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Numpy UCS-4 codec

Source: R/codec.R
zarr_codec_ucs4.Rd

The Numpy UCS-4 format is a fixed-length character string format where shorter string are padded on the right with 0's. This is not a Zarr codec but specific to Numpy. It is included here because many Zarr v.2 stores have been written with this formatting of character strings. Since it does not use a codec in Zarr v.2, it is an invalid configuration in Zarr v.3 and this package because it embodies the array -> bytes step that is mandatory in Zarr v.3 - this is why this mock codec is included. This "codec" encodes an R character object to a raw byte string, and decodes a raw byte string to a R character object. The character object, typically a vector but possibly a matrix or array, should use UTF-8 encoding, which is the standard on modern platforms running R.

This codec is not part of the Zarr v.3 core specification but a commonly used process in Zarr v.2 on Python to serialize character strings into Zarr chunks. This implementation enables the use of the Zarr v.2 "<U*" data type. As a consequence, this codec can only decode data - new data is not written in this format.

Super classes

zarr::zarr_extension -> zarr::zarr_codec -> zarr_codec_ucs4

Active bindings

endian

(read-only) Retrieve the endianness of the storage of the data with this codec. A string with value of "big" or "little".

Methods

Public methods

Inherited methods

Method new()

Create a new UCS-4 codec object.

Usage

zarr_codec_ucs4$new(chunk_shape, configuration)

Arguments

chunk_shape

The shape of a chunk of data of the array, an integer vector.

configuration

A list with the configuration parameters for this codec. This is a list created in this package, it does not exist in the Zarr store as the Numpy UCS-4 method is not a real codec. The element endian specifies the byte ordering of the data type of the Zarr array. A string with value "big" or "little". The element width given the fixed padded string width.

Returns

An instance of this class.

Method copy()

Create a new, independent copy of this codec.

Usage

zarr_codec_ucs4$copy()

Returns

An instance of zarr_codec_ucs4.

Method metadata_fragment()

Return the metadata fragment that describes this codec.

Usage

zarr_codec_ucs4$metadata_fragment()

Returns

A list with the metadata of this codec, just the name.

Method decode()

This method takes a raw UCS-4 vector and converts it to an R character object.

Usage

zarr_codec_ucs4$decode(data)

Arguments

data

The data to be decoded.

Returns

An R character object with the shape of a chunk from the array.