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);
public LTrieNodeStruct(long ownPointer, ReadOnlySpan <byte> data)
{
var lineLen = data.ReadUInt16BigEndian();
OwnPointer = ownPointer;
ExternalLinkSlotCount = (lineLen - Sizes.DefaultPointerLen) / Sizes.ExternalLinkLength;
InternalLinkPointer = (long)data.Slice(2).BigEndianToLongDynamic();
FirstExternalLink = new LTrieNodeExternalLinkStruct(OwnPointer + 2 + Sizes.DefaultPointerLen, data.Slice(2 + Sizes.DefaultPointerLen));
}
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));
}
internal async IAsyncEnumerable <LTrieValue> EnumerateStartsWith(ReadOnlyMemory <byte> startWithKey, EnumerationOrder order)
{
AssertNotEnumerating();
try
{
enumerating = true;
var res = await FindBestMatch(startWithKey);
// In this case, we don't have an exact match, and no children either
if (res.ValueLink is null && res.MissingValue is byte)
{
yield break;
}
if (res.ValueLink is Link l && l.Label is null)
{
var record = await GetValueIfStartWith(startWithKey, res.ValueLink.Pointer);
if (record is LTrieValue)
{
yield return(record);
}
}
var nextNodes = new Stack <(int Depth, LTrieNodeStruct Node, int NextLinkIndex)>();
(int Depth, LTrieNodeStruct Node, int NextLinkIndex)current =
(res.BestNode.MinKeyLength, await ReadNodeStruct(res.BestNode.OwnPointer), 0);
while (current.Depth > -1 || nextNodes.TryPop(out current))
{
LTrieNodeExternalLinkStruct link = default;
if (current.NextLinkIndex == 0 && current.Node.ExternalLinkSlotCount == 1)
{
link = current.Node.FirstExternalLink;
}
else
{
link = await GetOrderedExternalLink(current.Node, current.NextLinkIndex, order);
}
if (link.Pointer == 0)
{
current.Depth = -1;
continue;
}
if (!link.LinkToNode)
{
var record = await GetValueIfStartWith(startWithKey, link.Pointer);
if (record is LTrieValue)
{
yield return(record);
}
current.NextLinkIndex++;
if (current.NextLinkIndex >= current.Node.ExternalLinkSlotCount)
{
current.Depth = -1;
}
}
else
{
var childNode = await ReadNodeStruct(link.Pointer);
if (childNode.InternalLinkPointer != 0)
{
var record = await GetValueIfStartWith(startWithKey, childNode.InternalLinkPointer);
if (record is LTrieValue)
{
yield return(record);
}
}
current.NextLinkIndex++;
if (current.NextLinkIndex < current.Node.ExternalLinkSlotCount)
{
nextNodes.Push((current.Depth, current.Node, current.NextLinkIndex));
}
current = (current.Depth + 1, childNode, 0);
if (current.NextLinkIndex >= childNode.ExternalLinkSlotCount)
{
current.Depth = -1;
}
}
}
}
finally
{
enumerating = false;
}
}
