1 //===--- SourceCode.h - Manipulating source code as strings -----*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 #include "SourceCode.h"
10 
11 #include "Logger.h"
12 #include "clang/AST/ASTContext.h"
13 #include "clang/Basic/SourceManager.h"
14 #include "clang/Lex/Lexer.h"
15 #include "llvm/Support/Errc.h"
16 #include "llvm/Support/Error.h"
17 #include "llvm/Support/Path.h"
18 
19 namespace clang {
20 namespace clangd {
21 using namespace llvm;
22 
23 // Here be dragons. LSP positions use columns measured in *UTF-16 code units*!
24 // Clangd uses UTF-8 and byte-offsets internally, so conversion is nontrivial.
25 
26 // Iterates over unicode codepoints in the (UTF-8) string. For each,
27 // invokes CB(UTF-8 length, UTF-16 length), and breaks if it returns true.
28 // Returns true if CB returned true, false if we hit the end of string.
29 template <typename Callback>
30 static bool iterateCodepoints(StringRef U8, const Callback &CB) {
31   for (size_t I = 0; I < U8.size();) {
32     unsigned char C = static_cast<unsigned char>(U8[I]);
33     if (LLVM_LIKELY(!(C & 0x80))) { // ASCII character.
34       if (CB(1, 1))
35         return true;
36       ++I;
37       continue;
38     }
39     // This convenient property of UTF-8 holds for all non-ASCII characters.
40     size_t UTF8Length = countLeadingOnes(C);
41     // 0xxx is ASCII, handled above. 10xxx is a trailing byte, invalid here.
42     // 11111xxx is not valid UTF-8 at all. Assert because it's probably our bug.
43     assert((UTF8Length >= 2 && UTF8Length <= 4) &&
44            "Invalid UTF-8, or transcoding bug?");
45     I += UTF8Length; // Skip over all trailing bytes.
46     // A codepoint takes two UTF-16 code unit if it's astral (outside BMP).
47     // Astral codepoints are encoded as 4 bytes in UTF-8 (11110xxx ...)
48     if (CB(UTF8Length, UTF8Length == 4 ? 2 : 1))
49       return true;
50   }
51   return false;
52 }
53 
54 // Returns the offset into the string that matches \p Units UTF-16 code units.
55 // Conceptually, this converts to UTF-16, truncates to CodeUnits, converts back
56 // to UTF-8, and returns the length in bytes.
57 static size_t measureUTF16(StringRef U8, int U16Units, bool &Valid) {
58   size_t Result = 0;
59   Valid = U16Units == 0 || iterateCodepoints(U8, [&](int U8Len, int U16Len) {
60             Result += U8Len;
61             U16Units -= U16Len;
62             return U16Units <= 0;
63           });
64   if (U16Units < 0) // Offset was into the middle of a surrogate pair.
65     Valid = false;
66   // Don't return an out-of-range index if we overran.
67   return std::min(Result, U8.size());
68 }
69 
70 // Counts the number of UTF-16 code units needed to represent a string.
71 // Like most strings in clangd, the input is UTF-8 encoded.
72 static size_t utf16Len(StringRef U8) {
73   // A codepoint takes two UTF-16 code unit if it's astral (outside BMP).
74   // Astral codepoints are encoded as 4 bytes in UTF-8, starting with 11110xxx.
75   size_t Count = 0;
76   iterateCodepoints(U8, [&](int U8Len, int U16Len) {
77     Count += U16Len;
78     return false;
79   });
80   return Count;
81 }
82 
83 llvm::Expected<size_t> positionToOffset(StringRef Code, Position P,
84                                         bool AllowColumnsBeyondLineLength) {
85   if (P.line < 0)
86     return llvm::make_error<llvm::StringError>(
87         llvm::formatv("Line value can't be negative ({0})", P.line),
88         llvm::errc::invalid_argument);
89   if (P.character < 0)
90     return llvm::make_error<llvm::StringError>(
91         llvm::formatv("Character value can't be negative ({0})", P.character),
92         llvm::errc::invalid_argument);
93   size_t StartOfLine = 0;
94   for (int I = 0; I != P.line; ++I) {
95     size_t NextNL = Code.find('\n', StartOfLine);
96     if (NextNL == StringRef::npos)
97       return llvm::make_error<llvm::StringError>(
98           llvm::formatv("Line value is out of range ({0})", P.line),
99           llvm::errc::invalid_argument);
100     StartOfLine = NextNL + 1;
101   }
102 
103   size_t NextNL = Code.find('\n', StartOfLine);
104   if (NextNL == StringRef::npos)
105     NextNL = Code.size();
106 
107   bool Valid;
108   size_t ByteOffsetInLine = measureUTF16(
109       Code.substr(StartOfLine, NextNL - StartOfLine), P.character, Valid);
110   if (!Valid && !AllowColumnsBeyondLineLength)
111     return llvm::make_error<llvm::StringError>(
112         llvm::formatv("UTF-16 offset {0} is invalid for line {1}", P.character,
113                       P.line),
114         llvm::errc::invalid_argument);
115   return StartOfLine + ByteOffsetInLine;
116 }
117 
118 Position offsetToPosition(StringRef Code, size_t Offset) {
119   Offset = std::min(Code.size(), Offset);
120   StringRef Before = Code.substr(0, Offset);
121   int Lines = Before.count('\n');
122   size_t PrevNL = Before.rfind('\n');
123   size_t StartOfLine = (PrevNL == StringRef::npos) ? 0 : (PrevNL + 1);
124   Position Pos;
125   Pos.line = Lines;
126   Pos.character = utf16Len(Before.substr(StartOfLine));
127   return Pos;
128 }
129 
130 Position sourceLocToPosition(const SourceManager &SM, SourceLocation Loc) {
131   // We use the SourceManager's line tables, but its column number is in bytes.
132   FileID FID;
133   unsigned Offset;
134   std::tie(FID, Offset) = SM.getDecomposedSpellingLoc(Loc);
135   Position P;
136   P.line = static_cast<int>(SM.getLineNumber(FID, Offset)) - 1;
137   bool Invalid = false;
138   StringRef Code = SM.getBufferData(FID, &Invalid);
139   if (!Invalid) {
140     auto ColumnInBytes = SM.getColumnNumber(FID, Offset) - 1;
141     auto LineSoFar = Code.substr(Offset - ColumnInBytes, ColumnInBytes);
142     P.character = utf16Len(LineSoFar);
143   }
144   return P;
145 }
146 
147 Range halfOpenToRange(const SourceManager &SM, CharSourceRange R) {
148   // Clang is 1-based, LSP uses 0-based indexes.
149   Position Begin = sourceLocToPosition(SM, R.getBegin());
150   Position End = sourceLocToPosition(SM, R.getEnd());
151 
152   return {Begin, End};
153 }
154 
155 std::pair<size_t, size_t> offsetToClangLineColumn(StringRef Code,
156                                                   size_t Offset) {
157   Offset = std::min(Code.size(), Offset);
158   StringRef Before = Code.substr(0, Offset);
159   int Lines = Before.count('\n');
160   size_t PrevNL = Before.rfind('\n');
161   size_t StartOfLine = (PrevNL == StringRef::npos) ? 0 : (PrevNL + 1);
162   return {Lines + 1, Offset - StartOfLine + 1};
163 }
164 
165 std::pair<llvm::StringRef, llvm::StringRef>
166 splitQualifiedName(llvm::StringRef QName) {
167   size_t Pos = QName.rfind("::");
168   if (Pos == llvm::StringRef::npos)
169     return {StringRef(), QName};
170   return {QName.substr(0, Pos + 2), QName.substr(Pos + 2)};
171 }
172 
173 TextEdit replacementToEdit(StringRef Code, const tooling::Replacement &R) {
174   Range ReplacementRange = {
175       offsetToPosition(Code, R.getOffset()),
176       offsetToPosition(Code, R.getOffset() + R.getLength())};
177   return {ReplacementRange, R.getReplacementText()};
178 }
179 
180 std::vector<TextEdit> replacementsToEdits(StringRef Code,
181                                           const tooling::Replacements &Repls) {
182   std::vector<TextEdit> Edits;
183   for (const auto &R : Repls)
184     Edits.push_back(replacementToEdit(Code, R));
185   return Edits;
186 }
187 
188 llvm::Optional<std::string> getRealPath(const FileEntry *F,
189                                         const SourceManager &SourceMgr) {
190   // Ideally, we get the real path from the FileEntry object.
191   SmallString<128> FilePath = F->tryGetRealPathName();
192   if (!FilePath.empty()) {
193     return FilePath.str().str();
194   }
195 
196   // Otherwise, we try to compute ourselves.
197   vlog("FileEntry for {0} did not contain the real path.", F->getName());
198 
199   llvm::SmallString<128> Path = F->getName();
200 
201   if (!llvm::sys::path::is_absolute(Path)) {
202     if (!SourceMgr.getFileManager().makeAbsolutePath(Path)) {
203       log("Could not turn relative path to absolute: {0}", Path);
204       return llvm::None;
205     }
206   }
207 
208   llvm::SmallString<128> RealPath;
209   if (SourceMgr.getFileManager().getVirtualFileSystem()->getRealPath(
210           Path, RealPath)) {
211     log("Could not compute real path: {0}", Path);
212     return Path.str().str();
213   }
214 
215   return RealPath.str().str();
216 }
217 
218 TextEdit toTextEdit(const FixItHint &FixIt, const SourceManager &M,
219                     const LangOptions &L) {
220   TextEdit Result;
221   Result.range =
222       halfOpenToRange(M, Lexer::makeFileCharRange(FixIt.RemoveRange, M, L));
223   Result.newText = FixIt.CodeToInsert;
224   return Result;
225 }
226 
227 bool IsRangeConsecutive(const Range &Left, const Range &Right) {
228   return Left.end.line == Right.start.line &&
229          Left.end.character == Right.start.character;
230 }
231 
232 } // namespace clangd
233 } // namespace clang
234