) || n.Len() == 0 {
		newNode := []interface{}{CompactEncode(key), value}

		return t.Put(newNode)
	}

	currentNode := t.GetNode(node)
	// Check for "special" 2 slice type node
	if currentNode.Len() == 2 {
		// Decode the key

		k := CompactDecode(currentNode.Get(0).Str())
		v := currentNode.Get(1).Raw()

		// Matching key pair (ie. there's already an object with this key)
		if CompareIntSlice(k, key) {
			newNode := []interface{}{CompactEncode(key), value}
			return t.Put(newNode)
		}

		var newHash interface{}
		matchingLength := MatchingNibbleLength(key, k)
		if matchingLength == len(k) {
			// Insert the hash, creating a new node
			newHash = t.InsertState(v, key[matchingLength:], value)
		} else {
			// Expand the 2 length slice to a 17 length slice
			oldNode := t.InsertState("", k[matchingLength+1:], v)
			newNode := t.InsertState("", key[matchingLength+1:], value)
			// Create an expanded slice
			scaledSlice := EmptyStringSlice(17)
			// Set the copied and new node
			scaledSlice[k[matchingLength]] = oldNode
			scaledSlice[key[matchingLength]] = newNode

			newHash = t.Put(scaledSlice)
		}

		if matchingLength == 0 {
			// End of the chain, return
			return newHash
		} else {
			newNode := []interface{}{CompactEncode(key[:matchingLength]), newHash}
			return t.Put(newNode)
		}
	} else {

		// Copy the current node over to the new node and replace the first nibble in the key
		newNode := EmptyStringSlice(17)

		for i := 0; i < 17; i++ {
			cpy := currentNode.Get(i).Raw()
			if cpy != nil {
				newNode[i] = cpy
			}
		}

		newNode[key[0]] = t.InsertState(currentNode.Get(key[0]).Raw(), key[1:], value)

		return t.Put(newNode)
	}

	return ""
}

func (t *Trie) DeleteState(node interface{}, key []int) interface{} {
	if len(key) == 0 {
		return ""
	}

	// New node
	n := NewValue(node)
	if node == nil || (n.Type() == reflect.String && (n.Str() == "" || n.Get(0).IsNil())) || n.Len() == 0 {
		return ""
	}

	currentNode := t.GetNode(node)
	// Check for "special" 2 slice type node
	if currentNode.Len() == 2 {
		// Decode the key
		k := CompactDecode(currentNode.Get(0).Str())
		v := currentNode.Get(1).Raw()

		// Matching key pair (ie. there's already an object with this key)
		if CompareIntSlice(k, key) {
			return ""
		} else if CompareIntSlice(key[:len(k)], k) {
			hash := t.DeleteState(v, key[len(k):])
			child := t.GetNode(hash)

			var newNode []interface{}
			if child.Len() == 2 {
				newKey := append(k, CompactDecode(child.Get(0).Str())...)
				newNode = []interface{}{CompactEncode(newKey), child.Get(1).Raw()}
			} else {
				newNode = []interface{}{currentNode.Get(0).Str(), hash}
			}

			return t.Put(newNode)
		} else {
			return node
		}
	} else {
		// Copy the current node over to the new node and replace the first nibble in the key
		n := EmptyStringSlice(17)
		var newNode []interface{}

		for i := 0; i < 17; i++ {
			cpy := currentNode.Get(i).Raw()
			if cpy != nil {
				n[i] = cpy
			}
		}

		n[key[0]] = t.DeleteState(n[key[0]], key[1:])
		amount := -1
		for i := 0; i < 17; i++ {
			if n[i] != "" {
				if amount == -1 {
					amount = i
				} else {
					amount = -2
				}
			}
		}
		if amount == 16 {
			newNode = []interface{}{CompactEncode([]int{16}), n[amount]}
		} else if amount >= 0 {
			child := t.GetNode(n[amount])
			if child.Len() == 17 {
				newNode = []interface{}{CompactEncode([]int{amount}), n[amount]}
			} else if child.Len() == 2 {
				key := append([]int{amount}, CompactDecode(child.Get(0).Str())...)
				newNode = []interface{}{CompactEncode(key), child.Get(1).Str()}
			}

		} else {
			newNode = n
		}

		return t.Put(newNode)
	}

	return ""
}

// Simple compare function which creates a rlp value out of the evaluated objects
func (t *Trie) Cmp(trie *Trie) bool {
	return NewValue(t.Root).Cmp(NewValue(trie.Root))
}

// Returns a copy of this trie
func (t *Trie) Copy() *Trie {
	trie := NewTrie(t.cache.db, t.Root)
	for key, node := range t.cache.nodes {
		trie.cache.nodes[key] = node.Copy()
	}

	return trie
}

type TrieIterator struct {
	trie  *Trie
	key   string
	value string

	shas   [][]byte
	values []string
}

func (t *Trie) NewIterator() *TrieIterator {
	return &TrieIterator{trie: t}
}

// Some time in the near future this will need refactoring :-)
// XXX Note to self, IsSlice == inline node. Str == sha3 to node
func (it *TrieIterator) workNode(currentNode *Value) {
	if currentNode.Len() == 2 {
		k := CompactDecode(currentNode.Get(0).Str())

		if currentNode.Get(1).Str() == "" {
			it.workNode(currentNode.Get(1))
		} else {
			if k[len(k)-1] == 16 {
				it.values = append(it.values, currentNode.Get(1).Str())
			} else {
				it.shas = append(it.shas, currentNode.Get(1).Bytes())
				it.getNode(currentNode.Get(1).Bytes())
			}
		}
	} else {
		for i := 0; i < currentNode.Len(); i++ {
			if i == 16 && currentNode.Get(i).Len() != 0 {
				it.values = append(it.values, currentNode.Get(i).Str())
			} else {
				if currentNode.Get(i).Str() == "" {
					it.workNode(currentNode.Get(i))
				} else {
					val := currentNode.Get(i).Str()
					if val != "" {
						it.shas = append(it.shas, currentNode.Get(1).Bytes())
						it.getNode([]byte(val))
					}
				}
			}
		}
	}
}

func (it *TrieIterator) getNode(node []byte) {
	currentNode := it.trie.cache.Get(node)
	it.workNode(currentNode)
}

func (it *TrieIterator) Collect() [][]byte {
	if it.trie.Root == "" {
		return nil
	}

	it.getNode(NewValue(it.trie.Root).Bytes())

	return it.shas
}

func (it *TrieIterator) Purge() int {
	shas := it.Collect()
	for _, sha := range shas {
		it.trie.cache.Delete(sha)
	}
	return len(it.values)
}

func (it *TrieIterator) Key() string {
	return ""
}

func (it *TrieIterator) Value() string {
	return ""
}