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      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_
    133