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cursor.h

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00001 /*-------------------------------------------------------------------------
00002  *
00003  *   FILE
00004  *      pqxx/cursor.h
00005  *
00006  *   DESCRIPTION
00007  *      definition of the pqxx::Cursor class.
00008  *   pqxx::Cursor represents a database cursor.
00009  *
00010  * Copyright (c) 2001-2003, Jeroen T. Vermeulen <jtv@xs4all.nl>
00011  *
00012  * See COPYING for copyright license.  If you did not receive a file called
00013  * COPYING with this source code, please notify the distributor of this mistake,
00014  * or contact the author.
00015  *
00016  *-------------------------------------------------------------------------
00017  */
00018 #ifndef PQXX_CURSOR_H
00019 #define PQXX_CURSOR_H
00020 
00021 #include "pqxx/result.h"
00022 #include "pqxx/transaction_base.h"
00023 #include "pqxx/util.h"
00024 
00025 /* Methods tested in eg. self-test program test1 are marked with "//[t1]"
00026  */
00027 
00028 namespace pqxx
00029 {
00030 class result;
00031 
00032 
00033 // Work around bug in CodeWarrior 8.3
00034 #ifdef __MWERKS__
00035 #pragma defer_defarg_parsing on
00036 #endif
00037 
00038 
00040 
00066 class PQXX_LIBEXPORT Cursor
00067 {
00068 public:
00069   // TODO: Split Cursor into different levels of intelligence
00070   // TODO: Forward-only cursors
00071   // TODO: Iterator interface (random-access==absolute)
00072   typedef result::size_type size_type;
00073 
00074   enum pos { pos_unknown = -1, pos_start = 0 };
00075 
00077   struct PQXX_LIBEXPORT unknown_position : PGSTD::runtime_error
00078   {
00079     unknown_position(const PGSTD::string &cursorname) :
00080       PGSTD::runtime_error("Position for cursor '" + cursorname + "' "
00081                            "is unknown") 
00082     {
00083     }
00084   };
00085 
00086   // TODO: Allow usage of SCROLL ("DECLARE foo SCROLL CURSOR FOR ...")
00088 
00096   template<typename TRANSACTION> 
00097     Cursor(TRANSACTION &T,
00098            const char Query[], 
00099            const PGSTD::string &BaseName="cur",
00100            size_type Count=NEXT()) :                                    //[t3]
00101       m_Trans(T),
00102       m_Name(),
00103       m_Count(Count),
00104       m_Done(false),
00105       m_Pos(pos_start),
00106       m_Size(pos_unknown)
00107   {
00108     // Trigger build error if T has insufficient isolation level
00109     error_permitted_isolation_level(typename TRANSACTION::isolation_tag());
00110     init(BaseName, Query);
00111   }
00112 
00114 
00144   template<typename TRANSACTION>
00145     Cursor(TRANSACTION &T,
00146            const result::field &Name,
00147            size_type Count=NEXT()) :                                    //[t45]
00148       m_Trans(T),
00149       m_Name(Name.c_str()),
00150       m_Count(Count),
00151       m_Done(false),
00152       m_Pos(pos_unknown),
00153       m_Size(pos_unknown)
00154   {
00155     // Trigger build error if T has insufficient isolation level
00156     error_permitted_isolation_level(typename TRANSACTION::isolation_tag());
00157   }
00158 
00160   size_type SetCount(size_type);                                        //[t19]
00161 
00163 
00172   result Fetch(size_type Count);                                        //[t19]
00173 
00175 
00183   size_type Move(size_type Count);                                      //[t42]
00184 
00185   void MoveTo(size_type);                                               //[t44]
00186 
00188 
00192   static size_type ALL() throw ()                                       //[t3]
00193         { return PGSTD::numeric_limits<result::size_type>::max(); }
00194 
00196   static size_type NEXT() throw () { return 1; }                        //[t19]
00197 
00199   static size_type PRIOR() throw () { return -1; }                      //[t19]
00200 
00203 
00207   static size_type BACKWARD_ALL() throw ()                              //[t19]
00208         { return PGSTD::numeric_limits<result::size_type>::min() + 1; }
00209 
00211 
00218   Cursor &operator>>(result &);                                         //[t3]
00219 
00221   operator bool() const throw () { return !m_Done; }                    //[t3]
00223   bool operator!() const throw () { return m_Done; }                    //[t3]
00224 
00226   Cursor &operator+=(size_type N) { Move(N); return *this;}             //[t19]
00228   Cursor &operator-=(size_type N) { Move(-N); return *this;}            //[t19]
00229 
00231 
00242   size_type size() const throw () { return m_Size; }                    //[t44]
00243 
00245 
00252   size_type Pos() const throw (unknown_position)                        //[t43]
00253   { if (m_Pos==pos_unknown) throw unknown_position(m_Name); return m_Pos; }
00254 
00255 
00256 private:
00257   static PGSTD::string OffsetString(size_type);
00258   void init(const PGSTD::string &BaseName, const char Query[]);
00259   PGSTD::string MakeFetchCmd(size_type) const;
00260   size_type NormalizedMove(size_type Intended, size_type Actual);
00261 
00263 
00267   template<typename ISOLATIONTAG> 
00268     static inline void error_permitted_isolation_level(ISOLATIONTAG) throw();
00269 
00270   transaction_base &m_Trans;
00271   PGSTD::string m_Name;
00272   size_type m_Count;
00273   bool m_Done;
00274   size_type m_Pos;
00275   size_type m_Size;
00276 
00277   // Not allowed:
00278   Cursor(const Cursor &);
00279   Cursor &operator=(const Cursor &);
00280 };
00281 
00282 template<> inline void 
00283 Cursor::error_permitted_isolation_level(isolation_traits<serializable>) throw ()
00284         {}
00285 
00286 }
00287 
00288 #endif
00289 

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