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