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 23namespace clang { 24namespace format { 25namespace encoding { 26 27enum 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. 34inline 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. 45inline 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. 61inline 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. 78inline 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 87inline bool isOctDigit(char c) { return '0' <= c && c <= '7'; } 88 89inline 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. 97inline 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