clang  8.0.0svn
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.
51 std::unique_ptr<HeaderMap> HeaderMap::Create(const FileEntry *FE,
52  FileManager &FM) {
53  // If the file is too small to be a header map, ignore it.
54  unsigned FileSize = FE->getSize();
55  if (FileSize <= sizeof(HMapHeader)) return nullptr;
56 
57  auto FileBuffer = FM.getBufferForFile(FE);
58  if (!FileBuffer || !*FileBuffer)
59  return nullptr;
60  bool NeedsByteSwap;
61  if (!checkHeader(**FileBuffer, NeedsByteSwap))
62  return nullptr;
63  return std::unique_ptr<HeaderMap>(new HeaderMap(std::move(*FileBuffer), NeedsByteSwap));
64 }
65 
66 bool HeaderMapImpl::checkHeader(const llvm::MemoryBuffer &File,
67  bool &NeedsByteSwap) {
68  if (File.getBufferSize() <= sizeof(HMapHeader))
69  return false;
70  const char *FileStart = File.getBufferStart();
71 
72  // We know the file is at least as big as the header, check it now.
73  const HMapHeader *Header = reinterpret_cast<const HMapHeader*>(FileStart);
74 
75  // Sniff it to see if it's a headermap by checking the magic number and
76  // version.
77  if (Header->Magic == HMAP_HeaderMagicNumber &&
78  Header->Version == HMAP_HeaderVersion)
79  NeedsByteSwap = false;
80  else if (Header->Magic == llvm::ByteSwap_32(HMAP_HeaderMagicNumber) &&
81  Header->Version == llvm::ByteSwap_16(HMAP_HeaderVersion))
82  NeedsByteSwap = true; // Mixed endianness headermap.
83  else
84  return false; // Not a header map.
85 
86  if (Header->Reserved != 0)
87  return false;
88 
89  // Check the number of buckets. It should be a power of two, and there
90  // should be enough space in the file for all of them.
91  uint32_t NumBuckets = NeedsByteSwap
92  ? llvm::sys::getSwappedBytes(Header->NumBuckets)
93  : Header->NumBuckets;
94  if (!llvm::isPowerOf2_32(NumBuckets))
95  return false;
96  if (File.getBufferSize() <
97  sizeof(HMapHeader) + sizeof(HMapBucket) * NumBuckets)
98  return false;
99 
100  // Okay, everything looks good.
101  return true;
102 }
103 
104 //===----------------------------------------------------------------------===//
105 // Utility Methods
106 //===----------------------------------------------------------------------===//
107 
108 
109 /// getFileName - Return the filename of the headermap.
110 StringRef HeaderMapImpl::getFileName() const {
111  return FileBuffer->getBufferIdentifier();
112 }
113 
114 unsigned HeaderMapImpl::getEndianAdjustedWord(unsigned X) const {
115  if (!NeedsBSwap) return X;
116  return llvm::ByteSwap_32(X);
117 }
118 
119 /// getHeader - Return a reference to the file header, in unbyte-swapped form.
120 /// This method cannot fail.
121 const HMapHeader &HeaderMapImpl::getHeader() const {
122  // We know the file is at least as big as the header. Return it.
123  return *reinterpret_cast<const HMapHeader*>(FileBuffer->getBufferStart());
124 }
125 
126 /// getBucket - Return the specified hash table bucket from the header map,
127 /// bswap'ing its fields as appropriate. If the bucket number is not valid,
128 /// this return a bucket with an empty key (0).
129 HMapBucket HeaderMapImpl::getBucket(unsigned BucketNo) const {
130  assert(FileBuffer->getBufferSize() >=
131  sizeof(HMapHeader) + sizeof(HMapBucket) * BucketNo &&
132  "Expected bucket to be in range");
133 
135  Result.Key = HMAP_EmptyBucketKey;
136 
137  const HMapBucket *BucketArray =
138  reinterpret_cast<const HMapBucket*>(FileBuffer->getBufferStart() +
139  sizeof(HMapHeader));
140  const HMapBucket *BucketPtr = BucketArray+BucketNo;
141 
142  // Load the values, bswapping as needed.
143  Result.Key = getEndianAdjustedWord(BucketPtr->Key);
144  Result.Prefix = getEndianAdjustedWord(BucketPtr->Prefix);
145  Result.Suffix = getEndianAdjustedWord(BucketPtr->Suffix);
146  return Result;
147 }
148 
149 Optional<StringRef> HeaderMapImpl::getString(unsigned StrTabIdx) const {
150  // Add the start of the string table to the idx.
151  StrTabIdx += getEndianAdjustedWord(getHeader().StringsOffset);
152 
153  // Check for invalid index.
154  if (StrTabIdx >= FileBuffer->getBufferSize())
155  return None;
156 
157  const char *Data = FileBuffer->getBufferStart() + StrTabIdx;
158  unsigned MaxLen = FileBuffer->getBufferSize() - StrTabIdx;
159  unsigned Len = strnlen(Data, MaxLen);
160 
161  // Check whether the buffer is null-terminated.
162  if (Len == MaxLen && Data[Len - 1])
163  return None;
164 
165  return StringRef(Data, Len);
166 }
167 
168 //===----------------------------------------------------------------------===//
169 // The Main Drivers
170 //===----------------------------------------------------------------------===//
171 
172 /// dump - Print the contents of this headermap to stderr.
173 LLVM_DUMP_METHOD void HeaderMapImpl::dump() const {
174  const HMapHeader &Hdr = getHeader();
175  unsigned NumBuckets = getEndianAdjustedWord(Hdr.NumBuckets);
176 
177  llvm::dbgs() << "Header Map " << getFileName() << ":\n " << NumBuckets
178  << ", " << getEndianAdjustedWord(Hdr.NumEntries) << "\n";
179 
180  auto getStringOrInvalid = [this](unsigned Id) -> StringRef {
181  if (Optional<StringRef> S = getString(Id))
182  return *S;
183  return "<invalid>";
184  };
185 
186  for (unsigned i = 0; i != NumBuckets; ++i) {
187  HMapBucket B = getBucket(i);
188  if (B.Key == HMAP_EmptyBucketKey) continue;
189 
190  StringRef Key = getStringOrInvalid(B.Key);
191  StringRef Prefix = getStringOrInvalid(B.Prefix);
192  StringRef Suffix = getStringOrInvalid(B.Suffix);
193  llvm::dbgs() << " " << i << ". " << Key << " -> '" << Prefix << "' '"
194  << Suffix << "'\n";
195  }
196 }
197 
198 /// LookupFile - Check to see if the specified relative filename is located in
199 /// this HeaderMap. If so, open it and return its FileEntry.
201  StringRef Filename, FileManager &FM) const {
202 
203  SmallString<1024> Path;
204  StringRef Dest = HeaderMapImpl::lookupFilename(Filename, Path);
205  if (Dest.empty())
206  return nullptr;
207 
208  return FM.getFile(Dest);
209 }
210 
212  SmallVectorImpl<char> &DestPath) const {
213  const HMapHeader &Hdr = getHeader();
214  unsigned NumBuckets = getEndianAdjustedWord(Hdr.NumBuckets);
215 
216  // Don't probe infinitely. This should be checked before constructing.
217  assert(llvm::isPowerOf2_32(NumBuckets) && "Expected power of 2");
218 
219  // Linearly probe the hash table.
220  for (unsigned Bucket = HashHMapKey(Filename);; ++Bucket) {
221  HMapBucket B = getBucket(Bucket & (NumBuckets-1));
222  if (B.Key == HMAP_EmptyBucketKey) return StringRef(); // Hash miss.
223 
224  // See if the key matches. If not, probe on.
225  Optional<StringRef> Key = getString(B.Key);
226  if (LLVM_UNLIKELY(!Key))
227  continue;
228  if (!Filename.equals_lower(*Key))
229  continue;
230 
231  // If so, we have a match in the hash table. Construct the destination
232  // path.
233  Optional<StringRef> Prefix = getString(B.Prefix);
234  Optional<StringRef> Suffix = getString(B.Suffix);
235 
236  DestPath.clear();
237  if (LLVM_LIKELY(Prefix && Suffix)) {
238  DestPath.append(Prefix->begin(), Prefix->end());
239  DestPath.append(Suffix->begin(), Suffix->end());
240  }
241  return StringRef(DestPath.begin(), DestPath.size());
242  }
243 }
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:66
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:211
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:173
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:1602
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:200
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:13824
StringRef getFileName() const
Return the filename of the headermap.
Definition: HeaderMap.cpp:110
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
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:51