clang 19.0.0git
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"
17#include "llvm/ADT/SmallString.h"
18#include "llvm/Support/Compiler.h"
19#include "llvm/Support/DataTypes.h"
20#include "llvm/Support/Debug.h"
21#include "llvm/Support/MathExtras.h"
22#include "llvm/Support/MemoryBuffer.h"
23#include "llvm/Support/SwapByteOrder.h"
24#include "llvm/Support/SystemZ/zOSSupport.h"
25#include <cstring>
26#include <memory>
27#include <optional>
28using namespace clang;
29
30/// HashHMapKey - This is the 'well known' hash function required by the file
31/// format, used to look up keys in the hash table. The hash table uses simple
32/// linear probing based on this function.
33static inline unsigned HashHMapKey(StringRef Str) {
34 unsigned Result = 0;
35 const char *S = Str.begin(), *End = Str.end();
36
37 for (; S != End; S++)
38 Result += toLowercase(*S) * 13;
39 return Result;
40}
41
42
43
44//===----------------------------------------------------------------------===//
45// Verification and Construction
46//===----------------------------------------------------------------------===//
47
48/// HeaderMap::Create - This attempts to load the specified file as a header
49/// map. If it doesn't look like a HeaderMap, it gives up and returns null.
50/// If it looks like a HeaderMap but is obviously corrupted, it puts a reason
51/// into the string error argument and returns null.
52std::unique_ptr<HeaderMap> HeaderMap::Create(FileEntryRef FE, 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}
66bool 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<uint32_t>(HMAP_HeaderMagicNumber) &&
81 Header->Version == llvm::byteswap<uint16_t>(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 =
92 NeedsByteSwap ? llvm::byteswap(Header->NumBuckets) : 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.
109StringRef HeaderMapImpl::getFileName() const {
110 return FileBuffer->getBufferIdentifier();
111}
112
113unsigned HeaderMapImpl::getEndianAdjustedWord(unsigned X) const {
114 if (!NeedsBSwap) return X;
115 return llvm::byteswap<uint32_t>(X);
116}
117
118/// getHeader - Return a reference to the file header, in unbyte-swapped form.
119/// This method cannot fail.
120const 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).
128HMapBucket HeaderMapImpl::getBucket(unsigned BucketNo) const {
129 assert(FileBuffer->getBufferSize() >=
130 sizeof(HMapHeader) + sizeof(HMapBucket) * BucketNo &&
131 "Expected bucket to be in range");
132
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
148std::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 std::nullopt;
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 std::nullopt;
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.
172LLVM_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 (std::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 std::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 std::optional<StringRef> Prefix = getString(B.Prefix);
220 std::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
231StringRef 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 std::optional<StringRef> Key = getString(B.Key);
244 std::optional<StringRef> Prefix = getString(B.Prefix);
245 std::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}
int Id
Definition: ASTDiff.cpp:190
Defines the clang::FileManager interface and associated types.
StringRef Filename
Definition: Format.cpp:2974
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:33
#define X(type, name)
Definition: Value.h:142
A reference to a FileEntry that includes the name of the file as it was accessed by the FileManager's...
Definition: FileEntry.h:57
off_t getSize() const
Definition: FileEntry.h:340
Implements support for file system lookup, file system caching, and directory search management.
Definition: FileManager.h:53
llvm::ErrorOr< std::unique_ptr< llvm::MemoryBuffer > > getBufferForFile(FileEntryRef Entry, bool isVolatile=false, bool RequiresNullTerminator=true)
Open the specified file as a MemoryBuffer, returning a new MemoryBuffer if successful,...
StringRef getFileName() const
Return the filename of the headermap.
Definition: HeaderMap.cpp:109
StringRef reverseLookupFilename(StringRef DestPath) const
Return key for specifed path.
Definition: HeaderMap.cpp:231
void dump() const
Print the contents of this headermap to stderr.
Definition: HeaderMap.cpp:172
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
static bool checkHeader(const llvm::MemoryBuffer &File, bool &NeedsByteSwap)
Definition: HeaderMap.cpp:66
This class represents an Apple concept known as a 'header map'.
Definition: HeaderMap.h:84
static std::unique_ptr< HeaderMap > Create(FileEntryRef FE, FileManager &FM)
This attempts to load the specified file as a header map.
Definition: HeaderMap.cpp:52
The JSON file list parser is used to communicate input to InstallAPI.
@ HMAP_HeaderVersion
@ HMAP_EmptyBucketKey
@ HMAP_HeaderMagicNumber
LLVM_READONLY char toLowercase(char c)
Converts the given ASCII character to its lowercase equivalent.
Definition: CharInfo.h:224
@ Result
The result type of a method or function.