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 {
29 Encoding_UTF8,
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.
detectEncoding(StringRef Text)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
getCodePointCountUTF8(StringRef Text)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.
getCodePointCount(StringRef Text,Encoding 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.
columnWidth(StringRef Text,Encoding 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.
columnWidthWithTabs(StringRef Text,unsigned StartColumn,unsigned TabWidth,Encoding 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.
getCodePointNumBytes(char FirstChar,Encoding 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
isOctDigit(char c)106 inline bool isOctDigit(char c) { return '0' <= c && c <= '7'; }
107
isHexDigit(char c)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.
getEscapeSequenceLength(StringRef Text)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
148