source: thirdparty/blosc/README_HEADER.rst @ 00587dc

Revision 00587dc, 1.1 KB checked in by Hal Finkel <hfinkel@…>, 9 years ago (diff)

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[00587dc]1Blosc Header Format
2===================
3
4Blosc (as of Version 1.0.0) has the following 16 byte header that stores
5information about the compressed buffer::
6
7    |-0-|-1-|-2-|-3-|-4-|-5-|-6-|-7-|-8-|-9-|-A-|-B-|-C-|-D-|-E-|-F-|
8      ^   ^   ^   ^ |     nbytes    |   blocksize   |    ctbytes    |
9      |   |   |   |
10      |   |   |   +--typesize
11      |   |   +------flags
12      |   +----------versionlz
13      +--------------version
14
15Datatypes of the Header Entries
16-------------------------------
17
18All entries are little endian.
19
20:version:
21    (``uint8``) Blosc format version.
22:versionlz:
23    (``uint8``) Blosclz format  version (internal Lempel-Ziv algorithm).
24:flags:
25    (``bitfield``) The flags of the buffer.
26
27    :bit 0 (``0x01``):
28        Whether the shuffle filter has been applied or not.
29    :bit 1 (``0x02``):
30        Whether the internal buffer is a pure memcpy or not.
31
32:typesize:
33    (``uint8``) Number of bytes for the atomic type.
34:nbytes:
35    (``uint32``) Uncompressed size of the buffer.
36:blocksize:
37    (``uint32``) Size of internal blocks.
38:ctbytes:
39    (``uint32``) Compressed size of the buffer.
40
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