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   // This constructor will be handy even when we move away from int64s, just
  47   // for unit tests.
  48   inline Id() : s_("r") { }
  49   inline Id(const Id& that) {
  50     Copy(that);
  51   }
  52   inline Id& operator = (const Id& that) {
  53     Copy(that);
  54     return *this;
  55   }
  56   inline void Copy(const Id& that) {
  57     this->s_ = that.s_;
  58   }
  59   inline bool IsRoot() const {
  60     return "r" == s_;
  61   }
  62   inline bool ServerKnows() const {
  63     return s_[0] == 's' || s_ == "r";
  64   }
  65
  66   // TODO(sync): We could use null here, but to ease conversion we use "r".
  67   // fix this, this is madness :)
  68   inline bool IsNull() const {
  69     return IsRoot();
  70   }
  71   inline void Clear() {
  72     s_ = "r";
  73   }
  74   inline int compare(const Id& that) const {
  75     return s_.compare(that.s_);
  76   }
  77   inline bool operator == (const Id& that) const {
  78     return s_ == that.s_;
  79   }
  80   inline bool operator != (const Id& that) const {
  81     return s_ != that.s_;
  82   }
  83   inline bool operator < (const Id& that) const {
  84     return s_ < that.s_;
  85   }
  86   inline bool operator > (const Id& that) const {
  87     return s_ > that.s_;
  88   }
  89
  90   const std::string& value() const {
  91     return s_;
  92   }
  93
  94   // Return the next highest ID in the lexicographic ordering.  This is
  95   // useful for computing upper bounds on std::sets that are ordered
  96   // by operator<.
  97   Id GetLexicographicSuccessor() const;
  98
  99   // Dumps the ID as a value and returns it.  Transfers ownership of
 100   // the StringValue to the caller.
 101   base::StringValue* ToValue() const;
 102
 103   // Three functions are used to work with our proto buffers.
 104   std::string GetServerId() const;
 105   static Id CreateFromServerId(const std::string& server_id);
 106   // This should only be used if you get back a reference to a local
 107   // id from the server. Returns a client only opaque id.
 108   static Id CreateFromClientString(const std::string& local_id);
 109
 110   // This method returns an ID that will compare less than any valid ID.
 111   // The returned ID is not a valid ID itself.  This is useful for
 112   // computing lower bounds on std::sets that are ordered by operator<.
 113   static Id GetLeastIdForLexicographicComparison();
 114
 115  private:
 116   friend scoped_ptr<EntryKernel> UnpackEntry(sql::Statement* statement);
 117   friend void BindFields(const EntryKernel& entry,
 118                          sql::Statement* statement);
 119   SYNC_EXPORT_PRIVATE friend std::ostream& operator<<(std::ostream& out,
 120                                                       const Id& id);
 121   friend class MockConnectionManager;
 122   friend class SyncableIdTest;
 123
 124   std::string s_;
 125 };
 126
 127 SYNC_EXPORT_PRIVATE Id GetNullId();
 128
 129 }  // namespace syncable
 130 }  // namespace syncer
 131
 132 #endif  // SYNC_SYNCABLE_SYNCABLE_ID_H_