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1 //===--- HeaderMap.h - A file that acts like dir of symlinks ----*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file defines the HeaderMap interface.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_LEX_HEADERMAP_H
15 #define LLVM_CLANG_LEX_HEADERMAP_H
16 
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 
23 namespace clang {
24 
25 class FileEntry;
26 class FileManager;
27 struct HMapBucket;
28 struct HMapHeader;
29 
30 /// Implementation for \a HeaderMap that doesn't depend on \a FileManager.
31 class HeaderMapImpl {
32   std::unique_ptr<const llvm::MemoryBuffer> FileBuffer;
33   bool NeedsBSwap;
34 
35 public:
HeaderMapImpl(std::unique_ptr<const llvm::MemoryBuffer> File,bool NeedsBSwap)36   HeaderMapImpl(std::unique_ptr<const llvm::MemoryBuffer> File, bool NeedsBSwap)
37       : FileBuffer(std::move(File)), NeedsBSwap(NeedsBSwap) {}
38 
39   // Check for a valid header and extract the byte swap.
40   static bool checkHeader(const llvm::MemoryBuffer &File, bool &NeedsByteSwap);
41 
42   /// If the specified relative filename is located in this HeaderMap return
43   /// the filename it is mapped to, otherwise return an empty StringRef.
44   StringRef lookupFilename(StringRef Filename,
45                            SmallVectorImpl<char> &DestPath) const;
46 
47   /// Return the filename of the headermap.
48   const char *getFileName() const;
49 
50   /// Print the contents of this headermap to stderr.
51   void dump() const;
52 
53 private:
54   unsigned getEndianAdjustedWord(unsigned X) const;
55   const HMapHeader &getHeader() const;
56   HMapBucket getBucket(unsigned BucketNo) const;
57 
58   /// Look up the specified string in the string table.  If the string index is
59   /// not valid, return None.
60   Optional<StringRef> getString(unsigned StrTabIdx) const;
61 };
62 
63 /// This class represents an Apple concept known as a 'header map'.  To the
64 /// \#include file resolution process, it basically acts like a directory of
65 /// symlinks to files.  Its advantages are that it is dense and more efficient
66 /// to create and process than a directory of symlinks.
67 class HeaderMap : private HeaderMapImpl {
HeaderMap(std::unique_ptr<const llvm::MemoryBuffer> File,bool BSwap)68   HeaderMap(std::unique_ptr<const llvm::MemoryBuffer> File, bool BSwap)
69       : HeaderMapImpl(std::move(File), BSwap) {}
70 
71 public:
72   /// This attempts to load the specified file as a header map.  If it doesn't
73   /// look like a HeaderMap, it gives up and returns null.
74   static const HeaderMap *Create(const FileEntry *FE, FileManager &FM);
75 
76   /// Check to see if the specified relative filename is located in this
77   /// HeaderMap.  If so, open it and return its FileEntry.  If RawPath is not
78   /// NULL and the file is found, RawPath will be set to the raw path at which
79   /// the file was found in the file system. For example, for a search path
80   /// ".." and a filename "../file.h" this would be "../../file.h".
81   const FileEntry *LookupFile(StringRef Filename, FileManager &FM) const;
82 
83   using HeaderMapImpl::lookupFilename;
84   using HeaderMapImpl::getFileName;
85   using HeaderMapImpl::dump;
86 };
87 
88 } // end namespace clang.
89 
90 #endif
91