/// <summary>
/// Entry point to the detection process. Provided with a <see cref="Match"/>
/// configured with the information about the request.
/// </summary>
/// <remarks>
/// The dataSet may be used by other threads in parallel and is not assumed to be used
/// by only one detection process at a time.
/// </remarks>
/// <param name="match">
/// The match object to be updated.
/// </param>
/// <remarks>
/// The memory implementation of the data set will always perform fastest but does
/// consume more memory.
/// </remarks>
internal static void Match(
Match match)
{
if (match.DataSet.Disposed)
throw new InvalidOperationException(
"Data Set has been disposed and can't be used for match");
// If the user agent is too short then don't try to match and
// return defaults.
if (match.TargetUserAgentArray.Length == 0 ||
match.TargetUserAgentArray.Length < match.DataSet.MinUserAgentLength)
{
// Set the default values.
MatchDefault(match);
}
else
{
// Starting at the far right evaluate the nodes in the data
// set recording matched nodes. Continue until all character
// positions have been checked.
Evaluate(match);
// Can a precise match be found based on the nodes?
var signatureIndex = match.GetExactSignatureIndex();
if (signatureIndex >= 0)
{
// Yes a precise match was found.
match._signature = match.DataSet.Signatures[signatureIndex];
match._method = MatchMethods.Exact;
match.LowestScore = 0;
}
else
{
// No. So find any other nodes that match if numeric differences
// are considered.
EvaluateNumeric(match);
// Can a precise match be found based on the nodes?
signatureIndex = match.GetExactSignatureIndex();
if (signatureIndex >= 0)
{
// Yes a precise match was found.
match._signature = match.DataSet.Signatures[signatureIndex];
match._method = MatchMethods.Numeric;
}
else if (match.Nodes.Count > 0)
{
// Look for the closest signatures to the nodes found.
var closestSignatures = match.GetClosestSignatures();
#if DEBUG
// Validate the list is in ascending order of ranked signature index.
var enumerator = closestSignatures.GetEnumerator();
var lastIndex = -1;
while (enumerator.MoveNext())
{
Debug.Assert(lastIndex < enumerator.Current);
lastIndex = enumerator.Current;
}
#endif
// Try finding a signature with identical nodes just not in exactly the
// same place.
_nearest.EvaluateSignatures(match, closestSignatures.Select(i =>
match.DataSet.Signatures[match.DataSet.RankedSignatureIndexes[i].Value]));
if (match._signature != null)
{
// All the sub strings matched, just in different character positions.
match._method = MatchMethods.Nearest;
}
else
{
// Find the closest signatures and compare them
// to the target looking at the smallest character
// difference.
_closest.EvaluateSignatures(match, closestSignatures.Select(i =>
match.DataSet.Signatures[match.DataSet.RankedSignatureIndexes[i].Value]));
match._method = MatchMethods.Closest;
}
}
}
// If there still isn't a signature then set the default.
if (match._profiles == null &&
match._signature == null)
MatchDefault(match);
}
}
