private bool ContainsAncestor(FeatureExpressionInternal candidate, List <FeatureExpressionInternal> validFeature)
{
if (candidate.Source.Parent == null)
{
return(false);
}
if (validFeature.Any(valid => object.ReferenceEquals(valid.Source, candidate.Source.Parent)))
{
return(true);
}
var parent = this.allFeatures.First(f => object.ReferenceEquals(f.Source, candidate.Source.Parent));
return(ContainsAncestor(parent, validFeature));
}
/// <summary>
/// Instantiate the meta information object such as <see cref="PreHashedFeature"/>
/// for a given feature.
/// </summary>
/// <param name="featureInternal">The feature.</param>
/// <param name="namespace">The namespace.</param>
/// <returns>The "new" expression for the meta information object.</returns>
private Expression CreateFeature(FeatureExpressionInternal featureInternal, Expression @namespace)
{
FeatureExpression feature = featureInternal.Source;
var metaFeatureType = featureInternal.MarshalMethod.MetaFeatureType;
if (metaFeatureType.IsGenericType && metaFeatureType.GetGenericTypeDefinition() == typeof(EnumerizedFeature <>))
{
// preemptively calculate all hashes for each enum value
var featureParameter = Expression.Parameter(metaFeatureType);
var valueParameter = Expression.Parameter(feature.FeatureType);
var body = new List <Expression>();
var hashVariables = new List <ParameterExpression>();
foreach (var value in Enum.GetValues(feature.FeatureType))
{
var hashVar = Expression.Variable(typeof(UInt64));
hashVariables.Add(hashVar);
// CODE hashVar = feature.FeatureHashInternal(value);
body.Add(Expression.Assign(hashVar,
Expression.Call(featureParameter,
metaFeatureType.GetMethod("FeatureHashInternal"),
Expression.Constant(value))));
}
var cases = Enum.GetValues(feature.FeatureType)
.Cast <object>()
.Zip(hashVariables, (value, hash) => Expression.SwitchCase(
hash,
Expression.Constant(value, feature.FeatureType)))
.ToArray();
// expand the switch(value) { case enum1: return hash1; .... }
var hashSwitch = Expression.Switch(valueParameter,
Expression.Block(Expression.Throw(Expression.New(typeof(NotSupportedException))), Expression.Constant((UInt64)0, typeof(UInt64))),
cases);
// CODE return value => switch(value) { .... }
body.Add(Expression.Lambda(hashSwitch, valueParameter));
return(CreateNew(
metaFeatureType,
this.vwParameter,
@namespace,
Expression.Constant(feature.Name, typeof(string)),
Expression.Constant(feature.AddAnchor),
Expression.Constant(feature.Dictify),
Expression.Lambda(Expression.Block(hashVariables, body), featureParameter)));
}
else if (metaFeatureType == typeof(PreHashedFeature))
{
// CODE new PreHashedFeature(vw, namespace, "Name", "AddAnchor");
return(CreateNew(
typeof(PreHashedFeature),
this.vwParameter,
@namespace,
Expression.Constant(feature.Name, typeof(string)),
Expression.Constant(feature.AddAnchor),
Expression.Constant(feature.Dictify)));
}
else
{
// CODE new Feature("Name", ...)
return(CreateNew(
metaFeatureType,
Expression.Constant(feature.Name, typeof(string)),
Expression.Constant(feature.AddAnchor),
Expression.Constant(feature.Dictify)));
}
}
