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