[gdal-dev] vsicurl configuration design decisions

[Even Rouault]

Craig,

> True, but that does eliminate ambiguity in the URL, and does so in a
> well-known way.
> 
> Does the current scheme use any encoding?

No

> How would you escape text in
> option values that might use `=` and `,` etc? Or are there guaranteed to be
> no freeform-text options in these paths?

Currently, given the supported set of options and values, yes. In case of future ambiguity, 
yes, we'd need to define some escaping rules.

> 
> 
> 
> Tangential, but related: I've also just discovered the 2.2+ curly-brace
> syntax for vsizip/vsitar paths, which allows nested archives:

That's a side effect. The main motivation was that there are .tar or .zip files in the wild that 
for good or wrong reasons have non standard extensions.

> 
> /vsizip/{/vsizip/{/path/to/outer.zip}/path/to/inner.zip}/file.shp
> 
> 
> The curly braces are a definite improvement on the ambiguous older syntax
> for these paths. However, we noted the nesting order looks inside-out, and
> thought it would have been more intuitive to put the path *inside* the
> 
> archive in the braces. i.e. nesting would look like:
> > /vsizip//path/to/outer.zip/{/vsizip//path/to/inner.zip/{file.shp}}

Hum, that doesn't seem really better to me, and I can't see how that could be implemented. /
vsizip//path/to/inner.zip/{file.shp} couldn't be succesfully resolved by the vsizip VFS since /
path/to/inner.zip isn't a regular file itself.

/vsizip/{/vsizip/{/path/to/outer.zip}/path/to/inner.zip}/file.shp is really closer how it works 
internally, and is close to function-like syntax f(g(h(x))) where you start evaluating the most 
internal member.

So you have /vsizip/{something}/file.shp, which means we'll expose a file handle, for a file.shp 
in a zip archive accessed through "something"
"something" happens to expand to /vsizip/{/path/to/outer.zip}/path/to/inner.zip which 
means we will return a file (that happens to be itself a zip, but at that stage, only  /vsizip/
{something}/file.shp cares that is  a zip), that is in a zip file /path/to/outer.zip, which happens 
to be a regular file.


> 
> Of course, this latter syntax was added in 2.2, so perhaps that ship has
> already sailed.

Yes


Even

-- 
Spatialys - Geospatial professional services
http://www.spatialys.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/gdal-dev/attachments/20171013/bbc06394/attachment.html>