LLVM  3.7.0
Format.h
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1 //===- Format.h - Efficient printf-style formatting for streams -*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements the format() function, which can be used with other
11 // LLVM subsystems to provide printf-style formatting. This gives all the power
12 // and risk of printf. This can be used like this (with raw_ostreams as an
13 // example):
14 //
15 // OS << "mynumber: " << format("%4.5f", 1234.412) << '\n';
16 //
17 // Or if you prefer:
18 //
19 // OS << format("mynumber: %4.5f\n", 1234.412);
20 //
21 //===----------------------------------------------------------------------===//
22 
23 #ifndef LLVM_SUPPORT_FORMAT_H
24 #define LLVM_SUPPORT_FORMAT_H
25 
26 #include "llvm/ADT/STLExtras.h"
27 #include "llvm/ADT/StringRef.h"
28 #include "llvm/Support/DataTypes.h"
29 #include <cassert>
30 #include <cstdio>
31 #include <tuple>
32 
33 namespace llvm {
34 
35 /// This is a helper class used for handling formatted output. It is the
36 /// abstract base class of a templated derived class.
38 protected:
39  const char *Fmt;
40  ~format_object_base() = default; // Disallow polymorphic deletion.
41  format_object_base(const format_object_base &) = default;
42  virtual void home(); // Out of line virtual method.
43 
44  /// Call snprintf() for this object, on the given buffer and size.
45  virtual int snprint(char *Buffer, unsigned BufferSize) const = 0;
46 
47 public:
48  format_object_base(const char *fmt) : Fmt(fmt) {}
49 
50  /// Format the object into the specified buffer. On success, this returns
51  /// the length of the formatted string. If the buffer is too small, this
52  /// returns a length to retry with, which will be larger than BufferSize.
53  unsigned print(char *Buffer, unsigned BufferSize) const {
54  assert(BufferSize && "Invalid buffer size!");
55 
56  // Print the string, leaving room for the terminating null.
57  int N = snprint(Buffer, BufferSize);
58 
59  // VC++ and old GlibC return negative on overflow, just double the size.
60  if (N < 0)
61  return BufferSize * 2;
62 
63  // Other implementations yield number of bytes needed, not including the
64  // final '\0'.
65  if (unsigned(N) >= BufferSize)
66  return N + 1;
67 
68  // Otherwise N is the length of output (not including the final '\0').
69  return N;
70  }
71 };
72 
73 /// These are templated helper classes used by the format function that
74 /// capture the object to be formated and the format string. When actually
75 /// printed, this synthesizes the string into a temporary buffer provided and
76 /// returns whether or not it is big enough.
77 
78 template <typename... Ts>
79 class format_object final : public format_object_base {
80  std::tuple<Ts...> Vals;
81 
82  template <std::size_t... Is>
83  int snprint_tuple(char *Buffer, unsigned BufferSize,
84  index_sequence<Is...>) const {
85 #ifdef _MSC_VER
86  return _snprintf(Buffer, BufferSize, Fmt, std::get<Is>(Vals)...);
87 #else
88  return snprintf(Buffer, BufferSize, Fmt, std::get<Is>(Vals)...);
89 #endif
90  }
91 
92 public:
93  format_object(const char *fmt, const Ts &... vals)
94  : format_object_base(fmt), Vals(vals...) {}
95 
96  int snprint(char *Buffer, unsigned BufferSize) const override {
97  return snprint_tuple(Buffer, BufferSize, index_sequence_for<Ts...>());
98  }
99 };
100 
101 /// These are helper functions used to produce formatted output. They use
102 /// template type deduction to construct the appropriate instance of the
103 /// format_object class to simplify their construction.
104 ///
105 /// This is typically used like:
106 /// \code
107 /// OS << format("%0.4f", myfloat) << '\n';
108 /// \endcode
109 
110 template <typename... Ts>
111 inline format_object<Ts...> format(const char *Fmt, const Ts &... Vals) {
112  return format_object<Ts...>(Fmt, Vals...);
113 }
114 
115 /// This is a helper class used for left_justify() and right_justify().
117  StringRef Str;
118  unsigned Width;
119  bool RightJustify;
120  friend class raw_ostream;
121 public:
122  FormattedString(StringRef S, unsigned W, bool R)
123  : Str(S), Width(W), RightJustify(R) { }
124 };
125 
126 /// left_justify - append spaces after string so total output is
127 /// \p Width characters. If \p Str is larger that \p Width, full string
128 /// is written with no padding.
129 inline FormattedString left_justify(StringRef Str, unsigned Width) {
130  return FormattedString(Str, Width, false);
131 }
132 
133 /// right_justify - add spaces before string so total output is
134 /// \p Width characters. If \p Str is larger that \p Width, full string
135 /// is written with no padding.
136 inline FormattedString right_justify(StringRef Str, unsigned Width) {
137  return FormattedString(Str, Width, true);
138 }
139 
140 /// This is a helper class used for format_hex() and format_decimal().
142  uint64_t HexValue;
143  int64_t DecValue;
144  unsigned Width;
145  bool Hex;
146  bool Upper;
147  bool HexPrefix;
148  friend class raw_ostream;
149 public:
150  FormattedNumber(uint64_t HV, int64_t DV, unsigned W, bool H, bool U,
151  bool Prefix)
152  : HexValue(HV), DecValue(DV), Width(W), Hex(H), Upper(U),
153  HexPrefix(Prefix) {}
154 };
155 
156 /// format_hex - Output \p N as a fixed width hexadecimal. If number will not
157 /// fit in width, full number is still printed. Examples:
158 /// OS << format_hex(255, 4) => 0xff
159 /// OS << format_hex(255, 4, true) => 0xFF
160 /// OS << format_hex(255, 6) => 0x00ff
161 /// OS << format_hex(255, 2) => 0xff
162 inline FormattedNumber format_hex(uint64_t N, unsigned Width,
163  bool Upper = false) {
164  assert(Width <= 18 && "hex width must be <= 18");
165  return FormattedNumber(N, 0, Width, true, Upper, true);
166 }
167 
168 /// format_hex_no_prefix - Output \p N as a fixed width hexadecimal. Does not
169 /// prepend '0x' to the outputted string. If number will not fit in width,
170 /// full number is still printed. Examples:
171 /// OS << format_hex_no_prefix(255, 4) => ff
172 /// OS << format_hex_no_prefix(255, 4, true) => FF
173 /// OS << format_hex_no_prefix(255, 6) => 00ff
174 /// OS << format_hex_no_prefix(255, 2) => ff
175 inline FormattedNumber format_hex_no_prefix(uint64_t N, unsigned Width,
176  bool Upper = false) {
177  assert(Width <= 18 && "hex width must be <= 18");
178  return FormattedNumber(N, 0, Width, true, Upper, false);
179 }
180 
181 /// format_decimal - Output \p N as a right justified, fixed-width decimal. If
182 /// number will not fit in width, full number is still printed. Examples:
183 /// OS << format_decimal(0, 5) => " 0"
184 /// OS << format_decimal(255, 5) => " 255"
185 /// OS << format_decimal(-1, 3) => " -1"
186 /// OS << format_decimal(12345, 3) => "12345"
187 inline FormattedNumber format_decimal(int64_t N, unsigned Width) {
188  return FormattedNumber(0, N, Width, false, false, false);
189 }
190 
191 
192 } // end namespace llvm
193 
194 #endif
format_object(const char *fmt, const Ts &...vals)
Definition: Format.h:93
FormattedString left_justify(StringRef Str, unsigned Width)
left_justify - append spaces after string so total output is Width characters.
Definition: Format.h:129
FormattedNumber format_hex(uint64_t N, unsigned Width, bool Upper=false)
format_hex - Output N as a fixed width hexadecimal.
Definition: Format.h:162
const char * Fmt
Definition: Format.h:39
virtual int snprint(char *Buffer, unsigned BufferSize) const =0
Call snprintf() for this object, on the given buffer and size.
This is a helper class used for left_justify() and right_justify().
Definition: Format.h:116
Alias for the common case of a sequence of size_ts.
Definition: STLExtras.h:230
This is a helper class used for handling formatted output.
Definition: Format.h:37
FormattedString right_justify(StringRef Str, unsigned Width)
right_justify - add spaces before string so total output is Width characters.
Definition: Format.h:136
format_object< Ts...> format(const char *Fmt, const Ts &...Vals)
These are helper functions used to produce formatted output.
Definition: Format.h:111
unsigned print(char *Buffer, unsigned BufferSize) const
Format the object into the specified buffer.
Definition: Format.h:53
#define H(x, y, z)
Definition: MD5.cpp:53
This is a helper class used for format_hex() and format_decimal().
Definition: Format.h:141
FormattedNumber(uint64_t HV, int64_t DV, unsigned W, bool H, bool U, bool Prefix)
Definition: Format.h:150
Creates a compile-time integer sequence for a parameter pack.
Definition: STLExtras.h:239
format_object_base(const char *fmt)
Definition: Format.h:48
FormattedNumber format_decimal(int64_t N, unsigned Width)
format_decimal - Output N as a right justified, fixed-width decimal.
Definition: Format.h:187
FormattedString(StringRef S, unsigned W, bool R)
Definition: Format.h:122
These are templated helper classes used by the format function that capture the object to be formated...
Definition: Format.h:79
FormattedNumber format_hex_no_prefix(uint64_t N, unsigned Width, bool Upper=false)
format_hex_no_prefix - Output N as a fixed width hexadecimal.
Definition: Format.h:175
#define N
format_object_base(const format_object_base &)=default
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:38
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:40
int snprint(char *Buffer, unsigned BufferSize) const override
Call snprintf() for this object, on the given buffer and size.
Definition: Format.h:96