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