Ejemplo n.º 1
0
        public SyncIndexInput(SyncDirectory directory, string name)
        {
            if (directory == null)
            {
                throw new ArgumentNullException(nameof(directory));
            }

            _name          = name;
            _syncDirectory = directory;

#if FULLDEBUG
            Trace.WriteLine($"opening {_name} ");
#endif
            _fileMutex = SyncMutexManager.GrabMutex(_syncDirectory, _name);
            _fileMutex.WaitOne();
            try
            {
                var fileName = _name;

                var fFileNeeded = false;
                if (!CacheDirectory.FileExists(fileName))
                {
                    fFileNeeded = true;
                }
                else
                {
                    long cachedLength = CacheDirectory.FileLength(fileName);
                    long masterLength = MasterDirectory.FileLength(fileName);

                    if (cachedLength != masterLength)
                    {
                        fFileNeeded = true;
                    }
                    else
                    {
                        long cacheDate  = CacheDirectory.FileModified(fileName);
                        long masterDate = MasterDirectory.FileModified(fileName);

                        //we need to compare to the second instead of by ticks because when we call
                        //TouchFile in SyncIndexOutput this won't set the files to be identical
                        DateTime start = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
                        var      cachedLastModifiedUTC = start.AddMilliseconds(cacheDate).ToUniversalTime();
                        var      masterLastModifiedUTC = start.AddMilliseconds(masterDate).ToUniversalTime();

                        if (cachedLastModifiedUTC != masterLastModifiedUTC)
                        {
                            var timeSpan = masterLastModifiedUTC.Subtract(cachedLastModifiedUTC);

                            //NOTE: This heavily depends on TouchFile in SyncIndexOutput which sets both the
                            //master and slave files to be 'Now', in theory this operation shouldn't
                            //make the file times any bigger than 1 second
                            if (timeSpan.TotalSeconds > 2)
                            {
                                fFileNeeded = true;
                            }
                            else
                            {
#if FULLDEBUG
                                Debug.WriteLine(timeSpan.TotalSeconds);
#endif
                                // file not needed
                            }
                        }
                    }
                }

                // if the file does not exist
                // or if it exists and it is older then the lastmodified time in the blobproperties (which always comes from the blob storage)
                if (fFileNeeded)
                {
                    //get the master file stream
                    using (var masterStream = new StreamInput(MasterDirectory.OpenInput(fileName)))
                        using (var cacheStream = _syncDirectory.CreateCachedOutputAsStream(fileName))
                        {
                            //copy this to the cached file stream
                            masterStream.CopyTo(cacheStream);

                            cacheStream.Flush();
                            Debug.WriteLine($"GET {_name} RETREIVED {cacheStream.Length} bytes");
                        }

                    // and open it as an input
                    _indexInput = CacheDirectory.OpenInput(fileName);
                }
                else
                {
#if FULLDEBUG
                    Debug.WriteLine($"Using cached file for {_name}");
#endif

                    // open the file in read only mode
                    _indexInput = CacheDirectory.OpenInput(fileName);
                }
            }
            finally
            {
                _fileMutex.ReleaseMutex();
            }
        }