ISIS3 label parse issue

[thare]

It appears a new lunar image label is causing the GDAL ISIS3 label parser some grief. I have narrowed it down to a PVL continuation flag. You can see an example in the "Group = Radiometry" section within the parent "Object = IsisCube".

example:

    DarkFile                  = /usr/local/isis3/data/lro/calibration/NACL_Av-
                                erageDarks.0004.cub
    NonlinearOffset           = /usr/local/isis3/data/lro/calibration/NACL_Li-
                                nearizationOffsets.0004.cub
    LinearizationCoefficients = /usr/local/isis3/data/lro/calibration/NACL_Li-
                                nearizationCoefficients.0003.txt
    FlatFile                  = /usr/local/isis3/data/lro/calibration/NACL_Fl-
                                atfield.0005.cub

Deleting those four lines fixes the parsing. So the "-" (which is not escaped) needs to be recognized as a line continuation flag. Once found at the end of a line, the next line should be appended to it once the white space in the front has been removed.

Note that in the same image, inside the group above, a line continuation is also used. That currently works since the value is wrapped in parentheses.

BTW, this cube also has many "Object = Table" sections but those are correctly ignored. I am mentioning this since I have not seen the use of those sections in many labels.

An example (~15mb): ​ftp://pdsimage2.wr.usgs.gov/pub/pigpen/.temp/M102135625LE.smallmap.cub.gz

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Here is a good article on the whole PVL topic - ​http://www.orrery.us/node/44 . If the next generation of planetary images continue to use PVL (maybe be called PDS4), it might be worth looking into one the libraries mentioned on that page for GDAL. However, I have also heard the next generation might be switching to an XML label. We'll see.

thanks, Trent

[warmerdam]

The PDS documents (​http://pds.jpl.nasa.gov/documents/sr/Chapter12.pdf) don't mention anything about line continuation marks, but clearly they are being used in the product. I shall endevour to add handling.

I did review the referenced article, and have included a pointer to it in the "nasakeywordhandler.cpp" file header for future reference.

[warmerdam]

I have added support in ReadWord() for line continuation marks, and added some minimal testing for it in trunk (r19832) and 1.7 (r19833).