path: root/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) 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 NewTrie(db Database, Root interface{}) *Trie {
    return &Trie{cache: NewCache(db), Root: Root, prevRoot: Root}
}

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

func (t *Trie) Put(node interface{}) interface{} {
    /*
        enc := Encode(node)
        if len(enc) >= 32 {
            var sha []byte
            sha = Sha3Bin(enc)
            //t.db.Put([]byte(sha), enc)

            return sha
        }
        return node
    */

    /*
        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 ""
}

// 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
}