trie: new package (#3729)

This implements a simple trie tree for minio server/tools.
This package borrows idea from
https://godoc.org/golang.org/x/text/internal/triegen.

pkg/trie/trie_test.go

@@ -0,0 +1,71 @@
+/*
+ * Minio Cloud Storage, (C) 2016, 2017 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 trie
+
+import (
+	"testing"
+)
+
+// Simply make sure creating a new tree works.
+func TestNewTrie(t *testing.T) {
+	var trie *Trie
+	trie = NewTrie()
+
+	if trie.size != 0 {
+		t.Errorf("expected size 0, got: %d", trie.size)
+	}
+}
+
+// Ensure that we can insert new keys into the tree, then check the size.
+func TestInsert(t *testing.T) {
+	var trie *Trie
+	trie = NewTrie()
+
+	// We need to have an empty tree to begin with.
+	if trie.size != 0 {
+		t.Errorf("expected size 0, got: %d", trie.size)
+	}
+
+	trie.Insert("key")
+	trie.Insert("keyy")
+
+	// After inserting, we should have a size of two.
+	if trie.size != 2 {
+		t.Errorf("expected size 2, got: %d", trie.size)
+	}
+}
+
+// Ensure that PrefixMatch gives us the correct two keys in the tree.
+func TestPrefixMatch(t *testing.T) {
+	var trie *Trie
+	trie = NewTrie()
+
+	// Feed it some fodder: only 'minio' and 'miny-os' should trip the matcher.
+	trie.Insert("minio")
+	trie.Insert("amazon")
+	trie.Insert("cheerio")
+	trie.Insert("miny-o's")
+
+	matches := trie.PrefixMatch("min")
+	if len(matches) != 2 {
+		t.Errorf("expected two matches, got: %d", len(matches))
+	}
+
+	if matches[0] != "minio" && matches[1] != "minio" {
+		t.Errorf("expected one match to be 'minio', got: '%s' and '%s'", matches[0], matches[1])
+	}
+}