1 //===- FormatVariadicDetails.h - Helpers for FormatVariadic.h ----*- C++-*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8
9 #ifndef LLVM_SUPPORT_FORMATVARIADICDETAILS_H
10 #define LLVM_SUPPORT_FORMATVARIADICDETAILS_H
11
12 #include "llvm/ADT/StringRef.h"
13 #include "llvm/ADT/STLExtras.h"
14 #include "llvm/Support/raw_ostream.h"
15
16 #include <type_traits>
17
18 namespace llvm {
19 template <typename T, typename Enable = void> struct format_provider {};
20 class Error;
21
22 namespace support {
23 namespace detail {
24 class format_adapter {
25 virtual void anchor();
26
27 protected:
28 virtual ~format_adapter() = default;
29
30 public:
31 virtual void format(raw_ostream &S, StringRef Options) = 0;
32 };
33
34 template <typename T> class provider_format_adapter : public format_adapter {
35 T Item;
36
37 public:
provider_format_adapter(T && Item)38 explicit provider_format_adapter(T &&Item) : Item(std::forward<T>(Item)) {}
39
format(llvm::raw_ostream & S,StringRef Options)40 void format(llvm::raw_ostream &S, StringRef Options) override {
41 format_provider<std::decay_t<T>>::format(Item, S, Options);
42 }
43 };
44
45 template <typename T>
46 class stream_operator_format_adapter : public format_adapter {
47 T Item;
48
49 public:
stream_operator_format_adapter(T && Item)50 explicit stream_operator_format_adapter(T &&Item)
51 : Item(std::forward<T>(Item)) {}
52
format(llvm::raw_ostream & S,StringRef)53 void format(llvm::raw_ostream &S, StringRef) override { S << Item; }
54 };
55
56 template <typename T> class missing_format_adapter;
57
58 // Test if format_provider<T> is defined on T and contains a member function
59 // with the signature:
60 // static void format(const T&, raw_stream &, StringRef);
61 //
62 template <class T> class has_FormatProvider {
63 public:
64 using Decayed = std::decay_t<T>;
65 typedef void (*Signature_format)(const Decayed &, llvm::raw_ostream &,
66 StringRef);
67
68 template <typename U>
69 static char test(SameType<Signature_format, &U::format> *);
70
71 template <typename U> static double test(...);
72
73 static bool const value =
74 (sizeof(test<llvm::format_provider<Decayed>>(nullptr)) == 1);
75 };
76
77 // Test if raw_ostream& << T -> raw_ostream& is findable via ADL.
78 template <class T> class has_StreamOperator {
79 public:
80 using ConstRefT = const std::decay_t<T> &;
81
82 template <typename U>
83 static char test(std::enable_if_t<
84 std::is_same_v<decltype(std::declval<llvm::raw_ostream &>()
85 << std::declval<U>()),
86 llvm::raw_ostream &>,
87 int *>);
88
89 template <typename U> static double test(...);
90
91 static bool const value = (sizeof(test<ConstRefT>(nullptr)) == 1);
92 };
93
94 // Simple template that decides whether a type T should use the member-function
95 // based format() invocation.
96 template <typename T>
97 struct uses_format_member
98 : public std::integral_constant<
99 bool, std::is_base_of_v<format_adapter, std::remove_reference_t<T>>> {
100 };
101
102 // Simple template that decides whether a type T should use the format_provider
103 // based format() invocation. The member function takes priority, so this test
104 // will only be true if there is not ALSO a format member.
105 template <typename T>
106 struct uses_format_provider
107 : public std::integral_constant<
108 bool, !uses_format_member<T>::value && has_FormatProvider<T>::value> {
109 };
110
111 // Simple template that decides whether a type T should use the operator<<
112 // based format() invocation. This takes last priority.
113 template <typename T>
114 struct uses_stream_operator
115 : public std::integral_constant<bool, !uses_format_member<T>::value &&
116 !uses_format_provider<T>::value &&
117 has_StreamOperator<T>::value> {};
118
119 // Simple template that decides whether a type T has neither a member-function
120 // nor format_provider based implementation that it can use. Mostly used so
121 // that the compiler spits out a nice diagnostic when a type with no format
122 // implementation can be located.
123 template <typename T>
124 struct uses_missing_provider
125 : public std::integral_constant<bool, !uses_format_member<T>::value &&
126 !uses_format_provider<T>::value &&
127 !uses_stream_operator<T>::value> {
128 };
129
130 template <typename T>
131 std::enable_if_t<uses_format_member<T>::value, T>
build_format_adapter(T && Item)132 build_format_adapter(T &&Item) {
133 return std::forward<T>(Item);
134 }
135
136 template <typename T>
137 std::enable_if_t<uses_format_provider<T>::value, provider_format_adapter<T>>
build_format_adapter(T && Item)138 build_format_adapter(T &&Item) {
139 return provider_format_adapter<T>(std::forward<T>(Item));
140 }
141
142 template <typename T>
143 std::enable_if_t<uses_stream_operator<T>::value,
144 stream_operator_format_adapter<T>>
build_format_adapter(T && Item)145 build_format_adapter(T &&Item) {
146 // If the caller passed an Error by value, then stream_operator_format_adapter
147 // would be responsible for consuming it.
148 // Make the caller opt into this by calling fmt_consume().
149 static_assert(
150 !std::is_same_v<llvm::Error, std::remove_cv_t<T>>,
151 "llvm::Error-by-value must be wrapped in fmt_consume() for formatv");
152 return stream_operator_format_adapter<T>(std::forward<T>(Item));
153 }
154
155 template <typename T>
156 std::enable_if_t<uses_missing_provider<T>::value, missing_format_adapter<T>>
build_format_adapter(T &&)157 build_format_adapter(T &&) {
158 return missing_format_adapter<T>();
159 }
160 } // namespace detail
161 } // namespace support
162 } // namespace llvm
163
164 #endif
165