SERVER-23891 implement ShardId class

1 files changed, 105 insertions, 0 deletions

diff --git a/src/mongo/s/shard_id.h b/src/mongo/s/shard_id.h
new file mode 100644
index 00000000000..6456fc41677
--- /dev/null
+++ b/src/mongo/s/shard_id.h
@@ -0,0 +1,105 @@
+/**
+ *    Copyright (C) 2016 MongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the GNU Affero General Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include <iostream>
+#include <string>
+
+#include "mongo/base/string_data.h"
+#include "mongo/bson/util/builder.h"
+
+
+namespace mongo {
+
+class NamespaceString;
+
+/**
+ *  Representation of a shard identifier.
+ */
+class ShardId {
+public:
+    friend std::ostream& operator<<(std::ostream&, const ShardId&);
+
+    ShardId() = default;
+
+    // Note that this c-tor allows the implicit conversion from std::string
+    ShardId(const std::string shardId) : _shardId(std::move(shardId)) {}
+
+    // Implicit StringData conversion
+    operator StringData();
+
+    bool operator==(const ShardId&) const;
+    bool operator!=(const ShardId&) const;
+    bool operator==(const std::string&) const;
+    bool operator!=(const std::string&) const;
+
+    template <size_t N>
+    bool operator==(const char (&val)[N]) const {
+        return (strncmp(val, _shardId.data(), N) == 0);
+    }
+
+    template <size_t N>
+    bool operator!=(const char (&val)[N]) const {
+        return (strncmp(val, _shardId.data(), N) != 0);
+    }
+
+    // The operator<  is needed to do proper comparison in a std::map
+    bool operator<(const ShardId&) const;
+
+    const std::string& toString() const;
+
+    /**
+     * Returns -1, 0, or 1 if 'this' is less, equal, or greater than 'other' in
+     * lexicographical order.
+     */
+    int compare(const ShardId& other) const;
+
+    /**
+     *  Returns true if _shardId is empty. Subject to include more validations in the future.
+     */
+    bool isValid() const;
+
+    /**
+     * Functor compatible with std::hash for std::unordered_{map,set}
+     */
+    struct Hasher {
+        std::size_t operator()(const ShardId&) const;
+    };
+
+private:
+    std::string _shardId;
+};
+
+template <typename Allocator>
+StringBuilderImpl<Allocator>& operator<<(StringBuilderImpl<Allocator>& stream,
+                                         const ShardId& shardId) {
+    return stream << shardId.toString();
+}
+
+}  // namespace mongo