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