server: Move all the top level files into cmd folder. (#2490)

This change brings a change which was done for the 'mc'
package to allow for clean repo and have a cleaner
github drop in experience.

cmd/trie.go

@@ -0,0 +1,112 @@
+/*
+ * Minio Cloud Storage, (C) 2015 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cmd
+
+// This package borrows idea from - https://godoc.org/golang.org/x/text/internal/triegen
+
+// Trie trie container
+type Trie struct {
+	root *trieNode
+	size int
+}
+
+// newTrie get new trie
+func newTrie() *Trie {
+	return &Trie{
+		root: newTrieNode(),
+		size: 0,
+	}
+}
+
+// trieNode trie tree node container carries value and children
+type trieNode struct {
+	exists bool
+	value  interface{}
+	child  map[rune]*trieNode // runes as child
+}
+
+func newTrieNode() *trieNode {
+	return &trieNode{
+		exists: false,
+		value:  nil,
+		child:  make(map[rune]*trieNode),
+	}
+}
+
+// Insert insert a key
+func (t *Trie) Insert(key string) {
+	curNode := t.root
+	for _, v := range key {
+		if curNode.child[v] == nil {
+			curNode.child[v] = newTrieNode()
+		}
+		curNode = curNode.child[v]
+	}
+
+	if !curNode.exists {
+		// increment when new rune child is added
+		t.size++
+		curNode.exists = true
+	}
+	// value is stored for retrieval in future
+	curNode.value = key
+}
+
+// PrefixMatch - prefix match
+func (t *Trie) PrefixMatch(key string) []interface{} {
+	node, _ := t.findNode(key)
+	if node != nil {
+		return t.walk(node)
+	}
+	return []interface{}{}
+}
+
+// walk the tree
+func (t *Trie) walk(node *trieNode) (ret []interface{}) {
+	if node.exists {
+		ret = append(ret, node.value)
+	}
+	for _, v := range node.child {
+		ret = append(ret, t.walk(v)...)
+	}
+	return
+}
+
+// find nodes corresponding to key
+func (t *Trie) findNode(key string) (node *trieNode, index int) {
+	curNode := t.root
+	f := false
+	for k, v := range key {
+		if f {
+			index = k
+			f = false
+		}
+		if curNode.child[v] == nil {
+			return nil, index
+		}
+		curNode = curNode.child[v]
+		if curNode.exists {
+			f = true
+		}
+	}
+
+	if curNode.exists {
+		index = len(key)
+	}
+
+	return curNode, index
+}