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//===--- 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
void FileSystemStatCache::anchor() { }
/// 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;
}
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