1 files changed, 242 insertions, 0 deletions
diff --git a/clang/lib/Lex/HeaderMap.cpp b/clang/lib/Lex/HeaderMap.cpp
new file mode 100644
index 000000000000..d44ef29c05d1
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+++ b/clang/lib/Lex/HeaderMap.cpp
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+//===--- 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());
+  }
+}