internal async ValueTask <MatchResult> FindBestMatch(ReadOnlyMemory <byte> key)
{
LTrieNodeStruct gn = await ReadNodeStruct();
LTrieNodeStruct prev = default;
if (key.Length == 0)
{
return(await CreateMatchResult(0, gn.GetInternalLinkObject(), gn, prev));
}
for (int i = 0; i < key.Length; i++)
{
LTrieNodeExternalLinkStruct externalLink = default;
if (key.Span[i] == gn.FirstExternalLink.Value)
{
externalLink = gn.FirstExternalLink;
}
else if (gn.ExternalLinkSlotCount > 1)
{
externalLink = await GetRemainingExternalLink(gn, key.Span[i]);
}
if (externalLink.Pointer == 0)
{
var result = await CreateMatchResult(i, null, gn, prev);
result.MissingValue = key.Span[i];
result.KeyIndex = i;
return(result);
}
if (!externalLink.LinkToNode)
{
var result = await CreateMatchResult(i, externalLink.ToLinkObject(), gn, prev);
result.KeyIndex = i;
return(result);
}
prev = gn;
gn = await ReadNodeStruct(externalLink.Pointer);
}
return(await CreateMatchResult(key.Length, gn.GetInternalLinkObject(), gn, prev));
}
private async ValueTask <LTrieNode> ToLTrieNodeObject(LTrieNodeStruct nodeStruct, int minKeyLength)
{
LTrieNode?cached = null;
NodeCache?.TryGetValue(nodeStruct.OwnPointer, out cached);
if (cached is LTrieNode)
{
if (cached.MinKeyLength != minKeyLength)
{
throw new InvalidOperationException("Inconsistent depth, bug in DBTrie");
}
if (cached.OwnPointer != nodeStruct.OwnPointer)
{
throw new InvalidOperationException("Inconsistent pointer in cache, bug in DBTrie");
}
await cached.AssertConsistency();
return(cached);
}
var node = await FetchNodeFromStruct(nodeStruct, minKeyLength);
NodeCache?.Add(nodeStruct.OwnPointer, node);
return(node);
}
private async ValueTask <LTrieNodeExternalLinkStruct> GetRemainingExternalLink(LTrieNodeStruct gn, byte value)
{
IMemoryOwner <byte>?owner = null;
var restLength = gn.GetRestLength();
var secondLinkPointer = gn.GetSecondExternalLinkOwnPointer();
if (!Storage.TryDirectRead(secondLinkPointer, restLength, out var memory))
{
owner = MemoryPool.Rent(restLength);
var outputMemory = owner.Memory.Slice(0, restLength);
await Storage.Read(secondLinkPointer, outputMemory);
memory = outputMemory;
}
for (int linkIndex = 0; linkIndex < gn.ExternalLinkSlotCount - 1; linkIndex++)
{
var linkOwnPointer = secondLinkPointer + linkIndex * Sizes.ExternalLinkLength;
var l = new LTrieNodeExternalLinkStruct(linkOwnPointer, memory.Span.Slice(linkIndex * Sizes.ExternalLinkLength, Sizes.ExternalLinkLength));
if (l.Pointer != 0 && l.Value == value)
{
owner?.Dispose();
return(l);
}
}
owner?.Dispose();
return(default);