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path: root/trie/iterator.go
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package trie

import "bytes"

type Iterator struct {
    trie *Trie

    Key   []byte
    Value []byte
}

func NewIterator(trie *Trie) *Iterator {
    return &Iterator{trie: trie, Key: make([]byte, 32)}
}

func (self *Iterator) Next() bool {
    self.trie.mu.Lock()
    defer self.trie.mu.Unlock()

    key := RemTerm(CompactHexDecode(string(self.Key)))
    k := self.next(self.trie.root, key)

    self.Key = []byte(DecodeCompact(k))

    return len(k) > 0
}

func (self *Iterator) next(node Node, key []byte) []byte {
    if node == nil {
        return nil
    }

    switch node := node.(type) {
    case *FullNode:
        if len(key) > 0 {
            k := self.next(node.branch(key[0]), key[1:])
            if k != nil {
                return append([]byte{key[0]}, k...)
            }
        }

        var r byte
        if len(key) > 0 {
            r = key[0] + 1
        }

        for i := r; i < 16; i++ {
            k := self.key(node.branch(byte(i)))
            if k != nil {
                return append([]byte{i}, k...)
            }
        }

    case *ShortNode:
        k := RemTerm(node.Key())
        if vnode, ok := node.Value().(*ValueNode); ok {
            if bytes.Compare([]byte(k), key) > 0 {
                self.Value = vnode.Val()
                return k
            }
        } else {
            cnode := node.Value()

            var ret []byte
            skey := key[len(k):]
            if BeginsWith(key, k) {
                ret = self.next(cnode, skey)
            } else if bytes.Compare(k, key[:len(k)]) > 0 {
                return self.key(node)
            }

            if ret != nil {
                return append(k, ret...)
            }
        }
    }

    return nil
}

func (self *Iterator) key(node Node) []byte {
    switch node := node.(type) {
    case *ShortNode:
        // Leaf node
        if vnode, ok := node.Value().(*ValueNode); ok {
            k := RemTerm(node.Key())
            self.Value = vnode.Val()

            return k
        } else {
            k := RemTerm(node.Key())
            return append(k, self.key(node.Value())...)
        }
    case *FullNode:
        if node.Value() != nil {
            self.Value = node.Value().(*ValueNode).Val()

            return []byte{16}
        }

        for i := 0; i < 16; i++ {
            k := self.key(node.branch(byte(i)))
            if k != nil {
                return append([]byte{byte(i)}, k...)
            }
        }
    }

    return nil
}