[ 
https://issues.apache.org/jira/browse/PDFBOX-2824?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14581290#comment-14581290
 ] 

John Hewson commented on PDFBOX-2824:
-------------------------------------

I can see what the problem is there. In TTFGlyph2D.getPathForGID, we see the 
line:

{code}
GlyphData glyph = ttf.getGlyph().getGlyph(gid);
{code}

Now, getGlyph() is synchronized and the getGlyph(gid) method of GlyphTable is 
too, however GlyphTable #getGlyph(gid) is synchronized on the GlyphTable 
instance, while TrueTypeFont#getGlyph() is synchronized on the TrueTypeFont 
instance. Both share the same TTFDataStream, so we're failing to synchronize on 
the resource which is actually being shared and the result is simultaneous 
reads.

P.S. You can include quoted code in [JIRA 
markup|https://issues.apache.org/jira/secure/WikiRendererHelpAction.jspa?section=advanced].

> ArrayIndexOutOfBoundsException in GlyfSimpleDescript.readFlags() when 
> multithreading
> ------------------------------------------------------------------------------------
>
>                 Key: PDFBOX-2824
>                 URL: https://issues.apache.org/jira/browse/PDFBOX-2824
>             Project: PDFBox
>          Issue Type: Bug
>          Components: FontBox
>    Affects Versions: 2.0.0
>            Reporter: Tilman Hausherr
>            Priority: Critical
>
> From Kenneth K. in the mailing list:
> I have a client application that convert pdf documents into single page tiff 
> images.  Since the user export large quantities of documents I use a 
> multithreaded approach.  Each thread loads it own document and converts the 
> pages one by one.
> The pdf file is serialized to the client thread and then each thread executes 
> the following code.  If I only use 1 thread there is no problem.  I checked 
> to make sure objects are shared between threads.
> {code}
>             docin = PDDocument.load(new 
> ByteArrayInputStream(documentResult.getImage().getContent()),true);
>             if(null==docin)
>               throw new Exception("Invalid PDF document or an occured during 
> retrieval");
>                int numPages = docin.getNumberOfPages();
>                      String strPath = getPath(numPages);
>                      int iPage = 0;
>             PDFRenderer renderer = new PDFRenderer(docin);
>             for (int i=0;i<numPages;i++)
>             {
>               PDPage page = docin.getPage(i);
>               PDRectangle rect = page.getMediaBox();
>               BufferedImage pageImage = null;
>               pageImage = renderer.renderImageWithDPI(i, 200f, 
> ImageType.BINARY);
>               ...
>             }
> {code}
> {code}
> Array index out of range: 8
>        at 
> org.apache.fontbox.ttf.GlyfSimpleDescript.readFlags(GlyfSimpleDescript.java:202)
>        at 
> org.apache.fontbox.ttf.GlyfSimpleDescript.<init>(GlyfSimpleDescript.java:77)
>        at org.apache.fontbox.ttf.GlyphData.initData(GlyphData.java:58)
>        at org.apache.fontbox.ttf.GlyphTable.getGlyph(GlyphTable.java:161)
>        at 
> org.apache.pdfbox.rendering.TTFGlyph2D.getPathForGID(TTFGlyph2D.java:140)
>        at 
> org.apache.pdfbox.rendering.TTFGlyph2D.getPathForCharacterCode(TTFGlyph2D.java:92)
>        at 
> org.apache.pdfbox.rendering.PageDrawer.drawGlyph2D(PageDrawer.java:333)
>        at 
> org.apache.pdfbox.rendering.PageDrawer.showFontGlyph(PageDrawer.java:314)
>        at 
> org.apache.pdfbox.contentstream.PDFStreamEngine.showGlyph(PDFStreamEngine.java:731)
>        at 
> org.apache.pdfbox.contentstream.PDFStreamEngine.showText(PDFStreamEngine.java:690)
>        at org.apache.pdfbox.rendering.PageDrawer.showText(PageDrawer.java:296)
>        at 
> org.apache.pdfbox.contentstream.PDFStreamEngine.showTextStrings(PDFStreamEngine.java:600)
>        at 
> org.apache.pdfbox.contentstream.operator.text.ShowTextAdjusted.process(ShowTextAdjusted.java:38)
>        at 
> org.apache.pdfbox.contentstream.PDFStreamEngine.processOperator(PDFStreamEngine.java:802)
>        at 
> org.apache.pdfbox.contentstream.PDFStreamEngine.processStreamOperators(PDFStreamEngine.java:464)
>        at 
> org.apache.pdfbox.contentstream.PDFStreamEngine.processStream(PDFStreamEngine.java:438)
>        at 
> org.apache.pdfbox.contentstream.PDFStreamEngine.processPage(PDFStreamEngine.java:149)
>        at org.apache.pdfbox.rendering.PageDrawer.drawPage(PageDrawer.java:179)
>        at 
> org.apache.pdfbox.rendering.PDFRenderer.renderPage(PDFRenderer.java:205)
>        at 
> org.apache.pdfbox.rendering.PDFRenderer.renderImage(PDFRenderer.java:136)
>        at 
> org.apache.pdfbox.rendering.PDFRenderer.renderImageWithDPI(PDFRenderer.java:95)
>        at 
> org.ilsos.cm.export.client.rmi.workers.Pdf2SinglePageTiff.processResult(Pdf2SinglePageTiff.java:142)
>        at 
> org.ilsos.cm.export.client.rmi.ExportWorker.run(ExportWorker.java:72)
>        at java.lang.Thread.run(Thread.java:784)
> {code}



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