FileSystemStatCache.cpp revision 263508
1//===--- FileSystemStatCache.cpp - Caching for 'stat' calls ---------------===// 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#include "clang/Basic/FileSystemStatCache.h" 15#include "llvm/Support/FileSystem.h" 16#include "llvm/Support/Path.h" 17 18// FIXME: This is terrible, we need this for ::close. 19#if !defined(_MSC_VER) && !defined(__MINGW32__) 20#include <unistd.h> 21#include <sys/uio.h> 22#else 23#include <io.h> 24#endif 25using namespace clang; 26 27#if defined(_MSC_VER) 28#define S_ISDIR(s) ((_S_IFDIR & s) !=0) 29#endif 30 31void FileSystemStatCache::anchor() { } 32 33static void copyStatusToFileData(const llvm::sys::fs::file_status &Status, 34 FileData &Data) { 35 Data.Size = Status.getSize(); 36 Data.ModTime = Status.getLastModificationTime().toEpochTime(); 37 Data.UniqueID = Status.getUniqueID(); 38 Data.IsDirectory = is_directory(Status); 39 Data.IsNamedPipe = Status.type() == llvm::sys::fs::file_type::fifo_file; 40 Data.InPCH = false; 41} 42 43/// FileSystemStatCache::get - Get the 'stat' information for the specified 44/// path, using the cache to accelerate it if possible. This returns true if 45/// the path does not exist or 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. 52bool FileSystemStatCache::get(const char *Path, FileData &Data, bool isFile, 53 int *FileDescriptor, FileSystemStatCache *Cache) { 54 LookupResult R; 55 bool isForDir = !isFile; 56 57 // If we have a cache, use it to resolve the stat query. 58 if (Cache) 59 R = Cache->getStat(Path, Data, isFile, FileDescriptor); 60 else if (isForDir || !FileDescriptor) { 61 // If this is a directory or a file descriptor is not needed and we have 62 // no cache, just go to the file system. 63 llvm::sys::fs::file_status Status; 64 if (llvm::sys::fs::status(Path, Status)) { 65 R = CacheMissing; 66 } else { 67 R = CacheExists; 68 copyStatusToFileData(Status, Data); 69 } 70 } else { 71 // Otherwise, we have to go to the filesystem. We can always just use 72 // 'stat' here, but (for files) the client is asking whether the file exists 73 // because it wants to turn around and *open* it. It is more efficient to 74 // do "open+fstat" on success than it is to do "stat+open". 75 // 76 // Because of this, check to see if the file exists with 'open'. If the 77 // open succeeds, use fstat to get the stat info. 78 llvm::error_code EC = llvm::sys::fs::openFileForRead(Path, *FileDescriptor); 79 80 if (EC) { 81 // If the open fails, our "stat" fails. 82 R = CacheMissing; 83 } else { 84 // Otherwise, the open succeeded. Do an fstat to get the information 85 // about the file. We'll end up returning the open file descriptor to the 86 // client to do what they please with it. 87 llvm::sys::fs::file_status Status; 88 if (!llvm::sys::fs::status(*FileDescriptor, Status)) { 89 R = CacheExists; 90 copyStatusToFileData(Status, Data); 91 } else { 92 // fstat rarely fails. If it does, claim the initial open didn't 93 // succeed. 94 R = CacheMissing; 95 ::close(*FileDescriptor); 96 *FileDescriptor = -1; 97 } 98 } 99 } 100 101 // If the path doesn't exist, return failure. 102 if (R == CacheMissing) return true; 103 104 // If the path exists, make sure that its "directoryness" matches the clients 105 // demands. 106 if (Data.IsDirectory != isForDir) { 107 // If not, close the file if opened. 108 if (FileDescriptor && *FileDescriptor != -1) { 109 ::close(*FileDescriptor); 110 *FileDescriptor = -1; 111 } 112 113 return true; 114 } 115 116 return false; 117} 118 119MemorizeStatCalls::LookupResult 120MemorizeStatCalls::getStat(const char *Path, FileData &Data, bool isFile, 121 int *FileDescriptor) { 122 LookupResult Result = statChained(Path, Data, isFile, FileDescriptor); 123 124 // Do not cache failed stats, it is easy to construct common inconsistent 125 // situations if we do, and they are not important for PCH performance (which 126 // currently only needs the stats to construct the initial FileManager 127 // entries). 128 if (Result == CacheMissing) 129 return Result; 130 131 // Cache file 'stat' results and directories with absolutely paths. 132 if (!Data.IsDirectory || llvm::sys::path::is_absolute(Path)) 133 StatCalls[Path] = Data; 134 135 return Result; 136} 137