1//===--- HeaderMap.h - A file that acts like dir of symlinks ----*- C++ -*-===//
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 defines the HeaderMap interface.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_CLANG_LEX_HEADERMAP_H
14#define LLVM_CLANG_LEX_HEADERMAP_H
15
16#include "clang/Basic/FileManager.h"
17#include "clang/Basic/LLVM.h"
18#include "llvm/ADT/Optional.h"
19#include "llvm/Support/Compiler.h"
20#include "llvm/Support/MemoryBuffer.h"
21#include <memory>
22
23namespace clang {
24
25struct HMapBucket;
26struct HMapHeader;
27
28/// Implementation for \a HeaderMap that doesn't depend on \a FileManager.
29class HeaderMapImpl {
30  std::unique_ptr<const llvm::MemoryBuffer> FileBuffer;
31  bool NeedsBSwap;
32
33public:
34  HeaderMapImpl(std::unique_ptr<const llvm::MemoryBuffer> File, bool NeedsBSwap)
35      : FileBuffer(std::move(File)), NeedsBSwap(NeedsBSwap) {}
36
37  // Check for a valid header and extract the byte swap.
38  static bool checkHeader(const llvm::MemoryBuffer &File, bool &NeedsByteSwap);
39
40  /// If the specified relative filename is located in this HeaderMap return
41  /// the filename it is mapped to, otherwise return an empty StringRef.
42  StringRef lookupFilename(StringRef Filename,
43                           SmallVectorImpl<char> &DestPath) const;
44
45  /// Return the filename of the headermap.
46  StringRef getFileName() const;
47
48  /// Print the contents of this headermap to stderr.
49  void dump() const;
50
51private:
52  unsigned getEndianAdjustedWord(unsigned X) const;
53  const HMapHeader &getHeader() const;
54  HMapBucket getBucket(unsigned BucketNo) const;
55
56  /// Look up the specified string in the string table.  If the string index is
57  /// not valid, return None.
58  Optional<StringRef> getString(unsigned StrTabIdx) const;
59};
60
61/// This class represents an Apple concept known as a 'header map'.  To the
62/// \#include file resolution process, it basically acts like a directory of
63/// symlinks to files.  Its advantages are that it is dense and more efficient
64/// to create and process than a directory of symlinks.
65class HeaderMap : private HeaderMapImpl {
66  HeaderMap(std::unique_ptr<const llvm::MemoryBuffer> File, bool BSwap)
67      : HeaderMapImpl(std::move(File), BSwap) {}
68
69public:
70  /// This attempts to load the specified file as a header map.  If it doesn't
71  /// look like a HeaderMap, it gives up and returns null.
72  static std::unique_ptr<HeaderMap> Create(const FileEntry *FE,
73                                           FileManager &FM);
74
75  /// Check to see if the specified relative filename is located in this
76  /// HeaderMap.  If so, open it and return its FileEntry.  If RawPath is not
77  /// NULL and the file is found, RawPath will be set to the raw path at which
78  /// the file was found in the file system. For example, for a search path
79  /// ".." and a filename "../file.h" this would be "../../file.h".
80  Optional<FileEntryRef> LookupFile(StringRef Filename, FileManager &FM) const;
81
82  using HeaderMapImpl::lookupFilename;
83  using HeaderMapImpl::getFileName;
84  using HeaderMapImpl::dump;
85};
86
87} // end namespace clang.
88
89#endif
90