fn:unparsed-binary: accessing and manipulating binary types

[birodb]

Dear All,
When working with binary types currently one has to fall back to string conversions and/or extensions.
A few ideas on nice to have functions that operate on binary types:
-accessing a single byte at a specific position
-splitting binary data at byte boundary (aka binary-subsequence)
-converting to/from a sequence of byte(s)
-joining binary data together
-(optionally) loading data directly as (base64)binary (some extensions are using unparsed-text with proprietary decoding 'x-binarytobase64' to retrieve a base64 castable string)
-standard bit-wise operators and, or, xor, not, rshift, lshift

If considered, then each needs to be discussed in detail separately -ex. which type to support signed/unsigned, 8 bit etc.-, I merely intend as conversation starter in case others encountered similar issues/limitations.

p.s.: Not sure if this is the right channel to raise this issue, so feel free to close/move/split accordingly.

[michaelhkay]

These features are all in the EXPath binary module -- see http://expath.org/modules/binary/ -- which I think is supported in those products that are implementing the 4.0 specifications. We could consider integrating this module into the main specifications, but I'm not sure whether the editorial effort in doing so would achieve any practical benefits. Other than, perhaps, making the specs more visible to people who haven't come across them!

[michaelhkay]

One think we perhaps do need to add, I think, is a function to read a binary resource. That's currently available in the EXPath file module, but we certainly don't want to bring in the whole of the file module because many of the functions have side-effects and it's therefore very difficult to define clean semantics for them.

[birodb]

Thank you very much, it's a fair point. I think adding a direct link to the EXPath binary module (maybe even as optional feature) will improve the visibility sufficiently - it definitely slipped under my radar, it's been a relatively long time since I've last looked at those modules.

[ChristianGruen]

One think we perhaps do need to add, I think, is a function to read a binary resource.

I’ve updated the title of the issue to reflect this requirement (whatever the name will be called).

As indicated in #748 (comment), we should clarify if this function can be nondeterministic.

[ChristianGruen]

I‘ve added the »Propose for V4.0« label: Function such as fn:parse-html are able to process xs:base64Binary, and others might follow (see #748), so we should have a function for generating such data (apart from xs:base64Binary(...)).

[Arithmeticus]

Some related discussion at #414 , concerning detecting availability of a binary resource, and getting it.

[ndw]

The issues discussed here are also discussed in #1127 which appears to superscede this one.

[ndw]

The CG agreed to close this issue without further action at meeting 081