| //===--- FileSystemStatCache.cpp - Caching for 'stat' calls ---------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines the FileSystemStatCache interface. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "clang/Basic/FileSystemStatCache.h" |
| #include "llvm/Support/Path.h" |
| #include <fcntl.h> |
| |
| // FIXME: This is terrible, we need this for ::close. |
| #if !defined(_MSC_VER) && !defined(__MINGW32__) |
| #include <unistd.h> |
| #include <sys/uio.h> |
| #else |
| #include <io.h> |
| #endif |
| using namespace clang; |
| |
| #if defined(_MSC_VER) |
| #define S_ISDIR(s) ((_S_IFDIR & s) !=0) |
| #endif |
| |
| /// FileSystemStatCache::get - Get the 'stat' information for the specified |
| /// path, using the cache to accelerate it if possible. This returns true if |
| /// the path does not exist or false if it exists. |
| /// |
| /// If FileDescriptor is non-null, then this lookup should only return success |
| /// for files (not directories). If it is null this lookup should only return |
| /// success for directories (not files). On a successful file lookup, the |
| /// implementation can optionally fill in FileDescriptor with a valid |
| /// descriptor and the client guarantees that it will close it. |
| bool FileSystemStatCache::get(const char *Path, struct stat &StatBuf, |
| int *FileDescriptor, FileSystemStatCache *Cache) { |
| LookupResult R; |
| bool isForDir = FileDescriptor == 0; |
| |
| // If we have a cache, use it to resolve the stat query. |
| if (Cache) |
| R = Cache->getStat(Path, StatBuf, FileDescriptor); |
| else if (isForDir) { |
| // If this is a directory and we have no cache, just go to the file system. |
| R = ::stat(Path, &StatBuf) != 0 ? CacheMissing : CacheExists; |
| } else { |
| // Otherwise, we have to go to the filesystem. We can always just use |
| // 'stat' here, but (for files) the client is asking whether the file exists |
| // because it wants to turn around and *open* it. It is more efficient to |
| // do "open+fstat" on success than it is to do "stat+open". |
| // |
| // Because of this, check to see if the file exists with 'open'. If the |
| // open succeeds, use fstat to get the stat info. |
| int OpenFlags = O_RDONLY; |
| #ifdef O_BINARY |
| OpenFlags |= O_BINARY; // Open input file in binary mode on win32. |
| #endif |
| *FileDescriptor = ::open(Path, OpenFlags); |
| |
| if (*FileDescriptor == -1) { |
| // If the open fails, our "stat" fails. |
| R = CacheMissing; |
| } else { |
| // Otherwise, the open succeeded. Do an fstat to get the information |
| // about the file. We'll end up returning the open file descriptor to the |
| // client to do what they please with it. |
| if (::fstat(*FileDescriptor, &StatBuf) == 0) |
| R = CacheExists; |
| else { |
| // fstat rarely fails. If it does, claim the initial open didn't |
| // succeed. |
| R = CacheMissing; |
| ::close(*FileDescriptor); |
| *FileDescriptor = -1; |
| } |
| } |
| } |
| |
| // If the path doesn't exist, return failure. |
| if (R == CacheMissing) return true; |
| |
| // If the path exists, make sure that its "directoryness" matches the clients |
| // demands. |
| if (S_ISDIR(StatBuf.st_mode) != isForDir) { |
| // If not, close the file if opened. |
| if (FileDescriptor && *FileDescriptor != -1) { |
| ::close(*FileDescriptor); |
| *FileDescriptor = -1; |
| } |
| |
| return true; |
| } |
| |
| return false; |
| } |
| |
| |
| MemorizeStatCalls::LookupResult |
| MemorizeStatCalls::getStat(const char *Path, struct stat &StatBuf, |
| int *FileDescriptor) { |
| LookupResult Result = statChained(Path, StatBuf, FileDescriptor); |
| |
| // Do not cache failed stats, it is easy to construct common inconsistent |
| // situations if we do, and they are not important for PCH performance (which |
| // currently only needs the stats to construct the initial FileManager |
| // entries). |
| if (Result == CacheMissing) |
| return Result; |
| |
| // Cache file 'stat' results and directories with absolutely paths. |
| if (!S_ISDIR(StatBuf.st_mode) || llvm::sys::path::is_absolute(Path)) |
| StatCalls[Path] = StatBuf; |
| |
| return Result; |
| } |