XMLReader

Introduction

vtkXMLReader is a source object that parses a VTK XML input file.

Methods

extend

Method used to decorate a given object (publicAPI+model) with vtkXMLReader characteristics.

Argument	Type	Required	Description
publicAPI		Yes	object on which methods will be bounds (public)
model		Yes	object on which data structure will be bounds (protected)
initialValues	IXMLReaderInitialValues	No	(default: {})

getBaseURL

getDataAccessHelper

getUrl

Get the url of the object to load.

loadData

Load the object data.

Argument	Type	Required	Description
options	IXMLReaderOptions	No

parse

Parse data.

Argument	Type	Required	Description
content	String or ArrayBuffer	Yes	The content to parse.

parseAsArrayBuffer

Parse data as ArrayBuffer.

Argument	Type	Required	Description
content	ArrayBuffer	Yes	The content to parse.

parseAsText

Parse data as text.

Argument	Type	Required	Description
content	String	Yes	The content to parse.

processCells

Argument	Type	Required	Description
size	Number	Yes
containerElem	HTMLElement	Yes
compressor	String	Yes
byteOrder	String	Yes
headerType	String	Yes
binaryBuffer	ArrayBuffer	Yes

processDataArray

Argument	Type	Required	Description
size	Number	Yes
dataArrayElem	HTMLElement	Yes
compressor	String	Yes
byteOrder	String	Yes
headerType	String	Yes
binaryBuffer	ArrayBuffer	Yes

processFieldData

Argument	Type	Required	Description
size	Number	Yes
fieldElem	HTMLElement	Yes
fieldContainer	HTMLElement	Yes
compressor	String	Yes
byteOrder	String	Yes
headerType	String	Yes
binaryBuffer	ArrayBuffer	Yes

requestData

Argument	Type	Required	Description
inData		Yes
outData		Yes

setDataAccessHelper

Argument	Type	Required	Description
dataAccessHelper		Yes

setUrl

Set the url of the object to load.

Argument	Type	Required	Description
url	String	Yes	the url of the object to load.
option	IXMLReaderOptions	No	The XML reader options.

Source

index.d.ts

import { vtkAlgorithm, vtkObject } from '../../../interfaces';
import HtmlDataAccessHelper from '../../Core/DataAccessHelper/HtmlDataAccessHelper';
import HttpDataAccessHelper from '../../Core/DataAccessHelper/HttpDataAccessHelper';
import JSZipDataAccessHelper from '../../Core/DataAccessHelper/JSZipDataAccessHelper';
import LiteHttpDataAccessHelper from '../../Core/DataAccessHelper/LiteHttpDataAccessHelper';

interface IXMLReaderOptions {
  binary?: boolean;
  compression?: string;
  progressCallback?: any;
}

interface IRet {
  name: string;
  numberOfComponents: number;
  values: any;
}

/**
 *
 */
export interface IXMLReaderInitialValues {}

type vtkXMLReaderBase = vtkObject &
  Omit<
    vtkAlgorithm,
    | 'getInputData'
    | 'setInputData'
    | 'setInputConnection'
    | 'getInputConnection'
    | 'addInputConnection'
    | 'addInputData'
  >;

export interface vtkXMLReader extends vtkXMLReaderBase {
  /**
   *
   */
  getBaseURL(): string;

  /**
   *
   */
  getDataAccessHelper():
    | HtmlDataAccessHelper
    | HttpDataAccessHelper
    | JSZipDataAccessHelper
    | LiteHttpDataAccessHelper;

  /**
   * Get the url of the object to load.
   */
  getUrl(): string;

  /**
   * Load the object data.
   * @param {IXMLReaderOptions} [options]
   */
  loadData(options?: IXMLReaderOptions): Promise<any>;

  /**
   * Parse data.
   * @param {String | ArrayBuffer} content The content to parse.
   */
  parse(content: string | ArrayBuffer): void;

  /**
   * Parse data as ArrayBuffer.
   * @param {ArrayBuffer} content The content to parse.
   */
  parseAsArrayBuffer(content: ArrayBuffer): void;

  /**
   * Parse data as text.
   * @param {String} content The content to parse.
   */
  parseAsText(content: string): void;
  /**
   *
   * @param inData
   * @param outData
   */
  requestData(inData: any, outData: any): void;

  /**
   *
   * @param dataAccessHelper
   */
  setDataAccessHelper(
    dataAccessHelper:
      | HtmlDataAccessHelper
      | HttpDataAccessHelper
      | JSZipDataAccessHelper
      | LiteHttpDataAccessHelper
  ): boolean;

  /**
   * Set the url of the object to load.
   * @param {String} url the url of the object to load.
   * @param {IXMLReaderOptions} [option] The XML reader options.
   */
  setUrl(url: string, option?: IXMLReaderOptions): Promise<any>;
}

/**
 * Method used to decorate a given object (publicAPI+model) with vtkXMLReader characteristics.
 *
 * @param publicAPI object on which methods will be bounds (public)
 * @param model object on which data structure will be bounds (protected)
 * @param {IXMLReaderInitialValues} [initialValues] (default: {})
 */
export function extend(
  publicAPI: object,
  model: object,
  initialValues?: IXMLReaderInitialValues
): void;

/**
 * @param {Number} size
 * @param {HTMLElement} dataArrayElem
 * @param {String} compressor
 * @param {String} byteOrder
 * @param {String} headerType
 * @param {ArrayBuffer} binaryBuffer
 */
export function processDataArray(
  size: number,
  dataArrayElem: HTMLElement,
  compressor: string,
  byteOrder: string,
  headerType: string,
  binaryBuffer: ArrayBuffer
): IRet;

/**
 * @param {Number} size
 * @param {HTMLElement} containerElem
 * @param {String} compressor
 * @param {String} byteOrder
 * @param {String} headerType
 * @param {ArrayBuffer} binaryBuffer
 */
export function processCells(
  size: number,
  containerElem: HTMLElement,
  compressor: string,
  byteOrder: string,
  headerType: string,
  binaryBuffer: ArrayBuffer
): Uint32Array;

/**
 * @param {Number} size
 * @param {HTMLElement} fieldElem
 * @param {HTMLElement} fieldContainer
 * @param {String} compressor
 * @param {String} byteOrder
 * @param {String} headerType
 * @param {ArrayBuffer} binaryBuffer
 */
export function processFieldData(
  size: number,
  fieldElem: HTMLElement,
  fieldContainer: HTMLElement,
  compressor: string,
  byteOrder: string,
  headerType: string,
  binaryBuffer: ArrayBuffer
): void;

/**
 * vtkXMLReader is a source object that parses a VTK XML input file.
 */
export declare const vtkXMLReader: {
  extend: typeof extend;
  processDataArray: typeof processDataArray;
  processCells: typeof processCells;
  processFieldData: typeof processFieldData;
};
export default vtkXMLReader;

index.js

import { create } from 'xmlbuilder2';
import { decompressSync } from 'fflate';

import DataAccessHelper from 'vtk.js/Sources/IO/Core/DataAccessHelper';
import Base64 from 'vtk.js/Sources/Common/Core/Base64';
import macro from 'vtk.js/Sources/macros';
import vtkDataArray from 'vtk.js/Sources/Common/Core/DataArray';
import vtkStringArray from 'vtk.js/Sources/Common/Core/StringArray';
import BinaryHelper from 'vtk.js/Sources/IO/Core/BinaryHelper';

// Enable data soure for DataAccessHelper
import 'vtk.js/Sources/IO/Core/DataAccessHelper/LiteHttpDataAccessHelper'; // Just need HTTP
// import 'vtk.js/Sources/IO/Core/DataAccessHelper/HttpDataAccessHelper'; // HTTP + zip
// import 'vtk.js/Sources/IO/Core/DataAccessHelper/HtmlDataAccessHelper'; // html + base64 + zip
// import 'vtk.js/Sources/IO/Core/DataAccessHelper/JSZipDataAccessHelper'; // zip

// ----------------------------------------------------------------------------
// Global methods
// ----------------------------------------------------------------------------

export function findAllTags(node, tagName) {
  return [...node.getElementsByTagName(tagName)];
}

export function findFirstTag(node, tagName) {
  return findAllTags(node, tagName)[0];
}

function parseXML(xmlStr) {
  // see xmlbuilder2 docs on the object format
  return create(xmlStr);
}

function extractAppendedData(buffer) {
  // search for appended data tag
  const prefixRegex = /^\s*<AppendedData\s+encoding="raw">\s*_/m;
  const suffixRegex = /\n\s*<\/AppendedData>/m;
  return BinaryHelper.extractBinary(buffer, prefixRegex, suffixRegex);
}

// ----------------------------------------------------------------------------

const TYPED_ARRAY = {
  Int8: Int8Array,
  UInt8: Uint8Array,
  Int16: Int16Array,
  UInt16: Uint16Array,
  Int32: Int32Array,
  UInt32: Uint32Array,
  Int64: Int32Array, // Not supported with JavaScript will cause error in binary
  UInt64: Uint32Array, // Not supported with JavaScript will cause error in binary
  Float32: Float32Array,
  Float64: Float64Array,
};

// ----------------------------------------------------------------------------

const TYPED_ARRAY_BYTES = {
  Int8: 1,
  UInt8: 1,
  Int16: 2,
  UInt16: 2,
  Int32: 4,
  UInt32: 4,
  Int64: 8, // Not supported with JavaScript will cause error in binary
  UInt64: 8, // Not supported with JavaScript will cause error in binary
  Float32: 4,
  Float64: 8,
};

// ----------------------------------------------------------------------------

function integer64to32(array) {
  const maxIdx = array.length - 1; // Skip last
  return array.filter((v, i) => i < maxIdx && i % 2 === 0);
}

// ----------------------------------------------------------------------------

/**
 * Reads the data of a length-prefixed blob.
 *
 * Int64 headers and values are not supported.
 *
 * @param {Uint8Array} uint8 a uint8 view of the length-prefixed blob.
 * @param {string} dataType
 * @param {string} headerType either UInt64 or UInt32
 */
function readLengthPrefixedData(uint8, dataType, headerType) {
  if (!['UInt64', 'UInt32'].includes(headerType)) {
    throw new Error(`Cannot handle a header type of ${headerType}`);
  }

  let HeaderTypedArray = TYPED_ARRAY[headerType];
  let DataTypedArray = TYPED_ARRAY[dataType];
  let dataFallbackTo32 = false;

  if (headerType === 'UInt64') {
    HeaderTypedArray = TYPED_ARRAY.UInt32;
  }

  if (/^U?Int64$/.test(dataType)) {
    dataFallbackTo32 = true;
    DataTypedArray = TYPED_ARRAY[dataType.replace('64', '32')];
  }

  const { byteOffset } = uint8;
  const dataWordSize = TYPED_ARRAY_BYTES[dataType];
  const headerWordSize = TYPED_ARRAY_BYTES[headerType];

  // slice if offset is not word aligned
  let header;
  if (byteOffset % headerWordSize === 0) {
    header = new HeaderTypedArray(uint8.buffer, byteOffset, 1);
  } else {
    header = new HeaderTypedArray(
      uint8.buffer.slice(byteOffset, byteOffset + headerWordSize)
    );
  }

  const dataByteLength = Number(header[0]);

  // read values
  let values;
  let arraySize = dataByteLength / dataWordSize;

  if (dataFallbackTo32) {
    // We are reading int64 data with an int32 typed array.
    arraySize *= 2;
  }

  // slice if offset is not word aligned
  const dataOffset = byteOffset + headerWordSize;
  if (dataOffset % dataWordSize === 0) {
    values = new DataTypedArray(uint8.buffer, dataOffset, arraySize);
  } else {
    values = new DataTypedArray(
      uint8.buffer.slice(dataOffset, dataOffset + dataByteLength)
    );
  }

  if (dataFallbackTo32) {
    // remove higher order 32 bits
    values = integer64to32(values);
  }

  return values;
}

// ----------------------------------------------------------------------------

function readerHeader(uint8, headerType) {
  // We do not handle endianness or if more than 32 bits are needed to encode the data
  if (headerType === 'UInt64') {
    const offset = 8;
    let uint32 = new Uint32Array(uint8.buffer, 0, 6);
    const nbBlocks = uint32[0];
    const s1 = uint32[2];
    const s2 = uint32[4];
    const resultArray = [offset, nbBlocks, s1, s2];
    uint32 = new Uint32Array(uint8.buffer, 3 * 8, nbBlocks * 2);
    for (let i = 0; i < nbBlocks; i++) {
      resultArray.push(uint32[i * 2]);
    }
    return resultArray;
  }
  // UInt32
  let uint32 = new Uint32Array(uint8.buffer, 0, 3);
  const offset = 4;
  const nbBlocks = uint32[0];
  const s1 = uint32[1];
  const s2 = uint32[2];
  const resultArray = [offset, nbBlocks, s1, s2];
  uint32 = new Uint32Array(uint8.buffer, 3 * 4, nbBlocks);
  for (let i = 0; i < nbBlocks; i++) {
    resultArray.push(uint32[i]);
  }
  return resultArray;
}

// ----------------------------------------------------------------------------

/**
 * Given the return value of readerHeader, return header byte length.
 */
function getHeaderByteLength(header, headerType) {
  // ignore the first number, which isn't actually part of the header.
  const [headerWordSize] = header;
  return (header.length - 1) * headerWordSize;
}

// ----------------------------------------------------------------------------

function uncompressBlock(compressedUint8, output) {
  const uncompressedBlock = decompressSync(compressedUint8);
  output.uint8.set(uncompressedBlock, output.offset);
  output.offset += uncompressedBlock.length;
}

// ----------------------------------------------------------------------------

function decompressZLib(bytes, headerType) {
  // ----------------------------------------------------------------------
  // Layout of the data
  // header[N, s1, s2, blockSize1, ..., blockSizeN], [padding???], block[compressedData], ..., block[compressedData]
  // [header] N, s1 and s2 are uint 32 or 64 (defined by header_type="UInt64" attribute on the root node)
  // [header] s1: uncompress size of each block except the last one
  // [header] s2: uncompress size of the last blocks
  // [header] blockSize: size of the block in compressed space that represent to bloc to inflate in zlib. (This also give the offset to the next block)
  // ----------------------------------------------------------------------

  // Header reading: [offset, numBlocks, s1, s2]
  const header = readerHeader(bytes, headerType);
  const nbBlocks = header[1];
  const s1 = header[2];
  const s2 = header[3];
  let dataByteLength = 0;

  if (nbBlocks > 0) {
    // If the last block's size is labeled as 0, that means the last block
    // really has size header[2].
    if (s2 === 0) {
      dataByteLength = nbBlocks * s1;
    } else {
      dataByteLength = (nbBlocks - 1) * s1 + s2;
    }
  }

  const buffer = new ArrayBuffer(dataByteLength);
  const output = {
    offset: 0,
    uint8: new Uint8Array(buffer),
  };

  let offset = getHeaderByteLength(header, headerType);
  // Starting from end of the data header, find the zlib header, which starts with 0x78.
  // This accounts for any padding between the header and the compressed data.
  while (offset < bytes.length && bytes[offset] !== 0x78) {
    offset++;
  }

  for (let i = 0; i < nbBlocks; i++) {
    const blockSize = header[4 + i];
    const compressedBlock = new Uint8Array(bytes.buffer, offset, blockSize);
    uncompressBlock(compressedBlock, output);
    offset += blockSize;
  }

  return output.uint8;
}

// ----------------------------------------------------------------------------

function processDataArray(
  size,
  dataArrayElem,
  compressor,
  byteOrder,
  headerType,
  binaryBuffer
) {
  const dataType = dataArrayElem.getAttribute('type');
  const name = dataArrayElem.getAttribute('Name');
  const format = dataArrayElem.getAttribute('format'); // binary, ascii, appended
  const numberOfComponents = Number(
    dataArrayElem.getAttribute('NumberOfComponents') || '1'
  );
  let values = null;

  if (format === 'ascii') {
    values = new TYPED_ARRAY[dataType](size * numberOfComponents);
    let offset = 0;
    dataArrayElem.firstChild.nodeValue.split(/[\\t \\n]+/).forEach((token) => {
      if (token.trim().length) {
        values[offset++] = Number(token);
      }
    });
  } else if (format === 'binary') {
    const uint8 = new Uint8Array(
      Base64.toArrayBuffer(dataArrayElem.firstChild.nodeValue.trim())
    );
    if (compressor === 'vtkZLibDataCompressor') {
      const data = decompressZLib(uint8, headerType);
      values = new TYPED_ARRAY[dataType](data.buffer);

      // Handle (u)int64 hoping for no overflow...
      if (/^U?Int64$/.test(dataType)) {
        values = integer64to32(values);
      }
    } else {
      values = new TYPED_ARRAY[dataType](
        uint8.buffer,
        TYPED_ARRAY_BYTES[headerType]
      );

      // Handle (u)int64 hoping no overflow...
      if (dataType.indexOf('Int64') !== -1) {
        values = integer64to32(values);
      }
    }
  } else if (format === 'appended') {
    const offset = Number(dataArrayElem.getAttribute('offset'));
    values = readLengthPrefixedData(
      new Uint8Array(binaryBuffer, offset),
      dataType,
      headerType
    );
  } else {
    console.error('Format not supported', format);
  }

  return { name, values, numberOfComponents };
}

// ----------------------------------------------------------------------------

function decodeStringArrayFromBytes(bytes) {
  const decoder = new TextDecoder();
  const decoded = decoder.decode(bytes);

  // strings are null-terminated
  return decoded.split('\x00').slice(0, -1);
}

// ----------------------------------------------------------------------------

function processStringArray(
  stringArrayElem,
  compressor,
  byteOrder,
  headerType,
  binaryBuffer
) {
  const name = stringArrayElem.getAttribute('Name');
  const format = stringArrayElem.getAttribute('format'); // binary, ascii, appended
  const numberOfComponents = Number(
    stringArrayElem.getAttribute('NumberOfComponents') || '1'
  );
  const numberOfTuples = Number(
    stringArrayElem.getAttribute('NumberOfTuples') || '1'
  );
  const nbStrings = numberOfTuples * numberOfComponents;
  const strings = [];

  if (format === 'ascii') {
    const tokens = stringArrayElem.firstChild.nodeValue.trim().split(/\s+/);
    let tokIdx = 0;
    const strChars = [];

    while (strings.length < nbStrings) {
      const token = Number(tokens[tokIdx++]);
      if (token === 0) {
        strings.push(strChars.join(''));
        strChars.length = 0;
      } else {
        strChars.push(String.fromCharCode(token));
      }
    }
  } else if (format === 'binary') {
    const uint8 = new Uint8Array(
      Base64.toArrayBuffer(stringArrayElem.firstChild.nodeValue.trim())
    );
    if (compressor === 'vtkZLibDataCompressor') {
      const decompressed = decompressZLib(uint8, headerType);
      strings.push(...decodeStringArrayFromBytes(decompressed));
    } else {
      const strData = readLengthPrefixedData(uint8, 'UInt8', headerType);
      strings.push(...decodeStringArrayFromBytes(strData));
    }
  } else if (format === 'appended') {
    const offset = Number(stringArrayElem.getAttribute('offset'));
    const values = readLengthPrefixedData(
      new Uint8Array(binaryBuffer, offset),
      'UInt8',
      headerType
    );
    strings.push(...decodeStringArrayFromBytes(values));
  } else {
    macro.vtkErrorMacro(`Format not supported: ${format}`);
  }

  return { name, values: strings, numberOfComponents };
}

// ----------------------------------------------------------------------------

function processCells(
  size,
  containerElem,
  compressor,
  byteOrder,
  headerType,
  binaryBuffer
) {
  const arrayElems = {};
  const dataArrayElems = containerElem.getElementsByTagName('DataArray');
  for (let elIdx = 0; elIdx < dataArrayElems.length; elIdx++) {
    const el = dataArrayElems[elIdx];
    arrayElems[el.getAttribute('Name')] = el;
  }

  const offsets = processDataArray(
    size,
    arrayElems.offsets,
    compressor,
    byteOrder,
    headerType,
    binaryBuffer
  ).values;
  const connectivitySize = offsets[offsets.length - 1];
  const connectivity = processDataArray(
    connectivitySize,
    arrayElems.connectivity,
    compressor,
    byteOrder,
    headerType,
    binaryBuffer
  ).values;
  const values = new Uint32Array(size + connectivitySize);
  let writeOffset = 0;
  let previousOffset = 0;
  offsets.forEach((v) => {
    const cellSize = v - previousOffset;
    values[writeOffset++] = cellSize;

    for (let i = 0; i < cellSize; i++) {
      values[writeOffset++] = connectivity[previousOffset + i];
    }

    // save previous offset
    previousOffset = v;
  });

  return values;
}

// ----------------------------------------------------------------------------

function processFieldData(
  size,
  fieldElem,
  fieldContainer,
  compressor,
  byteOrder,
  headerType,
  binaryBuffer
) {
  if (fieldElem) {
    const attributes = ['Scalars', 'Vectors', 'Normals', 'Tensors', 'TCoords'];
    const nameBinding = {};
    attributes.forEach((attrName) => {
      const arrayName = fieldElem.getAttribute(attrName);
      if (arrayName) {
        nameBinding[arrayName] = fieldContainer[`set${attrName}`];
      }
    });

    const dataArrayElems = fieldElem.getElementsByTagName('DataArray');
    const nbArrays = dataArrayElems.length;
    for (let idx = 0; idx < nbArrays; idx++) {
      const array = dataArrayElems[idx];
      const dataArray = vtkDataArray.newInstance(
        processDataArray(
          size,
          array,
          compressor,
          byteOrder,
          headerType,
          binaryBuffer
        )
      );
      const name = dataArray.getName();
      (nameBinding[name] || fieldContainer.addArray)(dataArray);
    }
  }
}

// ----------------------------------------------------------------------------
function handleFieldDataArrays(
  fieldDataElem,
  compressor,
  byteOrder,
  headerType,
  binaryBuffer
) {
  const dataArrays = [...fieldDataElem.getElementsByTagName('DataArray')].map(
    (daElem) =>
      vtkDataArray.newInstance(
        processDataArray(
          Number(daElem.getAttribute('NumberOfTuples')),
          daElem,
          compressor,
          byteOrder,
          headerType,
          binaryBuffer
        )
      )
  );

  const stringArrays = [...fieldDataElem.getElementsByTagName('Array')]
    .filter((elem) => elem.getAttribute('type') === 'String')
    .map((arrElem) => {
      const sa = vtkStringArray.newInstance(
        processStringArray(
          arrElem,
          compressor,
          byteOrder,
          headerType,
          binaryBuffer
        )
      );
      return sa;
    });

  return [...dataArrays, ...stringArrays];
}

// ----------------------------------------------------------------------------
// vtkXMLReader methods
// ----------------------------------------------------------------------------

function vtkXMLReader(publicAPI, model) {
  // Set our className
  model.classHierarchy.push('vtkXMLReader');

  // Create default dataAccessHelper if not available
  if (!model.dataAccessHelper) {
    model.dataAccessHelper = DataAccessHelper.get('http');
  }

  // Internal method to fetch Array
  function fetchData(url, option = {}) {
    return model.dataAccessHelper.fetchBinary(url, option);
  }

  // Set DataSet url
  publicAPI.setUrl = (url, option = {}) => {
    model.url = url;

    // Remove the file in the URL
    const path = url.split('/');
    path.pop();
    model.baseURL = path.join('/');

    // Fetch metadata
    return publicAPI.loadData(option);
  };

  // Fetch the actual data arrays
  publicAPI.loadData = (option = {}) =>
    fetchData(model.url, option).then(publicAPI.parseAsArrayBuffer);

  publicAPI.parseAsArrayBuffer = (arrayBuffer) => {
    if (!arrayBuffer) {
      return false;
    }
    if (arrayBuffer !== model.rawDataBuffer) {
      publicAPI.modified();
    } else {
      return true;
    }

    const { text: content, binaryBuffer } = extractAppendedData(arrayBuffer);
    model.rawDataBuffer = arrayBuffer;
    model.binaryBuffer = binaryBuffer;

    // Parse data here...
    const doc = parseXML(content);
    const root = doc.root();
    const rootElem = root.node;
    const type = rootElem.getAttribute('type');
    const compressor = rootElem.getAttribute('compressor');
    const byteOrder = rootElem.getAttribute('byte_order');
    // default to UInt32. I think version 0.1 vtp/vti files default to UInt32.
    const headerType = rootElem.getAttribute('header_type') || 'UInt32';

    if (compressor && compressor !== 'vtkZLibDataCompressor') {
      console.error('Invalid compressor', compressor);
      return false;
    }

    if (byteOrder && byteOrder !== 'LittleEndian') {
      console.error('Only LittleEndian encoding is supported');
      return false;
    }

    if (type !== model.dataType) {
      console.error('Invalid data type', type, 'expecting', model.dataType);
      return false;
    }

    // appended format
    if (findFirstTag(rootElem, 'AppendedData')) {
      const appendedDataElem = findFirstTag(rootElem, 'AppendedData');
      const encoding = appendedDataElem.getAttribute('encoding');
      const arrays = root
        .filter(
          (xmlNode) => {
            const { node } = xmlNode;
            return (
              node.nodeType === Node.ELEMENT_NODE &&
              node.getAttribute('format') === 'appended' &&
              node.hasAttribute('offset')
            );
          },
          false,
          true
        )
        .map((xmlNode) => ({
          node: xmlNode.node,
          offset: Number(xmlNode.node.getAttribute('offset')),
        }));

      // sort dataElems by increasing offset
      arrays.sort((a, b) => a.offset - b.offset);

      let appendedBuffer = model.binaryBuffer;

      if (encoding === 'base64') {
        // substr(1) is to remove the '_' prefix
        appendedBuffer = appendedDataElem.textContent.trim().substr(1);
      }

      // get data array chunks
      const dataArrays = [];
      for (let i = 0; i < arrays.length; ++i) {
        const offset = arrays[i].offset;
        let nextOffset = 0;
        if (i === arrays.length - 1) {
          nextOffset = appendedBuffer.length || appendedBuffer.byteLength;
        } else {
          nextOffset = arrays[i + 1].offset;
        }

        if (encoding === 'base64') {
          dataArrays.push(
            new Uint8Array(
              Base64.toArrayBuffer(appendedBuffer.substring(offset, nextOffset))
            )
          );
        } else {
          // encoding === 'raw'
          // Need to slice the ArrayBuffer so readerHeader() works properly
          dataArrays.push(
            new Uint8Array(appendedBuffer.slice(offset, nextOffset))
          );
        }
      }

      if (compressor === 'vtkZLibDataCompressor') {
        for (let arrayidx = 0; arrayidx < dataArrays.length; ++arrayidx) {
          const dataArray = dataArrays[arrayidx];

          const uncompressed = decompressZLib(dataArray, headerType);

          const data = new Uint8Array(
            uncompressed.length + TYPED_ARRAY_BYTES[headerType]
          );
          // set length header
          // TODO this does not work for lengths that are greater than the max Uint32 value.
          new TYPED_ARRAY[headerType](data.buffer, 0, 1)[0] =
            uncompressed.length;
          data.set(uncompressed, TYPED_ARRAY_BYTES[headerType]);

          dataArrays[arrayidx] = data;
        }
      }

      const bufferLength = dataArrays.reduce((acc, arr) => acc + arr.length, 0);
      const buffer = new ArrayBuffer(bufferLength);
      const view = new Uint8Array(buffer);

      for (let i = 0, offset = 0; i < dataArrays.length; ++i) {
        // set correct offsets
        arrays[i].node.setAttribute('offset', offset);
        // set final buffer data
        view.set(dataArrays[i], offset);
        offset += dataArrays[i].length;
      }

      model.binaryBuffer = buffer;

      if (!model.binaryBuffer) {
        console.error(
          'Processing appended data format: requires binaryBuffer to parse'
        );
        return false;
      }
    }

    publicAPI.parseXML(rootElem, type, compressor, byteOrder, headerType);

    const datasetElem = rootElem.getElementsByTagName(type)[0];
    const fieldDataElem = datasetElem.getElementsByTagName('FieldData')[0];

    if (fieldDataElem) {
      const fieldDataArrays = handleFieldDataArrays(
        fieldDataElem,
        compressor,
        byteOrder,
        headerType,
        model.binaryBuffer
      );

      for (let i = 0; i < model.output.length; i++) {
        const fieldData = model.output[i].getFieldData();
        for (let j = 0; j < fieldDataArrays.length; j++) {
          fieldData.addArray(fieldDataArrays[j]);
        }
      }
    }

    return true;
  };

  publicAPI.requestData = (inData, outData) => {
    publicAPI.parseAsArrayBuffer(model.rawDataBuffer);
  };
}

// ----------------------------------------------------------------------------
// Object factory
// ----------------------------------------------------------------------------

const DEFAULT_VALUES = {
  // baseURL: null,
  // dataAccessHelper: null,
  // url: null,
};

// ----------------------------------------------------------------------------

export function extend(publicAPI, model, initialValues = {}) {
  Object.assign(model, DEFAULT_VALUES, initialValues);

  // Build VTK API
  macro.obj(publicAPI, model);
  macro.get(publicAPI, model, ['url', 'baseURL']);
  macro.setGet(publicAPI, model, ['dataAccessHelper']);
  macro.algo(publicAPI, model, 0, 1);

  // vtkXMLReader methods
  vtkXMLReader(publicAPI, model);
}

// ----------------------------------------------------------------------------

export default { extend, processDataArray, processFieldData, processCells };