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/stat.h> 22 #include <sys/types.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: ~FileSystemStatCache()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 isFile is true, then this lookup should only return success for files 48 /// (not directories). If it is false 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, 53 bool isFile, int *FileDescriptor, 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. setNextStatCache(FileSystemStatCache * Cache)58 void setNextStatCache(FileSystemStatCache *Cache) { 59 NextStatCache.reset(Cache); 60 } 61 62 /// \brief Retrieve the next stat call cache in the chain. getNextStatCache()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. takeNextStatCache()68 FileSystemStatCache *takeNextStatCache() { return NextStatCache.take(); } 69 70 protected: 71 virtual LookupResult getStat(const char *Path, struct stat &StatBuf, 72 bool isFile, int *FileDescriptor) = 0; 73 statChained(const char * Path,struct stat & StatBuf,bool isFile,int * FileDescriptor)74 LookupResult statChained(const char *Path, struct stat &StatBuf, 75 bool isFile, int *FileDescriptor) { 76 if (FileSystemStatCache *Next = getNextStatCache()) 77 return Next->getStat(Path, StatBuf, isFile, 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, 82 isFile, FileDescriptor, 0) ? CacheMissing : CacheExists; 83 } 84 }; 85 86 /// \brief A stat "cache" that can be used by FileManager to keep 87 /// track of the results of stat() calls that occur throughout the 88 /// execution of the front end. 89 class MemorizeStatCalls : public FileSystemStatCache { 90 public: 91 /// \brief The set of stat() calls that have been seen. 92 llvm::StringMap<struct stat, llvm::BumpPtrAllocator> StatCalls; 93 94 typedef llvm::StringMap<struct stat, llvm::BumpPtrAllocator>::const_iterator 95 iterator; 96 begin()97 iterator begin() const { return StatCalls.begin(); } end()98 iterator end() const { return StatCalls.end(); } 99 100 virtual LookupResult getStat(const char *Path, struct stat &StatBuf, 101 bool isFile, int *FileDescriptor); 102 }; 103 104 } // end namespace clang 105 106 #endif 107