1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
|
//
// Copyright (c) 2022 Klemens Morgenstern (klemens.morgenstern@gmx.net)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#include <boost/sqlite.hpp>
#include <boost/unordered_map.hpp>
#include <boost/describe.hpp>
#include <boost/variant2/variant.hpp>
#include <iomanip>
#include <iostream>
// This example shows how a virtual table can be created using boost.describe
using namespace boost;
// add more conversions here if you need more types in the described struct
void assign_value(std::int64_t & res, sqlite::value val) { res = val.get_int();}
void assign_value(std::string & res, sqlite::value val) { res = val.get_text();}
template<typename T>
struct describe_cursor final : sqlite::vtab::cursor<>
{
describe_cursor(
typename boost::unordered_map<sqlite3_int64, T>::const_iterator itr,
typename boost::unordered_map<sqlite3_int64, T>::const_iterator end
) : itr(itr), end(end)
{
}
typename boost::unordered_map<sqlite3_int64, T>::const_iterator itr, end;
constexpr static std::size_t column_count = mp11::mp_size<describe::describe_members<T, describe::mod_any_access>>::value;
sqlite::result<void> next() {itr++; return {};}
sqlite::result<sqlite3_int64> row_id() {return itr->first;}
void column(sqlite::context<> ctx, int i, bool /* no_change */)
{
mp11::mp_with_index<column_count>(
i, [&](auto Idx)
{
using type = mp11::mp_at_c<describe::describe_members<T, describe::mod_public>, Idx>;
ctx.set_result(itr->second.*type::pointer);
});
}
bool eof() noexcept {return itr == end;}
};
template<typename T>
struct describe_table final :
sqlite::vtab::table<describe_cursor<T>>,
sqlite::vtab::modifiable
{
boost::unordered_map<sqlite3_int64, T> &data;
describe_table(boost::unordered_map<sqlite3_int64, T> &data) : data(data) {}
std::string decl;
const char * declaration()
{
if (!decl.empty())
return decl.c_str();
mp11::mp_for_each<describe::describe_members<T, describe::mod_public>>(
[&](auto elem)
{
if (decl.empty())
decl += "create table x(";
else
decl += ", ";
decl += elem.name;
});
decl += ");";
return decl.c_str();
}
sqlite3_int64 last_index = 0;
sqlite::result<describe_cursor<T>> open()
{
return describe_cursor<T>{data.begin(), data.end()};
}
sqlite::result<void> delete_(sqlite::value key)
{
data.erase(key.get_int());
return {};
}
sqlite::result<sqlite_int64> insert(sqlite::value key, span<sqlite::value> values, int /*on_conflict*/)
{
T res;
sqlite_int64 id = key.is_null() ? last_index++ : key.get_int();
auto vtr = values.begin();
mp11::mp_for_each<describe::describe_members<T, describe::mod_public>>(
[&](auto elem)
{
assign_value(res.*elem.pointer , *vtr);
vtr++;
});
auto itr = data.emplace(id, std::move(res)).first;
return itr->first;
}
sqlite::result<sqlite_int64> update(sqlite::value old_key, sqlite::value new_key,
span<sqlite::value> values, int /*on_conflict*/)
{
if (new_key.get_int() != old_key.get_int())
data.erase(old_key.get_int());
auto & res = data[new_key.get_int()];
auto vtr = values.begin();
mp11::mp_for_each<describe::describe_members<T, describe::mod_public>>(
[&](auto elem)
{
assign_value(res.*elem.pointer , *vtr);
vtr++;
});
return 0u;
}
};
template<typename T>
struct describe_module final : sqlite::vtab::eponymous_module<describe_table<T>>
{
boost::unordered_map<sqlite3_int64, T> data;
constexpr static std::size_t column_count = mp11::mp_size<describe::describe_members<T, describe::mod_any_access>>::value;
sqlite::result<describe_table<T>> connect(sqlite::connection ,
int, const char * const [])
{
return describe_table<T>{data};
}
};
void print_table(std::ostream & str, sqlite::resultset res)
{
for (auto i = 0u; i < res.column_count(); i ++)
str << "| " << std::setfill(' ') << std::setw(15) << res.column_name(i) << " ";
str << "|\n";
for (auto i = 0u; i < res.column_count(); i ++)
str << "|-----------------";
str << "|\n";
for (auto && r : res)
{
for (auto i = 0u; i < res.column_count(); i ++)
str << "| " << std::setfill(' ') << std::setw(15) << r.at(i).get_text() << " ";
str << "|\n" ;
}
str << std::endl;
}
struct boost_library
{
std::string name;
std::int64_t first_released;
std::int64_t standard;
};
BOOST_DESCRIBE_STRUCT(boost_library, (), (name, first_released, standard));
int main (int /*argc*/, char * /*argv*/[])
{
sqlite::connection conn{":memory:"};
auto & md = sqlite::create_module(conn, "boost_libraries", describe_module<boost_library>());
{
auto p = conn.prepare("insert into boost_libraries (name, first_released, standard) values ($name, $version, $std);");
p.execute({{"name", "process"}, {"version", 64}, {"std", 11}});
p.execute({{"name", "asio"}, {"version", 35}, {"std", 98}});
p.execute({{"name", "bimap"}, {"version", 35}, {"std", 98}});
p.execute({{"name", "circular_buffer"}, {"version", 35}, {"std", 98}});
p.execute({{"name", "mpi"}, {"version", 35}, {"std", 98}});
p.execute({{"name", "beast"}, {"version", 66}, {"std", 11}});
p.execute({{"name", "describe"}, {"version", 77}, {"std", 14}});
}
print_table(std::cout, conn.query("select * from boost_libraries;"));
// same as conn.execute("update boost_libraries set standard = 11 where standard = 98;");
for (auto & p : md.data)
if (p.second.standard == 98)
p.second.standard = 11;
print_table(std::cout, conn.query("select * from boost_libraries;"));
conn.prepare("delete from boost_libraries where name = ?").execute({"mpi"});
print_table(std::cout, conn.query("select * from boost_libraries;"));
return 0;
}
|
