/// <summary>
/// Serializes the given graph to the given stream using Turtle data format.
/// </summary>
internal static void Serialize(RDFGraph graph, Stream outputStream)
{
try {
#region serialize
using (StreamWriter sw = new StreamWriter(outputStream, Encoding.UTF8)) {
#region prefixes
//Write the namespaces collected by the graph
foreach (var ns in RDFModelUtilities.GetGraphNamespaces(graph).OrderBy(n => n.NamespacePrefix))
{
sw.WriteLine("@prefix " + ns.NamespacePrefix + ": <" + ns.NamespaceUri + ">.");
}
sw.WriteLine("@base <" + graph.Context + ">.\n");
#endregion
#region linq
//Group the graph's triples by subj and pred
var groupedList = (from triple in graph
orderby triple.Subject.ToString(), triple.Predicate.ToString()
group triple by new {
subj = triple.Subject.ToString(),
pred = triple.Predicate.ToString()
});
var groupedListLast = groupedList.Last();
#endregion
#region triples
String actualSubj = String.Empty;
String abbreviatedSubj = String.Empty;
String actualPred = String.Empty;
String abbreviatedPred = String.Empty;
const String spaceConst = " ";
StringBuilder result = new StringBuilder();
//Iterate over the calculated groups
foreach (var group in groupedList)
{
var groupLast = group.Last();
#region subj
//Reset the flag of subj printing for the new iteration
Boolean subjPrint = false;
//New subj found: write the finished Turtle token to the file, then start collecting the new one
if (!actualSubj.Equals(group.Key.subj, StringComparison.Ordinal))
{
if (result.Length > 0)
{
result.Replace(";", ".", result.Length - 4, 1);
sw.Write(result.ToString());
result.Remove(0, result.Length - 1);
}
actualSubj = group.Key.subj;
actualPred = String.Empty;
if (!actualSubj.StartsWith("_:"))
{
abbreviatedSubj = AbbreviateNamespace(actualSubj);
}
else
{
abbreviatedSubj = actualSubj;
}
result.Append(abbreviatedSubj + " ");
subjPrint = true;
}
#endregion
#region predObjList
//Iterate over the triples of the current group
foreach (var triple in group)
{
#region pred
//New pred found: collect it to the actual Turtle token.
if (!actualPred.Equals(triple.Predicate.ToString(), StringComparison.Ordinal))
{
if (!subjPrint)
{
result.Append(spaceConst.PadRight(abbreviatedSubj.Length + 1)); //pretty-printing spaces to align the predList
}
actualPred = triple.Predicate.ToString();
abbreviatedPred = AbbreviateNamespace(actualPred);
//Turtle goody for "rdf:type" shortcutting to "a"
if (abbreviatedPred == RDFVocabulary.RDF.PREFIX + ":type")
{
abbreviatedPred = "a";
}
result.Append(abbreviatedPred + " ");
}
#endregion
#region object
//Collect the object or the literal to the Turtle token
if (triple.TripleFlavor == RDFModelEnums.RDFTripleFlavors.SPO)
{
String obj = triple.Object.ToString();
if (!obj.StartsWith("_:"))
{
result.Append(AbbreviateNamespace(obj));
}
else
{
result.Append(obj);
}
}
#endregion
#region literal
else
{
//Detect presence of long-literals
var litValDelim = "\"";
if (regexTTL.Match(triple.Object.ToString()).Success)
{
litValDelim = "\"\"\"";
}
if (triple.Object is RDFTypedLiteral)
{
String tLit = litValDelim + ((RDFTypedLiteral)triple.Object).Value.Replace("\\", "\\\\") + litValDelim + "^^" + AbbreviateNamespace(RDFModelUtilities.GetDatatypeFromEnum(((RDFTypedLiteral)triple.Object).Datatype));
result.Append(tLit);
}
else
{
String pLit = litValDelim + ((RDFPlainLiteral)triple.Object).Value.Replace("\\", "\\\\") + litValDelim;
if (((RDFPlainLiteral)triple.Object).Language != String.Empty)
{
pLit = pLit + "@" + ((RDFPlainLiteral)triple.Object).Language;
}
result.Append(pLit);
}
}
#endregion
#region continuation goody
//Then append the appropriated Turtle continuation goody ("," or ";")
if (!triple.Equals(groupLast))
{
result.Append(", ");
}
else
{
result.AppendLine("; ");
}
#endregion
}
#endregion
#region last group
//This is only for the last group, which is not written into the cycle as the others
if (group.Key.Equals(groupedListLast.Key))
{
result.Replace(";", ".", result.Length - 4, 1);
sw.Write(result.ToString());
}
#endregion
}
#endregion
}
#endregion
}
catch (Exception ex) {
throw new RDFModelException("Cannot serialize Turtle because: " + ex.Message, ex);
}
}
