1 files changed, 120 insertions, 0 deletions
diff --git a/lib/Basic/FileSystemStatCache.cpp b/lib/Basic/FileSystemStatCache.cpp
new file mode 100644
index 000000000000..c8b07af295da
--- /dev/null
+++ b/lib/Basic/FileSystemStatCache.cpp
@@ -0,0 +1,120 @@
+//===--- 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;
+}