/// <summary>
/// <para>
/// Instantiates a sorter based on the sortCriteria string. The basic algorithm for
/// sorting is to supply a comma-separated-value (CSV) listing of property names
/// (easily retrieved from using <see cref="Tags"/>'s indexer with the
/// <see cref="CommonPropertyNames"/>,
/// <see cref="_DC"/>,
/// <see cref="_UPNP"/>, or
/// <see cref="_ATTRIB"/>
/// enumerators.)
/// with each property name having a + or - sign to indicate ascending or descending
/// order of the sorting for that property name. Assuming "T" is an instance of a
/// <see cref="Tags"/> object.
/// Example below.
/// </para>
///
/// <para>
/// <list type="table">
/// <item>
/// <term>"+" +T[CommonPropertyNames.title]+ ",-" +T[CommonPropertyNames.creator]</term>
/// <description>Sorts with ascending titles first, then descending creators</description>
/// </item>
/// </list>
/// </para>
///
/// </summary>
/// <param name="forceDistinction">if true, then any comparison that evaluates to equal will force an arbitrary ordering of the two objects in question</param>
/// <param name="sortCriteria">a string with the property names in a CSV list, where
/// each property name has a + or - sign to indicate ascending or descending order</param>
public MediaSorter(bool forceDistinction, string sortCriteria)
{
this.forceDistinction = forceDistinction;
if (sortCriteria != null)
{
if (sortCriteria != "")
{
DText parser = new DText();
parser.ATTRMARK = ",";
parser[0] = sortCriteria;
int size = parser.DCOUNT();
this.sortKeys = new ArrayList(size);
// iterate through properties for sorting
//
for (int i = 1; i <= size; i++)
{
string prop = parser[i].Trim();
char asc_dsc = prop[0];
string property = prop.Substring(1);
bool ascending = true;
if (asc_dsc == '-')
{
ascending = false;
}
else if (asc_dsc == '+')
{
ascending = true;
}
else
{
throw new UPnPCustomException(709, "Invalid sort flag.");
}
MetadataValueComparer mvc = new MetadataValueComparer(property, ascending);
this.sortKeys.Add(mvc);
}
}
}
if (this.sortKeys == null)
{
this.sortKeys = new ArrayList(0);
}
}
/// <summary>
/// Evaluates a subexpression of a whole expression.
/// </summary>
/// <param name="media">the media object with the metadata</param>
/// <param name="prop">the property/attribute metadata to examine</param>
/// <param name="op">the operator to use for examination</param>
/// <param name="val">the value to compare against in string form</param>
/// <returns></returns>
/// <exception cref="OpenSource.UPnP.AV.CdsMetadata.Error_MalformedSearchCriteria">
/// Thrown when the expression provided at constructor time could not
/// be used to evaluate the media because of syntax errors in
/// the expression.
/// </exception>
private bool Evaluate(IUPnPMedia media, string prop, OperatorTokens op, string val)
{
bool result = false;
TagExtractor te = (TagExtractor)this.m_PE[prop];
IList values = te.Extract(media);
if (op == OperatorTokens.Exists)
{
bool testVal = (string.Compare(val, "true", true) == 0);
result = (
((values.Count > 0) && (testVal)) ||
((values.Count == 0) && (testVal == false))
);
}
else
{
foreach (object testVal in values)
{
int opCode = (int)op;
if ((opCode >= (int)OperatorTokens.Equal) && (opCode <= (int)OperatorTokens.GreaterThanEqualTo))
{
// Compare using a relational operator
//
try
{
int relResult = MetadataValueComparer.CompareTagValues(testVal, val, this.IgnoreCase);
if (relResult == 0)
{
result = true;
break;
}
}
catch //(Exception e)
{
string opString = Enum.GetName(typeof(OperatorTokens), opCode);
throw new Error_MalformedSearchCriteria("(" + val + ") " + opString + " " + testVal.ToString() + ") could not occur.");
}
}
else if (op == OperatorTokens.Contains)
{
string tv = testVal.ToString();
int pos = tv.IndexOf(val);
result = (pos >= 0);
}
else if (op == OperatorTokens.DoesNotContain)
{
string tv = testVal.ToString();
int pos = tv.IndexOf(val);
result = (pos < 0);
}
else if (op == OperatorTokens.DerivedFrom)
{
string tv = testVal.ToString();
result = tv.StartsWith(val);
}
}
}
return(result);
}
/// <summary>
/// <para>
/// Instantiates a sorter based on the sortCriteria string. The basic algorithm for
/// sorting is to supply a comma-separated-value (CSV) listing of property names
/// (easily retrieved from using <see cref="Tags"/>'s indexer with the
/// <see cref="CommonPropertyNames"/>,
/// <see cref="_DC"/>,
/// <see cref="_UPNP"/>, or
/// <see cref="_ATTRIB"/>
/// enumerators.)
/// with each property name having a + or - sign to indicate ascending or descending
/// order of the sorting for that property name. Assuming "T" is an instance of a
/// <see cref="Tags"/> object.
/// Example below.
/// </para>
///
/// <para>
/// <list type="table">
/// <item>
/// <term>"+" +T[CommonPropertyNames.title]+ ",-" +T[CommonPropertyNames.creator]</term>
/// <description>Sorts with ascending titles first, then descending creators</description>
/// </item>
/// </list>
/// </para>
///
/// </summary>
/// <param name="forceDistinction">if true, then any comparison that evaluates to equal will force an arbitrary ordering of the two objects in question</param>
/// <param name="sortCriteria">a string with the property names in a CSV list, where
/// each property name has a + or - sign to indicate ascending or descending order</param>
public MediaSorter (bool forceDistinction, string sortCriteria)
{
this.forceDistinction = forceDistinction;
if (sortCriteria != null)
{
if (sortCriteria != "")
{
DText parser = new DText();
parser.ATTRMARK = ",";
parser[0] = sortCriteria;
int size = parser.DCOUNT();
this.sortKeys = new ArrayList(size);
// iterate through properties for sorting
//
for (int i=1; i <= size; i++)
{
string prop = parser[i].Trim();
char asc_dsc = prop[0];
string property = prop.Substring(1);
bool ascending = true;
if (asc_dsc == '-')
{
ascending = false;
}
else if (asc_dsc == '+')
{
ascending = true;
}
else
{
throw new UPnPCustomException(709, "Invalid sort flag.");
}
MetadataValueComparer mvc = new MetadataValueComparer(property, ascending);
this.sortKeys.Add(mvc);
}
}
}
if (this.sortKeys == null)
{
this.sortKeys = new ArrayList(0);
}
}
