/// <summary>
/// Matches and parses the XRefTable in the this instances PDF data stream that is
/// specified pased on the position value between the startXRefPos and the end of file marker
/// </summary>
/// <param name="startxrefPos"></param>
/// <param name="eofPos"></param>
/// <param name="trailerPrevOffset">The offset marked in the trailer dictionary of any previous XRefTable this file contains.</param>
/// <returns></returns>
protected PDFXRefTable GetXRefTable(PDFFileRange startxrefPos, PDFFileRange eofPos, long trailerPrevOffset)
{
long xrefPos = long.Parse(this.Searcher.GetInnerText(startxrefPos, eofPos).Trim());
this.Searcher.Position = xrefPos;
string fullXRef = this.Searcher.GetInnerText((int)(eofPos.StartOffset - xrefPos));
int end;
PDFXRefTable table = PDFXRefTable.Parse(fullXRef, 0, out end);
table.Offset = xrefPos;
if (trailerPrevOffset > 0) // we have a previous entry
{
this.Searcher.Position = trailerPrevOffset;
if (startxrefPos.Found)
{
eofPos = this.Searcher.MatchForwardString(EndOfFileMarker);
startxrefPos = AssertFoundRange(this.Searcher.MatchBackwardString(XRefMarker), XRefMarker);
PDFFileRange trailerPos = AssertFoundRange(this.Searcher.MatchBackwardString(TrailerMarker), TrailerMarker);
PDFDictionary trailer = GetTrailerDictionary(trailerPos, startxrefPos);
IFileObject prevEntry;
if (trailer.TryGetValue(PrevXRefName, out prevEntry))
{
if (prevEntry is PDFNumber)
{
trailerPrevOffset = ((PDFNumber)prevEntry).Value;
}
else if (prevEntry is PDFReal)
{
trailerPrevOffset = (long)((PDFReal)prevEntry).Value;
}
else
{
trailerPrevOffset = -1;
}
}
else
{
trailerPrevOffset = -1;
}
PDFXRefTable prevTable = GetXRefTable(startxrefPos, eofPos, trailerPrevOffset);
table.Previous = prevTable;
}
}
return(table);
}
protected static PDFObjectRef AssertGetObjectRef(PDFDictionary dict, PDFName entry, string errorMessage)
{
IFileObject found;
if (!dict.TryGetValue(entry, out found))
{
throw new PDFNativeParserException(errorMessage);
}
if (found.Type != PDFObjectTypes.ObjectRef)
{
throw new PDFNativeParserException(errorMessage);
}
return((PDFObjectRef)found);
}
/// <summary>
/// Initializes the known PDF file data such as trailers, xref tables and catalogs
/// </summary>
protected override void InitData(PDFTraceLog log)
{
try
{
if (log.ShouldLog(TraceLevel.Debug))
{
log.Add(TraceLevel.Debug, "PDFReader", "Finding end of file, startxref and trailer positions");
}
this.Searcher.Position = this.Searcher.Length;
PDFFileRange eofPos = AssertFoundRange(Searcher.MatchBackwardString(EndOfFileMarker), EndOfFileMarker);
PDFFileRange startxrefPos = AssertFoundRange(Searcher.MatchBackwardString(StartXRefMarker), StartXRefMarker);
PDFFileRange trailerPos = AssertFoundRange(Searcher.MatchBackwardString(TrailerMarker), TrailerMarker);
if (log.ShouldLog(TraceLevel.Debug))
{
log.Add(TraceLevel.Debug, "PDFReader", "Markers found, loading the trailer dictionary");
}
PDFDictionary trailer = GetTrailerDictionary(trailerPos, startxrefPos);
this._trailer = trailer;
if (log.ShouldLog(TraceLevel.Debug))
{
log.Add(TraceLevel.Debug, "PDFReader", "Markers found, loading the XRef table");
}
PDFObjectRef catalogRef = AssertGetObjectRef(trailer, CatalogObjName, "The '" + CatalogObjName + "' entry couldnot be found in the documents trailer dictionary");
PDFObjectRef infoRef = AssertGetObjectRef(trailer, InfoObjName, "The '" + InfoObjName + "' entry couldnot be found in the documents trailer dictionary");
IFileObject prevXRefObj;
trailer.TryGetValue(PrevXRefName, out prevXRefObj);
long prevOffset = -1;
if (prevXRefObj is PDFNumber)
{
prevOffset = ((PDFNumber)prevXRefObj).Value;
}
else if (prevXRefObj is PDFReal)
{
prevOffset = (long)((PDFNumber)prevXRefObj).Value;
}
PDFXRefTable xref = GetXRefTable(startxrefPos, eofPos, prevOffset);
if (log.ShouldLog(TraceLevel.Debug))
{
log.Add(TraceLevel.Debug, "PDFReader", "References for the catalog and document info found");
}
this._xreftable = xref;
this._info = (PDFFileIndirectObject)this.GetObject(infoRef);
if (log.ShouldLog(TraceLevel.Debug))
{
log.Add(TraceLevel.Debug, "PDFReader", "Loaded the document Info indirect object");
}
this._catalog = (PDFFileIndirectObject)this.GetObject(catalogRef);
if (log.ShouldLog(TraceLevel.Debug))
{
log.Add(TraceLevel.Debug, "PDFReader", "Loaded the document Catalog indirect object");
}
//TODO: Look for more updates and read those in too
}
catch (Exception ex)
{
throw new PDFNativeParserException(CommonErrors.CouldNotInitializeThePDFReader, ex);
}
}