Re: [PATCH/RFC] crypto: compress - Return produced bytes in crypto_{,de}compress_{update,final}()(was: Re: [PATCH/RFC] crypto: compress - Add comp_request.total_out

[Phillip Lougher]

Geert Uytterhoeven wrote:
> On Tue, 17 Mar 2009, Geert Uytterhoeven wrote:
> > On Wed, 11 Mar 2009, Geert Uytterhoeven wrote:
> > > On Sun, 8 Mar 2009, Phillip Lougher wrote:
> > > > Two API issues of concern (one major, one minor).  Both of these relate to the
> > > > way Squashfs drives the decompression code, where it repeatedly calls it
> > > > supplying additional input/output buffers, rather than using a "single-shot"
> > > > approach where it calls the decompression code once supplying all the
> > > > necessary input and output buffer space.
> > > >
> > > > 1. Minor issue -the lack of a stream.total_out field.  The current
> > > > zlib_inflate code collects the total number of bytes decompressed over the
> > > > multiple calls into the stream.total_out field.
> > > >
> > > >    There is clearly no such field available in the cryto API, leading to the
> > > > somewhat clumsy need to track it, i.e. it leads to the following additional
> > > > code.
> > > If people feel the need for a total_out field, I can add it to struct
> > > comp_request.
> > >
> > > BTW, what about total_in, which is also provided by plain zlib's z_stream?
> > > Do people see a need for a similar field?
> > The patch below (on top of the updated one to convert SquashFS to pcomp) adds
> > comp_request.total_out, so you don't have to calculate and accumulate the
> > decompressed output sizes in SquashFS.
> >
> > Notes:
> >   - This required the addition of a `struct comp_request *' parameter to
> >     crypto_{,de}compress_init()
> >   - Still, there's one of the 
> >
> > 	produced = req.avail_out;
> > 	...
> > 	produced -= req.avail_out;
> >
> >     left, as this is part of the logic to discover the end of decompression
> >     (no bytes produced, no error returned).
> >
> > Perhaps it's better to instead make crypto_{,de}compress_{update,final}()
> > return the (positive) number of output bytes (of the current step)?
> >
> > Currently it returns zero (no error) or a negative error value.
> > That would allow to get rid of both `produced = ... / produced -= ...'
> > constructs, but the user would have to accumulate the total output size again
> > (which is not such a big deal, IMHO).
>
> Here's an alternative patch, which does exactly that.
> Phillip, what do you think?

From a quick look, it looks OK :-)  I'm not ignoring this, but I'm trying to get a release of
the 4.0 tools finished ASAP (now 2.6.29 is out).

Phillip
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