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
22namespace clang {
23namespace format {
24namespace encoding {
25
26enum 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.
33inline 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(source: &Ptr, sourceEnd: 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.
44inline 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.
60inline 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(C: '\t');
66 if (TabPos == StringRef::npos)
67 return TotalWidth + columnWidth(Text: Tail, Encoding);
68 TotalWidth += columnWidth(Text: Tail.substr(Start: 0, N: TabPos), Encoding);
69 if (TabWidth)
70 TotalWidth += TabWidth - (TotalWidth + StartColumn) % TabWidth;
71 Tail = Tail.substr(Start: 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.
77inline unsigned getCodePointNumBytes(char FirstChar, Encoding Encoding) {
78 switch (Encoding) {
79 case Encoding_UTF8:
80 return llvm::getNumBytesForUTF8(firstByte: FirstChar);
81 default:
82 return 1;
83 }
84}
85
86inline bool isOctDigit(char c) { return '0' <= c && c <= '7'; }
87
88inline 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.
96inline 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(c: Text[I]))
109 ++I;
110 return I;
111 }
112 default:
113 if (isOctDigit(c: Text[1])) {
114 unsigned I = 1;
115 while (I < Text.size() && I < 4 && isOctDigit(c: Text[I]))
116 ++I;
117 return I;
118 }
119 return 1 + llvm::getNumBytesForUTF8(firstByte: Text[1]);
120 }
121}
122
123} // namespace encoding
124} // namespace format
125} // namespace clang
126
127#endif
128