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
|
/* Copyright (c) 1997-2024
Ewgenij Gawrilow, Michael Joswig, and the polymake team
Technische Universität Berlin, Germany
https://polymake.org
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version: http://www.gnu.org/licenses/gpl.txt.
This program is distributed in the hope that it will be useful,
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
--------------------------------------------------------------------------------
This file is part of the polymake database interface polyDB.
@author Andreas Paffenholz
(c) 2015-2023
https://polydb.org
https://www.mathematik.tu-darmstadt.de/~paffenholz
*/
#pragma once
#include <iterator>
#include "polymake/common/PolyDB.h"
#include "polymake/common/PolyDBFunctions.h"
#include "polymake/Array.h"
namespace polymake {
namespace common {
namespace polydb {
/**
* @brief a class containing a cursor into a collection of polyDB
*
*/
class PolyDBCursor {
public:
PolyDBCursor( std::shared_ptr<mongoc_cursor_t> c ) : cursor_(c) {
result_stored_ = false;
}
PolyDBCursor ( PolyDBCursor &&c ) : cursor_(c.cursor_) {
result_ = c.result_;
result_stored_ = c.result_stored_;
}
// FIXME why do we need a copy constructor?
PolyDBCursor ( const PolyDBCursor &c ) : cursor_(c.cursor_) {
result_ = c.result_;
result_stored_ = c.result_stored_;
}
/**
* @brief checks if we can read another document from the cursor
*
* @return true if we can read another document from the cursor
*/
const bool has_next() const {
if ( result_stored_ ) {
return true;
}
const bson_t * result;
bool has_next = mongoc_cursor_next(cursor_.get(), &result);
if ( !has_next ) {
return false;
}
result_ = to_string_and_free(bson_as_relaxed_extended_json ( result, nullptr ));
result_stored_ = true;
return true;
}
/**
* @brief obtains the next document from the cursor
* this may already be cached
*
* @return const std::string the next object as json string
*/
const std::string next() const {
if ( !has_next() ) {
throw std::runtime_error("No more documents in query");
}
result_stored_ = false;
return result_;
}
/**
* @brief read all documents from the cursor and return them as array
*
* @return const Array<std::string> the list of objects as json string
*/
const Array<std::string> all() const {
std::vector<std::string> v;
const bson_t * doc;
while ( mongoc_cursor_next (cursor_.get(), &doc) ) {
std::string res = to_string_and_free(bson_as_relaxed_extended_json (doc, nullptr));
v.push_back(res);
}
return Array<std::string>(v.size(),entire(v));
}
private:
// the cached next result from the
mutable std::string result_;
// whether we have stored a result in the cache
mutable bool result_stored_;
// the actual mongoc cursor
std::shared_ptr<mongoc_cursor_t> cursor_;
};
}}}
|
