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/Path.h" 16#include <fcntl.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 31/// FileSystemStatCache::get - Get the 'stat' information for the specified 32/// path, using the cache to accelerate it if possible. This returns true if 33/// the path does not exist or false if it exists. 34/// 35/// If FileDescriptor is non-null, then this lookup should only return success 36/// for files (not directories). If it is null this lookup should only return 37/// success for directories (not files). On a successful file lookup, the 38/// implementation can optionally fill in FileDescriptor with a valid 39/// descriptor and the client guarantees that it will close it. 40bool FileSystemStatCache::get(const char *Path, struct stat &StatBuf, 41 int *FileDescriptor, FileSystemStatCache *Cache) { 42 LookupResult R; 43 bool isForDir = FileDescriptor == 0; 44 45 // If we have a cache, use it to resolve the stat query. 46 if (Cache) 47 R = Cache->getStat(Path, StatBuf, FileDescriptor); 48 else if (isForDir) { 49 // If this is a directory and we have no cache, just go to the file system. 50 R = ::stat(Path, &StatBuf) != 0 ? CacheMissing : CacheExists; 51 } else { 52 // Otherwise, we have to go to the filesystem. We can always just use 53 // 'stat' here, but (for files) the client is asking whether the file exists 54 // because it wants to turn around and *open* it. It is more efficient to 55 // do "open+fstat" on success than it is to do "stat+open". 56 // 57 // Because of this, check to see if the file exists with 'open'. If the 58 // open succeeds, use fstat to get the stat info. 59 int OpenFlags = O_RDONLY; 60#ifdef O_BINARY 61 OpenFlags |= O_BINARY; // Open input file in binary mode on win32. 62#endif 63 *FileDescriptor = ::open(Path, OpenFlags); 64 65 if (*FileDescriptor == -1) { 66 // If the open fails, our "stat" fails. 67 R = CacheMissing; 68 } else { 69 // Otherwise, the open succeeded. Do an fstat to get the information 70 // about the file. We'll end up returning the open file descriptor to the 71 // client to do what they please with it. 72 if (::fstat(*FileDescriptor, &StatBuf) == 0) 73 R = CacheExists; 74 else { 75 // fstat rarely fails. If it does, claim the initial open didn't 76 // succeed. 77 R = CacheMissing; 78 ::close(*FileDescriptor); 79 *FileDescriptor = -1; 80 } 81 } 82 } 83 84 // If the path doesn't exist, return failure. 85 if (R == CacheMissing) return true; 86 87 // If the path exists, make sure that its "directoryness" matches the clients 88 // demands. 89 if (S_ISDIR(StatBuf.st_mode) != isForDir) { 90 // If not, close the file if opened. 91 if (FileDescriptor && *FileDescriptor != -1) { 92 ::close(*FileDescriptor); 93 *FileDescriptor = -1; 94 } 95 96 return true; 97 } 98 99 return false; 100} 101 102 103MemorizeStatCalls::LookupResult 104MemorizeStatCalls::getStat(const char *Path, struct stat &StatBuf, 105 int *FileDescriptor) { 106 LookupResult Result = statChained(Path, StatBuf, FileDescriptor); 107 108 // Do not cache failed stats, it is easy to construct common inconsistent 109 // situations if we do, and they are not important for PCH performance (which 110 // currently only needs the stats to construct the initial FileManager 111 // entries). 112 if (Result == CacheMissing) 113 return Result; 114 115 // Cache file 'stat' results and directories with absolutely paths. 116 if (!S_ISDIR(StatBuf.st_mode) || llvm::sys::path::is_absolute(Path)) 117 StatCalls[Path] = StatBuf; 118 119 return Result; 120} 121