1 //===--- FileSystemStatCache.h - Caching for 'stat' calls -------*- 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 /// \file 11 /// \brief Defines the FileSystemStatCache interface. 12 /// 13 //===----------------------------------------------------------------------===// 14 15 #ifndef LLVM_CLANG_FILESYSTEMSTATCACHE_H 16 #define LLVM_CLANG_FILESYSTEMSTATCACHE_H 17 18 #include "clang/Basic/LLVM.h" 19 #include "llvm/ADT/OwningPtr.h" 20 #include "llvm/ADT/StringMap.h" 21 #include <sys/types.h> 22 #include <sys/stat.h> 23 24 namespace clang { 25 26 /// \brief Abstract interface for introducing a FileManager cache for 'stat' 27 /// system calls, which is used by precompiled and pretokenized headers to 28 /// improve performance. 29 class FileSystemStatCache { 30 virtual void anchor(); 31 protected: 32 OwningPtr<FileSystemStatCache> NextStatCache; 33 34 public: 35 virtual ~FileSystemStatCache() {} 36 37 enum LookupResult { 38 CacheExists, ///< We know the file exists and its cached stat data. 39 CacheMissing ///< We know that the file doesn't exist. 40 }; 41 42 /// \brief Get the 'stat' information for the specified path, using the cache 43 /// to accelerate it if possible. 44 /// 45 /// \returns \c true if the path does not exist or \c false if it exists. 46 /// 47 /// If FileDescriptor is non-null, then this lookup should only return success 48 /// for files (not directories). If it is null this lookup should only return 49 /// success for directories (not files). On a successful file lookup, the 50 /// implementation can optionally fill in FileDescriptor with a valid 51 /// descriptor and the client guarantees that it will close it. 52 static bool get(const char *Path, struct stat &StatBuf, int *FileDescriptor, 53 FileSystemStatCache *Cache); 54 55 56 /// \brief Sets the next stat call cache in the chain of stat caches. 57 /// Takes ownership of the given stat cache. 58 void setNextStatCache(FileSystemStatCache *Cache) { 59 NextStatCache.reset(Cache); 60 } 61 62 /// \brief Retrieve the next stat call cache in the chain. 63 FileSystemStatCache *getNextStatCache() { return NextStatCache.get(); } 64 65 /// \brief Retrieve the next stat call cache in the chain, transferring 66 /// ownership of this cache (and, transitively, all of the remaining caches) 67 /// to the caller. 68 FileSystemStatCache *takeNextStatCache() { return NextStatCache.take(); } 69 70 protected: 71 virtual LookupResult getStat(const char *Path, struct stat &StatBuf, 72 int *FileDescriptor) = 0; 73 74 LookupResult statChained(const char *Path, struct stat &StatBuf, 75 int *FileDescriptor) { 76 if (FileSystemStatCache *Next = getNextStatCache()) 77 return Next->getStat(Path, StatBuf, FileDescriptor); 78 79 // If we hit the end of the list of stat caches to try, just compute and 80 // return it without a cache. 81 return get(Path, StatBuf, FileDescriptor, 0) ? CacheMissing : CacheExists; 82 } 83 }; 84 85 /// \brief A stat "cache" that can be used by FileManager to keep 86 /// track of the results of stat() calls that occur throughout the 87 /// execution of the front end. 88 class MemorizeStatCalls : public FileSystemStatCache { 89 public: 90 /// \brief The set of stat() calls that have been seen. 91 llvm::StringMap<struct stat, llvm::BumpPtrAllocator> StatCalls; 92 93 typedef llvm::StringMap<struct stat, llvm::BumpPtrAllocator>::const_iterator 94 iterator; 95 96 iterator begin() const { return StatCalls.begin(); } 97 iterator end() const { return StatCalls.end(); } 98 99 virtual LookupResult getStat(const char *Path, struct stat &StatBuf, 100 int *FileDescriptor); 101 }; 102 103 } // end namespace clang 104 105 #endif 106
