wallet-core/node_modules/yazl/index.js

var fs = require("fs");
var Transform = require("stream").Transform;
var PassThrough = require("stream").PassThrough;
var zlib = require("zlib");
var util = require("util");
var EventEmitter = require("events").EventEmitter;
var crc32 = require("buffer-crc32");

exports.ZipFile = ZipFile;
exports.dateToDosDateTime = dateToDosDateTime;

util.inherits(ZipFile, EventEmitter);
function ZipFile() {
  this.outputStream = new PassThrough();
  this.entries = [];
  this.outputStreamCursor = 0;
  this.ended = false; // .end() sets this
  this.allDone = false; // set when we've written the last bytes
  this.forceZip64Eocd = false; // configurable in .end()
}

ZipFile.prototype.addFile = function(realPath, metadataPath, options) {
  var self = this;
  metadataPath = validateMetadataPath(metadataPath, false);
  if (options == null) options = {};

  var entry = new Entry(metadataPath, false, options);
  self.entries.push(entry);
  fs.stat(realPath, function(err, stats) {
    if (err) return self.emit("error", err);
    if (!stats.isFile()) return self.emit("error", new Error("not a file: " + realPath));
    entry.uncompressedSize = stats.size;
    if (options.mtime == null) entry.setLastModDate(stats.mtime);
    if (options.mode == null) entry.setFileAttributesMode(stats.mode);
    entry.setFileDataPumpFunction(function() {
      var readStream = fs.createReadStream(realPath);
      entry.state = Entry.FILE_DATA_IN_PROGRESS;
      readStream.on("error", function(err) {
        self.emit("error", err);
      });
      pumpFileDataReadStream(self, entry, readStream);
    });
    pumpEntries(self);
  });
};

ZipFile.prototype.addReadStream = function(readStream, metadataPath, options) {
  var self = this;
  metadataPath = validateMetadataPath(metadataPath, false);
  if (options == null) options = {};
  var entry = new Entry(metadataPath, false, options);
  self.entries.push(entry);
  entry.setFileDataPumpFunction(function() {
    entry.state = Entry.FILE_DATA_IN_PROGRESS;
    pumpFileDataReadStream(self, entry, readStream);
  });
  pumpEntries(self);
};

ZipFile.prototype.addBuffer = function(buffer, metadataPath, options) {
  var self = this;
  metadataPath = validateMetadataPath(metadataPath, false);
  if (buffer.length > 0x3fffffff) throw new Error("buffer too large: " + buffer.length + " > " + 0x3fffffff);
  if (options == null) options = {};
  if (options.size != null) throw new Error("options.size not allowed");
  var entry = new Entry(metadataPath, false, options);
  entry.uncompressedSize = buffer.length;
  entry.crc32 = crc32.unsigned(buffer);
  entry.crcAndFileSizeKnown = true;
  self.entries.push(entry);
  if (!entry.compress) {
    setCompressedBuffer(buffer);
  } else {
    zlib.deflateRaw(buffer, function(err, compressedBuffer) {
      setCompressedBuffer(compressedBuffer);
    });
  }
  function setCompressedBuffer(compressedBuffer) {
    entry.compressedSize = compressedBuffer.length;
    entry.setFileDataPumpFunction(function() {
      writeToOutputStream(self, compressedBuffer);
      writeToOutputStream(self, entry.getDataDescriptor());
      entry.state = Entry.FILE_DATA_DONE;

      // don't call pumpEntries() recursively.
      // (also, don't call process.nextTick recursively.)
      setImmediate(function() {
        pumpEntries(self);
      });
    });
    pumpEntries(self);
  }
};

ZipFile.prototype.addEmptyDirectory = function(metadataPath, options) {
  var self = this;
  metadataPath = validateMetadataPath(metadataPath, true);
  if (options == null) options = {};
  if (options.size != null) throw new Error("options.size not allowed");
  if (options.compress != null) throw new Error("options.compress not allowed");
  var entry = new Entry(metadataPath, true, options);
  self.entries.push(entry);
  entry.setFileDataPumpFunction(function() {
    writeToOutputStream(self, entry.getDataDescriptor());
    entry.state = Entry.FILE_DATA_DONE;
    pumpEntries(self);
  });
  pumpEntries(self);
};

ZipFile.prototype.end = function(options, finalSizeCallback) {
  if (typeof options === "function") {
    finalSizeCallback = options;
    options = null;
  }
  if (options == null) options = {};
  if (this.ended) return;
  this.ended = true;
  this.finalSizeCallback = finalSizeCallback;
  this.forceZip64Eocd = !!options.forceZip64Format;
  pumpEntries(this);
};

function writeToOutputStream(self, buffer) {
  self.outputStream.write(buffer);
  self.outputStreamCursor += buffer.length;
}

function pumpFileDataReadStream(self, entry, readStream) {
  var crc32Watcher = new Crc32Watcher();
  var uncompressedSizeCounter = new ByteCounter();
  var compressor = entry.compress ? new zlib.DeflateRaw() : new PassThrough();
  var compressedSizeCounter = new ByteCounter();
  readStream.pipe(crc32Watcher)
            .pipe(uncompressedSizeCounter)
            .pipe(compressor)
            .pipe(compressedSizeCounter)
            .pipe(self.outputStream, {end: false});
  compressedSizeCounter.on("end", function() {
    entry.crc32 = crc32Watcher.crc32;
    if (entry.uncompressedSize == null) {
      entry.uncompressedSize = uncompressedSizeCounter.byteCount;
    } else {
      if (entry.uncompressedSize !== uncompressedSizeCounter.byteCount) return self.emit("error", new Error("file data stream has unexpected number of bytes"));
    }
    entry.compressedSize = compressedSizeCounter.byteCount;
    self.outputStreamCursor += entry.compressedSize;
    writeToOutputStream(self, entry.getDataDescriptor());
    entry.state = Entry.FILE_DATA_DONE;
    pumpEntries(self);
  });
}

function pumpEntries(self) {
  if (self.allDone) return;
  // first check if finalSize is finally known
  if (self.ended && self.finalSizeCallback != null) {
    var finalSize = calculateFinalSize(self);
    if (finalSize != null) {
      // we have an answer
      self.finalSizeCallback(finalSize);
      self.finalSizeCallback = null;
    }
  }

  // pump entries
  var entry = getFirstNotDoneEntry();
  function getFirstNotDoneEntry() {
    for (var i = 0; i < self.entries.length; i++) {
      var entry = self.entries[i];
      if (entry.state < Entry.FILE_DATA_DONE) return entry;
    }
    return null;
  }
  if (entry != null) {
    // this entry is not done yet
    if (entry.state < Entry.READY_TO_PUMP_FILE_DATA) return; // input file not open yet
    if (entry.state === Entry.FILE_DATA_IN_PROGRESS) return; // we'll get there
    // start with local file header
    entry.relativeOffsetOfLocalHeader = self.outputStreamCursor;
    var localFileHeader = entry.getLocalFileHeader();
    writeToOutputStream(self, localFileHeader);
    entry.doFileDataPump();
  } else {
    // all cought up on writing entries
    if (self.ended) {
      // head for the exit
      self.offsetOfStartOfCentralDirectory = self.outputStreamCursor;
      self.entries.forEach(function(entry) {
        var centralDirectoryRecord = entry.getCentralDirectoryRecord();
        writeToOutputStream(self, centralDirectoryRecord);
      });
      writeToOutputStream(self, getEndOfCentralDirectoryRecord(self));
      self.outputStream.end();
      self.allDone = true;
    }
  }
}

function calculateFinalSize(self) {
  var pretendOutputCursor = 0;
  var centralDirectorySize = 0;
  for (var i = 0; i < self.entries.length; i++) {
    var entry = self.entries[i];
    // compression is too hard to predict
    if (entry.compress) return -1;
    if (entry.state >= Entry.READY_TO_PUMP_FILE_DATA) {
      // if addReadStream was called without providing the size, we can't predict the final size
      if (entry.uncompressedSize == null) return -1;
    } else {
      // if we're still waiting for fs.stat, we might learn the size someday
      if (entry.uncompressedSize == null) return null;
    }
    // we know this for sure, and this is important to know if we need ZIP64 format.
    entry.relativeOffsetOfLocalHeader = pretendOutputCursor;
    var useZip64Format = entry.useZip64Format();

    pretendOutputCursor += LOCAL_FILE_HEADER_FIXED_SIZE + entry.utf8FileName.length;
    pretendOutputCursor += entry.uncompressedSize;
    if (!entry.crcAndFileSizeKnown) {
      // use a data descriptor
      if (useZip64Format) {
        pretendOutputCursor += ZIP64_DATA_DESCRIPTOR_SIZE;
      } else {
        pretendOutputCursor += DATA_DESCRIPTOR_SIZE;
      }
    }

    centralDirectorySize += CENTRAL_DIRECTORY_RECORD_FIXED_SIZE + entry.utf8FileName.length;
    if (useZip64Format) {
      centralDirectorySize += ZIP64_EXTENDED_INFORMATION_EXTRA_FIELD_SIZE;
    }
  }

  var endOfCentralDirectorySize = 0;
  if (self.forceZip64Eocd ||
      self.entries.length >= 0xffff ||
      centralDirectorySize >= 0xffff ||
      pretendOutputCursor >= 0xffffffff) {
    // use zip64 end of central directory stuff
    endOfCentralDirectorySize += ZIP64_END_OF_CENTRAL_DIRECTORY_RECORD_SIZE + ZIP64_END_OF_CENTRAL_DIRECTORY_LOCATOR_SIZE;
  }
  endOfCentralDirectorySize += END_OF_CENTRAL_DIRECTORY_RECORD_SIZE;
  return pretendOutputCursor + centralDirectorySize + endOfCentralDirectorySize;
}

var ZIP64_END_OF_CENTRAL_DIRECTORY_RECORD_SIZE = 56;
var ZIP64_END_OF_CENTRAL_DIRECTORY_LOCATOR_SIZE = 20;
var END_OF_CENTRAL_DIRECTORY_RECORD_SIZE = 22;
function getEndOfCentralDirectoryRecord(self, actuallyJustTellMeHowLongItWouldBe) {
  var needZip64Format = false;
  var normalEntriesLength = self.entries.length;
  if (self.forceZip64Eocd || self.entries.length >= 0xffff) {
    normalEntriesLength = 0xffff;
    needZip64Format = true;
  }
  var sizeOfCentralDirectory = self.outputStreamCursor - self.offsetOfStartOfCentralDirectory;
  var normalSizeOfCentralDirectory = sizeOfCentralDirectory;
  if (self.forceZip64Eocd || sizeOfCentralDirectory >= 0xffffffff) {
    normalSizeOfCentralDirectory = 0xffffffff;
    needZip64Format = true;
  }
  var normalOffsetOfStartOfCentralDirectory = self.offsetOfStartOfCentralDirectory;
  if (self.forceZip64Eocd || self.offsetOfStartOfCentralDirectory >= 0xffffffff) {
    normalOffsetOfStartOfCentralDirectory = 0xffffffff;
    needZip64Format = true;
  }
  if (actuallyJustTellMeHowLongItWouldBe) {
    if (needZip64Format) {
      return (
        ZIP64_END_OF_CENTRAL_DIRECTORY_RECORD_SIZE +
        ZIP64_END_OF_CENTRAL_DIRECTORY_LOCATOR_SIZE +
        END_OF_CENTRAL_DIRECTORY_RECORD_SIZE
      );
    } else {
      return END_OF_CENTRAL_DIRECTORY_RECORD_SIZE;
    }
  }

  var eocdrBuffer = new Buffer(END_OF_CENTRAL_DIRECTORY_RECORD_SIZE);
  // end of central dir signature                       4 bytes  (0x06054b50)
  eocdrBuffer.writeUInt32LE(0x06054b50, 0);
  // number of this disk                                2 bytes
  eocdrBuffer.writeUInt16LE(0, 4);
  // number of the disk with the start of the central directory  2 bytes
  eocdrBuffer.writeUInt16LE(0, 6);
  // total number of entries in the central directory on this disk  2 bytes
  eocdrBuffer.writeUInt16LE(normalEntriesLength, 8);
  // total number of entries in the central directory   2 bytes
  eocdrBuffer.writeUInt16LE(normalEntriesLength, 10);
  // size of the central directory                      4 bytes
  eocdrBuffer.writeUInt32LE(normalSizeOfCentralDirectory, 12);
  // offset of start of central directory with respect to the starting disk number  4 bytes
  eocdrBuffer.writeUInt32LE(normalOffsetOfStartOfCentralDirectory, 16);
  // .ZIP file comment length                           2 bytes
  eocdrBuffer.writeUInt16LE(0, 20);
  // .ZIP file comment                                  (variable size)
  // no comment

  if (!needZip64Format) return eocdrBuffer;

  // ZIP64 format
  // ZIP64 End of Central Directory Record
  var zip64EocdrBuffer = new Buffer(ZIP64_END_OF_CENTRAL_DIRECTORY_RECORD_SIZE);
  // zip64 end of central dir signature                                             4 bytes  (0x06064b50)
  zip64EocdrBuffer.writeUInt32LE(0x06064b50, 0);
  // size of zip64 end of central directory record                                  8 bytes
  writeUInt64LE(zip64EocdrBuffer, ZIP64_END_OF_CENTRAL_DIRECTORY_RECORD_SIZE - 12, 4);
  // version made by                                                                2 bytes
  zip64EocdrBuffer.writeUInt16LE(VERSION_MADE_BY, 12);
  // version needed to extract                                                      2 bytes
  zip64EocdrBuffer.writeUInt16LE(VERSION_NEEDED_TO_EXTRACT_ZIP64, 14);
  // number of this disk                                                            4 bytes
  zip64EocdrBuffer.writeUInt32LE(0, 16);
  // number of the disk with the start of the central directory                     4 bytes
  zip64EocdrBuffer.writeUInt32LE(0, 20);
  // total number of entries in the central directory on this disk                  8 bytes
  writeUInt64LE(zip64EocdrBuffer, self.entries.length, 24);
  // total number of entries in the central directory                               8 bytes
  writeUInt64LE(zip64EocdrBuffer, self.entries.length, 32);
  // size of the central directory                                                  8 bytes
  writeUInt64LE(zip64EocdrBuffer, sizeOfCentralDirectory, 40);
  // offset of start of central directory with respect to the starting disk number  8 bytes
  writeUInt64LE(zip64EocdrBuffer, self.offsetOfStartOfCentralDirectory, 48);
  // zip64 extensible data sector                                                   (variable size)
  // nothing in the zip64 extensible data sector


  // ZIP64 End of Central Directory Locator
  var zip64EocdlBuffer = new Buffer(ZIP64_END_OF_CENTRAL_DIRECTORY_LOCATOR_SIZE);
  // zip64 end of central dir locator signature                               4 bytes  (0x07064b50)
  zip64EocdlBuffer.writeUInt32LE(0x07064b50, 0);
  // number of the disk with the start of the zip64 end of central directory  4 bytes
  zip64EocdlBuffer.writeUInt32LE(0, 4);
  // relative offset of the zip64 end of central directory record             8 bytes
  writeUInt64LE(zip64EocdlBuffer, self.outputStreamCursor, 8);
  // total number of disks                                                    4 bytes
  zip64EocdlBuffer.writeUInt32LE(1, 16);


  return Buffer.concat([
    zip64EocdrBuffer,
    zip64EocdlBuffer,
    eocdrBuffer,
  ]);
}

function validateMetadataPath(metadataPath, isDirectory) {
  if (metadataPath === "") throw new Error("empty metadataPath");
  metadataPath = metadataPath.replace(/\\/g, "/");
  if (/^[a-zA-Z]:/.test(metadataPath) || /^\//.test(metadataPath)) throw new Error("absolute path: " + metadataPath);
  if (metadataPath.split("/").indexOf("..") !== -1) throw new Error("invalid relative path: " + metadataPath);
  var looksLikeDirectory = /\/$/.test(metadataPath);
  if (isDirectory) {
    // append a trailing '/' if necessary.
    if (!looksLikeDirectory) metadataPath += "/";
  } else {
    if (looksLikeDirectory) throw new Error("file path cannot end with '/': " + metadataPath);
  }
  return metadataPath;
}

// this class is not part of the public API
function Entry(metadataPath, isDirectory, options) {
  this.utf8FileName = new Buffer(metadataPath);
  if (this.utf8FileName.length > 0xffff) throw new Error("utf8 file name too long. " + utf8FileName.length + " > " + 0xffff);
  this.isDirectory = isDirectory;
  this.state = Entry.WAITING_FOR_METADATA;
  this.setLastModDate(options.mtime != null ? options.mtime : new Date());
  if (options.mode != null) {
    this.setFileAttributesMode(options.mode);
  } else {
    this.setFileAttributesMode(isDirectory ? 040775 : 0100664);
  }
  if (isDirectory) {
    this.crcAndFileSizeKnown = true;
    this.crc32 = 0;
    this.uncompressedSize = 0;
    this.compressedSize = 0;
  } else {
    // unknown so far
    this.crcAndFileSizeKnown = false;
    this.crc32 = null;
    this.uncompressedSize = null;
    this.compressedSize = null;
    if (options.size != null) this.uncompressedSize = options.size;
  }
  if (isDirectory) {
    this.compress = false;
  } else {
    this.compress = true; // default
    if (options.compress != null) this.compress = !!options.compress;
  }
  this.forceZip64Format = !!options.forceZip64Format;
}
Entry.WAITING_FOR_METADATA = 0;
Entry.READY_TO_PUMP_FILE_DATA = 1;
Entry.FILE_DATA_IN_PROGRESS = 2;
Entry.FILE_DATA_DONE = 3;
Entry.prototype.setLastModDate = function(date) {
  var dosDateTime = dateToDosDateTime(date);
  this.lastModFileTime = dosDateTime.time;
  this.lastModFileDate = dosDateTime.date;
};
Entry.prototype.setFileAttributesMode = function(mode) {
  if ((mode & 0xffff) !== mode) throw new Error("invalid mode. expected: 0 <= " + mode + " <= " + 0xffff);
  // http://unix.stackexchange.com/questions/14705/the-zip-formats-external-file-attribute/14727#14727
  this.externalFileAttributes = (mode << 16) >>> 0;
};
// doFileDataPump() should not call pumpEntries() directly. see issue #9.
Entry.prototype.setFileDataPumpFunction = function(doFileDataPump) {
  this.doFileDataPump = doFileDataPump;
  this.state = Entry.READY_TO_PUMP_FILE_DATA;
};
Entry.prototype.useZip64Format = function() {
  return (
    (this.forceZip64Format) ||
    (this.uncompressedSize != null && this.uncompressedSize > 0xfffffffe) ||
    (this.compressedSize != null && this.compressedSize > 0xfffffffe) ||
    (this.relativeOffsetOfLocalHeader != null && this.relativeOffsetOfLocalHeader > 0xfffffffe)
  );
}
var LOCAL_FILE_HEADER_FIXED_SIZE = 30;
var VERSION_NEEDED_TO_EXTRACT_UTF8 = 20;
var VERSION_NEEDED_TO_EXTRACT_ZIP64 = 45;
// 3 = unix. 63 = spec version 6.3
var VERSION_MADE_BY = (3 << 8) | 63;
var FILE_NAME_IS_UTF8 = 1 << 11;
var UNKNOWN_CRC32_AND_FILE_SIZES = 1 << 3;
Entry.prototype.getLocalFileHeader = function() {
  var crc32 = 0;
  var compressedSize = 0;
  var uncompressedSize = 0;
  if (this.crcAndFileSizeKnown) {
    crc32 = this.crc32;
    compressedSize = this.compressedSize;
    uncompressedSize = this.uncompressedSize;
  }

  var fixedSizeStuff = new Buffer(LOCAL_FILE_HEADER_FIXED_SIZE);
  var generalPurposeBitFlag = FILE_NAME_IS_UTF8;
  if (!this.crcAndFileSizeKnown) generalPurposeBitFlag |= UNKNOWN_CRC32_AND_FILE_SIZES;

  // local file header signature     4 bytes  (0x04034b50)
  fixedSizeStuff.writeUInt32LE(0x04034b50, 0);
  // version needed to extract       2 bytes
  fixedSizeStuff.writeUInt16LE(VERSION_NEEDED_TO_EXTRACT_UTF8, 4);
  // general purpose bit flag        2 bytes
  fixedSizeStuff.writeUInt16LE(generalPurposeBitFlag, 6);
  // compression method              2 bytes
  fixedSizeStuff.writeUInt16LE(this.getCompressionMethod(), 8);
  // last mod file time              2 bytes
  fixedSizeStuff.writeUInt16LE(this.lastModFileTime, 10);
  // last mod file date              2 bytes
  fixedSizeStuff.writeUInt16LE(this.lastModFileDate, 12);
  // crc-32                          4 bytes
  fixedSizeStuff.writeUInt32LE(crc32, 14);
  // compressed size                 4 bytes
  fixedSizeStuff.writeUInt32LE(compressedSize, 18);
  // uncompressed size               4 bytes
  fixedSizeStuff.writeUInt32LE(uncompressedSize, 22);
  // file name length                2 bytes
  fixedSizeStuff.writeUInt16LE(this.utf8FileName.length, 26);
  // extra field length              2 bytes
  fixedSizeStuff.writeUInt16LE(0, 28);
  return Buffer.concat([
    fixedSizeStuff,
    // file name (variable size)
    this.utf8FileName,
    // extra field (variable size)
    // no extra fields
  ]);
};
var DATA_DESCRIPTOR_SIZE = 16;
var ZIP64_DATA_DESCRIPTOR_SIZE = 24;
Entry.prototype.getDataDescriptor = function() {
  if (this.crcAndFileSizeKnown) {
    // the Mac Archive Utility requires this not be present unless we set general purpose bit 3
    return new Buffer(0);
  }
  if (!this.useZip64Format()) {
    var buffer = new Buffer(DATA_DESCRIPTOR_SIZE);
    // optional signature (required according to Archive Utility)
    buffer.writeUInt32LE(0x08074b50, 0);
    // crc-32                          4 bytes
    buffer.writeUInt32LE(this.crc32, 4);
    // compressed size                 4 bytes
    buffer.writeUInt32LE(this.compressedSize, 8);
    // uncompressed size               4 bytes
    buffer.writeUInt32LE(this.uncompressedSize, 12);
    return buffer;
  } else {
    // ZIP64 format
    var buffer = new Buffer(ZIP64_DATA_DESCRIPTOR_SIZE);
    // optional signature (unknown if anyone cares about this)
    buffer.writeUInt32LE(0x08074b50, 0);
    // crc-32                          4 bytes
    buffer.writeUInt32LE(this.crc32, 4);
    // compressed size                 8 bytes
    writeUInt64LE(buffer, this.compressedSize, 8);
    // uncompressed size               8 bytes
    writeUInt64LE(buffer, this.uncompressedSize, 16);
    return buffer;
  }
};
var CENTRAL_DIRECTORY_RECORD_FIXED_SIZE = 46;
var ZIP64_EXTENDED_INFORMATION_EXTRA_FIELD_SIZE = 28;
Entry.prototype.getCentralDirectoryRecord = function() {
  var fixedSizeStuff = new Buffer(CENTRAL_DIRECTORY_RECORD_FIXED_SIZE);
  var generalPurposeBitFlag = FILE_NAME_IS_UTF8;
  if (!this.crcAndFileSizeKnown) generalPurposeBitFlag |= UNKNOWN_CRC32_AND_FILE_SIZES;

  var normalCompressedSize = this.compressedSize;
  var normalUncompressedSize = this.uncompressedSize;
  var normalRelativeOffsetOfLocalHeader = this.relativeOffsetOfLocalHeader;
  var versionNeededToExtract;
  var zeiefBuffer;
  if (this.useZip64Format()) {
    normalCompressedSize = 0xffffffff;
    normalUncompressedSize = 0xffffffff;
    normalRelativeOffsetOfLocalHeader = 0xffffffff;
    versionNeededToExtract = VERSION_NEEDED_TO_EXTRACT_ZIP64;

    // ZIP64 extended information extra field
    zeiefBuffer = new Buffer(ZIP64_EXTENDED_INFORMATION_EXTRA_FIELD_SIZE);
    // 0x0001                  2 bytes    Tag for this "extra" block type
    zeiefBuffer.writeUInt16LE(0x0001, 0);
    // Size                    2 bytes    Size of this "extra" block
    zeiefBuffer.writeUInt16LE(ZIP64_EXTENDED_INFORMATION_EXTRA_FIELD_SIZE - 4, 2);
    // Original Size           8 bytes    Original uncompressed file size
    writeUInt64LE(zeiefBuffer, this.uncompressedSize, 4);
    // Compressed Size         8 bytes    Size of compressed data
    writeUInt64LE(zeiefBuffer, this.compressedSize, 12);
    // Relative Header Offset  8 bytes    Offset of local header record
    writeUInt64LE(zeiefBuffer, this.relativeOffsetOfLocalHeader, 20);
    // Disk Start Number       4 bytes    Number of the disk on which this file starts
    // (omit)
  } else {
    versionNeededToExtract = VERSION_NEEDED_TO_EXTRACT_UTF8;
    zeiefBuffer = new Buffer(0);
  }

  // central file header signature   4 bytes  (0x02014b50)
  fixedSizeStuff.writeUInt32LE(0x02014b50, 0);
  // version made by                 2 bytes
  fixedSizeStuff.writeUInt16LE(VERSION_MADE_BY, 4);
  // version needed to extract       2 bytes
  fixedSizeStuff.writeUInt16LE(versionNeededToExtract, 6);
  // general purpose bit flag        2 bytes
  fixedSizeStuff.writeUInt16LE(generalPurposeBitFlag, 8);
  // compression method              2 bytes
  fixedSizeStuff.writeUInt16LE(this.getCompressionMethod(), 10);
  // last mod file time              2 bytes
  fixedSizeStuff.writeUInt16LE(this.lastModFileTime, 12);
  // last mod file date              2 bytes
  fixedSizeStuff.writeUInt16LE(this.lastModFileDate, 14);
  // crc-32                          4 bytes
  fixedSizeStuff.writeUInt32LE(this.crc32, 16);
  // compressed size                 4 bytes
  fixedSizeStuff.writeUInt32LE(normalCompressedSize, 20);
  // uncompressed size               4 bytes
  fixedSizeStuff.writeUInt32LE(normalUncompressedSize, 24);
  // file name length                2 bytes
  fixedSizeStuff.writeUInt16LE(this.utf8FileName.length, 28);
  // extra field length              2 bytes
  fixedSizeStuff.writeUInt16LE(zeiefBuffer.length, 30);
  // file comment length             2 bytes
  fixedSizeStuff.writeUInt16LE(0, 32);
  // disk number start               2 bytes
  fixedSizeStuff.writeUInt16LE(0, 34);
  // internal file attributes        2 bytes
  fixedSizeStuff.writeUInt16LE(0, 36);
  // external file attributes        4 bytes
  fixedSizeStuff.writeUInt32LE(this.externalFileAttributes, 38);
  // relative offset of local header 4 bytes
  fixedSizeStuff.writeUInt32LE(normalRelativeOffsetOfLocalHeader, 42);

  return Buffer.concat([
    fixedSizeStuff,
    // file name (variable size)
    this.utf8FileName,
    // extra field (variable size)
    zeiefBuffer,
    // file comment (variable size)
    // empty comment
  ]);
};
Entry.prototype.getCompressionMethod = function() {
  var NO_COMPRESSION = 0;
  var DEFLATE_COMPRESSION = 8;
  return this.compress ? DEFLATE_COMPRESSION : NO_COMPRESSION;
};

function dateToDosDateTime(jsDate) {
  var date = 0;
  date |= jsDate.getDate() & 0x1f; // 1-31
  date |= ((jsDate.getMonth() + 1) & 0xf) << 5; // 0-11, 1-12
  date |= ((jsDate.getFullYear() - 1980) & 0x7f) << 9; // 0-128, 1980-2108

  var time = 0;
  time |= Math.floor(jsDate.getSeconds() / 2); // 0-59, 0-29 (lose odd numbers)
  time |= (jsDate.getMinutes() & 0x3f) << 5; // 0-59
  time |= (jsDate.getHours() & 0x1f) << 11; // 0-23

  return {date: date, time: time};
}

function writeUInt64LE(buffer, n, offset) {
  // can't use bitshift here, because JavaScript only allows bitshiting on 32-bit integers.
  var high = Math.floor(n / 0x100000000);
  var low = n % 0x100000000;
  buffer.writeUInt32LE(low, offset);
  buffer.writeUInt32LE(high, offset + 4);
}

function defaultCallback(err) {
  if (err) throw err;
}

util.inherits(ByteCounter, Transform);
function ByteCounter(options) {
  Transform.call(this, options);
  this.byteCount = 0;
}
ByteCounter.prototype._transform = function(chunk, encoding, cb) {
  this.byteCount += chunk.length;
  cb(null, chunk);
};

util.inherits(Crc32Watcher, Transform);
function Crc32Watcher(options) {
  Transform.call(this, options);
  this.crc32 = 0;
}
Crc32Watcher.prototype._transform = function(chunk, encoding, cb) {
  this.crc32 = crc32.unsigned(chunk, this.crc32);
  cb(null, chunk);
};