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https://issues.apache.org/jira/browse/PDFBOX-1232?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13226084#comment-13226084
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Dave Smith commented on PDFBOX-1232:
------------------------------------
Sent in private .
> FlateDecoder in stream mode
> ---------------------------
>
> Key: PDFBOX-1232
> URL: https://issues.apache.org/jira/browse/PDFBOX-1232
> Project: PDFBox
> Issue Type: Bug
> Reporter: Dave Smith
>
> The zlib (the unlying spec for Flate compression) does not require an
> Z_STREAM_END to terminate the compression. The Java InflateInputStream is
> really assuming that you are reading a zip or gzip file which will always
> have a Z_STREAM_END (Z_STREAM_END is a constant in the zlib library which
> Java calls natively) . So the following chunk decodes fine using the jcraft
> zlib decoder, but fails using the InflateInputStream.
> 3 0 obj
> <<
> /Type /XObject
> /Subtype /Form
> /FormType 1
> /Resources << /Font 4 0 R
> /ProcSet [/PDF /ImageC /Text]>>
> /BBox [0 0 595 842]
> /Matrix [1 0 0 1 0 0]
> /Filter /FlateDecode
> /Length 5 >>
> stream
> H<89>^C^@
> endstream
> endobj
> The blob is 72, -119, 3, 0, 13 decimal. It decodes to an empty string.
> The fix is to use Inflater and check to see if it has consumed all of the
> input buffer and make sure it has nothing to write into the output buffer.
> protected ByteArrayOutputStream decompress(InputStream in)
> throws IOException, DataFormatException
> {
> ByteArrayOutputStream out = new ByteArrayOutputStream();
> byte buf[] = new byte[1000];
> Inflater inflater = new Inflater();
> int read = in.read(buf);
> if(read == 0)
> {
> return out;
> }
> inflater.setInput(buf,0,read);
> byte res[] = new byte[1000];
> while(true)
> {
> int resRead = inflater.inflate(res);
> if(resRead !=0)
> {
> out.write(res,0,resRead);
> continue;
> }
> if(inflater.finished() || inflater.needsDictionary() ||
> in.available()==0)
> {
> out.close();
> return out;
> }
> read = in.read(buf);
> inflater.setInput(buf,0,read);
>
> }
> }
> We then need to change FlateFilter.decode(InputStream compressedData,
> OutputStream result,
> COSDictionary options, int filterIndex )
> to look like ...
> if (compressedData.available() > 0)
> {
> try
> {
> baos = decompress(compressedData);
> }
> if (predictor==-1 || predictor == 1 )
> {
> result.write(baos.toByteArray());
> }
> else
> {
> use the bytearrayoutput stream as before ...
> }
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