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: 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(). 116 class FormattedString { 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(). 141 class FormattedNumber { 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 195
