clang  14.0.0git
HeaderMap.cpp
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1 //===--- HeaderMap.cpp - A file that acts like dir of symlinks ------------===//
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 // This file implements the HeaderMap interface.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "clang/Lex/HeaderMap.h"
15 #include "clang/Basic/CharInfo.h"
17 #include "llvm/ADT/SmallString.h"
18 #include "llvm/Support/Compiler.h"
19 #include "llvm/Support/DataTypes.h"
20 #include "llvm/Support/MathExtras.h"
21 #include "llvm/Support/MemoryBuffer.h"
22 #include "llvm/Support/SwapByteOrder.h"
23 #include "llvm/Support/Debug.h"
24 #include <cstring>
25 #include <memory>
26 using namespace clang;
27 
28 /// HashHMapKey - This is the 'well known' hash function required by the file
29 /// format, used to look up keys in the hash table. The hash table uses simple
30 /// linear probing based on this function.
31 static inline unsigned HashHMapKey(StringRef Str) {
32  unsigned Result = 0;
33  const char *S = Str.begin(), *End = Str.end();
34 
35  for (; S != End; S++)
36  Result += toLowercase(*S) * 13;
37  return Result;
38 }
39 
40 
41 
42 //===----------------------------------------------------------------------===//
43 // Verification and Construction
44 //===----------------------------------------------------------------------===//
45 
46 /// HeaderMap::Create - This attempts to load the specified file as a header
47 /// map. If it doesn't look like a HeaderMap, it gives up and returns null.
48 /// If it looks like a HeaderMap but is obviously corrupted, it puts a reason
49 /// into the string error argument and returns null.
50 std::unique_ptr<HeaderMap> HeaderMap::Create(const FileEntry *FE,
51  FileManager &FM) {
52  // If the file is too small to be a header map, ignore it.
53  unsigned FileSize = FE->getSize();
54  if (FileSize <= sizeof(HMapHeader)) return nullptr;
55 
56  auto FileBuffer = FM.getBufferForFile(FE);
57  if (!FileBuffer || !*FileBuffer)
58  return nullptr;
59  bool NeedsByteSwap;
60  if (!checkHeader(**FileBuffer, NeedsByteSwap))
61  return nullptr;
62  return std::unique_ptr<HeaderMap>(new HeaderMap(std::move(*FileBuffer), NeedsByteSwap));
63 }
64 
65 bool HeaderMapImpl::checkHeader(const llvm::MemoryBuffer &File,
66  bool &NeedsByteSwap) {
67  if (File.getBufferSize() <= sizeof(HMapHeader))
68  return false;
69  const char *FileStart = File.getBufferStart();
70 
71  // We know the file is at least as big as the header, check it now.
72  const HMapHeader *Header = reinterpret_cast<const HMapHeader*>(FileStart);
73 
74  // Sniff it to see if it's a headermap by checking the magic number and
75  // version.
76  if (Header->Magic == HMAP_HeaderMagicNumber &&
77  Header->Version == HMAP_HeaderVersion)
78  NeedsByteSwap = false;
79  else if (Header->Magic == llvm::ByteSwap_32(HMAP_HeaderMagicNumber) &&
80  Header->Version == llvm::ByteSwap_16(HMAP_HeaderVersion))
81  NeedsByteSwap = true; // Mixed endianness headermap.
82  else
83  return false; // Not a header map.
84 
85  if (Header->Reserved != 0)
86  return false;
87 
88  // Check the number of buckets. It should be a power of two, and there
89  // should be enough space in the file for all of them.
90  uint32_t NumBuckets = NeedsByteSwap
91  ? llvm::sys::getSwappedBytes(Header->NumBuckets)
92  : Header->NumBuckets;
93  if (!llvm::isPowerOf2_32(NumBuckets))
94  return false;
95  if (File.getBufferSize() <
96  sizeof(HMapHeader) + sizeof(HMapBucket) * NumBuckets)
97  return false;
98 
99  // Okay, everything looks good.
100  return true;
101 }
102 
103 //===----------------------------------------------------------------------===//
104 // Utility Methods
105 //===----------------------------------------------------------------------===//
106 
107 
108 /// getFileName - Return the filename of the headermap.
109 StringRef HeaderMapImpl::getFileName() const {
110  return FileBuffer->getBufferIdentifier();
111 }
112 
113 unsigned HeaderMapImpl::getEndianAdjustedWord(unsigned X) const {
114  if (!NeedsBSwap) return X;
115  return llvm::ByteSwap_32(X);
116 }
117 
118 /// getHeader - Return a reference to the file header, in unbyte-swapped form.
119 /// This method cannot fail.
120 const HMapHeader &HeaderMapImpl::getHeader() const {
121  // We know the file is at least as big as the header. Return it.
122  return *reinterpret_cast<const HMapHeader*>(FileBuffer->getBufferStart());
123 }
124 
125 /// getBucket - Return the specified hash table bucket from the header map,
126 /// bswap'ing its fields as appropriate. If the bucket number is not valid,
127 /// this return a bucket with an empty key (0).
128 HMapBucket HeaderMapImpl::getBucket(unsigned BucketNo) const {
129  assert(FileBuffer->getBufferSize() >=
130  sizeof(HMapHeader) + sizeof(HMapBucket) * BucketNo &&
131  "Expected bucket to be in range");
132 
133  HMapBucket Result;
134  Result.Key = HMAP_EmptyBucketKey;
135 
136  const HMapBucket *BucketArray =
137  reinterpret_cast<const HMapBucket*>(FileBuffer->getBufferStart() +
138  sizeof(HMapHeader));
139  const HMapBucket *BucketPtr = BucketArray+BucketNo;
140 
141  // Load the values, bswapping as needed.
142  Result.Key = getEndianAdjustedWord(BucketPtr->Key);
143  Result.Prefix = getEndianAdjustedWord(BucketPtr->Prefix);
144  Result.Suffix = getEndianAdjustedWord(BucketPtr->Suffix);
145  return Result;
146 }
147 
148 Optional<StringRef> HeaderMapImpl::getString(unsigned StrTabIdx) const {
149  // Add the start of the string table to the idx.
150  StrTabIdx += getEndianAdjustedWord(getHeader().StringsOffset);
151 
152  // Check for invalid index.
153  if (StrTabIdx >= FileBuffer->getBufferSize())
154  return None;
155 
156  const char *Data = FileBuffer->getBufferStart() + StrTabIdx;
157  unsigned MaxLen = FileBuffer->getBufferSize() - StrTabIdx;
158  unsigned Len = strnlen(Data, MaxLen);
159 
160  // Check whether the buffer is null-terminated.
161  if (Len == MaxLen && Data[Len - 1])
162  return None;
163 
164  return StringRef(Data, Len);
165 }
166 
167 //===----------------------------------------------------------------------===//
168 // The Main Drivers
169 //===----------------------------------------------------------------------===//
170 
171 /// dump - Print the contents of this headermap to stderr.
172 LLVM_DUMP_METHOD void HeaderMapImpl::dump() const {
173  const HMapHeader &Hdr = getHeader();
174  unsigned NumBuckets = getEndianAdjustedWord(Hdr.NumBuckets);
175 
176  llvm::dbgs() << "Header Map " << getFileName() << ":\n " << NumBuckets
177  << ", " << getEndianAdjustedWord(Hdr.NumEntries) << "\n";
178 
179  auto getStringOrInvalid = [this](unsigned Id) -> StringRef {
180  if (Optional<StringRef> S = getString(Id))
181  return *S;
182  return "<invalid>";
183  };
184 
185  for (unsigned i = 0; i != NumBuckets; ++i) {
186  HMapBucket B = getBucket(i);
187  if (B.Key == HMAP_EmptyBucketKey) continue;
188 
189  StringRef Key = getStringOrInvalid(B.Key);
190  StringRef Prefix = getStringOrInvalid(B.Prefix);
191  StringRef Suffix = getStringOrInvalid(B.Suffix);
192  llvm::dbgs() << " " << i << ". " << Key << " -> '" << Prefix << "' '"
193  << Suffix << "'\n";
194  }
195 }
196 
198  SmallVectorImpl<char> &DestPath) const {
199  const HMapHeader &Hdr = getHeader();
200  unsigned NumBuckets = getEndianAdjustedWord(Hdr.NumBuckets);
201 
202  // Don't probe infinitely. This should be checked before constructing.
203  assert(llvm::isPowerOf2_32(NumBuckets) && "Expected power of 2");
204 
205  // Linearly probe the hash table.
206  for (unsigned Bucket = HashHMapKey(Filename);; ++Bucket) {
207  HMapBucket B = getBucket(Bucket & (NumBuckets-1));
208  if (B.Key == HMAP_EmptyBucketKey) return StringRef(); // Hash miss.
209 
210  // See if the key matches. If not, probe on.
211  Optional<StringRef> Key = getString(B.Key);
212  if (LLVM_UNLIKELY(!Key))
213  continue;
214  if (!Filename.equals_insensitive(*Key))
215  continue;
216 
217  // If so, we have a match in the hash table. Construct the destination
218  // path.
219  Optional<StringRef> Prefix = getString(B.Prefix);
220  Optional<StringRef> Suffix = getString(B.Suffix);
221 
222  DestPath.clear();
223  if (LLVM_LIKELY(Prefix && Suffix)) {
224  DestPath.append(Prefix->begin(), Prefix->end());
225  DestPath.append(Suffix->begin(), Suffix->end());
226  }
227  return StringRef(DestPath.begin(), DestPath.size());
228  }
229 }
230 
231 StringRef HeaderMapImpl::reverseLookupFilename(StringRef DestPath) const {
232  if (!ReverseMap.empty())
233  return ReverseMap.lookup(DestPath);
234 
235  const HMapHeader &Hdr = getHeader();
236  unsigned NumBuckets = getEndianAdjustedWord(Hdr.NumBuckets);
237  StringRef RetKey;
238  for (unsigned i = 0; i != NumBuckets; ++i) {
239  HMapBucket B = getBucket(i);
240  if (B.Key == HMAP_EmptyBucketKey)
241  continue;
242 
243  Optional<StringRef> Key = getString(B.Key);
244  Optional<StringRef> Prefix = getString(B.Prefix);
245  Optional<StringRef> Suffix = getString(B.Suffix);
246  if (LLVM_LIKELY(Key && Prefix && Suffix)) {
248  Buf.append(Prefix->begin(), Prefix->end());
249  Buf.append(Suffix->begin(), Suffix->end());
250  StringRef Value(Buf.begin(), Buf.size());
251  ReverseMap[Value] = *Key;
252 
253  if (DestPath == Value)
254  RetKey = *Key;
255  }
256  }
257  return RetKey;
258 }
clang::HMapBucket::Prefix
uint32_t Prefix
Definition: HeaderMapTypes.h:24
clang::DeclaratorContext::File
@ File
llvm::SmallVector
Definition: LLVM.h:38
clang::HMapHeader::Reserved
uint16_t Reserved
Definition: HeaderMapTypes.h:31
clang::HMAP_EmptyBucketKey
@ HMAP_EmptyBucketKey
Definition: HeaderMapTypes.h:19
clang::HeaderMapImpl::reverseLookupFilename
StringRef reverseLookupFilename(StringRef DestPath) const
Return key for specifed path.
Definition: HeaderMap.cpp:231
Filename
StringRef Filename
Definition: Format.cpp:2333
llvm::Optional
Definition: LLVM.h:40
clang::tooling::X
static ToolExecutorPluginRegistry::Add< AllTUsToolExecutorPlugin > X("all-TUs", "Runs FrontendActions on all TUs in the compilation database. " "Tool results are stored in memory.")
clang::toLowercase
LLVM_READONLY char toLowercase(char c)
Converts the given ASCII character to its lowercase equivalent.
Definition: CharInfo.h:169
End
SourceLocation End
Definition: USRLocFinder.cpp:167
clang::HMapHeader::Version
uint16_t Version
Definition: HeaderMapTypes.h:30
clang::HeaderMap::Create
static std::unique_ptr< HeaderMap > Create(const FileEntry *FE, FileManager &FM)
This attempts to load the specified file as a header map.
Definition: HeaderMap.cpp:50
clang::HeaderMapImpl::getFileName
StringRef getFileName() const
Return the filename of the headermap.
Definition: HeaderMap.cpp:109
Id
int Id
Definition: ASTDiff.cpp:191
clang::XRayInstrKind::None
constexpr XRayInstrMask None
Definition: XRayInstr.h:38
clang::HMapHeader::Magic
uint32_t Magic
Definition: HeaderMapTypes.h:29
clang::HMapBucket::Suffix
uint32_t Suffix
Definition: HeaderMapTypes.h:25
clang::HeaderMap
This class represents an Apple concept known as a 'header map'.
Definition: HeaderMap.h:70
clang::HMapHeader::NumBuckets
uint32_t NumBuckets
Definition: HeaderMapTypes.h:34
clang::FileEntry
Cached information about one file (either on disk or in the virtual file system).
Definition: FileEntry.h:331
clang::HMapHeader::NumEntries
uint32_t NumEntries
Definition: HeaderMapTypes.h:33
clang::HeaderMapImpl::checkHeader
static bool checkHeader(const llvm::MemoryBuffer &File, bool &NeedsByteSwap)
Definition: HeaderMap.cpp:65
CharInfo.h
HeaderMapTypes.h
HeaderMap.h
clang::HMAP_HeaderMagicNumber
@ HMAP_HeaderMagicNumber
Definition: HeaderMapTypes.h:17
Value
Value
Definition: UninitializedValues.cpp:102
clang::HMapBucket
Definition: HeaderMapTypes.h:22
clang::FileManager::getBufferForFile
llvm::ErrorOr< std::unique_ptr< llvm::MemoryBuffer > > getBufferForFile(const FileEntry *Entry, bool isVolatile=false, bool RequiresNullTerminator=true)
Open the specified file as a MemoryBuffer, returning a new MemoryBuffer if successful,...
Definition: FileManager.cpp:521
clang::HeaderMapImpl::lookupFilename
StringRef lookupFilename(StringRef Filename, SmallVectorImpl< char > &DestPath) const
If the specified relative filename is located in this HeaderMap return the filename it is mapped to,...
Definition: HeaderMap.cpp:197
clang
Definition: CalledOnceCheck.h:17
clang::FileManager
Implements support for file system lookup, file system caching, and directory search management.
Definition: FileManager.h:53
clang::HeaderMapImpl::dump
void dump() const
Print the contents of this headermap to stderr.
Definition: HeaderMap.cpp:172
HashHMapKey
static unsigned HashHMapKey(StringRef Str)
HashHMapKey - This is the 'well known' hash function required by the file format, used to look up key...
Definition: HeaderMap.cpp:31
llvm::SmallVectorImpl< char >
FileManager.h
clang::FileEntry::getSize
off_t getSize() const
Definition: FileEntry.h:369
clang::HMapBucket::Key
uint32_t Key
Definition: HeaderMapTypes.h:23
clang::HMAP_HeaderVersion
@ HMAP_HeaderVersion
Definition: HeaderMapTypes.h:18
clang::HMapHeader
Definition: HeaderMapTypes.h:28