1 // -*- C++ -*-
2 //===----------------------------------------------------------------------===//
3 //
4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 // See https://llvm.org/LICENSE.txt for license information.
6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #ifndef _LIBCPP___FORMAT_FORMATTER_STRING_H
11 #define _LIBCPP___FORMAT_FORMATTER_STRING_H
12 
13 #include <__config>
14 #include <__format/format_error.h>
15 #include <__format/format_fwd.h>
16 #include <__format/format_string.h>
17 #include <__format/formatter.h>
18 #include <__format/parser_std_format_spec.h>
19 #include <algorithm>
20 #include <string_view>
21 
22 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
23 #pragma GCC system_header
24 #endif
25 
26 _LIBCPP_PUSH_MACROS
27 #include <__undef_macros>
28 
29 _LIBCPP_BEGIN_NAMESPACE_STD
30 
31 #if _LIBCPP_STD_VER > 17
32 
33 // TODO FMT Remove this once we require compilers with proper C++20 support.
34 // If the compiler has no concepts support, the format header will be disabled.
35 // Without concepts support enable_if needs to be used and that too much effort
36 // to support compilers with partial C++20 support.
37 #if !defined(_LIBCPP_HAS_NO_CONCEPTS)
38 
39 namespace __format_spec {
40 
41 template <__formatter::__char_type _CharT>
42 class _LIBCPP_TEMPLATE_VIS __formatter_string : public __parser_string<_CharT> {
43 public:
44   _LIBCPP_HIDE_FROM_ABI auto format(basic_string_view<_CharT> __str,
45                                     auto& __ctx) -> decltype(__ctx.out()) {
46 
47     _LIBCPP_ASSERT(this->__alignment != _Flags::_Alignment::__default,
48                    "The parser should not use these defaults");
49 
50     if (this->__width_needs_substitution())
51       this->__substitute_width_arg_id(__ctx.arg(this->__width));
52 
53     if (this->__precision_needs_substitution())
54       this->__substitute_precision_arg_id(__ctx.arg(this->__precision));
55 
56     return __formatter::__write_unicode(
57         __ctx.out(), __str, this->__width,
58         this->__has_precision_field() ? this->__precision : -1, this->__fill,
59         this->__alignment);
60   }
61 };
62 
63 } //namespace __format_spec
64 
65 // [format.formatter.spec]/2.2 For each charT, the string type specializations
66 
67 // Formatter const char*.
68 template <class _CharT>
69 struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT
70     formatter<const _CharT*, _CharT>
71     : public __format_spec::__formatter_string<_CharT> {
72   using _Base = __format_spec::__formatter_string<_CharT>;
73 
74   _LIBCPP_HIDE_FROM_ABI auto format(const _CharT* __str, auto& __ctx)
75       -> decltype(__ctx.out()) {
76     _LIBCPP_ASSERT(__str, "The basic_format_arg constructor should have "
77                           "prevented an invalid pointer.");
78 
79     // When using a center or right alignment and the width option the length
80     // of __str must be known to add the padding upfront. This case is handled
81     // by the base class by converting the argument to a basic_string_view.
82     //
83     // When using left alignment and the width option the padding is added
84     // after outputting __str so the length can be determined while outputting
85     // __str. The same holds true for the precision, during outputting __str it
86     // can be validated whether the precision threshold has been reached. For
87     // now these optimizations aren't implemented. Instead the base class
88     // handles these options.
89     // TODO FMT Implement these improvements.
90     if (this->__has_width_field() || this->__has_precision_field())
91       return _Base::format(__str, __ctx);
92 
93     // No formatting required, copy the string to the output.
94     auto __out_it = __ctx.out();
95     while (*__str)
96       *__out_it++ = *__str++;
97     return __out_it;
98   }
99 };
100 
101 // Formatter char*.
102 template <class _CharT>
103 struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT
104     formatter<_CharT*, _CharT> : public formatter<const _CharT*, _CharT> {
105   using _Base = formatter<const _CharT*, _CharT>;
106 
107   _LIBCPP_HIDE_FROM_ABI auto format(_CharT* __str, auto& __ctx)
108       -> decltype(__ctx.out()) {
109     return _Base::format(__str, __ctx);
110   }
111 };
112 
113 // Formatter const char[].
114 template <class _CharT, size_t _Size>
115 struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT
116     formatter<const _CharT[_Size], _CharT>
117     : public __format_spec::__formatter_string<_CharT> {
118   using _Base = __format_spec::__formatter_string<_CharT>;
119 
120   _LIBCPP_HIDE_FROM_ABI auto format(const _CharT __str[_Size], auto& __ctx)
121       -> decltype(__ctx.out()) {
122     return _Base::format(_VSTD::basic_string_view<_CharT>(__str, _Size), __ctx);
123   }
124 };
125 
126 // Formatter std::string.
127 template <class _CharT, class _Traits, class _Allocator>
128 struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT
129     formatter<basic_string<_CharT, _Traits, _Allocator>, _CharT>
130     : public __format_spec::__formatter_string<_CharT> {
131   using _Base = __format_spec::__formatter_string<_CharT>;
132 
133   _LIBCPP_HIDE_FROM_ABI auto
134   format(const basic_string<_CharT, _Traits, _Allocator>& __str, auto& __ctx)
135       -> decltype(__ctx.out()) {
136     return _Base::format(_VSTD::basic_string_view<_CharT>(__str), __ctx);
137   }
138 };
139 
140 // Formatter std::string_view.
141 template <class _CharT, class _Traits>
142 struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FORMAT
143     formatter<basic_string_view<_CharT, _Traits>, _CharT>
144     : public __format_spec::__formatter_string<_CharT> {};
145 
146 #endif // !defined(_LIBCPP_HAS_NO_CONCEPTS)
147 
148 #endif //_LIBCPP_STD_VER > 17
149 
150 _LIBCPP_END_NAMESPACE_STD
151 
152 _LIBCPP_POP_MACROS
153 
154 #endif // _LIBCPP___FORMAT_FORMATTER_STRING_H
155