clang  6.0.0svn
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 llvm::UTF8 *Ptr = reinterpret_cast<const llvm::UTF8 *>(Text.begin());
37  const llvm::UTF8 *BufEnd = reinterpret_cast<const llvm::UTF8 *>(Text.end());
38  if (llvm::isLegalUTF8String(&Ptr, BufEnd))
39  return Encoding_UTF8;
40  return Encoding_Unknown;
41 }
42 
43 /// \brief Returns the number of columns required to display the \p Text on a
44 /// generic Unicode-capable terminal. Text is assumed to use the specified
45 /// \p Encoding.
46 inline unsigned columnWidth(StringRef Text, Encoding Encoding) {
47  if (Encoding == Encoding_UTF8) {
48  int ContentWidth = llvm::sys::unicode::columnWidthUTF8(Text);
49  // FIXME: Figure out the correct way to handle this in the presence of both
50  // printable and unprintable multi-byte UTF-8 characters. Falling back to
51  // returning the number of bytes may cause problems, as columnWidth suddenly
52  // becomes non-additive.
53  if (ContentWidth >= 0)
54  return ContentWidth;
55  }
56  return Text.size();
57 }
58 
59 /// \brief Returns the number of columns required to display the \p Text,
60 /// starting from the \p StartColumn on a terminal with the \p TabWidth. The
61 /// text is assumed to use the specified \p Encoding.
62 inline unsigned columnWidthWithTabs(StringRef Text, unsigned StartColumn,
63  unsigned TabWidth, Encoding Encoding) {
64  unsigned TotalWidth = 0;
65  StringRef Tail = Text;
66  for (;;) {
67  StringRef::size_type TabPos = Tail.find('\t');
68  if (TabPos == StringRef::npos)
69  return TotalWidth + columnWidth(Tail, Encoding);
70  TotalWidth += columnWidth(Tail.substr(0, TabPos), Encoding);
71  TotalWidth += TabWidth - (TotalWidth + StartColumn) % TabWidth;
72  Tail = Tail.substr(TabPos + 1);
73  }
74 }
75 
76 /// \brief Gets the number of bytes in a sequence representing a single
77 /// codepoint and starting with FirstChar in the specified Encoding.
78 inline unsigned getCodePointNumBytes(char FirstChar, Encoding Encoding) {
79  switch (Encoding) {
80  case Encoding_UTF8:
81  return llvm::getNumBytesForUTF8(FirstChar);
82  default:
83  return 1;
84  }
85 }
86 
87 inline bool isOctDigit(char c) { return '0' <= c && c <= '7'; }
88 
89 inline bool isHexDigit(char c) {
90  return ('0' <= c && c <= '9') || ('a' <= c && c <= 'f') ||
91  ('A' <= c && c <= 'F');
92 }
93 
94 /// \brief Gets the length of an escape sequence inside a C++ string literal.
95 /// Text should span from the beginning of the escape sequence (starting with a
96 /// backslash) to the end of the string literal.
97 inline unsigned getEscapeSequenceLength(StringRef Text) {
98  assert(Text[0] == '\\');
99  if (Text.size() < 2)
100  return 1;
101 
102  switch (Text[1]) {
103  case 'u':
104  return 6;
105  case 'U':
106  return 10;
107  case 'x': {
108  unsigned I = 2; // Point after '\x'.
109  while (I < Text.size() && isHexDigit(Text[I]))
110  ++I;
111  return I;
112  }
113  default:
114  if (isOctDigit(Text[1])) {
115  unsigned I = 1;
116  while (I < Text.size() && I < 4 && isOctDigit(Text[I]))
117  ++I;
118  return I;
119  }
120  return 1 + llvm::getNumBytesForUTF8(Text[1]);
121  }
122 }
123 
124 } // namespace encoding
125 } // namespace format
126 } // namespace clang
127 
128 #endif
bool isOctDigit(char c)
Definition: Encoding.h:87
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:62
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:97
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:78
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:46
bool isHexDigit(char c)
Definition: Encoding.h:89
Encoding detectEncoding(StringRef Text)
Detects encoding of the Text.
Definition: Encoding.h:35
Dataflow Directional Tag Classes.
StringRef Text
Definition: Format.cpp:1346