clang  6.0.0svn
HeaderMap.cpp
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1 //===--- HeaderMap.cpp - A file that acts like dir of symlinks ------------===//
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 //
10 // This file implements the HeaderMap interface.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "clang/Lex/HeaderMap.h"
16 #include "clang/Basic/CharInfo.h"
18 #include "llvm/ADT/SmallString.h"
19 #include "llvm/Support/Compiler.h"
20 #include "llvm/Support/DataTypes.h"
21 #include "llvm/Support/MathExtras.h"
22 #include "llvm/Support/MemoryBuffer.h"
23 #include "llvm/Support/SwapByteOrder.h"
24 #include "llvm/Support/Debug.h"
25 #include <cstring>
26 #include <memory>
27 using namespace clang;
28 
29 /// HashHMapKey - This is the 'well known' hash function required by the file
30 /// format, used to look up keys in the hash table. The hash table uses simple
31 /// linear probing based on this function.
32 static inline unsigned HashHMapKey(StringRef Str) {
33  unsigned Result = 0;
34  const char *S = Str.begin(), *End = Str.end();
35 
36  for (; S != End; S++)
37  Result += toLowercase(*S) * 13;
38  return Result;
39 }
40 
41 
42 
43 //===----------------------------------------------------------------------===//
44 // Verification and Construction
45 //===----------------------------------------------------------------------===//
46 
47 /// HeaderMap::Create - This attempts to load the specified file as a header
48 /// map. If it doesn't look like a HeaderMap, it gives up and returns null.
49 /// If it looks like a HeaderMap but is obviously corrupted, it puts a reason
50 /// into the string error argument and returns null.
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 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 
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 
197 /// LookupFile - Check to see if the specified relative filename is located in
198 /// this HeaderMap. If so, open it and return its FileEntry.
200  StringRef Filename, FileManager &FM) const {
201 
202  SmallString<1024> Path;
203  StringRef Dest = HeaderMapImpl::lookupFilename(Filename, Path);
204  if (Dest.empty())
205  return nullptr;
206 
207  return FM.getFile(Dest);
208 }
209 
211  SmallVectorImpl<char> &DestPath) const {
212  const HMapHeader &Hdr = getHeader();
213  unsigned NumBuckets = getEndianAdjustedWord(Hdr.NumBuckets);
214 
215  // Don't probe infinitely. This should be checked before constructing.
216  assert(llvm::isPowerOf2_32(NumBuckets) && "Expected power of 2");
217 
218  // Linearly probe the hash table.
219  for (unsigned Bucket = HashHMapKey(Filename);; ++Bucket) {
220  HMapBucket B = getBucket(Bucket & (NumBuckets-1));
221  if (B.Key == HMAP_EmptyBucketKey) return StringRef(); // Hash miss.
222 
223  // See if the key matches. If not, probe on.
224  Optional<StringRef> Key = getString(B.Key);
225  if (LLVM_UNLIKELY(!Key))
226  continue;
227  if (!Filename.equals_lower(*Key))
228  continue;
229 
230  // If so, we have a match in the hash table. Construct the destination
231  // path.
232  Optional<StringRef> Prefix = getString(B.Prefix);
233  Optional<StringRef> Suffix = getString(B.Suffix);
234 
235  DestPath.clear();
236  if (LLVM_LIKELY(Prefix && Suffix)) {
237  DestPath.append(Prefix->begin(), Prefix->end());
238  DestPath.append(Suffix->begin(), Suffix->end());
239  }
240  return StringRef(DestPath.begin(), DestPath.size());
241  }
242 }
Implements support for file system lookup, file system caching, and directory search management...
Definition: FileManager.h:116
Defines the clang::FileManager interface and associated types.
static bool checkHeader(const llvm::MemoryBuffer &File, bool &NeedsByteSwap)
Definition: HeaderMap.cpp:65
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:210
static const HeaderMap * Create(const FileEntry *FE, FileManager &FM)
This attempts to load the specified file as a header map.
Definition: HeaderMap.cpp:51
This class represents an Apple concept known as a &#39;header map&#39;.
Definition: HeaderMap.h:67
void dump() const
Print the contents of this headermap to stderr.
Definition: HeaderMap.cpp:172
const FileEntry * getFile(StringRef Filename, bool OpenFile=false, bool CacheFailure=true)
Lookup, cache, and verify the specified file (real or virtual).
StringRef Filename
Definition: Format.cpp:1345
SourceLocation End
int Id
Definition: ASTDiff.cpp:191
The result type of a method or function.
const FileEntry * LookupFile(StringRef Filename, FileManager &FM) const
Check to see if the specified relative filename is located in this HeaderMap.
Definition: HeaderMap.cpp:199
LLVM_READONLY char toLowercase(char c)
Converts the given ASCII character to its lowercase equivalent.
Definition: CharInfo.h:165
Cached information about one file (either on disk or in the virtual file system). ...
Definition: FileManager.h:59
Dataflow Directional Tag Classes.
off_t getSize() const
Definition: FileManager.h:87
llvm::ErrorOr< std::unique_ptr< llvm::MemoryBuffer > > getBufferForFile(const FileEntry *Entry, bool isVolatile=false, bool ShouldCloseOpenFile=true)
Open the specified file as a MemoryBuffer, returning a new MemoryBuffer if successful, otherwise returning null.
X
Add a minimal nested name specifier fixit hint to allow lookup of a tag name from an outer enclosing ...
Definition: SemaDecl.cpp:13010
StringRef getFileName() const
Return the filename of the headermap.
Definition: HeaderMap.cpp:109
static unsigned HashHMapKey(StringRef Str)
HashHMapKey - This is the &#39;well known&#39; hash function required by the file format, used to look up key...
Definition: HeaderMap.cpp:32