Class XrefTrailerResolver

java.lang.Object
org.apache.pdfbox.pdfparser.XrefTrailerResolver

public class XrefTrailerResolver extends Object
This class will collect all XRef/trailer objects and creates correct xref/trailer information after all objects are read using startxref and 'Prev' information (unused XRef/trailer objects are discarded). In case of missing startxref or wrong startxref pointer all XRef/trailer objects are used to create xref table / trailer dictionary in order they occur. For each new xref object/XRef stream method nextXrefObj(long) must be called with start byte position. All following calls to setXRef(COSObjectKey, long) or setTrailer(COSDictionary) will add the data for this byte position. After all objects are parsed the startxref position must be provided using setStartxref(long). This is used to build the chain of active xref/trailer objects used for creating document trailer and xref table.
Author:
Timo Boehme (timo.boehme at ontochem.com)
  • Constructor Details

    • XrefTrailerResolver

      public XrefTrailerResolver()
  • Method Details

    • getFirstTrailer

      public final COSDictionary getFirstTrailer()
    • getLastTrailer

      public final COSDictionary getLastTrailer()
    • nextXrefObj

      public void nextXrefObj(long startBytePos)
      Signals that a new XRef object (table or stream) starts.
      Parameters:
      startBytePos - the offset to start at
    • setXRef

      public void setXRef(COSObjectKey objKey, long offset)
      Populate XRef HashMap of current XRef object. Will add an Xreftable entry that maps ObjectKeys to byte offsets in the file.
      Parameters:
      objKey - The objkey, with id and gen numbers
      offset - The byte offset in this file
    • setTrailer

      public void setTrailer(COSDictionary trailer)
      Adds trailer information for current XRef object.
      Parameters:
      trailer - the current document trailer dictionary
    • getCurrentTrailer

      public COSDictionary getCurrentTrailer()
      Returns the trailer last set by setTrailer(COSDictionary).
      Returns:
      the current trailer.
    • setStartxref

      public void setStartxref(long startxrefBytePosValue)
      Sets the byte position of the first XRef (has to be called after very last startxref was read). This is used to resolve chain of active XRef/trailer. In case startxref position is not found we output a warning and use all XRef/trailer objects combined in byte position order. Thus for incomplete PDF documents with missing startxref one could call this method with parameter value -1.
      Parameters:
      startxrefBytePosValue - starting position of the first XRef
    • getTrailer

      public COSDictionary getTrailer()
      Gets the resolved trailer. Might return null in case setStartxref(long) was not called before.
      Returns:
      the trailer if available
    • getXrefTable

      public Map<COSObjectKey,Long> getXrefTable()
      Gets the resolved xref table. Might return null in case setStartxref(long) was not called before.
      Returns:
      the xrefTable if available
    • getContainedObjectNumbers

      public Set<Long> getContainedObjectNumbers(int objstmObjNr)
      Returns object numbers which are referenced as contained in object stream with specified object number. This will scan resolved xref table for all entries having negated stream object number as value.
      Parameters:
      objstmObjNr - object number of object stream for which contained object numbers should be returned
      Returns:
      set of object numbers referenced for given object stream or null if setStartxref(long) was not called before so that no resolved xref table exists
    • clearResources

      public void clearResources()
      Release all used resources.