"Fossies" - the Fresh Open Source Software Archive

Member "cfe-9.0.0.src/lib/Basic/FileSystemStatCache.cpp" (16 Apr 2019, 4560 Bytes) of package /linux/misc/cfe-9.0.0.src.tar.xz:


As a special service "Fossies" has tried to format the requested source page into HTML format using (guessed) C and C++ source code syntax highlighting (style: standard) with prefixed line numbers and code folding option. Alternatively you can here view or download the uninterpreted source code file. See also the latest Fossies "Diffs" side-by-side code changes report for "FileSystemStatCache.cpp": 8.0.1_vs_9.0.0.

    1 //===- FileSystemStatCache.cpp - Caching for 'stat' calls -----------------===//
    2 //
    3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
    4 // See https://llvm.org/LICENSE.txt for license information.
    5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
    6 //
    7 //===----------------------------------------------------------------------===//
    8 //
    9 //  This file defines the FileSystemStatCache interface.
   10 //
   11 //===----------------------------------------------------------------------===//
   12 
   13 #include "clang/Basic/FileSystemStatCache.h"
   14 #include "llvm/Support/Chrono.h"
   15 #include "llvm/Support/ErrorOr.h"
   16 #include "llvm/Support/Path.h"
   17 #include "llvm/Support/VirtualFileSystem.h"
   18 #include <utility>
   19 
   20 using namespace clang;
   21 
   22 void FileSystemStatCache::anchor() {}
   23 
   24 /// FileSystemStatCache::get - Get the 'stat' information for the specified
   25 /// path, using the cache to accelerate it if possible.  This returns true if
   26 /// the path does not exist or false if it exists.
   27 ///
   28 /// If isFile is true, then this lookup should only return success for files
   29 /// (not directories).  If it is false this lookup should only return
   30 /// success for directories (not files).  On a successful file lookup, the
   31 /// implementation can optionally fill in FileDescriptor with a valid
   32 /// descriptor and the client guarantees that it will close it.
   33 std::error_code
   34 FileSystemStatCache::get(StringRef Path, llvm::vfs::Status &Status,
   35                          bool isFile, std::unique_ptr<llvm::vfs::File> *F,
   36                          FileSystemStatCache *Cache,
   37                          llvm::vfs::FileSystem &FS) {
   38   bool isForDir = !isFile;
   39   std::error_code RetCode;
   40 
   41   // If we have a cache, use it to resolve the stat query.
   42   if (Cache)
   43     RetCode = Cache->getStat(Path, Status, isFile, F, FS);
   44   else if (isForDir || !F) {
   45     // If this is a directory or a file descriptor is not needed and we have
   46     // no cache, just go to the file system.
   47     llvm::ErrorOr<llvm::vfs::Status> StatusOrErr = FS.status(Path);
   48     if (!StatusOrErr) {
   49       RetCode = StatusOrErr.getError();
   50     } else {
   51       Status = *StatusOrErr;
   52     }
   53   } else {
   54     // Otherwise, we have to go to the filesystem.  We can always just use
   55     // 'stat' here, but (for files) the client is asking whether the file exists
   56     // because it wants to turn around and *open* it.  It is more efficient to
   57     // do "open+fstat" on success than it is to do "stat+open".
   58     //
   59     // Because of this, check to see if the file exists with 'open'.  If the
   60     // open succeeds, use fstat to get the stat info.
   61     auto OwnedFile = FS.openFileForRead(Path);
   62 
   63     if (!OwnedFile) {
   64       // If the open fails, our "stat" fails.
   65       RetCode = OwnedFile.getError();
   66     } else {
   67       // Otherwise, the open succeeded.  Do an fstat to get the information
   68       // about the file.  We'll end up returning the open file descriptor to the
   69       // client to do what they please with it.
   70       llvm::ErrorOr<llvm::vfs::Status> StatusOrErr = (*OwnedFile)->status();
   71       if (StatusOrErr) {
   72         Status = *StatusOrErr;
   73         *F = std::move(*OwnedFile);
   74       } else {
   75         // fstat rarely fails.  If it does, claim the initial open didn't
   76         // succeed.
   77         *F = nullptr;
   78         RetCode = StatusOrErr.getError();
   79       }
   80     }
   81   }
   82 
   83   // If the path doesn't exist, return failure.
   84   if (RetCode)
   85     return RetCode;
   86 
   87   // If the path exists, make sure that its "directoryness" matches the clients
   88   // demands.
   89   if (Status.isDirectory() != isForDir) {
   90     // If not, close the file if opened.
   91     if (F)
   92       *F = nullptr;
   93     return std::make_error_code(
   94         Status.isDirectory() ?
   95             std::errc::is_a_directory : std::errc::not_a_directory);
   96   }
   97 
   98   return std::error_code();
   99 }
  100 
  101 std::error_code
  102 MemorizeStatCalls::getStat(StringRef Path, llvm::vfs::Status &Status,
  103                            bool isFile,
  104                            std::unique_ptr<llvm::vfs::File> *F,
  105                            llvm::vfs::FileSystem &FS) {
  106   auto err = get(Path, Status, isFile, F, nullptr, FS);
  107   if (err) {
  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
  110     // (which currently only needs the stats to construct the initial
  111     // FileManager entries).
  112     return err;
  113   }
  114 
  115   // Cache file 'stat' results and directories with absolutely paths.
  116   if (!Status.isDirectory() || llvm::sys::path::is_absolute(Path))
  117     StatCalls[Path] = Status;
  118 
  119   return std::error_code();
  120 }