clang  3.9.0
Encoding.h
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1 //===--- Encoding.h - Format C++ code -------------------------------------===//
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 /// \file
11 /// \brief Contains functions for text encoding manipulation. Supports UTF-8,
12 /// 8-bit encodings and escape sequences in C++ string literals.
13 ///
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_CLANG_LIB_FORMAT_ENCODING_H
17 #define LLVM_CLANG_LIB_FORMAT_ENCODING_H
18 
19 #include "clang/Basic/LLVM.h"
20 #include "llvm/ADT/StringRef.h"
21 #include "llvm/Support/ConvertUTF.h"
22 #include "llvm/Support/Unicode.h"
23 
24 namespace clang {
25 namespace format {
26 namespace encoding {
27 
28 enum Encoding {
30  Encoding_Unknown // We treat all other encodings as 8-bit encodings.
31 };
32 
33 /// \brief Detects encoding of the Text. If the Text can be decoded using UTF-8,
34 /// it is considered UTF8, otherwise we treat it as some 8-bit encoding.
35 inline Encoding detectEncoding(StringRef Text) {
36  const UTF8 *Ptr = reinterpret_cast<const UTF8 *>(Text.begin());
37  const UTF8 *BufEnd = reinterpret_cast<const UTF8 *>(Text.end());
38  if (::isLegalUTF8String(&Ptr, BufEnd))
39  return Encoding_UTF8;
40  return Encoding_Unknown;
41 }
42 
43 inline unsigned getCodePointCountUTF8(StringRef Text) {
44  unsigned CodePoints = 0;
45  for (size_t i = 0, e = Text.size(); i < e; i += getNumBytesForUTF8(Text[i])) {
46  ++CodePoints;
47  }
48  return CodePoints;
49 }
50 
51 /// \brief Gets the number of code points in the Text using the specified
52 /// Encoding.
53 inline unsigned getCodePointCount(StringRef Text, Encoding Encoding) {
54  switch (Encoding) {
55  case Encoding_UTF8:
56  return getCodePointCountUTF8(Text);
57  default:
58  return Text.size();
59  }
60 }
61 
62 /// \brief Returns the number of columns required to display the \p Text on a
63 /// generic Unicode-capable terminal. Text is assumed to use the specified
64 /// \p Encoding.
65 inline unsigned columnWidth(StringRef Text, Encoding Encoding) {
66  if (Encoding == Encoding_UTF8) {
67  int ContentWidth = llvm::sys::unicode::columnWidthUTF8(Text);
68  // FIXME: Figure out the correct way to handle this in the presence of both
69  // printable and unprintable multi-byte UTF-8 characters. Falling back to
70  // returning the number of bytes may cause problems, as columnWidth suddenly
71  // becomes non-additive.
72  if (ContentWidth >= 0)
73  return ContentWidth;
74  }
75  return Text.size();
76 }
77 
78 /// \brief Returns the number of columns required to display the \p Text,
79 /// starting from the \p StartColumn on a terminal with the \p TabWidth. The
80 /// text is assumed to use the specified \p Encoding.
81 inline unsigned columnWidthWithTabs(StringRef Text, unsigned StartColumn,
82  unsigned TabWidth, Encoding Encoding) {
83  unsigned TotalWidth = 0;
84  StringRef Tail = Text;
85  for (;;) {
86  StringRef::size_type TabPos = Tail.find('\t');
87  if (TabPos == StringRef::npos)
88  return TotalWidth + columnWidth(Tail, Encoding);
89  TotalWidth += columnWidth(Tail.substr(0, TabPos), Encoding);
90  TotalWidth += TabWidth - (TotalWidth + StartColumn) % TabWidth;
91  Tail = Tail.substr(TabPos + 1);
92  }
93 }
94 
95 /// \brief Gets the number of bytes in a sequence representing a single
96 /// codepoint and starting with FirstChar in the specified Encoding.
97 inline unsigned getCodePointNumBytes(char FirstChar, Encoding Encoding) {
98  switch (Encoding) {
99  case Encoding_UTF8:
100  return getNumBytesForUTF8(FirstChar);
101  default:
102  return 1;
103  }
104 }
105 
106 inline bool isOctDigit(char c) { return '0' <= c && c <= '7'; }
107 
108 inline bool isHexDigit(char c) {
109  return ('0' <= c && c <= '9') || ('a' <= c && c <= 'f') ||
110  ('A' <= c && c <= 'F');
111 }
112 
113 /// \brief Gets the length of an escape sequence inside a C++ string literal.
114 /// Text should span from the beginning of the escape sequence (starting with a
115 /// backslash) to the end of the string literal.
116 inline unsigned getEscapeSequenceLength(StringRef Text) {
117  assert(Text[0] == '\\');
118  if (Text.size() < 2)
119  return 1;
120 
121  switch (Text[1]) {
122  case 'u':
123  return 6;
124  case 'U':
125  return 10;
126  case 'x': {
127  unsigned I = 2; // Point after '\x'.
128  while (I < Text.size() && isHexDigit(Text[I]))
129  ++I;
130  return I;
131  }
132  default:
133  if (isOctDigit(Text[1])) {
134  unsigned I = 1;
135  while (I < Text.size() && I < 4 && isOctDigit(Text[I]))
136  ++I;
137  return I;
138  }
139  return 1 + getNumBytesForUTF8(Text[1]);
140  }
141 }
142 
143 } // namespace encoding
144 } // namespace format
145 } // namespace clang
146 
147 #endif
bool isOctDigit(char c)
Definition: Encoding.h:106
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:81
unsigned getCodePointCount(StringRef Text, Encoding Encoding)
Gets the number of code points in the Text using the specified Encoding.
Definition: Encoding.h:53
Forward-declares and imports various common LLVM datatypes that clang wants to use unqualified...
detail::InMemoryDirectory::const_iterator I
unsigned getEscapeSequenceLength(StringRef Text)
Gets the length of an escape sequence inside a C++ string literal.
Definition: Encoding.h:116
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:97
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:65
unsigned getCodePointCountUTF8(StringRef Text)
Definition: Encoding.h:43
bool isHexDigit(char c)
Definition: Encoding.h:108
Encoding detectEncoding(StringRef Text)
Detects encoding of the Text.
Definition: Encoding.h:35
StringRef Text
Definition: Format.cpp:1195