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      1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef CHROME_BROWSER_SYNC_SYNCABLE_SYNCABLE_ID_H_
      6 #define CHROME_BROWSER_SYNC_SYNCABLE_SYNCABLE_ID_H_
      7 #pragma once
      8 
      9 #include <iosfwd>
     10 #include <limits>
     11 #include <sstream>
     12 #include <string>
     13 
     14 #include "base/hash_tables.h"
     15 
     16 class StringValue;
     17 
     18 namespace syncable {
     19 struct EntryKernel;
     20 class Id;
     21 }
     22 
     23 class MockConnectionManager;
     24 class SQLStatement;
     25 
     26 namespace syncable {
     27 
     28 std::ostream& operator<<(std::ostream& out, const Id& id);
     29 
     30 // For historical reasons, 3 concepts got everloaded into the Id:
     31 // 1. A unique, opaque identifier for the object.
     32 // 2. Flag specifing whether server know about this object.
     33 // 3. Flag for root.
     34 //
     35 // We originally wrapped an integer for this information, but now we use a
     36 // string. It will have one of three forms:
     37 // 1. c<client only opaque id> for client items that have not been committed.
     38 // 2. r for the root item.
     39 // 3. s<server provided opaque id> for items that the server knows about.
     40 class Id {
     41   friend int UnpackEntry(SQLStatement* statement,
     42                          syncable::EntryKernel** kernel);
     43   friend int BindFields(const EntryKernel& entry, SQLStatement* statement);
     44   friend std::ostream& operator<<(std::ostream& out, const Id& id);
     45   friend class MockConnectionManager;
     46   friend class SyncableIdTest;
     47  public:
     48   // This constructor will be handy even when we move away from int64s, just
     49   // for unit tests.
     50   inline Id() : s_("r") { }
     51   inline Id(const Id& that) {
     52     Copy(that);
     53   }
     54   inline Id& operator = (const Id& that) {
     55     Copy(that);
     56     return *this;
     57   }
     58   inline void Copy(const Id& that) {
     59     this->s_ = that.s_;
     60   }
     61   inline bool IsRoot() const {
     62     return "r" == s_;
     63   }
     64   inline bool ServerKnows() const {
     65     return s_[0] == 's' || s_ == "r";
     66   }
     67 
     68   // TODO(sync): We could use null here, but to ease conversion we use "r".
     69   // fix this, this is madness :)
     70   inline bool IsNull() const {
     71     return IsRoot();
     72   }
     73   inline void Clear() {
     74     s_ = "r";
     75   }
     76   inline int compare(const Id& that) const {
     77     return s_.compare(that.s_);
     78   }
     79   inline bool operator == (const Id& that) const {
     80     return s_ == that.s_;
     81   }
     82   inline bool operator != (const Id& that) const {
     83     return s_ != that.s_;
     84   }
     85   inline bool operator < (const Id& that) const {
     86     return s_ < that.s_;
     87   }
     88   inline bool operator > (const Id& that) const {
     89     return s_ > that.s_;
     90   }
     91   // Return the next highest ID in the lexicographic ordering.  This is
     92   // useful for computing upper bounds on std::sets that are ordered
     93   // by operator<.
     94   Id GetLexicographicSuccessor() const;
     95 
     96   // Dumps the ID as a value and returns it.  Transfers ownership of
     97   // the StringValue to the caller.
     98   StringValue* ToValue() const;
     99 
    100   // Three functions are used to work with our proto buffers.
    101   std::string GetServerId() const;
    102   static Id CreateFromServerId(const std::string& server_id);
    103   // This should only be used if you get back a reference to a local
    104   // id from the server. Returns a client only opaque id.
    105   static Id CreateFromClientString(const std::string& local_id);
    106 
    107   // This method returns an ID that will compare less than any valid ID.
    108   // The returned ID is not a valid ID itself.  This is useful for
    109   // computing lower bounds on std::sets that are ordered by operator<.
    110   static Id GetLeastIdForLexicographicComparison();
    111 
    112  private:
    113   std::string s_;
    114 };
    115 
    116 extern const Id kNullId;
    117 
    118 }  // namespace syncable
    119 
    120 #endif  // CHROME_BROWSER_SYNC_SYNCABLE_SYNCABLE_ID_H_
    121