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transactionitf.h

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00001 /*-------------------------------------------------------------------------
00002  *
00003  *   FILE
00004  *      pqxx/transactionitf.h
00005  *
00006  *   DESCRIPTION
00007  *      common code and definitions for the transaction classes.
00008  *   pqxx::TransactionItf defines the interface for any abstract class that
00009  *   represents a database transaction
00010  *
00011  * Copyright (c) 2001-2003, Jeroen T. Vermeulen <jtv@xs4all.nl>
00012  *
00013  *-------------------------------------------------------------------------
00014  */
00015 #ifndef PQXX_TRANSACTIONITF_H
00016 #define PQXX_TRANSACTIONITF_H
00017 
00018 
00019 /* End-user programs need not include this file, unless they define their own
00020  * transaction classes.  This is not something the typical program should want
00021  * to do.
00022  *
00023  * However, reading this file is worthwhile because it defines the public
00024  * interface for the available transaction classes such as Transaction and 
00025  * NonTransaction.
00026  */
00027 
00028 
00029 #include "pqxx/connection.h"
00030 #include "pqxx/result.h"
00031 
00032 /* Methods tested in eg. self-test program test1 are marked with "//[t1]"
00033  */
00034 
00035 
00036 namespace pqxx
00037 {
00038 class Connection;       // See pqxx/connection.h
00039 class Result;           // See pqxx/result.h
00040 class TableStream;      // See pqxx/tablestream.h
00041 
00042 
00043 template<> inline PGSTD::string Classname(const TableStream *) 
00044 { 
00045   return "TableStream"; 
00046 }
00047 
00048 
00050 
00054 class PQXX_LIBEXPORT TransactionItf
00055 {
00056 public:
00057   virtual ~TransactionItf() =0;                                         //[t1]
00058 
00059   void Commit();                                                        //[t1]
00060   void Abort();                                                         //[t10]
00061 
00063   Result Exec(const char[]);                                            //[t1]
00064 
00066   Result Exec(const PGSTD::string &Q) { return Exec(Q.c_str()); }       //[t2]
00067 
00068   void ProcessNotice(const char Msg[]) { m_Conn.ProcessNotice(Msg); }   //[t1]
00069   void ProcessNotice(const PGSTD::string &Msg)                          //[t1]
00070         { m_Conn.ProcessNotice(Msg); }
00071 
00072   PGSTD::string Name() const { return m_Name; }                         //[t1]
00073 
00074 protected:
00077   explicit TransactionItf(Connection &, 
00078                           const PGSTD::string &TName=PGSTD::string());
00079 
00082   void Begin();
00083 
00085   void End() throw ();
00086 
00088   virtual void DoBegin() =0;
00089   virtual Result DoExec(const char C[]) =0;
00090   virtual void DoCommit() =0;
00091   virtual void DoAbort() =0;
00092 
00093   // For use by implementing class:
00094 
00096   Result DirectExec(const char C[], int Retries, const char OnReconnect[]);
00097   Connection &Conn() const { return m_Conn; }
00098 
00099  
00100 private:
00101   /* A Transaction goes through the following stages in its lifecycle:
00102    *  - nascent: the transaction hasn't actually begun yet.  If our connection 
00103    *    fails at this stage, the Connection may recover and the Transaction can 
00104    *    attempt to establish itself again.
00105    *  - active: the transaction has begun.  Since no commit command has been 
00106    *    issued, abortion is implicit if the connection fails now.
00107    *  - aborted: an abort has been issued; the transaction is terminated and 
00108    *    its changes to the database rolled back.  It will accept no further 
00109    *    commands.
00110    *  - committed: the transaction has completed successfully, meaning that a 
00111    *    commit has been issued.  No further commands are accepted.
00112    *  - in_doubt: the connection was lost at the exact wrong time, and there is
00113    *    no way of telling whether the transaction was committed or aborted.
00114    *
00115    * Checking and maintaining state machine logic is the responsibility of the 
00116    * base class (ie., this one).
00117    */
00118   enum Status 
00119   { 
00120     st_nascent, 
00121     st_active, 
00122     st_aborted, 
00123     st_committed,
00124     st_in_doubt
00125   };
00126 
00127 
00128   friend class Cursor;
00129   int GetUniqueCursorNum() { return m_UniqueCursorNum++; }
00130   void MakeEmpty(Result &R) const { m_Conn.MakeEmpty(R); }
00131 
00132   friend class TableStream;
00133   void RegisterStream(const TableStream *);
00134   void UnregisterStream(const TableStream *) throw ();
00135   void EndCopy() { m_Conn.EndCopy(); }
00136   friend class TableReader;
00137   void BeginCopyRead(const PGSTD::string &Table) 
00138         { m_Conn.BeginCopyRead(Table); }
00139   bool ReadCopyLine(PGSTD::string &L) { return m_Conn.ReadCopyLine(L); }
00140   friend class TableWriter;
00141   void BeginCopyWrite(const PGSTD::string &Table) 
00142         { m_Conn.BeginCopyWrite(Table); }
00143   void WriteCopyLine(const PGSTD::string &L) { m_Conn.WriteCopyLine(L); }
00144 
00145   Connection &m_Conn;
00146 
00147   PGSTD::string m_Name;
00148   int m_UniqueCursorNum;
00149   Unique<TableStream> m_Stream;
00150   Status m_Status;
00151   bool m_Registered;
00152 
00153   // Not allowed:
00154   TransactionItf();
00155   TransactionItf(const TransactionItf &);
00156   TransactionItf &operator=(const TransactionItf &);
00157 };
00158 
00159 
00161 
00167 class PQXX_LIBEXPORT in_doubt_error : public PGSTD::runtime_error
00168 {
00169 public:
00170   explicit in_doubt_error(const PGSTD::string &whatarg) : 
00171     PGSTD::runtime_error(whatarg) {}
00172 };
00173 
00174 }
00175 
00176 #endif
00177 

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