| //===--- HeaderMap.cpp - A file that acts like dir of symlinks ------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements the HeaderMap interface. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "clang/Lex/HeaderMap.h" |
| #include "clang/Lex/HeaderMapTypes.h" |
| #include "clang/Basic/CharInfo.h" |
| #include "clang/Basic/FileManager.h" |
| #include "llvm/ADT/SmallString.h" |
| #include "llvm/Support/Compiler.h" |
| #include "llvm/Support/DataTypes.h" |
| #include "llvm/Support/MathExtras.h" |
| #include "llvm/Support/MemoryBuffer.h" |
| #include "llvm/Support/SwapByteOrder.h" |
| #include "llvm/Support/Debug.h" |
| #include <cstring> |
| #include <memory> |
| using namespace clang; |
| |
| /// HashHMapKey - This is the 'well known' hash function required by the file |
| /// format, used to look up keys in the hash table. The hash table uses simple |
| /// linear probing based on this function. |
| static inline unsigned HashHMapKey(StringRef Str) { |
| unsigned Result = 0; |
| const char *S = Str.begin(), *End = Str.end(); |
| |
| for (; S != End; S++) |
| Result += toLowercase(*S) * 13; |
| return Result; |
| } |
| |
| |
| |
| //===----------------------------------------------------------------------===// |
| // Verification and Construction |
| //===----------------------------------------------------------------------===// |
| |
| /// HeaderMap::Create - This attempts to load the specified file as a header |
| /// map. If it doesn't look like a HeaderMap, it gives up and returns null. |
| /// If it looks like a HeaderMap but is obviously corrupted, it puts a reason |
| /// into the string error argument and returns null. |
| std::unique_ptr<HeaderMap> HeaderMap::Create(const FileEntry *FE, |
| FileManager &FM) { |
| // If the file is too small to be a header map, ignore it. |
| unsigned FileSize = FE->getSize(); |
| if (FileSize <= sizeof(HMapHeader)) return nullptr; |
| |
| auto FileBuffer = FM.getBufferForFile(FE); |
| if (!FileBuffer || !*FileBuffer) |
| return nullptr; |
| bool NeedsByteSwap; |
| if (!checkHeader(**FileBuffer, NeedsByteSwap)) |
| return nullptr; |
| return std::unique_ptr<HeaderMap>(new HeaderMap(std::move(*FileBuffer), NeedsByteSwap)); |
| } |
| |
| bool HeaderMapImpl::checkHeader(const llvm::MemoryBuffer &File, |
| bool &NeedsByteSwap) { |
| if (File.getBufferSize() <= sizeof(HMapHeader)) |
| return false; |
| const char *FileStart = File.getBufferStart(); |
| |
| // We know the file is at least as big as the header, check it now. |
| const HMapHeader *Header = reinterpret_cast<const HMapHeader*>(FileStart); |
| |
| // Sniff it to see if it's a headermap by checking the magic number and |
| // version. |
| if (Header->Magic == HMAP_HeaderMagicNumber && |
| Header->Version == HMAP_HeaderVersion) |
| NeedsByteSwap = false; |
| else if (Header->Magic == llvm::ByteSwap_32(HMAP_HeaderMagicNumber) && |
| Header->Version == llvm::ByteSwap_16(HMAP_HeaderVersion)) |
| NeedsByteSwap = true; // Mixed endianness headermap. |
| else |
| return false; // Not a header map. |
| |
| if (Header->Reserved != 0) |
| return false; |
| |
| // Check the number of buckets. It should be a power of two, and there |
| // should be enough space in the file for all of them. |
| uint32_t NumBuckets = NeedsByteSwap |
| ? llvm::sys::getSwappedBytes(Header->NumBuckets) |
| : Header->NumBuckets; |
| if (!llvm::isPowerOf2_32(NumBuckets)) |
| return false; |
| if (File.getBufferSize() < |
| sizeof(HMapHeader) + sizeof(HMapBucket) * NumBuckets) |
| return false; |
| |
| // Okay, everything looks good. |
| return true; |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // Utility Methods |
| //===----------------------------------------------------------------------===// |
| |
| |
| /// getFileName - Return the filename of the headermap. |
| StringRef HeaderMapImpl::getFileName() const { |
| return FileBuffer->getBufferIdentifier(); |
| } |
| |
| unsigned HeaderMapImpl::getEndianAdjustedWord(unsigned X) const { |
| if (!NeedsBSwap) return X; |
| return llvm::ByteSwap_32(X); |
| } |
| |
| /// getHeader - Return a reference to the file header, in unbyte-swapped form. |
| /// This method cannot fail. |
| const HMapHeader &HeaderMapImpl::getHeader() const { |
| // We know the file is at least as big as the header. Return it. |
| return *reinterpret_cast<const HMapHeader*>(FileBuffer->getBufferStart()); |
| } |
| |
| /// getBucket - Return the specified hash table bucket from the header map, |
| /// bswap'ing its fields as appropriate. If the bucket number is not valid, |
| /// this return a bucket with an empty key (0). |
| HMapBucket HeaderMapImpl::getBucket(unsigned BucketNo) const { |
| assert(FileBuffer->getBufferSize() >= |
| sizeof(HMapHeader) + sizeof(HMapBucket) * BucketNo && |
| "Expected bucket to be in range"); |
| |
| HMapBucket Result; |
| Result.Key = HMAP_EmptyBucketKey; |
| |
| const HMapBucket *BucketArray = |
| reinterpret_cast<const HMapBucket*>(FileBuffer->getBufferStart() + |
| sizeof(HMapHeader)); |
| const HMapBucket *BucketPtr = BucketArray+BucketNo; |
| |
| // Load the values, bswapping as needed. |
| Result.Key = getEndianAdjustedWord(BucketPtr->Key); |
| Result.Prefix = getEndianAdjustedWord(BucketPtr->Prefix); |
| Result.Suffix = getEndianAdjustedWord(BucketPtr->Suffix); |
| return Result; |
| } |
| |
| Optional<StringRef> HeaderMapImpl::getString(unsigned StrTabIdx) const { |
| // Add the start of the string table to the idx. |
| StrTabIdx += getEndianAdjustedWord(getHeader().StringsOffset); |
| |
| // Check for invalid index. |
| if (StrTabIdx >= FileBuffer->getBufferSize()) |
| return None; |
| |
| const char *Data = FileBuffer->getBufferStart() + StrTabIdx; |
| unsigned MaxLen = FileBuffer->getBufferSize() - StrTabIdx; |
| unsigned Len = strnlen(Data, MaxLen); |
| |
| // Check whether the buffer is null-terminated. |
| if (Len == MaxLen && Data[Len - 1]) |
| return None; |
| |
| return StringRef(Data, Len); |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // The Main Drivers |
| //===----------------------------------------------------------------------===// |
| |
| /// dump - Print the contents of this headermap to stderr. |
| LLVM_DUMP_METHOD void HeaderMapImpl::dump() const { |
| const HMapHeader &Hdr = getHeader(); |
| unsigned NumBuckets = getEndianAdjustedWord(Hdr.NumBuckets); |
| |
| llvm::dbgs() << "Header Map " << getFileName() << ":\n " << NumBuckets |
| << ", " << getEndianAdjustedWord(Hdr.NumEntries) << "\n"; |
| |
| auto getStringOrInvalid = [this](unsigned Id) -> StringRef { |
| if (Optional<StringRef> S = getString(Id)) |
| return *S; |
| return "<invalid>"; |
| }; |
| |
| for (unsigned i = 0; i != NumBuckets; ++i) { |
| HMapBucket B = getBucket(i); |
| if (B.Key == HMAP_EmptyBucketKey) continue; |
| |
| StringRef Key = getStringOrInvalid(B.Key); |
| StringRef Prefix = getStringOrInvalid(B.Prefix); |
| StringRef Suffix = getStringOrInvalid(B.Suffix); |
| llvm::dbgs() << " " << i << ". " << Key << " -> '" << Prefix << "' '" |
| << Suffix << "'\n"; |
| } |
| } |
| |
| /// LookupFile - Check to see if the specified relative filename is located in |
| /// this HeaderMap. If so, open it and return its FileEntry. |
| Optional<FileEntryRef> HeaderMap::LookupFile(StringRef Filename, |
| FileManager &FM) const { |
| |
| SmallString<1024> Path; |
| StringRef Dest = HeaderMapImpl::lookupFilename(Filename, Path); |
| if (Dest.empty()) |
| return None; |
| |
| return FM.getOptionalFileRef(Dest); |
| } |
| |
| StringRef HeaderMapImpl::lookupFilename(StringRef Filename, |
| SmallVectorImpl<char> &DestPath) const { |
| const HMapHeader &Hdr = getHeader(); |
| unsigned NumBuckets = getEndianAdjustedWord(Hdr.NumBuckets); |
| |
| // Don't probe infinitely. This should be checked before constructing. |
| assert(llvm::isPowerOf2_32(NumBuckets) && "Expected power of 2"); |
| |
| // Linearly probe the hash table. |
| for (unsigned Bucket = HashHMapKey(Filename);; ++Bucket) { |
| HMapBucket B = getBucket(Bucket & (NumBuckets-1)); |
| if (B.Key == HMAP_EmptyBucketKey) return StringRef(); // Hash miss. |
| |
| // See if the key matches. If not, probe on. |
| Optional<StringRef> Key = getString(B.Key); |
| if (LLVM_UNLIKELY(!Key)) |
| continue; |
| if (!Filename.equals_lower(*Key)) |
| continue; |
| |
| // If so, we have a match in the hash table. Construct the destination |
| // path. |
| Optional<StringRef> Prefix = getString(B.Prefix); |
| Optional<StringRef> Suffix = getString(B.Suffix); |
| |
| DestPath.clear(); |
| if (LLVM_LIKELY(Prefix && Suffix)) { |
| DestPath.append(Prefix->begin(), Prefix->end()); |
| DestPath.append(Suffix->begin(), Suffix->end()); |
| } |
| return StringRef(DestPath.begin(), DestPath.size()); |
| } |
| } |