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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 {
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