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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 
00069   void ProcessNotice(const char Msg[]) { m_Conn.ProcessNotice(Msg); }   //[t1]
00071   void ProcessNotice(const PGSTD::string &Msg)                          //[t1]
00072         { m_Conn.ProcessNotice(Msg); }
00073 
00074   PGSTD::string Name() const { return m_Name; }                         //[t1]
00075 
00077   Connection &Conn() const { return m_Conn; }                           //[]
00078 
00079 protected:
00082   explicit TransactionItf(Connection &, 
00083                           const PGSTD::string &TName=PGSTD::string());
00084 
00087   void Begin();
00088 
00090   void End() throw ();
00091 
00093   virtual void DoBegin() =0;
00094   virtual Result DoExec(const char C[]) =0;
00095   virtual void DoCommit() =0;
00096   virtual void DoAbort() =0;
00097 
00098   // For use by implementing class:
00099 
00101   Result DirectExec(const char C[], int Retries, const char OnReconnect[]);
00102  
00103 private:
00104   /* A Transaction goes through the following stages in its lifecycle:
00105    *  - nascent: the transaction hasn't actually begun yet.  If our connection 
00106    *    fails at this stage, the Connection may recover and the Transaction can 
00107    *    attempt to establish itself again.
00108    *  - active: the transaction has begun.  Since no commit command has been 
00109    *    issued, abortion is implicit if the connection fails now.
00110    *  - aborted: an abort has been issued; the transaction is terminated and 
00111    *    its changes to the database rolled back.  It will accept no further 
00112    *    commands.
00113    *  - committed: the transaction has completed successfully, meaning that a 
00114    *    commit has been issued.  No further commands are accepted.
00115    *  - in_doubt: the connection was lost at the exact wrong time, and there is
00116    *    no way of telling whether the transaction was committed or aborted.
00117    *
00118    * Checking and maintaining state machine logic is the responsibility of the 
00119    * base class (ie., this one).
00120    */
00121   enum Status 
00122   { 
00123     st_nascent, 
00124     st_active, 
00125     st_aborted, 
00126     st_committed,
00127     st_in_doubt
00128   };
00129 
00130 
00131   friend class Cursor;
00132   int GetUniqueCursorNum() { return m_UniqueCursorNum++; }
00133   void MakeEmpty(Result &R) const { m_Conn.MakeEmpty(R); }
00134 
00135   friend class TableStream;
00136   void RegisterStream(const TableStream *);
00137   void UnregisterStream(const TableStream *) throw ();
00138   void EndCopy() { m_Conn.EndCopy(); }
00139   friend class TableReader;
00140   void BeginCopyRead(const PGSTD::string &Table) 
00141         { m_Conn.BeginCopyRead(Table); }
00142   bool ReadCopyLine(PGSTD::string &L) { return m_Conn.ReadCopyLine(L); }
00143   friend class TableWriter;
00144   void BeginCopyWrite(const PGSTD::string &Table) 
00145         { m_Conn.BeginCopyWrite(Table); }
00146   void WriteCopyLine(const PGSTD::string &L) { m_Conn.WriteCopyLine(L); }
00147 
00148   Connection &m_Conn;
00149 
00150   PGSTD::string m_Name;
00151   int m_UniqueCursorNum;
00152   Unique<TableStream> m_Stream;
00153   Status m_Status;
00154   bool m_Registered;
00155 
00156   // Not allowed:
00157   TransactionItf();
00158   TransactionItf(const TransactionItf &);
00159   TransactionItf &operator=(const TransactionItf &);
00160 };
00161 
00162 
00164 
00170 class PQXX_LIBEXPORT in_doubt_error : public PGSTD::runtime_error
00171 {
00172 public:
00173   explicit in_doubt_error(const PGSTD::string &whatarg) : 
00174     PGSTD::runtime_error(whatarg) {}
00175 };
00176 
00177 }
00178 
00179 #endif
00180 

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