/// <summary>
/// Insert hash into the RAM Storage. Be careful, there should be a Track object already inserted into the Storage.
/// </summary>
/// <param name = "hash">Hash signature that corresponds to a specific track</param>
public void InsertHash(HashSignature hash)
{
fingerprints[hash.Track].Add(hash);
long[] signature = hash.Signature;
/*Lock insertion in the hash-tables as it keys are verified*/
lock (hashTables.SyncRoot)
{
for (int i = 0; i < numberOfHashTables; i++)
{
if (!hashTables[i].ContainsKey(signature[i]))
{
hashTables[i][signature[i]] = new HashSet<Track>();
}
hashTables[i][signature[i]].Add(hash.Track);
}
}
}
private IEnumerable<HashSignature> GetSignatures(IEnumerable<bool[]> fingerprints, Track track, int hashTables, int hashKeys)
{
List<HashSignature> signatures = new List<HashSignature>();
foreach (bool[] fingerprint in fingerprints)
{
long[] buckets = combinedHashingAlgorithm.Hash(fingerprint, hashTables, hashKeys).Item2;
long[] hashSignature = new long[buckets.Length];
int tableCount = 0;
foreach (long bucket in buckets)
{
hashSignature[tableCount++] = bucket;
}
HashSignature hash = new HashSignature(track, hashSignature); /*associate track to hash-signature*/
signatures.Add(hash);
}
return signatures; /*Return the signatures*/
}
/// <summary>
/// Get tracks that correspond to a specific hash signature and pass the threshold value
/// </summary>
/// <param name = "hashSignature">Hash signature of the track</param>
/// <param name = "hashTableThreshold">Number of threshold tables</param>
/// <returns>Possible candidates</returns>
public Dictionary<Track, int> GetTracks(HashSignature hashSignature, int hashTableThreshold)
{
Dictionary<Track, int> result = new Dictionary<Track, int>();
long[] signature = hashSignature.Signature;
// loop through all 25 hash tables
for (int i = 0; i < numberOfHashTables; i++)
{
if (hashTables[i].ContainsKey(signature[i]))
{
HashSet<Track> tracks = hashTables[i][signature[i]]; // get the set of tracks that map to a specific hash signature
// select all tracks except the original one
foreach (Track track in tracks.Where(t => t.Id != hashSignature.Track.Id))
{
if (!result.ContainsKey(track))
{
result[track] = 1;
}
else
{
result[track]++;
}
}
}
}
// select only those tracks that passed threshold votes
Dictionary<Track, int> filteredResult = result.Where(item => item.Value >= hashTableThreshold).ToDictionary(item => item.Key, item => item.Value);
return filteredResult;
}
