1//===- Format.h - Efficient printf-style formatting for streams -*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements the format() function, which can be used with other
10// LLVM subsystems to provide printf-style formatting. This gives all the power
11// and risk of printf. This can be used like this (with raw_ostreams as an
12// example):
13//
14// OS << "mynumber: " << format("%4.5f", 1234.412) << '\n';
15//
16// Or if you prefer:
17//
18// OS << format("mynumber: %4.5f\n", 1234.412);
19//
20//===----------------------------------------------------------------------===//
21
22#ifndef LLVM_SUPPORT_FORMAT_H
23#define LLVM_SUPPORT_FORMAT_H
24
25#include "llvm/ADT/ArrayRef.h"
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 <optional>
32#include <tuple>
33#include <utility>
34
35namespace llvm {
36
37/// This is a helper class used for handling formatted output. It is the
38/// abstract base class of a templated derived class.
39class format_object_base {
40protected:
41 const char *Fmt;
42 ~format_object_base() = default; // Disallow polymorphic deletion.
43 format_object_base(const format_object_base &) = default;
44 virtual void home(); // Out of line virtual method.
45
46 /// Call snprintf() for this object, on the given buffer and size.
47 virtual int snprint(char *Buffer, unsigned BufferSize) const = 0;
48
49public:
50 format_object_base(const char *fmt) : Fmt(fmt) {}
51
52 /// Format the object into the specified buffer. On success, this returns
53 /// the length of the formatted string. If the buffer is too small, this
54 /// returns a length to retry with, which will be larger than BufferSize.
55 unsigned print(char *Buffer, unsigned BufferSize) const {
56 assert(BufferSize && "Invalid buffer size!");
57
58 // Print the string, leaving room for the terminating null.
59 int N = snprint(Buffer, BufferSize);
60
61 // VC++ and old GlibC return negative on overflow, just double the size.
62 if (N < 0)
63 return BufferSize * 2;
64
65 // Other implementations yield number of bytes needed, not including the
66 // final '\0'.
67 if (unsigned(N) >= BufferSize)
68 return N + 1;
69
70 // Otherwise N is the length of output (not including the final '\0').
71 return N;
72 }
73};
74
75/// These are templated helper classes used by the format function that
76/// capture the object to be formatted and the format string. When actually
77/// printed, this synthesizes the string into a temporary buffer provided and
78/// returns whether or not it is big enough.
79
80// Helper to validate that format() parameters are scalars or pointers.
81template <typename... Args> struct validate_format_parameters;
82template <typename Arg, typename... Args>
83struct validate_format_parameters<Arg, Args...> {
84 static_assert(std::is_scalar_v<Arg>,
85 "format can't be used with non fundamental / non pointer type");
86 validate_format_parameters() { validate_format_parameters<Args...>(); }
87};
88template <> struct validate_format_parameters<> {};
89
90template <typename... Ts>
91class format_object final : public format_object_base {
92 std::tuple<Ts...> Vals;
93
94 template <std::size_t... Is>
95 int snprint_tuple(char *Buffer, unsigned BufferSize,
96 std::index_sequence<Is...>) const {
97#ifdef _MSC_VER
98 return _snprintf(Buffer, BufferSize, Fmt, std::get<Is>(Vals)...);
99#else
100 return snprintf(Buffer, BufferSize, Fmt, std::get<Is>(Vals)...);
101#endif
102 }
103
104public:
105 format_object(const char *fmt, const Ts &... vals)
106 : format_object_base(fmt), Vals(vals...) {
107 validate_format_parameters<Ts...>();
108 }
109
110 int snprint(char *Buffer, unsigned BufferSize) const override {
111 return snprint_tuple(Buffer, BufferSize, std::index_sequence_for<Ts...>());
112 }
113};
114
115/// These are helper functions used to produce formatted output. They use
116/// template type deduction to construct the appropriate instance of the
117/// format_object class to simplify their construction.
118///
119/// This is typically used like:
120/// \code
121/// OS << format("%0.4f", myfloat) << '\n';
122/// \endcode
123
124template <typename... Ts>
125inline format_object<Ts...> format(const char *Fmt, const Ts &... Vals) {
126 return format_object<Ts...>(Fmt, Vals...);
127}
128
129/// This is a helper class for left_justify, right_justify, and center_justify.
130class FormattedString {
131public:
132 enum Justification { JustifyNone, JustifyLeft, JustifyRight, JustifyCenter };
133 FormattedString(StringRef S, unsigned W, Justification J)
134 : Str(S), Width(W), Justify(J) {}
135
136private:
137 StringRef Str;
138 unsigned Width;
139 Justification Justify;
140 friend class raw_ostream;
141};
142
143/// left_justify - append spaces after string so total output is
144/// \p Width characters. If \p Str is larger that \p Width, full string
145/// is written with no padding.
146inline FormattedString left_justify(StringRef Str, unsigned Width) {
147 return FormattedString(Str, Width, FormattedString::JustifyLeft);
148}
149
150/// right_justify - add spaces before string so total output is
151/// \p Width characters. If \p Str is larger that \p Width, full string
152/// is written with no padding.
153inline FormattedString right_justify(StringRef Str, unsigned Width) {
154 return FormattedString(Str, Width, FormattedString::JustifyRight);
155}
156
157/// center_justify - add spaces before and after string so total output is
158/// \p Width characters. If \p Str is larger that \p Width, full string
159/// is written with no padding.
160inline FormattedString center_justify(StringRef Str, unsigned Width) {
161 return FormattedString(Str, Width, FormattedString::JustifyCenter);
162}
163
164/// This is a helper class used for format_hex() and format_decimal().
165class FormattedNumber {
166 uint64_t HexValue;
167 int64_t DecValue;
168 unsigned Width;
169 bool Hex;
170 bool Upper;
171 bool HexPrefix;
172 friend class raw_ostream;
173
174public:
175 FormattedNumber(uint64_t HV, int64_t DV, unsigned W, bool H, bool U,
176 bool Prefix)
177 : HexValue(HV), DecValue(DV), Width(W), Hex(H), Upper(U),
178 HexPrefix(Prefix) {}
179};
180
181/// format_hex - Output \p N as a fixed width hexadecimal. If number will not
182/// fit in width, full number is still printed. Examples:
183/// OS << format_hex(255, 4) => 0xff
184/// OS << format_hex(255, 4, true) => 0xFF
185/// OS << format_hex(255, 6) => 0x00ff
186/// OS << format_hex(255, 2) => 0xff
187inline FormattedNumber format_hex(uint64_t N, unsigned Width,
188 bool Upper = false) {
189 assert(Width <= 18 && "hex width must be <= 18");
190 return FormattedNumber(N, 0, Width, true, Upper, true);
191}
192
193/// format_hex_no_prefix - Output \p N as a fixed width hexadecimal. Does not
194/// prepend '0x' to the outputted string. If number will not fit in width,
195/// full number is still printed. Examples:
196/// OS << format_hex_no_prefix(255, 2) => ff
197/// OS << format_hex_no_prefix(255, 2, true) => FF
198/// OS << format_hex_no_prefix(255, 4) => 00ff
199/// OS << format_hex_no_prefix(255, 1) => ff
200inline FormattedNumber format_hex_no_prefix(uint64_t N, unsigned Width,
201 bool Upper = false) {
202 assert(Width <= 16 && "hex width must be <= 16");
203 return FormattedNumber(N, 0, Width, true, Upper, false);
204}
205
206/// format_decimal - Output \p N as a right justified, fixed-width decimal. If
207/// number will not fit in width, full number is still printed. Examples:
208/// OS << format_decimal(0, 5) => " 0"
209/// OS << format_decimal(255, 5) => " 255"
210/// OS << format_decimal(-1, 3) => " -1"
211/// OS << format_decimal(12345, 3) => "12345"
212inline FormattedNumber format_decimal(int64_t N, unsigned Width) {
213 return FormattedNumber(0, N, Width, false, false, false);
214}
215
216class FormattedBytes {
217 ArrayRef<uint8_t> Bytes;
218
219 // If not std::nullopt, display offsets for each line relative to starting
220 // value.
221 std::optional<uint64_t> FirstByteOffset;
222 uint32_t IndentLevel; // Number of characters to indent each line.
223 uint32_t NumPerLine; // Number of bytes to show per line.
224 uint8_t ByteGroupSize; // How many hex bytes are grouped without spaces
225 bool Upper; // Show offset and hex bytes as upper case.
226 bool ASCII; // Show the ASCII bytes for the hex bytes to the right.
227 friend class raw_ostream;
228
229public:
230 FormattedBytes(ArrayRef<uint8_t> B, uint32_t IL, std::optional<uint64_t> O,
231 uint32_t NPL, uint8_t BGS, bool U, bool A)
232 : Bytes(B), FirstByteOffset(O), IndentLevel(IL), NumPerLine(NPL),
233 ByteGroupSize(BGS), Upper(U), ASCII(A) {
234
235 if (ByteGroupSize > NumPerLine)
236 ByteGroupSize = NumPerLine;
237 }
238};
239
240inline FormattedBytes
241format_bytes(ArrayRef<uint8_t> Bytes,
242 std::optional<uint64_t> FirstByteOffset = std::nullopt,
243 uint32_t NumPerLine = 16, uint8_t ByteGroupSize = 4,
244 uint32_t IndentLevel = 0, bool Upper = false) {
245 return FormattedBytes(Bytes, IndentLevel, FirstByteOffset, NumPerLine,
246 ByteGroupSize, Upper, false);
247}
248
249inline FormattedBytes
250format_bytes_with_ascii(ArrayRef<uint8_t> Bytes,
251 std::optional<uint64_t> FirstByteOffset = std::nullopt,
252 uint32_t NumPerLine = 16, uint8_t ByteGroupSize = 4,
253 uint32_t IndentLevel = 0, bool Upper = false) {
254 return FormattedBytes(Bytes, IndentLevel, FirstByteOffset, NumPerLine,
255 ByteGroupSize, Upper, true);
256}
257
258} // end namespace llvm
259
260#endif
261

source code of include/llvm-17/llvm/Support/Format.h