public void Delete(long objId, SimhashResult simhash)
{
var store = new StringBuilder(41);
foreach (var key in GetEnumerableKeys(simhash))
{
var v = BuildKey(objId, simhash, store);
if (_bucket.TryGetValue(key, out var set))
{
set.Remove(v);
}
}
}
public void Add(long objId, SimhashResult simhash)
{
var store = new StringBuilder(41);
foreach (var key in GetEnumerableKeys(simhash))
{
var v = BuildKey(objId, simhash, store);
if (!_bucket.TryGetValue(key, out var values))
{
var bucketHashSet = new HashSet <string>()
{
v
};
_bucket.Add(key, bucketHashSet);
}
else
{
values.Add(v);
}
}
}
private static IEnumerable <string> GetEnumerableKeys(SimhashResult simhash)
{
if (_offsets.Count <= 0)
{
yield break;
}
var store = new StringBuilder(41);
for (var i = 0; i < _offsets.Count; i++)
{
var off = i == (_offsets.Count - 1) ? FpSizeStatic - _offsets[i] : _offsets[i + 1] - _offsets[i];
var m = (Math.Pow(2, off)) - 1;
var m64 = Convert.ToUInt64(m);
var c = simhash.Value >> _offsets[i] & m64;
yield return(store.Clear().Append(c).Append(',').Append(i).ToString());
}
}
public HashSet <long> GetNearDups(SimhashResult simhash)
{
/*
* "simhash" is an instance of Simhash
* return a list of obj_id, which is in type of long (for now)
*/
if (Simhash.FpSize != _fpSize)
{
throw new Exception();
}
var ans = new HashSet <long>();
foreach (var key in GetEnumerableKeys(simhash))
{
if (!_bucket.TryGetValue(key, out var dups))
{
continue;
}
foreach (var dup in dups)
{
var parts = dup.Split(',');
var fp = Convert.ToUInt64(parts[0]);
var objId = Convert.ToInt64(parts[1]);
var sim2 = new SimhashResult(fp);
var d = simhash.Distance(sim2);
if (d <= _kDistance)
{
ans.Add(objId);
}
}
}
return(ans);
}
private static string BuildKey(long objId, SimhashResult simhash, StringBuilder builder)
=> builder.Clear().Append(simhash.Value).Append(',').Append(objId).ToString();
public List <string> GetListKeys(SimhashResult simhash) => GetEnumerableKeys(simhash).ToList();
