This document describes CBOR tag 56500 which represents a compressed byte string.
- Tag: 56500
- Data Item: Array (major type 4).
- Semantics: Compressed byte string.
- Contact: Dirk Boye <dirk.boye@dectris.com>
Tag 56500 describes a byte string of compressed data. The compression algorithm used is represented in the tag content.
Compression algorithms commonly used with DECTRIS products are specified (see Compression Algorithms). Additional compression algorithms may be added in the future.
The tag content is an array of three elements: a text string specifying the compression algorithm used; an algorithm-dependent modifier item; and a byte string of the compressed data.
This tag is equivalent to a byte string of the decompressed data. In particular, it MAY be used with tags that require data items of major type 2, as allowed by the CBOR protocol (see Tag Equivalence).
| Algorithm | Modifier | Data |
|---|---|---|
"bslz4" |
Integer specifying the bitshuffle element size. | Byte string of bitshuffle-transposed blocks each compressed using LZ4. The format is the same as the bitshuffle HDF5 filter. |
#6.56500(["bslz4", 1, ...])
#6.56500(["bslz4", 2, ...])
#6.56500(["bslz4", 4, ...])
https://github.com/kiyo-masui/bitshuffle
https://github.com/lz4/lz4/blob/master/doc/lz4_Block_format.md
| Algorithm | Modifier | Data |
|---|---|---|
"lz4" |
Unused. | Byte string of LZ4 compressed blocks. The LZ4 filter format for HDF5 is used for framing. |
The modifier item is unused with this compression algorithm. The zero integer is serialized as a placeholder.
#6.56500(["lz4", 0, ...])
https://github.com/lz4/lz4/blob/master/doc/lz4_Block_format.md
https://support.hdfgroup.org/services/filters/HDF5_LZ4.pdf
pip install cbor2 dectris-compression~=0.3.0
import cbor2
from dectris.compression import decompress
def tag_hook(decoder, tag):
if tag.tag == 56500:
algorithm, elem_size, encoded = tag.value
return decompress(encoded, algorithm, elem_size=elem_size)
else:
return tag
cbor2.loads(message, tag_hook=tag_hook)