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
33namespace 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.
37class format_object_base {
38protected:
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
47public:
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
78template <typename... Ts>
79class 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
92public:
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
110template <typename... Ts>
111inline 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().
116class FormattedString {
117  StringRef Str;
118  unsigned Width;
119  bool RightJustify;
120  friend class raw_ostream;
121public:
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.
129inline 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.
136inline 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().
141class 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;
149public:
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
162inline 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
175inline 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"
187inline 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