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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-exception6//7//===----------------------------------------------------------------------===//8///9/// \file10/// 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_H16#define LLVM_CLANG_LIB_FORMAT_ENCODING_H17 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(&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 a42/// generic Unicode-capable terminal. Text is assumed to use the specified43/// \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 both48 // printable and unprintable multi-byte UTF-8 characters. Falling back to49 // returning the number of bytes may cause problems, as columnWidth suddenly50 // 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. The59/// 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('\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 single76/// 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(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 a95/// 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(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 encoding124} // namespace format125} // namespace clang126 127#endif128