Re: 1.8 file format

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Hi John,

On Jul 21, 2007, at 11:33 AM, John Caron wrote:

Hi Quincey:

I am working my way through various tests of HDF 1.6 features, hoping that 1.8 docs will be ready (or ready to work on) when Im done. ;^)

Sure. Vailin's finished up the major changes to the h5stat tool and is wrapping up some directory rearrangement and extra testing this week. Then she'll be starting on updating the file format specification for the 1.8 changes (with me).

At the moment, im seeing a chunked data variable whose btree has 0 entries. I assume that it was never written, and I should return fill values? It may or may not be notable thats its chunked size is equal to its dataspace size, and its in an Aura file.

Yes, any missing chunks in a B-tree (including empty B-trees) were never written and should return fill values. If there is no fill value message, then all zero bytes for the datatype elements are assumed.


Quincey Koziol wrote:
Hi John,
On Jul 13, 2007, at 11:43 AM, John Caron wrote:
Hi Quincey:

I'm just starting to look at the H5Fsuper.c (its been a while since i coded in C).

Meanwhile i have another question on a different topic:

The B-tree nodes I assume are sorted on the keys. Is this a simple sort on the byte values, or something else? For example, are nodes of chunked data sorted on chunk size, then filter mask, then chunk offset? Or do you just use the chunk offset? When sorting the chunk offset, can i assume you sort on offset for slowest dimension (0), then offset for dimension 1, etc
Yes, the B-trees are sorted on the keys. It's not a simple sort on the byte values though, each "class" of B-tree has a comparison function. For chunks we sort only on chunk offset and it's as you describe above: first on offset in the slowest dimension, then toward the fastest dimension.

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