clang 8.0.0

HeaderMap.cpp
Go to the documentation of this file.
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"
15 #include "clang/Lex/HeaderMapTypes.h"
16 #include "clang/Basic/CharInfo.h"
17 #include "clang/Basic/FileManager.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
134 HMapBucket Result;
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.
200 const FileEntry *HeaderMap::LookupFile(
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
211 StringRef HeaderMapImpl::lookupFilename(StringRef Filename,
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 }
clang::FileManager
Implements support for file system lookup, file system caching, and directory search management...
Definition: FileManager.h:121
FileManager.h
Defines the clang::FileManager interface and associated types.
clang::HeaderMapImpl::checkHeader
static bool checkHeader(const llvm::MemoryBuffer &File, bool &NeedsByteSwap)
Definition: HeaderMap.cpp:66
HeaderMapTypes.h
clang::HMAP_HeaderVersion
Definition: HeaderMapTypes.h:19
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:211
clang::HMapHeader::Reserved
uint16_t Reserved
Definition: HeaderMapTypes.h:32
llvm::Optional
Definition: LLVM.h:38
clang::HeaderMap
This class represents an Apple concept known as a &#39;header map&#39;.
Definition: HeaderMap.h:67
llvm::SmallVectorImpl
Definition: LLVM.h:37
clang::HeaderMapImpl::dump
void dump() const
Print the contents of this headermap to stderr.
Definition: HeaderMap.cpp:173
llvm::SmallString
Definition: LLVM.h:35
clang::FileManager::getFile
const FileEntry * getFile(StringRef Filename, bool OpenFile=false, bool CacheFailure=true)
Lookup, cache, and verify the specified file (real or virtual).
Definition: FileManager.cpp:183
CharInfo.h
Filename
StringRef Filename
Definition: Format.cpp:1629
clang::HMAP_EmptyBucketKey
Definition: HeaderMapTypes.h:20
HeaderMap.h
End
SourceLocation End
Definition: USRLocFinder.cpp:167
Id
int Id
Definition: ASTDiff.cpp:191
clang::HMapBucket
Definition: HeaderMapTypes.h:23
clang::HMapBucket::Key
uint32_t Key
Definition: HeaderMapTypes.h:24
clang::ObjCSubstitutionContext::Result
The result type of a method or function.
clang::HeaderMap::LookupFile
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
clang::toLowercase
LLVM_READONLY char toLowercase(char c)
Converts the given ASCII character to its lowercase equivalent.
Definition: CharInfo.h:165
clang::HMapBucket::Prefix
uint32_t Prefix
Definition: HeaderMapTypes.h:25
clang::FileEntry
Cached information about one file (either on disk or in the virtual file system). ...
Definition: FileManager.h:60
clang::HMAP_HeaderMagicNumber
Definition: HeaderMapTypes.h:18
clang::MultiVersionKind::None
clang
Dataflow Directional Tag Classes.
Definition: CFGReachabilityAnalysis.h:22
clang::FileEntry::getSize
off_t getSize() const
Definition: FileManager.h:88
clang::FileManager::getBufferForFile
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.
Definition: FileManager.cpp:401
clang::HMapHeader::Version
uint16_t Version
Definition: HeaderMapTypes.h:31
clang::HMapBucket::Suffix
uint32_t Suffix
Definition: HeaderMapTypes.h:26
clang::HMapHeader
Definition: HeaderMapTypes.h:29
clang::HMapHeader::NumEntries
uint32_t NumEntries
Definition: HeaderMapTypes.h:34
X
X
Add a minimal nested name specifier fixit hint to allow lookup of a tag name from an outer enclosing ...
Definition: SemaDecl.cpp:13954
clang::HeaderMapImpl::getFileName
StringRef getFileName() const
Return the filename of the headermap.
Definition: HeaderMap.cpp:110
HashHMapKey
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
clang::HMapHeader::Magic
uint32_t Magic
Definition: HeaderMapTypes.h:30
clang::HMapHeader::NumBuckets
uint32_t NumBuckets
Definition: HeaderMapTypes.h:35
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:51