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