/// <summary>
/// Find the items containing *any word* starting with the word passed
/// and add the union of all of them to the result set passed.
/// </summary>
/// <param name="prefix">Prefix to find</param>
/// <param name="result">Result to which to add matches</param>
public void WhereMatches(ByteBlock prefix, ShortSet result)
{
if (result == null)
{
throw new ArgumentNullException("result");
}
// Split each word in the input value
RangeSet prefixWords = _splitter.Split(prefix);
// Shortcut: If only one word, add directly to result set
if (prefixWords.Count == 1 && prefixWords.Ranges[0].Length == prefix.Length)
{
// Add matches for words starting with this prefix in every block
foreach (WordIndexBlock block in _blocks)
{
block.WhereMatches(prefix, result);
}
}
else
{
// We need to add (OR) the items which match all words (AND) in the split prefix
ShortSet matchesForAllWords = null;
ShortSet matchesForWord = new ShortSet(result.Capacity);
// For each found word, add all matches
for (int i = 0; i < prefixWords.Count; ++i)
{
Range word = prefixWords.Ranges[i];
ByteBlock wordBlock = new ByteBlock(prefix.Array, word.Index, word.Length);
matchesForWord.Clear();
// Add matches for words starting with this prefix in every block
foreach (WordIndexBlock block in _blocks)
{
block.WhereMatches(wordBlock, matchesForWord);
}
// AND matches for this word with each other word in the prefix
if (matchesForAllWords == null)
{
matchesForAllWords = new ShortSet(result.Capacity);
matchesForAllWords.Or(matchesForWord);
}
else
{
matchesForAllWords.And(matchesForWord);
}
}
// OR matches for ALL words with the final result
if (matchesForAllWords != null)
{
result.Or(matchesForAllWords);
}
}
}
/// <summary>
/// Get the IDs listed in the set for a given word and add them
/// to a result ShortSet.
/// </summary>
/// <param name="setId">ID of set/word to add</param>
/// <param name="result">ShortSet to which to add results</param>
public unsafe void GetInSet(ushort setId, ShortSet result)
{
ByteBlock set = _sets[setId];
fixed(byte *array = set.Array)
{
if (set.Length < DenseSetLengthCutoff)
{
// Sparse Set: Add values as individual ushorts.
ushort *valuesForWord = (ushort *)(array + set.Index);
ushort usedLength = FindUsedLength(valuesForWord, (ushort)(set.Length / 2));
result.Or(valuesForWord, usedLength);
}
else
{
// Dense Set: Add values as ulong bits.
ulong *bitsForWord = (ulong *)(array + set.Index);
result.Or(bitsForWord, (ushort)(set.Length / 8));
}
}
}