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