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       1                 :            : /***********************************************************************\
       2                 :            :  * gnc-sql-result.hpp: Encapsulate the results of a SQL query.         *
       3                 :            :  *                                                                     *
       4                 :            :  * Copyright 2016 John Ralls <jralls@ceridwen.us>                      *
       5                 :            :  *                                                                     *
       6                 :            :  * This program is free software; you can redistribute it and/or       *
       7                 :            :  * modify it under the terms of the GNU General Public License as      *
       8                 :            :  * published by the Free Software Foundation; either version 2 of      *
       9                 :            :  * the License, or (at your option) any later version.                 *
      10                 :            :  *                                                                     *
      11                 :            :  * This program is distributed in the hope that it will be useful,     *
      12                 :            :  * but WITHOUT ANY WARRANTY; without even the implied warranty of      *
      13                 :            :  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the       *
      14                 :            :  * GNU General Public License for more details.                        *
      15                 :            :  *                                                                     *
      16                 :            :  * You should have received a copy of the GNU General Public License   *
      17                 :            :  * along with this program; if not, contact:                           *
      18                 :            :  *                                                                     *
      19                 :            :  * Free Software Foundation           Voice:  +1-617-542-5942          *
      20                 :            :  * 51 Franklin Street, Fifth Floor    Fax:    +1-617-542-2652          *
      21                 :            :  * Boston, MA  02110-1301,  USA       gnu@gnu.org                      *
      22                 :            : \***********************************************************************/
      23                 :            : 
      24                 :            : #ifndef __GNC_SQL_RESULT_HPP__
      25                 :            : #define __GNC_SQL_RESULT_HPP__
      26                 :            : 
      27                 :            : #include <qof.h>
      28                 :            : 
      29                 :            : #include <cstdint>
      30                 :            : #include <optional>
      31                 :            : #include <string>
      32                 :            : #include <vector>
      33                 :            : 
      34                 :            : class GncSqlRow;
      35                 :            : /**
      36                 :            :  * Pure virtual class to iterate over a query result set.
      37                 :            :  */
      38                 :            : 
      39                 :            : class GncSqlResult
      40                 :            : {
      41                 :            : public:
      42                 :          0 :     virtual ~GncSqlResult() = default;
      43                 :            :     virtual uint64_t size() const noexcept = 0;
      44                 :            :     virtual GncSqlRow& begin() = 0;
      45                 :            :     virtual GncSqlRow& end() = 0;
      46                 :            :     friend GncSqlRow;
      47                 :            : protected:
      48                 :            :     class IteratorImpl {
      49                 :            :     public:
      50                 :          0 :         virtual ~IteratorImpl() = default;
      51                 :            :         virtual GncSqlRow& operator++() = 0;
      52                 :            :         virtual GncSqlResult* operator*() = 0;
      53                 :            :         virtual std::optional<int64_t> get_int_at_col (const char* col) const = 0;
      54                 :            :         virtual std::optional<double> get_float_at_col (const char* col) const = 0;
      55                 :            :         virtual std::optional<double> get_double_at_col (const char* col) const = 0;
      56                 :            :         virtual std::optional<std::string> get_string_at_col (const char* col) const = 0;
      57                 :            :         virtual std::optional<time64> get_time64_at_col (const char* col) const = 0;
      58                 :            :         virtual bool is_col_null (const char* col) const noexcept = 0;
      59                 :            :     };
      60                 :            : };
      61                 :            : 
      62                 :            : /**
      63                 :            :  * Row of SQL Query results.
      64                 :            :  *
      65                 :            :  * This is a "pointer" class of a pimpl pattern, the implementation being
      66                 :            :  * GncSqlResult::IteratorImpl. It's designed to present a std::forward_iterator
      67                 :            :  * like interface for use with range-for while allowing for wrapping a C API.
      68                 :            :  *
      69                 :            :  * Important Implementation Note: Operator++() as written requires that the
      70                 :            :  * sentinel GncSqlRow returned by GncSqlResult::end() has m_impl = nullptr in
      71                 :            :  * order to terminate the loop condition. This is a bit of a hack and might be a
      72                 :            :  * problem with a different SQL interface library from libdbi.
      73                 :            :  *
      74                 :            :  * Note that GncSqlResult::begin and GncSqlRow::operator++() return
      75                 :            :  * GncSqlRow&. This is necessary for operator++() to be called: Using operator
      76                 :            :  * ++() on a pointer performs pointer arithmetic rather than calling the
      77                 :            :  * pointed-to-class's operator++() and C++'s range-for uses operator++()
      78                 :            :  * directly on whatever begin() gives it.
      79                 :            :  */
      80                 :            : class GncSqlRow
      81                 :            : {
      82                 :            : public:
      83                 :          0 :     GncSqlRow (GncSqlResult::IteratorImpl* iter) : m_iter{iter} {}
      84                 :          0 :     ~GncSqlRow() { }
      85                 :            :     GncSqlRow& operator++();
      86                 :        275 :     GncSqlRow& operator*() { return *this; }
      87                 :            :     friend bool operator!=(const GncSqlRow&, const GncSqlRow&);
      88                 :        778 :     std::optional<int64_t> get_int_at_col (const char* col) const {
      89                 :        778 :         return m_iter->get_int_at_col (col); }
      90                 :         58 :     std::optional<double> get_float_at_col (const char* col) const {
      91                 :         58 :         return m_iter->get_float_at_col (col); }
      92                 :         52 :     std::optional<double> get_double_at_col (const char* col) const {
      93                 :         52 :         return m_iter->get_double_at_col (col); }
      94                 :       1175 :     std::optional<std::string> get_string_at_col (const char* col) const {
      95                 :       1175 :         return m_iter->get_string_at_col (col); }
      96                 :          0 :     std::optional<time64> get_time64_at_col (const char* col) const {
      97                 :          0 :         return m_iter->get_time64_at_col (col); }
      98                 :         71 :     bool is_col_null (const char* col) const noexcept {
      99                 :         71 :         return m_iter->is_col_null (col); }
     100                 :            : private:
     101                 :            :     GncSqlResult::IteratorImpl* m_iter;
     102                 :            : };
     103                 :            : 
     104                 :        745 : inline bool operator!=(const GncSqlRow& lr, const GncSqlRow& rr) {
     105                 :        745 :     return lr.m_iter != rr.m_iter;
     106                 :            : }
     107                 :            : 
     108                 :         26 : inline bool operator==(const GncSqlRow& lr, const GncSqlRow& rr) {
     109                 :         26 :     return !(lr != rr);
     110                 :            : }
     111                 :            : 
     112                 :            : 
     113                 :            : #endif //__GNC_SQL_RESULT_HPP__