openmedialibrary_reader/cbr.js/bitjs/untar.js

/**
 * untar.js
 *
 * Copyright(c) 2011 Google Inc.
 *
 * Reference Documentation:
 *
 * TAR format: http://www.gnu.org/software/automake/manual/tar/Standard.html
 */

// This file expects to be invoked as a Worker (see onmessage below).
importScripts('io.js');
importScripts('archive.js');

// Progress variables.
var currentFilename = "";
var currentFileNumber = 0;
var currentBytesUnarchivedInFile = 0;
var currentBytesUnarchived = 0;
var totalUncompressedBytesInArchive = 0;
var totalFilesInArchive = 0;

// Helper functions.
var info = function(str) {
  postMessage(new bitjs.archive.UnarchiveInfoEvent(str));
};
var err = function(str) {
  postMessage(new bitjs.archive.UnarchiveErrorEvent(str));
};
var postProgress = function() {
  postMessage(new bitjs.archive.UnarchiveProgressEvent(
      currentFilename,
      currentFileNumber,
      currentBytesUnarchivedInFile,
      currentBytesUnarchived,
      totalUncompressedBytesInArchive,
      totalFilesInArchive));
};

// Removes all characters from the first zero-byte in the string onwards.
var readCleanString = function(bstr, numBytes) {
  var str = bstr.readString(numBytes);
  var zIndex = str.indexOf(String.fromCharCode(0));
  return zIndex != -1 ? str.substr(0, zIndex) : str;
};

// takes a ByteStream and parses out the local file information
var TarLocalFile = function(bstream) {
  this.isValid = false;

  // Read in the header block
  this.name = readCleanString(bstream, 100);
  this.mode = readCleanString(bstream, 8);
  this.uid = readCleanString(bstream, 8);
  this.gid = readCleanString(bstream, 8);
  this.size = parseInt(readCleanString(bstream, 12), 8);
  this.mtime = readCleanString(bstream, 12);
  this.chksum = readCleanString(bstream, 8);
  this.typeflag = readCleanString(bstream, 1);
  this.linkname = readCleanString(bstream, 100);
  this.maybeMagic = readCleanString(bstream, 6);

  if (this.maybeMagic == "ustar") {
  	this.version = readCleanString(bstream, 2);
  	this.uname = readCleanString(bstream, 32);
  	this.gname = readCleanString(bstream, 32);
  	this.devmajor = readCleanString(bstream, 8);
  	this.devminor = readCleanString(bstream, 8);
  	this.prefix = readCleanString(bstream, 155);

  	if (this.prefix.length) {
      this.name = this.prefix + this.name;
  	}
  	bstream.readBytes(12); // 512 - 500
  } else {
  	bstream.readBytes(255); // 512 - 257
  }
  
  // Done header, now rest of blocks are the file contents.
  this.filename = this.name;
  this.fileData = null;

  info("Untarring file '" + this.filename + "'");
  info("  size = " + this.size);
  info("  typeflag = " + this.typeflag);

  // A regular file.
  if (this.typeflag == 0) {
  	info("  This is a regular file.");
  	var sizeInBytes = parseInt(this.size);
  	this.fileData = new Uint8Array(bstream.bytes.buffer, bstream.ptr, this.size);
    if (this.name.length > 0 && this.size > 0 && this.fileData && this.fileData.buffer) {
      this.isValid = true;
  	}

    bstream.readBytes(this.size);

  	// Round up to 512-byte blocks.
  	var remaining = 512 - this.size % 512;
  	if (remaining > 0 && remaining < 512) {
      bstream.readBytes(remaining);
  	}
  } else if (this.typeflag == 5) {
  	 info("  This is a directory.")
  }
};

// Takes an ArrayBuffer of a tar file in
// returns null on error
// returns an array of DecompressedFile objects on success
var untar = function(arrayBuffer) {
  currentFilename = "";
  currentFileNumber = 0;
  currentBytesUnarchivedInFile = 0;
  currentBytesUnarchived = 0;
  totalUncompressedBytesInArchive = 0;
  totalFilesInArchive = 0;

  postMessage(new bitjs.archive.UnarchiveStartEvent());
  var bstream = new bitjs.io.ByteStream(arrayBuffer);
  var localFiles = [];

  // While we don't encounter an empty block, keep making TarLocalFiles.
  while (bstream.peekNumber(4) != 0) {
  	var oneLocalFile = new TarLocalFile(bstream);
  	if (oneLocalFile && oneLocalFile.isValid) {
      localFiles.push(oneLocalFile);
      totalUncompressedBytesInArchive += oneLocalFile.size;
  	}
  }
  totalFilesInArchive = localFiles.length;

  // got all local files, now sort them
  localFiles.sort(function(a,b) {
      var aname = a.filename;
      var bname = b.filename;
      return aname > bname ? 1 : -1;

      // extract the number at the end of both filenames
      /*
      var aname = a.filename;
      var bname = b.filename;
      var aindex = aname.length, bindex = bname.length;

      // Find the last number character from the back of the filename.
      while (aname[aindex-1] < '0' || aname[aindex-1] > '9') --aindex;
      while (bname[bindex-1] < '0' || bname[bindex-1] > '9') --bindex;

      // Find the first number character from the back of the filename
      while (aname[aindex-1] >= '0' && aname[aindex-1] <= '9') --aindex;
      while (bname[bindex-1] >= '0' && bname[bindex-1] <= '9') --bindex;

      // parse them into numbers and return comparison
      var anum = parseInt(aname.substr(aindex), 10),
          bnum = parseInt(bname.substr(bindex), 10);
      return anum - bnum;
      */
  });

  // report # files and total length
  if (localFiles.length > 0) {
    postProgress();
  }

  // now do the shipping of each file
  for (var i = 0; i < localFiles.length; ++i) {
    var localfile = localFiles[i];
    info("Sending file '" + localfile.filename + "' up");

    // update progress
    currentFilename = localfile.filename;
    currentFileNumber = i;
    currentBytesUnarchivedInFile = localfile.size;
    currentBytesUnarchived += localfile.size;
    postMessage(new bitjs.archive.UnarchiveExtractEvent(localfile));
    postProgress();
  }

  postProgress();

  postMessage(new bitjs.archive.UnarchiveFinishEvent());
};

// event.data.file has the ArrayBuffer.
onmessage = function(event) {
  var ab = event.data.file;
  untar(ab);
};