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comparison clang/lib/Lex/HeaderMap.cpp @ 150:1d019706d866

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LLVM10
author anatofuz
date Thu, 13 Feb 2020 15:10:13 +0900
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children 2e18cbf3894f
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147:c2174574ed3a 150:1d019706d866
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"
14 #include "clang/Lex/HeaderMapTypes.h"
15 #include "clang/Basic/CharInfo.h"
16 #include "clang/Basic/FileManager.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
197 /// LookupFile - Check to see if the specified relative filename is located in
198 /// this HeaderMap. If so, open it and return its FileEntry.
199 Optional<FileEntryRef> HeaderMap::LookupFile(StringRef Filename,
200 FileManager &FM) const {
201
202 SmallString<1024> Path;
203 StringRef Dest = HeaderMapImpl::lookupFilename(Filename, Path);
204 if (Dest.empty())
205 return None;
206
207 return FM.getOptionalFileRef(Dest);
208 }
209
210 StringRef HeaderMapImpl::lookupFilename(StringRef Filename,
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 }