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/* ====================================================================
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this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
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http://www.apache.org/licenses/LICENSE-2.0
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==================================================================== */
/**
* Processes streams in the Horrible Property Set Format (HPSF) in POI filesystems.
* Microsoft Office documents, i.e. POI filesystems, usually contain meta data like author, title,
* last saving time etc. These items are called properties and stored in
* property set streams along with the document itself.
* These streams are commonly named {@code \005SummaryInformation} and {@code \005DocumentSummaryInformation}.
* However, a POI filesystem may contain further property sets of other names or types.
*
* In order to extract the properties from a POI filesystem, a property set stream's contents must be parsed into a
* {@link org.apache.poi.hpsf.PropertySet} instance. Its subclasses {@link org.apache.poi.hpsf.SummaryInformation}
* and {@link org.apache.poi.hpsf.DocumentSummaryInformation} deal with the well-known property set streams
* {@code \005SummaryInformation} and {@code \005DocumentSummaryInformation}.
* (However, the streams' names are irrelevant. What counts is the property set's first section's format ID - see below.)
*
* The factory method {@link org.apache.poi.hpsf.PropertySetFactory#create} creates a PropertySet instance.
* This method always returns the most specific property set:
* If it identifies the stream data as a Summary Information or as a Document Summary Information it returns an
* instance of the corresponding class, else the general PropertySet.
*
* A PropertySet contains a list of {@link org.apache.poi.hpsf.Section Sections} which can be
* retrieved with {@link org.apache.poi.hpsf.PropertySet#getSections}. Each Section contains a
* {@link org.apache.poi.hpsf.Property} array which can be retrieved with
* {@link org.apache.poi.hpsf.Section#getProperties}. Since the vast majority of PropertySets contains only a single Section,
* the convenience method {@link org.apache.poi.hpsf.PropertySet#getProperties} returns the properties of a
* PropertySets Section (throwing a {@link org.apache.poi.hpsf.NoSingleSectionException} if the PropertySet contains
* more (or less) than exactly one Section).
*
* Each Property has an ID, a type, and a value which can be
* retrieved with {@link org.apache.poi.hpsf.Property#getID}, {@link org.apache.poi.hpsf.Property#getType},
* and {@link org.apache.poi.hpsf.Property#getValue}, respectively. The value's class depends on the property's type.
* The current implementation does not yet support all property types and restricts the values' classes
* to String, Integer and Date. A value of a yet unknown type is returned as a byte array containing the values
* origin bytes from the property set stream.
*
* To retrieve the value of a specific Property, use {@link org.apache.poi.hpsf.Section#getProperty} or
* {@link org.apache.poi.hpsf.Section#getPropertyIntValue}.
*
* The SummaryInformation and DocumentSummaryInformation classes provide convenience methods for retrieving well-known
* properties. For example, an application that wants to retrieve a document's title string just calls
* {@link org.apache.poi.hpsf.SummaryInformation#getTitle} instead of going through the hassle of first finding out
* what the title's property ID is and then using this ID to get the property's value.
*
* @see [MS-OLEPS] Object Linking and Embedding (OLE) Property Set Data Structures
*/
package org.apache.poi.hpsf;