/// <summary> Instantiates a new DocumentCache. </summary>
/// <param name="cachePath"> Specifies the path to use to store cached items. </param>
public DocumentCache(string cachePath, int size)
{
// Prepare the folder
_cachePath = cachePath;
// Prepare the structures
_identifiers = new IdentifierIndex();
_cRC32s = new Dictionary <string, uint>(size);
_cache = new FixedSizeCache <string, string>(size);
LockDirectory();
try
{
try
{
DateTime indexFileTime = DateTime.MinValue; // Init as invalid
string indexFileName = Path.Combine(_cachePath, IndexFileName);
string[] cacheFiles = Directory.GetFiles(_cachePath, "*" + CacheFileExtension);
// Load the identifier index
if (File.Exists(indexFileName))
{
indexFileTime = File.GetLastWriteTimeUtc(indexFileName);
using (Stream stream = new FileStream(indexFileName, FileMode.Open, FileAccess.Read))
{
_identifiers.Load(stream);
}
// Initialize the CRC32s
string cRC32TableFileName = Path.Combine(_cachePath, RC32FileName);
if (File.Exists(cRC32TableFileName))
{
if (File.GetLastWriteTimeUtc(cRC32TableFileName) == indexFileTime)
{
using (FileStream stream = new FileStream(cRC32TableFileName, FileMode.Open, FileAccess.Read))
{
StreamUtility.LoadDictionary(stream, _cRC32s, typeof(String), typeof(UInt32));
}
}
else
{
indexFileTime = DateTime.MinValue; // CRC32 and Index file times doen't match. Invalid index.
}
}
else
{
indexFileTime = DateTime.MinValue; // No CRC32 table. Invalid index.
}
// Verify that ther are no cache files newer than the index
foreach (string fileName in cacheFiles)
{
if (File.GetLastWriteTimeUtc(fileName) > indexFileTime)
{
indexFileTime = DateTime.MinValue;
break;
}
}
}
if (indexFileTime == DateTime.MinValue) // If cache invalid, delete the files and clear cache
{
// Delete any existing cache files in the cache directory and clear the Identifiers
foreach (string fileName in Directory.GetFiles(_cachePath, "*." + CacheFileExtension))
{
if (File.GetLastWriteTimeUtc(fileName) > indexFileTime)
{
File.Delete(fileName);
}
}
_identifiers.Clear();
_cRC32s.Clear();
}
// Don't bother initializing the fixed sized cache. We'll let it be populated as requests come in. As a result, if the cache size has been reduced, it
// will not be effective until the new cache size limit has been reached.
}
catch
{
//Prevent future problems by clearing the directory
EmptyCacheDirectory();
throw;
}
}
catch
{
UnlockDirectory(false);
throw;
}
}
/// <summary> Loads index entries from XML data contained within a stream. </summary>
public void Load(Stream stream)
{
StreamUtility.LoadDictionary(stream, _table, typeof(String), typeof(String));
}