hdf5_ep

[svn-r3885] Purpose:
    Document bug fix
Description:
    IMPORTANT! IMPORTANT! IMPORTANT!
    A case where metadata in a file could get corrupted in certain unusual
    sitations was detected and fixed.

    In certain circumstances, metadata could get cached in the raw data cache,
    and if that particular piece of metadata was updated on disk while
    incorrectly cached, the new metadata would get overwritten with the stale
    metadata from the raw data cache when it was flushed out.

    Additionally, I've patched up the raw data cache to be smarter about how
    much it caches and how much I/O it triggers, leading to some speedups.

Solution:
    Changed the raw data I/O routines which perform caching to require a
    parameter with the size of the dataset being accessed and limited the
    cache to no more than that many bytes.

Platforms tested:
    FreeBSD 4.3 (hawkwind)