/// <summary>Intersect this tree reference with another, returning a new tree reference /// which contains all of the common elements, starting with the root element. /// /// Note that relative references by their nature can't share steps, so intersecting /// any (or by any) relative ref will result in the root ref. Additionally, if the /// two references don't share any steps, the intersection will consist of the root /// reference. /// /// </summary> /// <param name="b">The tree reference to intersect /// </param> /// <returns> The tree reference containing the common basis of this ref and b /// </returns> public virtual TreeReference intersect(TreeReference b) { if (!this.Absolute || !b.Absolute) { return(TreeReference.rootRef()); } if (this.Equals(b)) { return(this); } TreeReference a; //A should always be bigger if one ref is larger than the other if (this.size() < b.size()) { a = b.Clone(); b = this.Clone(); } else { a = this.Clone(); b = b.Clone(); } //Now, trim the refs to the same length. int diff = a.size() - b.size(); for (int i = 0; i < diff; ++i) { a.removeLastLevel(); } int aSize = a.size(); //easy, but requires a lot of re-evaluation. for (int i = 0; i <= aSize; ++i) { if (a.Equals(b)) { return(a); } else if (a.size() == 0) { return(TreeReference.rootRef()); } else { if (!a.removeLastLevel() || !b.removeLastLevel()) { //I don't think it should be possible for us to get here, so flip if we do throw new System.SystemException("Dug too deply into TreeReference during intersection"); } } } //The only way to get here is if a's size is -1 throw new System.SystemException("Impossible state"); }
//return a new reference that is this reference anchored to a passed-in parent reference //if this reference is absolute, return self //if this ref has 'parent' steps (..), it can only be anchored if the parent ref is a relative ref consisting only of other 'parent' steps //return null in these invalid situations public virtual TreeReference parent(TreeReference parentRef) { if (Absolute) { return(this); } else { TreeReference newRef = parentRef.Clone(); if (refLevel > 0) { if (!parentRef.Absolute && parentRef.size() == 0) { parentRef.refLevel += refLevel; } else { return(null); } } for (TreeReferenceLevel l: data) { newRef.add(l.shallowCopy()); } return(newRef); } }
//very similar to parent(), but assumes contextRef refers to a singular, existing node in the model //this means we can do '/a/b/c + ../../d/e/f = /a/d/e/f', which we couldn't do in parent() //return null if context ref is not absolute, or we parent up past the root node //NOTE: this function still works even when contextRef contains INDEX_UNBOUND multiplicites... conditions depend on this behavior, // even though it's slightly icky public virtual TreeReference anchor(TreeReference contextRef) { //TODO: Technically we should possibly be modifying context stuff here //instead of in the xpath stuff; if (Absolute) { return(this.Clone()); } else if (!contextRef.Absolute) { throw new XPathException("Could not resolve " + this.toString(true)); } else { TreeReference newRef = contextRef.Clone(); int contextSize = contextRef.size(); if (refLevel > contextSize) { //tried to do '/..' throw new XPathException("Could not resolve " + this.toString(true)); } else { for (int i = 0; i < refLevel; i++) { newRef.removeLastLevel(); } for (int i = 0; i < size(); i++) { newRef.add(data.elementAt(i).shallowCopy()); } return(newRef); } } }