1218887Sdim//===--- FileSystemStatCache.cpp - Caching for 'stat' calls ---------------===// 2218887Sdim// 3218887Sdim// The LLVM Compiler Infrastructure 4218887Sdim// 5218887Sdim// This file is distributed under the University of Illinois Open Source 6218887Sdim// License. See LICENSE.TXT for details. 7218887Sdim// 8218887Sdim//===----------------------------------------------------------------------===// 9218887Sdim// 10218887Sdim// This file defines the FileSystemStatCache interface. 11218887Sdim// 12218887Sdim//===----------------------------------------------------------------------===// 13218887Sdim 14218887Sdim#include "clang/Basic/FileSystemStatCache.h" 15218887Sdim#include "llvm/Support/Path.h" 16218887Sdim#include <fcntl.h> 17218887Sdim 18218887Sdim// FIXME: This is terrible, we need this for ::close. 19218887Sdim#if !defined(_MSC_VER) && !defined(__MINGW32__) 20218887Sdim#include <unistd.h> 21218887Sdim#include <sys/uio.h> 22218887Sdim#else 23218887Sdim#include <io.h> 24218887Sdim#endif 25218887Sdimusing namespace clang; 26218887Sdim 27218887Sdim#if defined(_MSC_VER) 28218887Sdim#define S_ISDIR(s) ((_S_IFDIR & s) !=0) 29218887Sdim#endif 30218887Sdim 31234353Sdimvoid FileSystemStatCache::anchor() { } 32234353Sdim 33218887Sdim/// FileSystemStatCache::get - Get the 'stat' information for the specified 34218887Sdim/// path, using the cache to accelerate it if possible. This returns true if 35218887Sdim/// the path does not exist or false if it exists. 36218887Sdim/// 37249423Sdim/// If isFile is true, then this lookup should only return success for files 38249423Sdim/// (not directories). If it is false this lookup should only return 39218887Sdim/// success for directories (not files). On a successful file lookup, the 40218887Sdim/// implementation can optionally fill in FileDescriptor with a valid 41218887Sdim/// descriptor and the client guarantees that it will close it. 42218887Sdimbool FileSystemStatCache::get(const char *Path, struct stat &StatBuf, 43249423Sdim bool isFile, int *FileDescriptor, 44249423Sdim FileSystemStatCache *Cache) { 45218887Sdim LookupResult R; 46249423Sdim bool isForDir = !isFile; 47218887Sdim 48218887Sdim // If we have a cache, use it to resolve the stat query. 49218887Sdim if (Cache) 50249423Sdim R = Cache->getStat(Path, StatBuf, isFile, FileDescriptor); 51249423Sdim else if (isForDir || !FileDescriptor) { 52249423Sdim // If this is a directory or a file descriptor is not needed and we have 53249423Sdim // no cache, just go to the file system. 54218887Sdim R = ::stat(Path, &StatBuf) != 0 ? CacheMissing : CacheExists; 55218887Sdim } else { 56218887Sdim // Otherwise, we have to go to the filesystem. We can always just use 57218887Sdim // 'stat' here, but (for files) the client is asking whether the file exists 58218887Sdim // because it wants to turn around and *open* it. It is more efficient to 59218887Sdim // do "open+fstat" on success than it is to do "stat+open". 60218887Sdim // 61218887Sdim // Because of this, check to see if the file exists with 'open'. If the 62218887Sdim // open succeeds, use fstat to get the stat info. 63218887Sdim int OpenFlags = O_RDONLY; 64218887Sdim#ifdef O_BINARY 65218887Sdim OpenFlags |= O_BINARY; // Open input file in binary mode on win32. 66218887Sdim#endif 67218887Sdim *FileDescriptor = ::open(Path, OpenFlags); 68218887Sdim 69218887Sdim if (*FileDescriptor == -1) { 70218887Sdim // If the open fails, our "stat" fails. 71218887Sdim R = CacheMissing; 72218887Sdim } else { 73218887Sdim // Otherwise, the open succeeded. Do an fstat to get the information 74218887Sdim // about the file. We'll end up returning the open file descriptor to the 75218887Sdim // client to do what they please with it. 76218887Sdim if (::fstat(*FileDescriptor, &StatBuf) == 0) 77218887Sdim R = CacheExists; 78218887Sdim else { 79218887Sdim // fstat rarely fails. If it does, claim the initial open didn't 80218887Sdim // succeed. 81218887Sdim R = CacheMissing; 82218887Sdim ::close(*FileDescriptor); 83218887Sdim *FileDescriptor = -1; 84218887Sdim } 85218887Sdim } 86218887Sdim } 87218887Sdim 88218887Sdim // If the path doesn't exist, return failure. 89218887Sdim if (R == CacheMissing) return true; 90218887Sdim 91218887Sdim // If the path exists, make sure that its "directoryness" matches the clients 92218887Sdim // demands. 93218887Sdim if (S_ISDIR(StatBuf.st_mode) != isForDir) { 94218887Sdim // If not, close the file if opened. 95218887Sdim if (FileDescriptor && *FileDescriptor != -1) { 96218887Sdim ::close(*FileDescriptor); 97218887Sdim *FileDescriptor = -1; 98218887Sdim } 99218887Sdim 100218887Sdim return true; 101218887Sdim } 102218887Sdim 103218887Sdim return false; 104218887Sdim} 105218887Sdim 106218887Sdim 107218887SdimMemorizeStatCalls::LookupResult 108218887SdimMemorizeStatCalls::getStat(const char *Path, struct stat &StatBuf, 109249423Sdim bool isFile, int *FileDescriptor) { 110249423Sdim LookupResult Result = statChained(Path, StatBuf, isFile, FileDescriptor); 111218887Sdim 112218887Sdim // Do not cache failed stats, it is easy to construct common inconsistent 113218887Sdim // situations if we do, and they are not important for PCH performance (which 114218887Sdim // currently only needs the stats to construct the initial FileManager 115218887Sdim // entries). 116218887Sdim if (Result == CacheMissing) 117218887Sdim return Result; 118218887Sdim 119218887Sdim // Cache file 'stat' results and directories with absolutely paths. 120218887Sdim if (!S_ISDIR(StatBuf.st_mode) || llvm::sys::path::is_absolute(Path)) 121218887Sdim StatCalls[Path] = StatBuf; 122218887Sdim 123218887Sdim return Result; 124218887Sdim} 125