Read data from an HDF5 attribute

Read data from an HDF5 attribute

Usage

H5Aread(h5attribute, buf = NULL, bit64conversion = c("int", "double", "bit64"))

Arguments

h5attribute

An object of class H5IdComponent representing an attribute. Normally created by H5Aopen() or similar.

buf

Optional buffer to store retrieved values. The buffer size has to fit the size of the memory space h5spaceMem. No extra memory will be allocated for the data. Default is NULL which means the function will return the attribute data.

bit64conversion

Defines how 64-bit integers are converted. (See the details section for more information on these options.)

Value

If buf=NULL returns the contents of the attribute. Otherwise return 0 if attribute is read successfully.

Details

Internally, R does not support 64-bit integers. All integers in R are 32-bit integers. By setting bit64conversion='int', a coercing to 32-bit integers is enforced, with the risk of data loss, but with the insurance that numbers are represented as integers. bit64conversion='double' coerces the 64-bit integers to floating point numbers. doubles can represent integers with up to 54-bits, but they are not represented as integer values anymore. For larger numbers there is again a data loss. bit64conversion='bit64' is recommended way of coercing. It represents the 64-bit integers as objects of class 'integer64' as defined in the package 'bit64'. Make sure that you have installed 'bit64'. The datatype 'integer64' is not part of base R, but defined in an external package. This can produce unexpected behaviour when working with the data.