sync/syncable/syncable_id.h

   1 // Copyright (c) 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/memory/scoped_ptr.h"
  14 #include "base/hash_tables.h"
  15
  16 class MockConnectionManager;
  17
  18 namespace base {
  19 class StringValue;
  20 }
  21
  22 namespace sql {
  23 class Statement;
  24 }
  25
  26 namespace syncer {
  27 namespace syncable {
  28 struct EntryKernel;
  29 class Id;
  30
  31 std::ostream& operator<<(std::ostream& out, const Id& id);
  32
  33 // For historical reasons, 3 concepts got everloaded into the Id:
  34 // 1. A unique, opaque identifier for the object.
  35 // 2. Flag specifing whether server know about this object.
  36 // 3. Flag for root.
  37 //
  38 // We originally wrapped an integer for this information, but now we use a
  39 // string. It will have one of three forms:
  40 // 1. c<client only opaque id> for client items that have not been committed.
  41 // 2. r for the root item.
  42 // 3. s<server provided opaque id> for items that the server knows about.
  43 class Id {
  44  public:
  45   // This constructor will be handy even when we move away from int64s, just
  46   // for unit tests.
  47   inline Id() : s_("r") { }
  48   inline Id(const Id& that) {
  49     Copy(that);
  50   }
  51   inline Id& operator = (const Id& that) {
  52     Copy(that);
  53     return *this;
  54   }
  55   inline void Copy(const Id& that) {
  56     this->s_ = that.s_;
  57   }
  58   inline bool IsRoot() const {
  59     return "r" == s_;
  60   }
  61   inline bool ServerKnows() const {
  62     return s_[0] == 's' || s_ == "r";
  63   }
  64
  65   // TODO(sync): We could use null here, but to ease conversion we use "r".
  66   // fix this, this is madness :)
  67   inline bool IsNull() const {
  68     return IsRoot();
  69   }
  70   inline void Clear() {
  71     s_ = "r";
  72   }
  73   inline int compare(const Id& that) const {
  74     return s_.compare(that.s_);
  75   }
  76   inline bool operator == (const Id& that) const {
  77     return s_ == 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
  89   const std::string& value() const {
  90     return s_;
  91   }
  92
  93   // Return the next highest ID in the lexicographic ordering.  This is
  94   // useful for computing upper bounds on std::sets that are ordered
  95   // by operator<.
  96   Id GetLexicographicSuccessor() const;
  97
  98   // Dumps the ID as a value and returns it.  Transfers ownership of
  99   // the StringValue to the caller.
 100   base::StringValue* ToValue() const;
 101
 102   // Three functions are used to work with our proto buffers.
 103   std::string GetServerId() const;
 104   static Id CreateFromServerId(const std::string& server_id);
 105   // This should only be used if you get back a reference to a local
 106   // id from the server. Returns a client only opaque id.
 107   static Id CreateFromClientString(const std::string& local_id);
 108
 109   // This method returns an ID that will compare less than any valid ID.
 110   // The returned ID is not a valid ID itself.  This is useful for
 111   // computing lower bounds on std::sets that are ordered by operator<.
 112   static Id GetLeastIdForLexicographicComparison();
 113
 114  private:
 115   friend scoped_ptr<EntryKernel> UnpackEntry(sql::Statement* statement);
 116   friend void BindFields(const EntryKernel& entry,
 117                          sql::Statement* statement);
 118   friend std::ostream& operator<<(std::ostream& out, const Id& id);
 119   friend class MockConnectionManager;
 120   friend class SyncableIdTest;
 121
 122   std::string s_;
 123 };
 124
 125 Id GetNullId();
 126
 127 }  // namespace syncable
 128 }  // namespace syncer
 129
 130 #endif  // SYNC_SYNCABLE_SYNCABLE_ID_H_