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();
}
}
