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using System;
using System.Collections;
using SemWeb;
namespace SemWeb {
public class MemoryStore : Store, IEnumerable {
ArrayList statements = new ArrayList();
Hashtable statementsAboutSubject = new Hashtable();
Hashtable statementsAboutObject = new Hashtable();
bool isIndexed = false;
internal bool allowIndexing = true;
public MemoryStore() {
}
public MemoryStore(StatementSource source) {
Import(source);
}
public IList Statements { get { return ArrayList.ReadOnly(statements); } }
public override int StatementCount { get { return statements.Count; } }
IEnumerator IEnumerable.GetEnumerator() {
return statements.GetEnumerator();
}
public override void Clear() {
statements.Clear();
statementsAboutSubject.Clear();
statementsAboutObject.Clear();
}
private ArrayList GetIndexArray(Hashtable from, Resource entity) {
ArrayList ret = (ArrayList)from[entity];
if (ret == null) {
ret = new ArrayList();
from[entity] = ret;
}
return ret;
}
public override void Add(Statement statement) {
if (statement.AnyNull) throw new ArgumentNullException();
statements.Add(statement);
if (isIndexed) {
GetIndexArray(statementsAboutSubject, statement.Subject).Add(statement);
GetIndexArray(statementsAboutObject, statement.Object).Add(statement);
}
}
public override void Remove(Statement statement) {
if (statement.AnyNull) {
for (int i = 0; i < statements.Count; i++) {
Statement s = (Statement)statements[i];
if (statement.Matches(s)) {
statements.RemoveAt(i); i--;
if (isIndexed) {
GetIndexArray(statementsAboutSubject, s.Subject).Remove(s);
GetIndexArray(statementsAboutObject, s.Object).Remove(s);
}
}
}
} else {
statements.Remove(statement);
if (isIndexed) {
GetIndexArray(statementsAboutSubject, statement.Subject).Remove(statement);
GetIndexArray(statementsAboutObject, statement.Object).Remove(statement);
}
}
}
public override Entity[] GetAllEntities() {
Hashtable h = new Hashtable();
foreach (Statement s in Statements) {
if (s.Subject != null) h[s.Subject] = h;
if (s.Predicate != null) h[s.Predicate] = h;
if (s.Object != null && s.Object is Entity) h[s.Object] = h;
if (s.Meta != null && s.Meta != Statement.DefaultMeta) h[s.Meta] = h;
}
return (Entity[])new ArrayList(h.Keys).ToArray(typeof(Entity));
}
public override Entity[] GetAllPredicates() {
Hashtable h = new Hashtable();
foreach (Statement s in Statements)
h[s.Predicate] = h;
return (Entity[])new ArrayList(h.Keys).ToArray(typeof(Entity));
}
private void ShorterList(ref IList list1, IList list2) {
if (list2.Count < list1.Count)
list1 = list2;
}
public override void Select(Statement template, SelectPartialFilter partialFilter, StatementSink result) {
IList source = statements;
// The first time select is called, turn indexing on for the store.
// TODO: Perform this index in a background thread if there are a lot
// of statements.
if (!isIndexed && allowIndexing) {
isIndexed = true;
foreach (Statement statement in statements) {
GetIndexArray(statementsAboutSubject, statement.Subject).Add(statement);
GetIndexArray(statementsAboutObject, statement.Object).Add(statement);
}
}
if (template.Subject != null) ShorterList(ref source, GetIndexArray(statementsAboutSubject, template.Subject));
else if (template.Object != null) ShorterList(ref source, GetIndexArray(statementsAboutObject, template.Object));
if (source == null) return;
foreach (Statement statement in source) {
if (!template.Matches(statement))
continue;
if (!result.Add(statement)) return;
}
}
public override void Select(Statement[] templates, SelectPartialFilter partialFilter, StatementSink result) {
foreach (Statement t in templates)
Select(t, result);
}
public override void Replace(Entity a, Entity b) {
foreach (Statement statement in statements) {
if ((statement.Subject != null && statement.Subject == a) || (statement.Predicate != null && statement.Predicate == a) || (statement.Object != null && statement.Object == a) || (statement.Meta != null && statement.Meta == a)) {
Remove(statement);
Add(new Statement(
statement.Subject == a ? b : a,
statement.Predicate == a ? b : a,
statement.Object == a ? b : a,
statement.Meta == a ? b : a
));
}
}
}
public override void Replace(Statement find, Statement replacement) {
if (find.AnyNull) throw new ArgumentNullException("find");
if (replacement.AnyNull) throw new ArgumentNullException("replacement");
if (find == replacement) return;
foreach (Statement match in Select(find)) {
Remove(match);
Add(replacement);
break; // should match just one statement anyway
}
}
public override Entity[] FindEntities(Statement[] filters) {
ArrayList ents = new ArrayList();
foreach (Statement s in Select(filters[0])) {
if (s.Subject != null && filters[0].Subject == null)
ents.Add(s.Subject);
if (s.Predicate != null && filters[0].Predicate == null)
ents.Add(s.Predicate);
if (s.Object != null && filters[0].Object == null && s.Object is Entity)
ents.Add(s.Object);
if (s.Meta != null && filters[0].Meta == null)
ents.Add(s.Meta);
}
foreach (Statement f in filters) {
if (f == filters[0]) continue;
ArrayList e2 = new ArrayList();
foreach (Entity e in ents) {
Statement fe = new Statement(
f.Subject == null ? e : f.Subject,
f.Predicate == null ? e : f.Predicate,
f.Object == null ? e : f.Object,
f.Meta == null ? e : f.Meta);
if (Contains(fe))
e2.Add(e);
}
ents = e2;
}
return (Entity[])ents.ToArray(typeof(Entity));
}
}
}
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