private IEnumerable <Expression> ParseFieldProviderParts(IFieldContext fieldContext, List <ParseFieldProviderExpressions> providerExpressionsList)
{
for (int i = 0; i < providerExpressionsList.Count; i++)
{
bool isLast = i == providerExpressionsList.Count - 1;
ParseFieldProviderExpressions providerExpressions = providerExpressionsList[i];
Expression test;
Expression fitsLowerBound = Expression.LessThanOrEqual(
providerExpressions.StartingIndex,
Expression.Property(fieldContext.ParseFieldParams.OffsetRecord, _readRecordID));
if (isLast)
{
test = fitsLowerBound;
}
else
{
Expression fitsUpperBound = Expression.LessThan(
Expression.Property(fieldContext.ParseFieldParams.OffsetRecord, _readRecordID),
providerExpressionsList[i + 1].StartingIndex);
test = Expression.And(fitsLowerBound, fitsUpperBound);
}
yield return
(Expression.IfThen(
test,
ParseFieldPart(fieldContext, providerExpressions)));
}
}
private Expression ParseFieldExpression()
{
ParameterExpression key = Expression.Parameter(typeof(int), "index");
IFieldContext fieldContext = new FieldContext(this, key);
LabelTarget labelBreak = Expression.Label("_break");
ParseFieldProviderExpressions providerExpressions = null;
if (_providers.Count == 1)
{
IFieldProvider provider = _providers[0];
providerExpressions = new ParseFieldProviderExpressions(provider, fieldContext);
return(ParseFieldPart(fieldContext, providerExpressions));
}
else
{
List <ParseFieldProviderExpressions> providerExpressionsList = _providers
.Select(p => new ParseFieldProviderExpressions(p, fieldContext))
.ToList();
IEnumerable <Expression> providerParseParts = ParseFieldProviderParts(fieldContext, providerExpressionsList);
return(Expression.Block(providerParseParts.ToArray()));
}
}
private Expression ParseFieldPart(IFieldContext fieldContext, ParseFieldProviderExpressions providerExpressions) => Expression.Block(
new ParameterExpression[] { fieldContext.Key },
Expression.Assign(
fieldContext.Key,
Expression.Subtract(
Expression.Property(ParseFieldParams.OffsetRecord, _readRecordID),
providerExpressions.StartingIndex)),
Expression.Assign(
Expression.Property(DeserializeParams.Stream, _streamPositionProperty),
Expression.Property(ParseFieldParams.OffsetRecord, _readRecordOffset)),
providerExpressions.DeserializeAndSaveFieldExpression);