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## org.apache.poi.poifs.filesystem
Class POIFSFileSystem

    java.lang.Object
      org.apache.poi.poifs.filesystem.POIFSFileSystem

All Implemented Interfaces:
  POIFSViewable

    public class POIFSFileSystem

extends java.lang.Object
implements POIFSViewable

This is the main class of the POIFS system; it manages the entire life cycle of the filesystem.

Author:
  Marc Johnson (mjohnson at apache dot org)

Constructor Summary
`POIFSFileSystem()` Constructor, intended for writing
`POIFSFileSystem(java.io.InputStream stream)` Create a POIFSFileSystem from an `InputStream`.

Method Summary
`DirectoryEntry` | `createDirectory(java.lang.String name)` create a new DirectoryEntry in the root directory
`DocumentEntry` | `createDocument(java.io.InputStream stream, java.lang.String name)` Create a new document to be added to the root directory
`DocumentEntry` | `createDocument(java.lang.String name, int size, POIFSWriterListener writer)` create a new DocumentEntry in the root entry; the data will be provided later
`DocumentInputStream` | `createDocumentInputStream(java.lang.String documentName)` open a document in the root entry's list of entries
`static java.io.InputStream` | `createNonClosingInputStream(java.io.InputStream is)` Convenience method for clients that want to avoid the auto-close behaviour of the constructor.
`int` | `getBigBlockSize()`
`POIFSBigBlockSize` | `getBigBlockSizeDetails()`
`DirectoryNode` | `getRoot()` get the root entry
`java.lang.String` | `getShortDescription()` Provides a short description of the object, to be used when a POIFSViewable object has not provided its contents.
`java.lang.Object[]` | `getViewableArray()` Get an array of objects, some of which may implement POIFSViewable
`java.util.Iterator` | `getViewableIterator()` Get an Iterator of objects, some of which may implement POIFSViewable
`static boolean` | `hasPOIFSHeader(java.io.InputStream inp)` Checks that the supplied InputStream (which MUST support mark and reset, or be a PushbackInputStream) has a POIFS (OLE2) header at the start of it.
`static void` | `main(java.lang.String[] args)` read in a file and write it back out again
`boolean` | `preferArray()` Give viewers a hint as to whether to call getViewableArray or getViewableIterator
`void` | `writeFilesystem(java.io.OutputStream stream)` Write the filesystem out

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### POIFSFileSystem

    public POIFSFileSystem()

  Constructor, intended for writing

### POIFSFileSystem

    public POIFSFileSystem(java.io.InputStream stream)
                    throws java.io.IOException

  Create a POIFSFileSystem from an `InputStream`. Normally the stream is read until EOF. The stream is always closed.

  Some streams are usable after reaching EOF (typically those that return `true` for `markSupported()`). In the unlikely case that the caller has such a stream and needs to use it after this constructor completes, a work around is to wrap the stream in order to trap the `close()` call. A convenience method ( `createNonClosingInputStream()`) has been provided for this purpose:

       InputStream wrappedStream = POIFSFileSystem.createNonClosingInputStream(is);
       HSSFWorkbook wb = new HSSFWorkbook(wrappedStream);
       is.reset();
       doSomethingElse(is);

  Note also the special case of `ByteArrayInputStream` for which the `close()` method does nothing.

       ByteArrayInputStream bais = ...
       HSSFWorkbook wb = new HSSFWorkbook(bais); // calls bais.close() !
       bais.reset(); // no problem
       doSomethingElse(bais);

  Parameters:
    `stream` - the InputStream from which to read the data
  Throws:
    `java.io.IOException` - on errors reading, or on invalid data

Method Detail

### createNonClosingInputStream

    public static java.io.InputStream createNonClosingInputStream(java.io.InputStream is)

  Convenience method for clients that want to avoid the auto-close behaviour of the constructor.

### hasPOIFSHeader

    public static boolean hasPOIFSHeader(java.io.InputStream inp)
                                  throws java.io.IOException

  Checks that the supplied InputStream (which MUST support mark and reset, or be a PushbackInputStream) has a POIFS (OLE2) header at the start of it. If your InputStream does not support mark / reset, then wrap it in a PushBackInputStream, then be sure to always use that, and not the original!

  Parameters:
    `inp` - An InputStream which supports either mark/reset, or is a PushbackInputStream
  Throws:
    `java.io.IOException`

### createDocument

    public DocumentEntry createDocument(java.io.InputStream stream,
                                        java.lang.String name)
                                 throws java.io.IOException

  Create a new document to be added to the root directory

  Parameters:
    `stream` - the InputStream from which the document's data will be obtained
    `name` - the name of the new POIFSDocument
  Returns:
    the new DocumentEntry
  Throws:
    `java.io.IOException` - on error creating the new POIFSDocument

### createDocument

    public DocumentEntry createDocument(java.lang.String name,
                                        int size,
                                        POIFSWriterListener writer)
                                 throws java.io.IOException

  create a new DocumentEntry in the root entry; the data will be provided later

  Parameters:
    `name` - the name of the new DocumentEntry
    `size` - the size of the new DocumentEntry
    `writer` - the writer of the new DocumentEntry
  Returns:
    the new DocumentEntry
  Throws:
    `java.io.IOException`

### createDirectory

    public DirectoryEntry createDirectory(java.lang.String name)
                                   throws java.io.IOException

  create a new DirectoryEntry in the root directory

  Parameters:
    `name` - the name of the new DirectoryEntry
  Returns:
    the new DirectoryEntry
  Throws:
    `java.io.IOException` - on name duplication

### writeFilesystem

    public void writeFilesystem(java.io.OutputStream stream)
                         throws java.io.IOException

  Write the filesystem out

  Parameters:
    `stream` - the OutputStream to which the filesystem will be written
  Throws:
    `java.io.IOException` - thrown on errors writing to the stream

### main

    public static void main(java.lang.String[] args)
                     throws java.io.IOException

  read in a file and write it back out again

  Parameters:
    `args` - names of the files; arg[ 0 ] is the input file, arg[ 1 ] is the output file
  Throws:
    `java.io.IOException`

### getRoot

    public DirectoryNode getRoot()

  get the root entry

  Returns:
    the root entry

### createDocumentInputStream

    public DocumentInputStream createDocumentInputStream(java.lang.String documentName)
                                                  throws java.io.IOException

  open a document in the root entry's list of entries

  Parameters:
    `documentName` - the name of the document to be opened
  Returns:
    a newly opened DocumentInputStream
  Throws:
    `java.io.IOException` - if the document does not exist or the name is that of a DirectoryEntry

### getViewableArray

    public java.lang.Object[] getViewableArray()

  Get an array of objects, some of which may implement POIFSViewable

  Specified by:
    `getViewableArray` in interface `POIFSViewable`
  Returns:
    an array of Object; may not be null, but may be empty

### getViewableIterator

    public java.util.Iterator getViewableIterator()

  Get an Iterator of objects, some of which may implement POIFSViewable

  Specified by:
    `getViewableIterator` in interface `POIFSViewable`
  Returns:
    an Iterator; may not be null, but may have an empty back end store

### preferArray

    public boolean preferArray()

  Give viewers a hint as to whether to call getViewableArray or getViewableIterator

  Specified by:
    `preferArray` in interface `POIFSViewable`
  Returns:
    true if a viewer should call getViewableArray, false if a viewer should call getViewableIterator

### getShortDescription

    public java.lang.String getShortDescription()

  Provides a short description of the object, to be used when a POIFSViewable object has not provided its contents.

  Specified by:
    `getShortDescription` in interface `POIFSViewable`
  Returns:
    short description

### getBigBlockSize

    public int getBigBlockSize()

  Returns:
    The Big Block size, normally 512 bytes, sometimes 4096 bytes

### getBigBlockSizeDetails

    public POIFSBigBlockSize getBigBlockSizeDetails()

  Returns:
    The Big Block size, normally 512 bytes, sometimes 4096 bytes

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