LLVM  9.0.0svn
FormatVariadicDetails.h
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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_FORMATVARIADIC_DETAILS_H
10 #define LLVM_SUPPORT_FORMATVARIADIC_DETAILS_H
11 
12 #include "llvm/ADT/StringRef.h"
14 
15 #include <type_traits>
16 
17 namespace llvm {
18 template <typename T, typename Enable = void> struct format_provider {};
19 class Error;
20 
21 namespace detail {
23  virtual void anchor();
24 
25 protected:
26  virtual ~format_adapter() {}
27 
28 public:
29  virtual void format(raw_ostream &S, StringRef Options) = 0;
30 };
31 
32 template <typename T> class provider_format_adapter : public format_adapter {
33  T Item;
34 
35 public:
36  explicit provider_format_adapter(T &&Item) : Item(std::forward<T>(Item)) {}
37 
38  void format(llvm::raw_ostream &S, StringRef Options) override {
40  }
41 };
42 
43 template <typename T>
45  T Item;
46 
47 public:
49  : Item(std::forward<T>(Item)) {}
50 
51  void format(llvm::raw_ostream &S, StringRef Options) override { S << Item; }
52 };
53 
54 template <typename T> class missing_format_adapter;
55 
56 // Test if format_provider<T> is defined on T and contains a member function
57 // with the signature:
58 // static void format(const T&, raw_stream &, StringRef);
59 //
60 template <class T> class has_FormatProvider {
61 public:
62  using Decayed = typename std::decay<T>::type;
63  typedef void (*Signature_format)(const Decayed &, llvm::raw_ostream &,
64  StringRef);
65 
66  template <typename U>
67  static char test(SameType<Signature_format, &U::format> *);
68 
69  template <typename U> static double test(...);
70 
71  static bool const value =
72  (sizeof(test<llvm::format_provider<Decayed>>(nullptr)) == 1);
73 };
74 
75 // Test if raw_ostream& << T -> raw_ostream& is findable via ADL.
76 template <class T> class has_StreamOperator {
77 public:
78  using ConstRefT = const typename std::decay<T>::type &;
79 
80  template <typename U>
81  static char test(typename std::enable_if<
82  std::is_same<decltype(std::declval<llvm::raw_ostream &>()
83  << std::declval<U>()),
84  llvm::raw_ostream &>::value,
85  int *>::type);
86 
87  template <typename U> static double test(...);
88 
89  static bool const value = (sizeof(test<ConstRefT>(nullptr)) == 1);
90 };
91 
92 // Simple template that decides whether a type T should use the member-function
93 // based format() invocation.
94 template <typename T>
96  : public std::integral_constant<
97  bool,
98  std::is_base_of<format_adapter,
99  typename std::remove_reference<T>::type>::value> {};
100 
101 // Simple template that decides whether a type T should use the format_provider
102 // based format() invocation. The member function takes priority, so this test
103 // will only be true if there is not ALSO a format member.
104 template <typename T>
106  : public std::integral_constant<
107  bool, !uses_format_member<T>::value && has_FormatProvider<T>::value> {
108 };
109 
110 // Simple template that decides whether a type T should use the operator<<
111 // based format() invocation. This takes last priority.
112 template <typename T>
114  : public std::integral_constant<bool, !uses_format_member<T>::value &&
115  !uses_format_provider<T>::value &&
116  has_StreamOperator<T>::value> {};
117 
118 // Simple template that decides whether a type T has neither a member-function
119 // nor format_provider based implementation that it can use. Mostly used so
120 // that the compiler spits out a nice diagnostic when a type with no format
121 // implementation can be located.
122 template <typename T>
124  : public std::integral_constant<bool, !uses_format_member<T>::value &&
125  !uses_format_provider<T>::value &&
126  !uses_stream_operator<T>::value> {
127 };
128 
129 template <typename T>
130 typename std::enable_if<uses_format_member<T>::value, T>::type
132  return std::forward<T>(Item);
133 }
134 
135 template <typename T>
136 typename std::enable_if<uses_format_provider<T>::value,
139  return provider_format_adapter<T>(std::forward<T>(Item));
140 }
141 
142 template <typename T>
143 typename std::enable_if<uses_stream_operator<T>::value,
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<llvm::Error, typename std::remove_cv<T>::type>::value,
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 typename std::enable_if<uses_missing_provider<T>::value,
159  return missing_format_adapter<T>();
160 }
161 }
162 }
163 
164 #endif
This class represents lattice values for constants.
Definition: AllocatorList.h:23
format_object< Ts... > format(const char *Fmt, const Ts &... Vals)
These are helper functions used to produce formatted output.
Definition: Format.h:123
void format(llvm::raw_ostream &S, StringRef Options) override
Definition: BitVector.h:937
std::enable_if< uses_missing_provider< T >::value, missing_format_adapter< T > >::type build_format_adapter(T &&Item)
void format(llvm::raw_ostream &S, StringRef Options) override
const typename std::decay< T >::type & ConstRefT
Lightweight error class with error context and mandatory checking.
Definition: Error.h:157
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:45
typename std::decay< T >::type Decayed
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:48