/// <summary>
/// This constructor takes a Boolean expression in infix format.
/// Some examples
/// are shown below. Assume <b>T</b> is an instance of the
/// <see cref="Tags"/>
/// class.
/// <list type="table">
/// <item>
/// T[CommonPropertyNames.title] contains "foo"
/// <term>
/// </term>
/// <description>
/// <see cref="MediaComparer.IsMatch"/> will return
/// true on media objects that have <i>foo</i> in the title.
/// </description>
/// </item>
///
/// <item>
/// T[CommonPropertyNames.creator] doesNotContain "\"HappyBand\""
/// <term>
/// </term>
/// <description>
/// <see cref="MediaComparer.IsMatch"/> will return
/// true on media objects that do not have <i>"HappyBand"</i> in the title.
/// </description>
/// </item>
///
/// <item>
/// (T[CommonPropertyNames.Class] = "object.item.audioItem.musicTrack" and Tags.PropertyAttributes.res_size > "40") or (T[CommonPropertyNames.author] exists true)
/// <term>
/// </term>
/// <description>
/// <see cref="MediaComparer.IsMatch"/> will return
/// true on media objects that are music tracks with at least one resource greater than 40 bytes
/// OR on media objects that have a value set for the author metadata.
/// </description>
/// </item>
/// </list>
/// </summary>
/// <param name="infix">The boolean infix expression conforming to the syntax and semantics of ContentDirectory's boolean query language.</param>
/// <exception cref="OpenSource.UPnP.AV.CdsMetadata.Error_MalformedSearchCriteria">
/// Thrown if the infix expression has a syntax error.
/// </exception>
public MediaComparer(string infix)
{
string allstring = infix.Trim();
if ((allstring == "") || (allstring == "*"))
{
this.m_AlwaysMatch = true;
return;
}
//Initialize an empty stack and empty result string variable.
//
Stack stack = new Stack();
m_Postfix = new Queue();
RelExpStates state = RelExpStates.unknown;
TokenResult token;
while (infix.Length > 0)
{
infix = infix.Trim();
token = GetToken(ref infix, state);
switch (state)
{
case RelExpStates.unknown:
if (token.TokenType == Tokens.PropertyName)
{
state = RelExpStates.expectOp;
}
break;
case RelExpStates.expectOp:
if (token.TokenType != Tokens.Operator)
{
throw new UPnPCustomException(402, "Invalid Args: Invalid operator " + token.Data);
}
state = RelExpStates.expectValue;
break;
case RelExpStates.expectValue:
if (token.TokenType != Tokens.PropertyValue)
{
throw new UPnPCustomException(402, "Invalid Args: Unexpected value " + token.Data);
}
state = RelExpStates.unknown;
break;
}
switch (token.TokenType)
{
case Tokens.Operator:
if (token.OpToken == OperatorTokens.LParen)
{
//left paren
//
stack.Push(token);
}
else if (token.OpToken == OperatorTokens.RParen)
{
//right paren
//
TokenResult tr = new TokenResult(false);
do
{
if (stack.Count > 0)
{
tr = (TokenResult)stack.Pop();
if (tr.OpToken != OperatorTokens.LParen)
{
m_Postfix.Enqueue(tr);
}
}
else
{
throw new UPnPCustomException(402, "Invalid Args: Missing Left Parenthesis.");
}
}while (tr.OpToken != OperatorTokens.LParen);
}
else
{
//standard operator
//
if (token.OpToken == OperatorTokens.Invalid)
{
throw new Exception("bad code");
}
while
(
(stack.Count > 0) &&
(((TokenResult)stack.Peek()).Precedence >= token.Precedence) &&
(((TokenResult)stack.Peek()).OpToken != OperatorTokens.LParen)
)
{
// While stack is not empty &&
// top operator has higher or equal precedence...
// pop operator and stuff into queue
m_Postfix.Enqueue(stack.Pop());
}
stack.Push(token);
}
break;
case Tokens.PropertyName:
m_Postfix.Enqueue(token);
TagExtractor te = new TagExtractor(token.Data);
this.m_PE[token.Data] = te;
break;
case Tokens.PropertyValue:
m_Postfix.Enqueue(token);
break;
}
}
// pop remaining items in stack and stuff into queue
//
while (stack.Count > 0)
{
TokenResult tr = (TokenResult)stack.Pop();
if (tr.OpToken != OperatorTokens.LParen)
{
m_Postfix.Enqueue(tr);
}
}
}
/// <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>
/// This constructor takes a Boolean expression in infix format.
/// Some examples
/// are shown below. Assume <b>T</b> is an instance of the
/// <see cref="Tags"/>
/// class.
/// <list type="table">
/// <item>
/// T[CommonPropertyNames.title] contains "foo"
/// <term>
/// </term>
/// <description>
/// <see cref="MediaComparer.IsMatch"/> will return
/// true on media objects that have <i>foo</i> in the title.
/// </description>
/// </item>
///
/// <item>
/// T[CommonPropertyNames.creator] doesNotContain "\"HappyBand\""
/// <term>
/// </term>
/// <description>
/// <see cref="MediaComparer.IsMatch"/> will return
/// true on media objects that do not have <i>"HappyBand"</i> in the title.
/// </description>
/// </item>
///
/// <item>
/// (T[CommonPropertyNames.Class] = "object.item.audioItem.musicTrack" and Tags.PropertyAttributes.res_size > "40") or (T[CommonPropertyNames.author] exists true)
/// <term>
/// </term>
/// <description>
/// <see cref="MediaComparer.IsMatch"/> will return
/// true on media objects that are music tracks with at least one resource greater than 40 bytes
/// OR on media objects that have a value set for the author metadata.
/// </description>
/// </item>
/// </list>
/// </summary>
/// <param name="infix">The boolean infix expression conforming to the syntax and semantics of ContentDirectory's boolean query language.</param>
/// <exception cref="OpenSource.UPnP.AV.CdsMetadata.Error_MalformedSearchCriteria">
/// Thrown if the infix expression has a syntax error.
/// </exception>
public MediaComparer (string infix)
{
string allstring = infix.Trim();
if ((allstring == "") || (allstring == "*"))
{
this.m_AlwaysMatch = true;
return;
}
//Initialize an empty stack and empty result string variable.
//
Stack stack = new Stack();
m_Postfix = new Queue();
RelExpStates state = RelExpStates.unknown;
TokenResult token;
while (infix.Length > 0)
{
infix = infix.Trim();
token = GetToken(ref infix, state);
switch (state)
{
case RelExpStates.unknown:
if (token.TokenType == Tokens.PropertyName)
{
state = RelExpStates.expectOp;
}
break;
case RelExpStates.expectOp:
if (token.TokenType != Tokens.Operator)
{
throw new UPnPCustomException(402, "Invalid Args: Invalid operator " + token.Data);
}
state = RelExpStates.expectValue;
break;
case RelExpStates.expectValue:
if (token.TokenType != Tokens.PropertyValue)
{
throw new UPnPCustomException(402, "Invalid Args: Unexpected value " + token.Data);
}
state = RelExpStates.unknown;
break;
}
switch (token.TokenType)
{
case Tokens.Operator:
if (token.OpToken == OperatorTokens.LParen)
{
//left paren
//
stack.Push(token);
}
else if (token.OpToken == OperatorTokens.RParen)
{
//right paren
//
TokenResult tr = new TokenResult(false);
do
{
if (stack.Count > 0)
{
tr = (TokenResult) stack.Pop();
if (tr.OpToken != OperatorTokens.LParen)
{
m_Postfix.Enqueue(tr);
}
}
else
{
throw new UPnPCustomException(402, "Invalid Args: Missing Left Parenthesis.");
}
}
while (tr.OpToken != OperatorTokens.LParen);
}
else
{
//standard operator
//
if (token.OpToken == OperatorTokens.Invalid)
{
throw new Exception("bad code");
}
while
(
(stack.Count > 0) &&
( ((TokenResult) stack.Peek()).Precedence >= token.Precedence) &&
( ((TokenResult) stack.Peek()).OpToken != OperatorTokens.LParen)
)
{
// While stack is not empty &&
// top operator has higher or equal precedence...
// pop operator and stuff into queue
m_Postfix.Enqueue( stack.Pop() );
}
stack.Push(token);
}
break;
case Tokens.PropertyName:
m_Postfix.Enqueue(token);
TagExtractor te = new TagExtractor(token.Data);
this.m_PE[token.Data] = te;
break;
case Tokens.PropertyValue:
m_Postfix.Enqueue(token);
break;
}
}
// pop remaining items in stack and stuff into queue
//
while (stack.Count > 0)
{
TokenResult tr = (TokenResult) stack.Pop();
if (tr.OpToken != OperatorTokens.LParen)
{
m_Postfix.Enqueue( tr );
}
}
}