/// <summary>Given a prefix mapping for a specific URI, this returns
/// the prefix mapping previously in effect for the same URI.</summary>
/// <remarks>This can be used to iterate backwards through the stack of
/// prefix mappings for a given URI.</remarks>
/// <param name="prefix"><see cref="ActiveMapping"/> instance for which
/// we want to find the instance previously in effect with the same URI.</param>
/// <returns><see cref="ActiveMapping"/> instance to look for,
/// or <c>null</c> if none exists.</returns>
public ActiveMapping PreviousUriMapping(ActiveMapping prefix)
{
string uri = prefix.Uri;
// check active mapping record
NamespaceMapping nsMapping = prefix.mappingsTop;
if (nsMapping == null || !nsMapping.declared)
{
string msg = Resources.GetString(RsId.UndeclaredMapping);
throw new XmlNamespacesException(String.Format(msg, prefix.Prefix));
}
// find a parent scope where the same URI maps to an "active" prefix
NamespaceScope scope = nsMapping.scope.parent;
while (scope != null)
{
nsMapping = scope.FindByUri(uri);
if (nsMapping != null)
{
ActiveMapping result = nsMapping.prefix;
// result must be different from prefix, since the same prefix
// cannot be "declared" with two different URIs at the same time
if (result.IsDeclared)
{
Debug.Assert(result != prefix, Resources.GetString(RsId.InternalNsError));
return(result);
}
}
scope = scope.parent;
}
return(null);
}
/// <summary>Returns the most recently added namespace mapping "in effect"
/// for a given URI.</summary>
/// <remarks>"In effect" means that the prefix mapping must <b>not</b> have
/// been "undeclared".</remarks>
/// <param name="uri">Namespace URI to get mapping for.</param>
/// <returns><see cref="ActiveMapping"/> instance for <c>uri</c>, or <c>null</c>
/// if there is no such mapping.</returns>
public ActiveMapping GetUriMapping(string uri)
{
NamespaceScope scope = topScope;
while (scope != null)
{
NamespaceMapping nsMapping = scope.FindByUri(uri);
if (nsMapping != null && nsMapping.declared)
{
return(nsMapping.prefix);
}
scope = scope.parent;
}
return(null);
}
