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diff --git a/sync/syncable/syncable_id.h b/sync/syncable/syncable_id.h
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+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SYNC_SYNCABLE_SYNCABLE_ID_H_
+#define SYNC_SYNCABLE_SYNCABLE_ID_H_
+#pragma once
+
+#include <iosfwd>
+#include <limits>
+#include <sstream>
+#include <string>
+
+#include "base/hash_tables.h"
+
+class MockConnectionManager;
+
+namespace base {
+class StringValue;
+}
+
+namespace sql {
+class Statement;
+}
+
+namespace syncable {
+struct EntryKernel;
+class Id;
+}
+
+namespace syncable {
+
+std::ostream& operator<<(std::ostream& out, const Id& id);
+
+// For historical reasons, 3 concepts got everloaded into the Id:
+// 1. A unique, opaque identifier for the object.
+// 2. Flag specifing whether server know about this object.
+// 3. Flag for root.
+//
+// We originally wrapped an integer for this information, but now we use a
+// string. It will have one of three forms:
+// 1. c<client only opaque id> for client items that have not been committed.
+// 2. r for the root item.
+// 3. s<server provided opaque id> for items that the server knows about.
+class Id {
+ public:
+  // This constructor will be handy even when we move away from int64s, just
+  // for unit tests.
+  inline Id() : s_("r") { }
+  inline Id(const Id& that) {
+    Copy(that);
+  }
+  inline Id& operator = (const Id& that) {
+    Copy(that);
+    return *this;
+  }
+  inline void Copy(const Id& that) {
+    this->s_ = that.s_;
+  }
+  inline bool IsRoot() const {
+    return "r" == s_;
+  }
+  inline bool ServerKnows() const {
+    return s_[0] == 's' || s_ == "r";
+  }
+
+  // TODO(sync): We could use null here, but to ease conversion we use "r".
+  // fix this, this is madness :)
+  inline bool IsNull() const {
+    return IsRoot();
+  }
+  inline void Clear() {
+    s_ = "r";
+  }
+  inline int compare(const Id& that) const {
+    return s_.compare(that.s_);
+  }
+  inline bool operator == (const Id& that) const {
+    return s_ == that.s_;
+  }
+  inline bool operator != (const Id& that) const {
+    return s_ != that.s_;
+  }
+  inline bool operator < (const Id& that) const {
+    return s_ < that.s_;
+  }
+  inline bool operator > (const Id& that) const {
+    return s_ > that.s_;
+  }
+
+  const std::string& value() const {
+    return s_;
+  }
+
+  // Return the next highest ID in the lexicographic ordering.  This is
+  // useful for computing upper bounds on std::sets that are ordered
+  // by operator<.
+  Id GetLexicographicSuccessor() const;
+
+  // Note: |lowercase_query| should be passed in as lower case.
+  bool ContainsStringCaseInsensitive(const std::string& lowercase_query) const;
+
+  // Dumps the ID as a value and returns it.  Transfers ownership of
+  // the StringValue to the caller.
+  base::StringValue* ToValue() const;
+
+  // Three functions are used to work with our proto buffers.
+  std::string GetServerId() const;
+  static Id CreateFromServerId(const std::string& server_id);
+  // This should only be used if you get back a reference to a local
+  // id from the server. Returns a client only opaque id.
+  static Id CreateFromClientString(const std::string& local_id);
+
+  // This method returns an ID that will compare less than any valid ID.
+  // The returned ID is not a valid ID itself.  This is useful for
+  // computing lower bounds on std::sets that are ordered by operator<.
+  static Id GetLeastIdForLexicographicComparison();
+
+ private:
+  friend EntryKernel* UnpackEntry(sql::Statement* statement);
+  friend void BindFields(const EntryKernel& entry,
+                         sql::Statement* statement);
+  friend std::ostream& operator<<(std::ostream& out, const Id& id);
+  friend class MockConnectionManager;
+  friend class SyncableIdTest;
+
+  std::string s_;
+};
+
+Id GetNullId();
+
+}  // namespace syncable
+
+#endif  // SYNC_SYNCABLE_SYNCABLE_ID_H_