1 //===--- Encoding.h - Format C++ code ---------------------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 ///
9 /// \file
10 /// Contains functions for text encoding manipulation. Supports UTF-8,
11 /// 8-bit encodings and escape sequences in C++ string literals.
12 ///
13 //===----------------------------------------------------------------------===//
14
15 #ifndef LLVM_CLANG_LIB_FORMAT_ENCODING_H
16 #define LLVM_CLANG_LIB_FORMAT_ENCODING_H
17
18 #include "clang/Basic/LLVM.h"
19 #include "llvm/Support/ConvertUTF.h"
20 #include "llvm/Support/Unicode.h"
21
22 namespace clang {
23 namespace format {
24 namespace encoding {
25
26 enum Encoding {
27 Encoding_UTF8,
28 Encoding_Unknown // We treat all other encodings as 8-bit encodings.
29 };
30
31 /// Detects encoding of the Text. If the Text can be decoded using UTF-8,
32 /// it is considered UTF8, otherwise we treat it as some 8-bit encoding.
detectEncoding(StringRef Text)33 inline Encoding detectEncoding(StringRef Text) {
34 const llvm::UTF8 *Ptr = reinterpret_cast<const llvm::UTF8 *>(Text.begin());
35 const llvm::UTF8 *BufEnd = reinterpret_cast<const llvm::UTF8 *>(Text.end());
36 if (llvm::isLegalUTF8String(&Ptr, BufEnd))
37 return Encoding_UTF8;
38 return Encoding_Unknown;
39 }
40
41 /// Returns the number of columns required to display the \p Text on a
42 /// generic Unicode-capable terminal. Text is assumed to use the specified
43 /// \p Encoding.
columnWidth(StringRef Text,Encoding Encoding)44 inline unsigned columnWidth(StringRef Text, Encoding Encoding) {
45 if (Encoding == Encoding_UTF8) {
46 int ContentWidth = llvm::sys::unicode::columnWidthUTF8(Text);
47 // FIXME: Figure out the correct way to handle this in the presence of both
48 // printable and unprintable multi-byte UTF-8 characters. Falling back to
49 // returning the number of bytes may cause problems, as columnWidth suddenly
50 // becomes non-additive.
51 if (ContentWidth >= 0)
52 return ContentWidth;
53 }
54 return Text.size();
55 }
56
57 /// Returns the number of columns required to display the \p Text,
58 /// starting from the \p StartColumn on a terminal with the \p TabWidth. The
59 /// text is assumed to use the specified \p Encoding.
columnWidthWithTabs(StringRef Text,unsigned StartColumn,unsigned TabWidth,Encoding Encoding)60 inline unsigned columnWidthWithTabs(StringRef Text, unsigned StartColumn,
61 unsigned TabWidth, Encoding Encoding) {
62 unsigned TotalWidth = 0;
63 StringRef Tail = Text;
64 for (;;) {
65 StringRef::size_type TabPos = Tail.find('\t');
66 if (TabPos == StringRef::npos)
67 return TotalWidth + columnWidth(Tail, Encoding);
68 TotalWidth += columnWidth(Tail.substr(0, TabPos), Encoding);
69 if (TabWidth)
70 TotalWidth += TabWidth - (TotalWidth + StartColumn) % TabWidth;
71 Tail = Tail.substr(TabPos + 1);
72 }
73 }
74
75 /// Gets the number of bytes in a sequence representing a single
76 /// codepoint and starting with FirstChar in the specified Encoding.
getCodePointNumBytes(char FirstChar,Encoding Encoding)77 inline unsigned getCodePointNumBytes(char FirstChar, Encoding Encoding) {
78 switch (Encoding) {
79 case Encoding_UTF8:
80 return llvm::getNumBytesForUTF8(FirstChar);
81 default:
82 return 1;
83 }
84 }
85
isOctDigit(char c)86 inline bool isOctDigit(char c) { return '0' <= c && c <= '7'; }
87
isHexDigit(char c)88 inline bool isHexDigit(char c) {
89 return ('0' <= c && c <= '9') || ('a' <= c && c <= 'f') ||
90 ('A' <= c && c <= 'F');
91 }
92
93 /// Gets the length of an escape sequence inside a C++ string literal.
94 /// Text should span from the beginning of the escape sequence (starting with a
95 /// backslash) to the end of the string literal.
getEscapeSequenceLength(StringRef Text)96 inline unsigned getEscapeSequenceLength(StringRef Text) {
97 assert(Text[0] == '\\');
98 if (Text.size() < 2)
99 return 1;
100
101 switch (Text[1]) {
102 case 'u':
103 return 6;
104 case 'U':
105 return 10;
106 case 'x': {
107 unsigned I = 2; // Point after '\x'.
108 while (I < Text.size() && isHexDigit(Text[I]))
109 ++I;
110 return I;
111 }
112 default:
113 if (isOctDigit(Text[1])) {
114 unsigned I = 1;
115 while (I < Text.size() && I < 4 && isOctDigit(Text[I]))
116 ++I;
117 return I;
118 }
119 return 1 + llvm::getNumBytesForUTF8(Text[1]);
120 }
121 }
122
123 } // namespace encoding
124 } // namespace format
125 } // namespace clang
126
127 #endif
128