Encoding.h revision 263508 
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_FORMAT_ENCODING_H
17#define LLVM_CLANG_FORMAT_ENCODING_H
18
19#include "clang/Basic/LLVM.h"
20#include "llvm/Support/ConvertUTF.h"
21#include "llvm/Support/Unicode.h"
22
23namespace clang {
24namespace format {
25namespace encoding {
26
27enum Encoding {
28  Encoding_UTF8,
29  Encoding_Unknown // We treat all other encodings as 8-bit encodings.
30};
31
32/// \brief 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.
34inline Encoding detectEncoding(StringRef Text) {
35  const UTF8 *Ptr = reinterpret_cast<const UTF8 *>(Text.begin());
36  const UTF8 *BufEnd = reinterpret_cast<const UTF8 *>(Text.end());
37  if (::isLegalUTF8String(&Ptr, BufEnd))
38    return Encoding_UTF8;
39  return Encoding_Unknown;
40}
41
42inline unsigned getCodePointCountUTF8(StringRef Text) {
43  unsigned CodePoints = 0;
44  for (size_t i = 0, e = Text.size(); i < e; i += getNumBytesForUTF8(Text[i])) {
45    ++CodePoints;
46  }
47  return CodePoints;
48}
49
50/// \brief Gets the number of code points in the Text using the specified
51/// Encoding.
52inline unsigned getCodePointCount(StringRef Text, Encoding Encoding) {
53  switch (Encoding) {
54  case Encoding_UTF8:
55    return getCodePointCountUTF8(Text);
56  default:
57    return Text.size();
58  }
59}
60
61/// \brief Returns the number of columns required to display the \p Text on a
62/// generic Unicode-capable terminal. Text is assumed to use the specified
63/// \p Encoding.
64inline unsigned columnWidth(StringRef Text, Encoding Encoding) {
65  if (Encoding == Encoding_UTF8) {
66    int ContentWidth = llvm::sys::unicode::columnWidthUTF8(Text);
67    if (ContentWidth >= 0)
68      return ContentWidth;
69  }
70  return Text.size();
71}
72
73/// \brief Returns the number of columns required to display the \p Text,
74/// starting from the \p StartColumn on a terminal with the \p TabWidth. The
75/// text is assumed to use the specified \p Encoding.
76inline unsigned columnWidthWithTabs(StringRef Text, unsigned StartColumn,
77                                    unsigned TabWidth, Encoding Encoding) {
78  unsigned TotalWidth = 0;
79  StringRef Tail = Text;
80  for (;;) {
81    StringRef::size_type TabPos = Tail.find('\t');
82    if (TabPos == StringRef::npos)
83      return TotalWidth + columnWidth(Tail, Encoding);
84    int Width = columnWidth(Tail.substr(0, TabPos), Encoding);
85    assert(Width >= 0);
86    TotalWidth += Width;
87    TotalWidth += TabWidth - (TotalWidth + StartColumn) % TabWidth;
88    Tail = Tail.substr(TabPos + 1);
89  }
90}
91
92/// \brief Gets the number of bytes in a sequence representing a single
93/// codepoint and starting with FirstChar in the specified Encoding.
94inline unsigned getCodePointNumBytes(char FirstChar, Encoding Encoding) {
95  switch (Encoding) {
96  case Encoding_UTF8:
97    return getNumBytesForUTF8(FirstChar);
98  default:
99    return 1;
100  }
101}
102
103inline bool isOctDigit(char c) { return '0' <= c && c <= '7'; }
104
105inline bool isHexDigit(char c) {
106  return ('0' <= c && c <= '9') || ('a' <= c && c <= 'f') ||
107         ('A' <= c && c <= 'F');
108}
109
110/// \brief Gets the length of an escape sequence inside a C++ string literal.
111/// Text should span from the beginning of the escape sequence (starting with a
112/// backslash) to the end of the string literal.
113inline unsigned getEscapeSequenceLength(StringRef Text) {
114  assert(Text[0] == '\\');
115  if (Text.size() < 2)
116    return 1;
117
118  switch (Text[1]) {
119  case 'u':
120    return 6;
121  case 'U':
122    return 10;
123  case 'x': {
124    unsigned I = 2; // Point after '\x'.
125    while (I < Text.size() && isHexDigit(Text[I]))
126      ++I;
127    return I;
128  }
129  default:
130    if (isOctDigit(Text[1])) {
131      unsigned I = 1;
132      while (I < Text.size() && I < 4 && isOctDigit(Text[I]))
133        ++I;
134      return I;
135    }
136    return 2;
137  }
138}
139
140} // namespace encoding
141} // namespace format
142} // namespace clang
143
144#endif // LLVM_CLANG_FORMAT_ENCODING_H
145