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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.
37 class format_object_base {
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:
format_object_base(const char * fmt)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.
print(char * Buffer,unsigned 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>
snprint_tuple(char * Buffer,unsigned BufferSize,index_sequence<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:
format_object(const char * fmt,const Ts &...vals)93   format_object(const char *fmt, const Ts &... vals)
94       : format_object_base(fmt), Vals(vals...) {}
95 
snprint(char * Buffer,unsigned BufferSize)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>
format(const char * Fmt,const Ts &...Vals)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().
116 class FormattedString {
117   StringRef Str;
118   unsigned Width;
119   bool RightJustify;
120   friend class raw_ostream;
121 
122 public:
FormattedString(StringRef S,unsigned W,bool R)123     FormattedString(StringRef S, unsigned W, bool R)
124       : Str(S), Width(W), RightJustify(R) { }
125 };
126 
127 /// left_justify - append spaces after string so total output is
128 /// \p Width characters.  If \p Str is larger that \p Width, full string
129 /// is written with no padding.
left_justify(StringRef Str,unsigned Width)130 inline FormattedString left_justify(StringRef Str, unsigned Width) {
131   return FormattedString(Str, Width, false);
132 }
133 
134 /// right_justify - add spaces before string so total output is
135 /// \p Width characters.  If \p Str is larger that \p Width, full string
136 /// is written with no padding.
right_justify(StringRef Str,unsigned Width)137 inline FormattedString right_justify(StringRef Str, unsigned Width) {
138   return FormattedString(Str, Width, true);
139 }
140 
141 /// This is a helper class used for format_hex() and format_decimal().
142 class FormattedNumber {
143   uint64_t HexValue;
144   int64_t DecValue;
145   unsigned Width;
146   bool Hex;
147   bool Upper;
148   bool HexPrefix;
149   friend class raw_ostream;
150 
151 public:
FormattedNumber(uint64_t HV,int64_t DV,unsigned W,bool H,bool U,bool Prefix)152   FormattedNumber(uint64_t HV, int64_t DV, unsigned W, bool H, bool U,
153                   bool Prefix)
154       : HexValue(HV), DecValue(DV), Width(W), Hex(H), Upper(U),
155         HexPrefix(Prefix) {}
156 };
157 
158 /// format_hex - Output \p N as a fixed width hexadecimal. If number will not
159 /// fit in width, full number is still printed.  Examples:
160 ///   OS << format_hex(255, 4)              => 0xff
161 ///   OS << format_hex(255, 4, true)        => 0xFF
162 ///   OS << format_hex(255, 6)              => 0x00ff
163 ///   OS << format_hex(255, 2)              => 0xff
164 inline FormattedNumber format_hex(uint64_t N, unsigned Width,
165                                   bool Upper = false) {
166   assert(Width <= 18 && "hex width must be <= 18");
167   return FormattedNumber(N, 0, Width, true, Upper, true);
168 }
169 
170 /// format_hex_no_prefix - Output \p N as a fixed width hexadecimal. Does not
171 /// prepend '0x' to the outputted string.  If number will not fit in width,
172 /// full number is still printed.  Examples:
173 ///   OS << format_hex_no_prefix(255, 2)              => ff
174 ///   OS << format_hex_no_prefix(255, 2, true)        => FF
175 ///   OS << format_hex_no_prefix(255, 4)              => 00ff
176 ///   OS << format_hex_no_prefix(255, 1)              => ff
177 inline FormattedNumber format_hex_no_prefix(uint64_t N, unsigned Width,
178                                             bool Upper = false) {
179   assert(Width <= 16 && "hex width must be <= 16");
180   return FormattedNumber(N, 0, Width, true, Upper, false);
181 }
182 
183 /// format_decimal - Output \p N as a right justified, fixed-width decimal. If
184 /// number will not fit in width, full number is still printed.  Examples:
185 ///   OS << format_decimal(0, 5)     => "    0"
186 ///   OS << format_decimal(255, 5)   => "  255"
187 ///   OS << format_decimal(-1, 3)    => " -1"
188 ///   OS << format_decimal(12345, 3) => "12345"
format_decimal(int64_t N,unsigned Width)189 inline FormattedNumber format_decimal(int64_t N, unsigned Width) {
190   return FormattedNumber(0, N, Width, false, false, false);
191 }
192 
193 } // end namespace llvm
194 
195 #endif
196