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4.Classes/Interfaces and Methods

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Important Classes/Interfaces

Essential Classes

• VTD Generator: VTDGen is the class that encapsulates the main parsing, index loading and index reading functions

• VTD Navigator: VTDNav is the class that (1) encapsulates XML, VTD, and hierarchical info (2) contains various navigation functions (3) performs various comparison and VTD to string or numerical data conversion functions

• Autopilot: A class containing functions that perform node-level iteration and XPath.

• XMLModifier: A class that takes advantage of VTD-XML's incremental update capability

Other Classes/Interfaces

• ILongBuffer: This is the interface for VTD record container.

• FastLongBuffer: This class implements ILongBuffer interface. Under the hood, it is a chunk-based buffer that will grow automatically.

• NodeRecorder: Save the node location.

• BookMark: A hashable, comparable way of saving a single copy of cursor position.

• TextIterator: This class allows one to access text nodes in a mix-content document.

• ParseException: The root class for any exception conditions during parse

• NavException: The root class for any exceptions during navigation

• XPathEvalException: Thrown when there is something during XPath evaluation

• XPathParseException: Thrown when an error occurred during the construction of XPathExpr

• XMLModiferException: Thrown when there is an exception condition during the modification of XML document

Member methods of VTDNav

In this sub-section, we categorize and selectively annotate member methods of VTDNav.

1. Methods designed for hierarchical view of VTD

   • Navigate the cursor
     * boolean toElement(int direction);
     * boolean toElement(int direction, String elementName);
     * boolean toElementNS(int direction, String URL, String local_name);

   • About the element at the cursor position
     * int getCurrentIndex()                    // return the VTD index of the current element
     * int getCurrentDepth()                    // return depth of current element
     * boolean matchElement(String s);    // match the element name (of the cursor) against a string value
     * boolean matchElementNS(String s); // match the element name (name space aware)

   * boolean matchTokens(int i1,VTDNav vn1, int i2); // match the element name (name space aware)

   • Attributes, Text, and CDATA
     * int getAttrVal(String attrName);
     * int getAttrValNS(String URL, String localName);
     * boolean hasAttr(String attrName);
     * boolean hasAttrNs(String URL, String localName);
     * int getText()            // return the index value of the text value (character data or CDATA), -1 if none found

   • Helper function
     * void push();
     * boolean pop();

   • Address an element fragment
     * long getElementFragment(); // get the length and offset of the element fragment;
                                                 // upper 32 bits length lower 32 bits offset
      

2. Methods for individual VTD records

   • Comparison
     * boolean matchRawTokenString(int, String); // Match the token against a string, entities and char
                                       // references are not resolved
     * boolean matchTokenString(int, String); // match the token against a string, entities and char
                                    // references are resolved
     * boolean matchTokens(int i1, VTDNav vn2,int i2) // match two VTD tokens
     
     * int compareRawTokenString(int, String); //lexically compare a VTD token with a string, returns
     // 1, 0 or -1
     * int compareTokenString(int, String); //lexically compare a VTD token with a string, returns
     // 1, 0 or -1
     * int compareTokens(int, VTDNav vn2, int); // lexically compare two VTD tokens

                                                                              

   • Query token parameters
     * int getTokenDepth(int index);
     * int getTokenLength(int index);
     * int getTokenOffset(int index);
     * int getTokenType(int index);

   • Token to String conversion
     * String toRawString(int index);            // entities and char references not resolved
     * String toString(int index);                  // entities and char reference resolved
     * String toNormalizedString(int index);  // Normalized

   • Tokens to numerical data conversion
     * int parseInt(int index);
     * long parseLong(int index);
     * float parseFloat(int index);
     * double parseDouble(int index);

   • Properties of XML and VTD
     * int getRootIndex();                   // Return the VTD index for the root element
     * IByteBuffer getXML();                // Get the document buffer
     * int getTokenCount();                 // Get the total number of VTD tokens

    

3. Methods for writing/loading index

   • Index writing

   *void writeIndex(OutputStream os);
   *void writeIndex(String FileName);

   • Index loading

   *VTDNav loadIndex(InputStream is);
   *VTDNav loadIndex(String FileName);
   *VTDNav loadIndex(byte[] ba);

4. Methods of AutoPilot for Doing Node Iteration

   • Select Elements
     * void selectElement(String elementName); // select element name before iterating
     * void selectElementNS(String URL, String elementName);       // the namespace aware version

   • Iterate the nodes
     * boolean iterate();

    

5. Methods of AutoPilot for XPath

   • Select XPath
     * void declareXPathNameSpace(String attrName);
     * void selectXPath(String XPathExpr);    // compile the XPath string

   • Evaluate XPath

   * int evalXPath();  // evaluate XPath and moves the cursor to various locations of the document
   * double evalXPathToNumber(); // evaluate XPath to a double
   * String evalXPathToString();  //evaluate XPath to a string
   * boolean evalXPathToBoolean(); // evaluate XPath to a boolean

   • Other Methods
     * void resetXPath();      // call this function will reset the internal state of XPath for reuse
     * void bind(VTDNav vn); //bind  VTDNav to an autoPilot

    

6. Methods for XMLModifier

• Remove

  *void remove()
  *void removeAttribute(String attrName)
  *void removeToken(int i)

• Insert

  *void insertAfterElement(String s)
  *void insertAfterElement(byte[] ba)
  *void insertBeforeElement(String s)
  *void insertBeforeElement(byte[] ba)
  *void insertAttribute(String s);
  *void insertAttribute(byte[] ba);

   

• Update

*void updateToken(byte[] b);
*void updateToken(String s);

• Other Methods

*output(OutputStream os);
*reset();

VTD in 30 seconds

VTD+XML Format

User's Guide

  0. Introduction

  1. Goals and Features   

  2. How to Process XML

  3. Navigate VTD

  4. Classes/Interfaces and Methods

  5. Comparison with DOM,  SAX, and Pull

  6. Table for Token Types

 7. The C version VTD-XML

Developer's Guide

VTD: A Technical Perspective

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FAQ

Getting Involved

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