clang  9.0.0svn
Encoding.h
Go to the documentation of this file.
1 //===--- Encoding.h - Format C++ code ---------------------------*- 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 /// \file
10 /// Contains functions for text encoding manipulation. Supports UTF-8,
11 /// 8-bit encodings and escape sequences in C++ string literals.
12 ///
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_CLANG_LIB_FORMAT_ENCODING_H
16 #define LLVM_CLANG_LIB_FORMAT_ENCODING_H
17 
18 #include "clang/Basic/LLVM.h"
19 #include "llvm/ADT/StringRef.h"
20 #include "llvm/Support/ConvertUTF.h"
21 #include "llvm/Support/Unicode.h"
22 
23 namespace clang {
24 namespace format {
25 namespace encoding {
26 
27 enum Encoding {
29  Encoding_Unknown // We treat all other encodings as 8-bit encodings.
30 };
31 
32 /// Detects encoding of the Text. If the Text can be decoded using UTF-8,
33 /// it is considered UTF8, otherwise we treat it as some 8-bit encoding.
34 inline Encoding detectEncoding(StringRef Text) {
35  const llvm::UTF8 *Ptr = reinterpret_cast<const llvm::UTF8 *>(Text.begin());
36  const llvm::UTF8 *BufEnd = reinterpret_cast<const llvm::UTF8 *>(Text.end());
37  if (llvm::isLegalUTF8String(&Ptr, BufEnd))
38  return Encoding_UTF8;
39  return Encoding_Unknown;
40 }
41 
42 /// Returns the number of columns required to display the \p Text on a
43 /// generic Unicode-capable terminal. Text is assumed to use the specified
44 /// \p Encoding.
45 inline unsigned columnWidth(StringRef Text, Encoding Encoding) {
46  if (Encoding == Encoding_UTF8) {
47  int ContentWidth = llvm::sys::unicode::columnWidthUTF8(Text);
48  // FIXME: Figure out the correct way to handle this in the presence of both
49  // printable and unprintable multi-byte UTF-8 characters. Falling back to
50  // returning the number of bytes may cause problems, as columnWidth suddenly
51  // becomes non-additive.
52  if (ContentWidth >= 0)
53  return ContentWidth;
54  }
55  return Text.size();
56 }
57 
58 /// Returns the number of columns required to display the \p Text,
59 /// starting from the \p StartColumn on a terminal with the \p TabWidth. The
60 /// text is assumed to use the specified \p Encoding.
61 inline unsigned columnWidthWithTabs(StringRef Text, unsigned StartColumn,
62  unsigned TabWidth, Encoding Encoding) {
63  unsigned TotalWidth = 0;
64  StringRef Tail = Text;
65  for (;;) {
66  StringRef::size_type TabPos = Tail.find('\t');
67  if (TabPos == StringRef::npos)
68  return TotalWidth + columnWidth(Tail, Encoding);
69  TotalWidth += columnWidth(Tail.substr(0, TabPos), Encoding);
70  TotalWidth += TabWidth - (TotalWidth + StartColumn) % TabWidth;
71  Tail = Tail.substr(TabPos + 1);
72  }
73 }
74 
75 /// Gets the number of bytes in a sequence representing a single
76 /// codepoint and starting with FirstChar in the specified Encoding.
77 inline unsigned getCodePointNumBytes(char FirstChar, Encoding Encoding) {
78  switch (Encoding) {
79  case Encoding_UTF8:
80  return llvm::getNumBytesForUTF8(FirstChar);
81  default:
82  return 1;
83  }
84 }
85 
86 inline bool isOctDigit(char c) { return '0' <= c && c <= '7'; }
87 
88 inline bool isHexDigit(char c) {
89  return ('0' <= c && c <= '9') || ('a' <= c && c <= 'f') ||
90  ('A' <= c && c <= 'F');
91 }
92 
93 /// Gets the length of an escape sequence inside a C++ string literal.
94 /// Text should span from the beginning of the escape sequence (starting with a
95 /// backslash) to the end of the string literal.
96 inline unsigned getEscapeSequenceLength(StringRef Text) {
97  assert(Text[0] == '\\');
98  if (Text.size() < 2)
99  return 1;
100 
101  switch (Text[1]) {
102  case 'u':
103  return 6;
104  case 'U':
105  return 10;
106  case 'x': {
107  unsigned I = 2; // Point after '\x'.
108  while (I < Text.size() && isHexDigit(Text[I]))
109  ++I;
110  return I;
111  }
112  default:
113  if (isOctDigit(Text[1])) {
114  unsigned I = 1;
115  while (I < Text.size() && I < 4 && isOctDigit(Text[I]))
116  ++I;
117  return I;
118  }
119  return 1 + llvm::getNumBytesForUTF8(Text[1]);
120  }
121 }
122 
123 } // namespace encoding
124 } // namespace format
125 } // namespace clang
126 
127 #endif
bool isOctDigit(char c)
Definition: Encoding.h:86
unsigned columnWidthWithTabs(StringRef Text, unsigned StartColumn, unsigned TabWidth, Encoding Encoding)
Returns the number of columns required to display the Text, starting from the StartColumn on a termin...
Definition: Encoding.h:61
Forward-declares and imports various common LLVM datatypes that clang wants to use unqualified...
unsigned getEscapeSequenceLength(StringRef Text)
Gets the length of an escape sequence inside a C++ string literal.
Definition: Encoding.h:96
unsigned getCodePointNumBytes(char FirstChar, Encoding Encoding)
Gets the number of bytes in a sequence representing a single codepoint and starting with FirstChar in...
Definition: Encoding.h:77
unsigned columnWidth(StringRef Text, Encoding Encoding)
Returns the number of columns required to display the Text on a generic Unicode-capable terminal...
Definition: Encoding.h:45
bool isHexDigit(char c)
Definition: Encoding.h:88
Encoding detectEncoding(StringRef Text)
Detects encoding of the Text.
Definition: Encoding.h:34
Dataflow Directional Tag Classes.
StringRef Text
Definition: Format.cpp:1675