libpqxx  7.4.1
zview.hxx
1 /* Zero-terminated string view.
2  *
3  * DO NOT INCLUDE THIS FILE DIRECTLY; include pqxx/zview instead.
4  *
5  * Copyright (c) 2000-2021, Jeroen T. Vermeulen.
6  *
7  * See COPYING for copyright license. If you did not receive a file called
8  * COPYING with this source code, please notify the distributor of this
9  * mistake, or contact the author.
10  */
11 #ifndef PQXX_H_ZVIEW
12 #define PQXX_H_ZVIEW
13 
14 #include "pqxx/compiler-public.hxx"
15 
16 #include <string>
17 #include <string_view>
18 #include <type_traits>
19 
20 
21 namespace pqxx
22 {
24 
37 class zview : public std::string_view
38 {
39 public:
40  constexpr zview() noexcept = default;
41 
43  constexpr zview(char const text[], std::ptrdiff_t len) :
44  std::string_view{text, static_cast<std::size_t>(len)}
45  {}
46 
48  constexpr zview(char text[], std::ptrdiff_t len) :
49  std::string_view{text, static_cast<std::size_t>(len)}
50  {}
51 
53 
55  template<typename... Args>
56  explicit constexpr zview(Args &&...args) :
57  std::string_view(std::forward<Args>(args)...)
58  {}
59 
61  zview(std::string const &str) : std::string_view{str.c_str(), std::size(str)}
62  {}
63 
65 
69  constexpr zview(char const str[]) : std::string_view{str} {}
70 
72 
80  template<size_t size>
81  constexpr zview(char const (&literal)[size]) : zview(literal, size - 1)
82  {}
83 
85  [[nodiscard]] constexpr char const *c_str() const noexcept { return data(); }
86 };
87 
88 
90 
95 constexpr zview operator"" _zv(char const str[], std::size_t len) noexcept
96 {
97  return zview{str, len};
98 }
99 } // namespace pqxx
100 
101 
102 #if defined(PQXX_HAVE_CONCEPTS)
103 namespace pqxx::internal
104 {
106 
110 template<typename T>
111 concept ZString =
112  std::is_convertible_v<T, char const *> or std::is_convertible_v<T, zview> or
113  std::is_convertible_v<T, std::string const &>;
114 } // namespace pqxx::internal
115 #endif // PQXX_HAVE_CONCEPTS
116 
117 
118 namespace pqxx::internal
119 {
121 inline constexpr char const *as_c_string(char const str[]) noexcept
122 {
123  return str;
124 }
126 template<std::size_t N>
127 inline constexpr char const *as_c_string(char (&str)[N]) noexcept
128 {
129  return str;
130 }
132 inline constexpr char const *as_c_string(pqxx::zview str) noexcept
133 {
134  return str.c_str();
135 }
136 // TODO: constexpr as of C++20.
138 inline char const *as_c_string(std::string const &str) noexcept
139 {
140  return str.c_str();
141 }
142 } // namespace pqxx::internal
143 
144 #endif
constexpr zview(Args &&...args)
Construct from any initialiser you might use for std::string_view.
Definition: zview.hxx:56
constexpr char const * as_c_string(char const str[]) noexcept
Get a raw C string pointer.
Definition: zview.hxx:121
The home of all libpqxx classes, functions, templates, etc.
Definition: array.hxx:25
constexpr zview(char const text[], std::ptrdiff_t len)
Convenience overload: construct using pointer and signed length.
Definition: zview.hxx:43
constexpr zview(char text[], std::ptrdiff_t len)
Convenience overload: construct using pointer and signed length.
Definition: zview.hxx:48
constexpr zview() noexcept=default
constexpr zview(char const str[])
Construct a zview from a C-style string.
Definition: zview.hxx:69
STL namespace.
zview(std::string const &str)
Definition: zview.hxx:61
Marker-type wrapper: zero-terminated std::string_view.
Definition: zview.hxx:37
constexpr zview(char const (&literal)[size])
Construct a zview from a string literal.
Definition: zview.hxx:81
Internal items for libpqxx&#39; own use. Do not use these yourself.
Definition: composite.hxx:73
constexpr char const * c_str() const noexcept
Either a null pointer, or a zero-terminated text buffer.
Definition: zview.hxx:85