internal ParameterProvider(ParameterExpression parameter, BindingFlags bindingFlags, NullCheckMode nullCheckMode)
{
this.parameter = parameter;
this.bindingFlags = bindingFlags;
this.nullCheckMode = nullCheckMode;
}
public Func <T, string> Compile <T>(string formatString, IFormatProvider formatProvider, NullCheckMode nullCheckMode)
{
// Guard anyway, since we may be used by things that don't understand nullable reference types
if (formatString == null)
{
throw new ArgumentNullException(nameof(formatString));
}
if (formatProvider == null)
{
throw new ArgumentNullException(nameof(formatProvider));
}
// Parse the string to a set of segments
IEnumerable <ISegment> segments = ParseFormatString(formatString);
// Create necessary constant expressions and parameterhelper
ParameterExpression parameter = Expression.Parameter(typeof(T));
Expression formatProviderExpression = Expression.Constant(formatProvider);
ParameterProvider <T> parameterProvider = new ParameterProvider <T>(parameter, BINDING_FLAGS, nullCheckMode);
// Compile segments to constituent expressions.
// Materialize the IEnumerable to a list in order to avoid recalculating the expressions while deciding which concatenation layout to use.
IEnumerable <Expression> segmentExpressions = segments.Select(s => s.ToExpression <T>(parameterProvider, formatProviderExpression)).ToList();
// Select the best method of forming the string
// TODO May be faster to nest concat operations up until a certain point before resorting to allocating an array object in the process. Perhaps a user preference?
Expression formatExpression;
if (segments.Count() == 1)
{
formatExpression = CompileToSingleton <T>(segmentExpressions.First());
}
else if (segments.Count() <= 4)
{
formatExpression = CompileToSingleConcat <T>(segmentExpressions);
}
else
{
formatExpression = CompileToArrayConcat <T>(segmentExpressions);
}
// Construct a lambda function from the compiled expression
return(Expression.Lambda <Func <T, string> >(
formatExpression,
"FastStringFormatAutogenerated",
new ParameterExpression[] { parameter }
).Compile());
}
