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38 lines
1.3 KiB
Plaintext
38 lines
1.3 KiB
Plaintext
/** \page Attributes
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\section secAttributes Attributes
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\subsection CB_LargeAttributes Creating "Large" HDF5 Attributes
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\par Problem
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You would like to use HDF5 attributes the size of whose values
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exceeds a few dozen kilobytes
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\par Solution
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A file format change in the HDF5 1.8.x family of library releases made it
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possible to have attributes larger than about 64 KiB. Ensure that the lower
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library version bound for new HDF5 item creation is at least 1.8.x, and create
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larger attributes as usual.\n
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In the example below, we create an attribute whose value occupies 4 MiB.
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\note This feature is only supported in HDF5 1.8.x+
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\snippet{lineno} Attributes.c large_attribute
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\par Discussion
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Large attributes are supported only in HDF5 versions 1.8.x and higher.
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This has implications for the accessibility of your HDF5 files and
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is your call.\n
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Since there are no size limitations for large attributes, it might
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seem tempting to mistake them for dataset stand-ins. This is not the
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case, for at least two reasons:
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1. Attributes decorate HDF5 objects, have their own local namespace,
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and can't be link targets.
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2. Attribute I/O treats the attribute value as atomic, i.e., there
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is no support for partial I/O. A large attribute will always be
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read or written in its entirety.
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\par See Also
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See \ref CB_MaintainCompat for HDF5 compatibility implications.
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*/ |