Hi all, To give some background context, I'm working on a Java project that deals with HDF files. I used to use the Java-interface to the native HDF library, however, I had some issues with it and I wanted to use a pure Java library. I didn't find any pure Java HDF libraries, so I decided to make my own. It's going very fine and it fits very well in my project. It's not complete yet, but I'm extending it bit-by-bit. All my work is open source. Currently, it's part of a bigger SpatialHadoop project [ https://github.com/aseldawy/spatialhadoop2]. However, I'm planning to ship it is a standalone library which will be available for the community.
Currently, I'm working on the Linked Block feature of HDF files. However, I'm having problems with this file http://e4ftl01.cr.usgs.gov/MOLT/MOD13Q1.005/2000.02.18/MOD13Q1.A2000049.h10v11.005.2006270195941.hdf The file opens fine in HDF viewer, which means that the file is correct. I'm following the HDF specs at http://www.hdfgroup.org/release4/doc/DSpec_html/DS.pdf Linked block elements are described in Section 10.3 on page 149 (160 in the PDF). First, there seems to be a problem in the documentation as it says that EXT_LINKED constant is 32-bits. This seems to be error because other extension identifiers are 16-bits (e.g., see SPECIAL_EXT in 10.4). Anyway, I fixed it myself and worked with a 16-bit identifier. However, I started to see some problems and I don't know if my fix of 32-bits to 16-bits was right or wrong. The file I mentioned above has an extended data block with tagID 1963 (DFTAG_VS) and reference no 49. The data of this object is located in offset 38215 and length 16 bytes. When I parse this block according to the specs, I get the following numbers which are inconsistent. Length: 57600 first_len: 4096 blk_len: 16 num_blk: 131072 Now these numbers do not make sense because if the length of the first block is 4096 and then we have 131072 blocks, each of 16-bytes length, the total length would be 2101248 which is much larger than 57600. I'm having more troubles when parsing the linked block table but let's resolve this issue first as the later might be related.
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