sync/syncable/syncable_id.h

   1 // Copyright 2012 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 SYNC_SYNCABLE_SYNCABLE_ID_H_
   6 #define SYNC_SYNCABLE_SYNCABLE_ID_H_
   7
   8 #include <iosfwd>
   9 #include <limits>
  10 #include <sstream>
  11 #include <string>
  12
  13 #include "base/containers/hash_tables.h"
  14 #include "base/memory/scoped_ptr.h"
  15 #include "sync/base/sync_export.h"
  16
  17 class MockConnectionManager;
  18
  19 namespace base {
  20 class StringValue;
  21 }
  22
  23 namespace sql {
  24 class Statement;
  25 }
  26
  27 namespace syncer {
  28 namespace syncable {
  29 struct EntryKernel;
  30 class Id;
  31
  32 SYNC_EXPORT_PRIVATE std::ostream& operator<<(std::ostream& out, const Id& id);
  33
  34 // For historical reasons, 3 concepts got everloaded into the Id:
  35 // 1. A unique, opaque identifier for the object.
  36 // 2. Flag specifing whether server know about this object.
  37 // 3. Flag for root.
  38 //
  39 // We originally wrapped an integer for this information, but now we use a
  40 // string. It will have one of three forms:
  41 // 1. c<client only opaque id> for client items that have not been committed.
  42 // 2. r for the root item.
  43 // 3. s<server provided opaque id> for items that the server knows about.
  44 class SYNC_EXPORT Id {
  45  public:
  46   inline Id() {}
  47   inline Id(const Id& that) {
  48     Copy(that);
  49   }
  50   inline Id& operator = (const Id& that) {
  51     Copy(that);
  52     return *this;
  53   }
  54   inline void Copy(const Id& that) {
  55     this->s_ = that.s_;
  56   }
  57   inline bool IsRoot() const {
  58     return "r" == s_;
  59   }
  60   inline bool ServerKnows() const {
  61     return !IsNull() && (s_[0] == 's' || s_ == "r");
  62   }
  63
  64   inline bool IsNull() const { return s_.empty(); }
  65   inline void Clear() { s_.clear(); }
  66   inline int compare(const Id& that) const {
  67     return s_.compare(that.s_);
  68   }
  69   inline bool operator == (const Id& that) const {
  70     return s_ == that.s_;
  71   }
  72   inline bool operator != (const Id& that) const {
  73     return s_ != that.s_;
  74   }
  75   inline bool operator < (const Id& that) const {
  76     return s_ < that.s_;
  77   }
  78   inline bool operator > (const Id& that) const {
  79     return s_ > that.s_;
  80   }
  81
  82   const std::string& value() const {
  83     return s_;
  84   }
  85
  86   // Return the next highest ID in the lexicographic ordering.  This is
  87   // useful for computing upper bounds on std::sets that are ordered
  88   // by operator<.
  89   Id GetLexicographicSuccessor() const;
  90
  91   // Dumps the ID as a value and returns it.  Transfers ownership of
  92   // the StringValue to the caller.
  93   base::StringValue* ToValue() const;
  94
  95   // Three functions are used to work with our proto buffers.
  96   std::string GetServerId() const;
  97   static Id CreateFromServerId(const std::string& server_id);
  98   // This should only be used if you get back a reference to a local
  99   // id from the server. Returns a client only opaque id.
 100   static Id CreateFromClientString(const std::string& local_id);
 101
 102   // This method returns an ID that will compare less than any valid ID.
 103   // The returned ID is not a valid ID itself.  This is useful for
 104   // computing lower bounds on std::sets that are ordered by operator<.
 105   static Id GetLeastIdForLexicographicComparison();
 106
 107   // Gets root ID.
 108   static Id GetRoot();
 109
 110  private:
 111   friend scoped_ptr<EntryKernel> UnpackEntry(sql::Statement* statement);
 112   friend void BindFields(const EntryKernel& entry,
 113                          sql::Statement* statement);
 114   SYNC_EXPORT_PRIVATE friend std::ostream& operator<<(std::ostream& out,
 115                                                       const Id& id);
 116   friend class MockConnectionManager;
 117   friend class SyncableIdTest;
 118
 119   std::string s_;
 120 };
 121
 122 }  // namespace syncable
 123 }  // namespace syncer
 124
 125 #endif  // SYNC_SYNCABLE_SYNCABLE_ID_H_