MySQL 8.0.32
Source Code Documentation
visible_fields.h
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22 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
23
24#ifndef SQL_VISIBLE_FIELDS_H
25#define SQL_VISIBLE_FIELDS_H
26
27/**
28 @file
29 An adapter class to support iteration over an iterator of Item *
30 (typically mem_root_deque<Item *>), while skipping over items that
31 are hidden (item->hidden == true). This is such a common operation
32 that it warrants having its own adapter. You can either do
33
34 for (Item *item : VisibleFields(fields))
35
36 or use select->visible_fields().
37
38 Behavior is undefined if you modify the hidden flag of an item during
39 iteration.
40
41 TODO(sgunders): When we get C++20, replace with an std::views::filter.
42 */
43
44#include <iterator>
45
46#include "mem_root_deque.h"
47#include "sql/item.h"
48
49template <class Iterator>
51 public:
52 VisibleFieldsAdapter(Iterator base, Iterator end) : m_it(base), m_end(end) {
53 while (m_it != m_end && (*m_it)->hidden) {
54 ++m_it;
55 }
56 }
57
58 // Pre-increment.
60 do {
61 ++m_it;
62 } while (m_it != m_end && (*m_it)->hidden);
63 return *this;
64 }
65
66 // Post-increment.
68 VisibleFieldsAdapter ret = *this;
69 do {
70 m_it++;
71 } while (m_it != m_end && (*m_it)->hidden);
72 return ret;
73 }
74
75 auto &operator*() const { return *m_it; }
76
77 bool operator==(const VisibleFieldsAdapter &other) const {
78 return m_it == other.m_it;
79 }
80 bool operator!=(const VisibleFieldsAdapter &other) const {
81 return m_it != other.m_it;
82 }
83
84 // Define aliases needed by std::iterator_traits, to allow using this iterator
85 // type with standard library templates.
86 using difference_type = typename Iterator::difference_type;
88 using pointer = typename Iterator::pointer;
89 using reference = typename Iterator::reference;
90 using iterator_category = std::forward_iterator_tag;
91
92 private:
93 Iterator m_it, m_end;
94};
95
96template <class Container, class Iterator>
98 public:
99 explicit VisibleFieldsContainer(Container &fields) : m_fields(fields) {}
101 return VisibleFieldsAdapter<Iterator>(m_fields.begin(), m_fields.end());
102 }
105 }
106
107 private:
108 Container &m_fields;
109};
110
114}
115
116inline auto VisibleFields(const mem_root_deque<Item *> &fields) {
119}
120
121#endif // SQL_VISIBLE_FIELDS_H
Definition: visible_fields.h:50
VisibleFieldsAdapter & operator++()
Definition: visible_fields.h:59
typename Iterator::difference_type difference_type
Definition: visible_fields.h:86
Iterator m_it
Definition: visible_fields.h:93
VisibleFieldsAdapter operator++(int)
Definition: visible_fields.h:67
typename Iterator::reference reference
Definition: visible_fields.h:89
bool operator==(const VisibleFieldsAdapter &other) const
Definition: visible_fields.h:77
bool operator!=(const VisibleFieldsAdapter &other) const
Definition: visible_fields.h:80
Iterator m_end
Definition: visible_fields.h:93
typename Iterator::pointer pointer
Definition: visible_fields.h:88
VisibleFieldsAdapter(Iterator base, Iterator end)
Definition: visible_fields.h:52
std::forward_iterator_tag iterator_category
Definition: visible_fields.h:90
typename Iterator::value_type value_type
Definition: visible_fields.h:87
auto & operator*() const
Definition: visible_fields.h:75
Definition: visible_fields.h:97
VisibleFieldsContainer(Container &fields)
Definition: visible_fields.h:99
VisibleFieldsAdapter< Iterator > begin()
Definition: visible_fields.h:100
Container & m_fields
Definition: visible_fields.h:108
VisibleFieldsAdapter< Iterator > end()
Definition: visible_fields.h:103
Definition: mem_root_deque.h:286
A (partial) implementation of std::deque allocating its blocks on a MEM_ROOT.
Definition: mem_root_deque.h:109
uint16_t value_type
Definition: vt100.h:183
Cursor end()
A past-the-end Cursor.
Definition: rules_table_service.cc:191
auto VisibleFields(mem_root_deque< Item * > &fields)
Definition: visible_fields.h:111