libpqxx 7.8.0
strconv.hxx
1/* String conversion definitions.
2 *
3 * DO NOT INCLUDE THIS FILE DIRECTLY; include pqxx/stringconv instead.
4 *
5 * Copyright (c) 2000-2023, 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_STRCONV
12#define PQXX_H_STRCONV
13
14#if !defined(PQXX_HEADER_PRE)
15# error "Include libpqxx headers as <pqxx/header>, not <pqxx/header.hxx>."
16#endif
17
18#include <algorithm>
19#include <cstring>
20#include <limits>
21#include <sstream>
22#include <stdexcept>
23#include <typeinfo>
24
25#if __has_include(<charconv>)
26# include <charconv>
27#endif
28
29#if defined(PQXX_HAVE_RANGES) && __has_include(<ranges>)
30# include <ranges>
31#endif
32
33#include "pqxx/except.hxx"
34#include "pqxx/util.hxx"
35#include "pqxx/zview.hxx"
36
37
38namespace pqxx::internal
39{
41PQXX_LIBEXPORT std::string demangle_type_name(char const[]);
42} // namespace pqxx::internal
43
44
45namespace pqxx
46{
71
73
81template<typename TYPE>
82std::string const type_name{internal::demangle_type_name(typeid(TYPE).name())};
83
84
86
92template<typename TYPE, typename ENABLE = void> struct nullness
93{
95 static bool has_null;
96
98 static bool always_null;
99
101 static bool is_null(TYPE const &value);
102
104
109 [[nodiscard]] static TYPE null();
110};
111
112
114template<typename TYPE> struct no_null
115{
117
127 static constexpr bool has_null = false;
128
130
133 static constexpr bool always_null = false;
134
136
140 [[nodiscard]] static constexpr bool is_null(TYPE const &) noexcept
141 {
142 return false;
143 }
144};
145
146
148
154template<typename TYPE> struct string_traits
155{
157
160 static constexpr bool converts_to_string{false};
161
163
166 static constexpr bool converts_from_string{false};
167
169
188 [[nodiscard]] static inline zview
189 to_buf(char *begin, char *end, TYPE const &value);
190
192 /* @warning A null value has no string representation. Do not pass a null.
193 *
194 * Writes value's string representation into the buffer, starting exactly at
195 * @c begin, and ensuring a trailing zero. Returns the address just beyond
196 * the trailing zero, so the caller could use it as the @c begin for another
197 * call to @c into_buf writing a next value.
198 */
199 static inline char *into_buf(char *begin, char *end, TYPE const &value);
200
202
207 [[nodiscard]] static inline TYPE from_string(std::string_view text);
208
209 // C++20: Can we make these all constexpr?
211
215 [[nodiscard]] static inline std::size_t
216 size_buffer(TYPE const &value) noexcept;
217
218 // TODO: Move is_unquoted_string into the traits after all?
219};
220
221
223
239template<typename TYPE> [[noreturn]]
241
242
244
249template<typename TYPE> struct forbidden_conversion
250{
251 static constexpr bool converts_to_string{false};
252 static constexpr bool converts_from_string{false};
253 [[noreturn]] static zview to_buf(char *, char *, TYPE const &)
254 { oops_forbidden_conversion<TYPE>(); }
255 [[noreturn]] static char *into_buf(char *, char *, TYPE const &)
256 { oops_forbidden_conversion<TYPE>(); }
257 [[noreturn]] static TYPE from_string(std::string_view)
258 { oops_forbidden_conversion<TYPE>(); }
259 [[noreturn]] static std::size_t size_buffer(TYPE const &) noexcept
260 { oops_forbidden_conversion<TYPE>(); }
261};
262
263
265
281template<> struct string_traits<char> : forbidden_conversion<char> {};
282
283
284
286
300template<>
301struct string_traits<unsigned char> : forbidden_conversion<unsigned char> {};
302
303
304
306
320template<>
321struct string_traits<signed char> : forbidden_conversion<signed char> {};
322
323
324
326
331template<>
332struct string_traits<std::byte> : forbidden_conversion<std::byte> {};
333
334
336template<typename ENUM>
337struct nullness<ENUM, std::enable_if_t<std::is_enum_v<ENUM>>> : no_null<ENUM>
338{};
339
340
341// C++20: Concepts for "converts from string" & "converts to string."
342} // namespace pqxx
343
344
345namespace pqxx::internal
346{
348
357template<typename ENUM> struct enum_traits
358{
359 using impl_type = std::underlying_type_t<ENUM>;
361
362 static constexpr bool converts_to_string{true};
363 static constexpr bool converts_from_string{true};
364
365 [[nodiscard]] static constexpr zview
366 to_buf(char *begin, char *end, ENUM const &value)
367 {
368 return impl_traits::to_buf(begin, end, to_underlying(value));
369 }
370
371 static constexpr char *into_buf(char *begin, char *end, ENUM const &value)
372 {
373 return impl_traits::into_buf(begin, end, to_underlying(value));
374 }
375
376 [[nodiscard]] static ENUM from_string(std::string_view text)
377 {
378 return static_cast<ENUM>(impl_traits::from_string(text));
379 }
380
381 [[nodiscard]] static std::size_t size_buffer(ENUM const &value) noexcept
382 {
383 return impl_traits::size_buffer(to_underlying(value));
384 }
385
386private:
387 // C++23: Replace with std::to_underlying.
388 static constexpr impl_type to_underlying(ENUM const &value) noexcept
389 {
390 return static_cast<impl_type>(value);
391 }
392};
393} // namespace pqxx::internal
394
395
396// We used to inline type_name<ENUM>, but this triggered a "double free" error
397// on program exit, when libpqxx was built as a shared library on Debian with
398// gcc 12.
399
401
412#define PQXX_DECLARE_ENUM_CONVERSION(ENUM) \
413 template<> struct string_traits<ENUM> : pqxx::internal::enum_traits<ENUM> \
414 {}; \
415 template<> inline std::string_view const type_name<ENUM> { #ENUM }
416
417
418namespace pqxx
419{
421
433template<typename TYPE>
434[[nodiscard]] inline TYPE from_string(std::string_view text)
435{
437}
438
439
441
447template<>
448[[nodiscard]] inline std::string_view from_string(std::string_view text)
449{
450 return text;
451}
452
453
455
462template<typename T> inline void from_string(std::string_view text, T &value)
463{
464 value = from_string<T>(text);
465}
466
467
469
474template<typename TYPE> inline std::string to_string(TYPE const &value);
475
476
478
485template<typename... TYPE>
486[[nodiscard]] inline std::vector<std::string_view>
487to_buf(char *here, char const *end, TYPE... value)
488{
489 return {[&here, end](auto v) {
490 auto begin = here;
491 here = string_traits<decltype(v)>::into_buf(begin, end, v);
492 // Exclude the trailing zero out of the string_view.
493 auto len{static_cast<std::size_t>(here - begin) - 1};
494 return std::string_view{begin, len};
495 }(value)...};
496}
497
499
502template<typename TYPE>
503inline void into_string(TYPE const &value, std::string &out);
504
505
507template<typename TYPE>
508[[nodiscard]] inline constexpr bool is_null(TYPE const &value) noexcept
509{
510 return nullness<strip_t<TYPE>>::is_null(value);
511}
512
513
515
518template<typename... TYPE>
519[[nodiscard]] inline std::size_t size_buffer(TYPE const &...value) noexcept
520{
521 return (string_traits<strip_t<TYPE>>::size_buffer(value) + ...);
522}
523
524
526
532template<typename TYPE> inline constexpr bool is_sql_array{false};
533
534
536
548template<typename TYPE> inline constexpr bool is_unquoted_safe{false};
549
550
552template<typename T> inline constexpr char array_separator{','};
553
554
556
563template<typename TYPE> inline constexpr format param_format(TYPE const &)
564{
565 return format::text;
566}
567
568
570
579template<typename TYPE>
580inline zview generic_to_buf(char *begin, char *end, TYPE const &value)
581{
582 using traits = string_traits<TYPE>;
583 // The trailing zero does not count towards the zview's size, so subtract 1
584 // from the result we get from into_buf().
585 if (is_null(value))
586 return {};
587 else
588 return {begin, traits::into_buf(begin, end, value) - begin - 1};
589}
590
591
592#if defined(PQXX_HAVE_CONCEPTS)
594
600template<class TYPE>
601concept binary = std::ranges::contiguous_range<TYPE> and
602 std::is_same_v<strip_t<value_type<TYPE>>, std::byte>;
603#endif
605} // namespace pqxx
606
607
608#include "pqxx/internal/conversions.hxx"
609#endif
The home of all libpqxx classes, functions, templates, etc.
Definition array.hxx:33
std::string const type_name
A human-readable name for a type, used in error messages and such.
Definition strconv.hxx:82
void into_string(TYPE const &value, std::string &out)
Convert a value to a readable string that PostgreSQL will understand.
std::remove_cv_t< std::remove_reference_t< TYPE > > strip_t
Remove any constness, volatile, and reference-ness from a type.
Definition types.hxx:91
std::vector< std::string_view > to_buf(char *here, char const *end, TYPE... value)
Convert multiple values to strings inside a single buffer.
Definition strconv.hxx:487
constexpr char array_separator
Element separator between SQL array elements of this type.
Definition strconv.hxx:552
constexpr bool is_unquoted_safe
Can we use this type in arrays and composite types without quoting them?
Definition strconv.hxx:548
std::size_t size_buffer(TYPE const &...value) noexcept
Estimate how much buffer space is needed to represent values as a string.
Definition strconv.hxx:519
void oops_forbidden_conversion() noexcept
Nonexistent function to indicate a disallowed type conversion.
constexpr bool is_null(TYPE const &value) noexcept
Is value null?
Definition strconv.hxx:508
zview generic_to_buf(char *begin, char *end, TYPE const &value)
Implement string_traits<TYPE>::to_buf by calling into_buf.
Definition strconv.hxx:580
constexpr format param_format(TYPE const &)
What's the preferred format for passing non-null parameters of this type?
Definition strconv.hxx:563
constexpr bool is_sql_array
Does this type translate to an SQL array?
Definition strconv.hxx:532
std::string to_string(field const &value)
Convert a field to a string.
Definition result.cxx:548
T from_string(field const &value)
Convert a field's value to type T.
Definition field.hxx:520
format
Format code: is data text or binary?
Definition types.hxx:81
Internal items for libpqxx' own use. Do not use these yourself.
Definition composite.hxx:84
std::string demangle_type_name(char const[])
Attempt to demangle std::type_info::name() to something human-readable.
Definition strconv.cxx:230
Traits describing a type's "null value," if any.
Definition strconv.hxx:93
static bool is_null(TYPE const &value)
Is value a null?
static TYPE null()
Return a null value.
static bool has_null
Does this type have a null value?
Definition strconv.hxx:95
static bool always_null
Is this type always null?
Definition strconv.hxx:98
Nullness traits describing a type which does not have a null value.
Definition strconv.hxx:115
static constexpr bool always_null
Are all values of this type null?
Definition strconv.hxx:133
static constexpr bool has_null
Does TYPE have a "built-in null value"?
Definition strconv.hxx:127
static constexpr bool is_null(TYPE const &) noexcept
Does a given value correspond to an SQL null value?
Definition strconv.hxx:140
Traits class for use in string conversions.
Definition strconv.hxx:155
static std::size_t size_buffer(TYPE const &value) noexcept
Estimate how much buffer space is needed to represent value.
static zview to_buf(char *begin, char *end, TYPE const &value)
Return a string_view representing value, plus terminating zero.
static TYPE from_string(std::string_view text)
Parse a string representation of a TYPE value.
Definition strconv.cxx:740
static constexpr bool converts_to_string
Is conversion from TYPE to strings supported?
Definition strconv.hxx:160
static char * into_buf(char *begin, char *end, TYPE const &value)
Write value's string representation into buffer at begin.
static constexpr bool converts_from_string
Is conversion from string_view to TYPE supported?
Definition strconv.hxx:166
String traits for a forbidden type conversion.
Definition strconv.hxx:250
static char * into_buf(char *, char *, TYPE const &)
Definition strconv.hxx:255
static TYPE from_string(std::string_view)
Definition strconv.hxx:257
static std::size_t size_buffer(TYPE const &) noexcept
Definition strconv.hxx:259
static zview to_buf(char *, char *, TYPE const &)
Definition strconv.hxx:253
Helper class for defining enum conversions.
Definition strconv.hxx:358
static std::size_t size_buffer(ENUM const &value) noexcept
Definition strconv.hxx:381
static constexpr zview to_buf(char *begin, char *end, ENUM const &value)
Definition strconv.hxx:366
static constexpr bool converts_from_string
Definition strconv.hxx:363
std::underlying_type_t< ENUM > impl_type
Definition strconv.hxx:359
static ENUM from_string(std::string_view text)
Definition strconv.hxx:376
static constexpr char * into_buf(char *begin, char *end, ENUM const &value)
Definition strconv.hxx:371
static constexpr bool converts_to_string
Definition strconv.hxx:362
Marker-type wrapper: zero-terminated std::string_view.
Definition zview.hxx:38