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<TITLE>sane-devel: Re: [snapscan] More USB Updates</TITLE>
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<H1>Re: [snapscan] More USB Updates</H1>
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<STRONG>From:</STRONG> Chris Bagwell (<A HREF="mailto:cbagwell@sprynet.com?Subject=Re:%20[snapscan]%20More%20USB%20Updates&In-Reply-To=&lt;3A19F4D8.943DFE8B@sprynet.com&gt;"><EM>cbagwell@sprynet.com</EM></A>)<BR>
<STRONG>Date:</STRONG> Mon Nov 20 2000 - 20:06:48 PST
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Steve,
<BR>
<P>Here is a more specific question I have for you regarding a code change
<BR>
I made to RGBRouter_remaining(). The original functions logic works out
<BR>
to the following (this version is closer to what Lawernce posted).
<BR>
<P>&nbsp;&nbsp;&nbsp;&nbsp;if (ps-&gt;cb_start &lt; 0)
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;remaining = (TxSource_remaining(pself) - ps-&gt;cb_size +
<BR>
ps-&gt;cb_line_size);
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;else
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;remaining = (TxSource_remaining(pself) + ps-&gt;cb_line_size -
<BR>
ps-&gt;pos);
<BR>
<P>&nbsp;&nbsp;&nbsp;&nbsp;return (remaining);
<BR>
<P>As far as I can tell, cb_start can only be &lt; 0 at two or three times:
<BR>
1) When you start a fake scan to get transfer speed, 2) When you start
<BR>
the real scan, 3) when your closing down everything. In case 1 &amp; 2 it
<BR>
seems to me that there are a lot of cases where the buffer will not be
<BR>
full (because the fake scan doesn't attempt to read a full buffer but
<BR>
that might be a bug or in case of the real scan I was thinking that the
<BR>
scanner might come back with an EAGAIN error or something and give us a
<BR>
partial buffer).
<BR>
<P>If I read your original email correctly you said the test for cb_start &lt;
<BR>
0 was for the end of the scan but I don't really see any code that would
<BR>
drain the circular buffer after the call to RGBRouter_done().
<BR>
<P>Would you mind commenting on this part to help clear up my confusion. I
<BR>
think my confusion revolves around the difference between the TxSource
<BR>
buffer and the circular buffer (is there a difference?).
<BR>
<P>Thanks,
<BR>
Chris
<BR>
<P><PRE>
--
Chris Bagwell (mailto:<A HREF="mailto:cbagwell@sprynet.com?Subject=Re:%20[snapscan]%20More%20USB%20Updates&In-Reply-To=&lt;3A19F4D8.943DFE8B@sprynet.com&gt;">cbagwell@sprynet.com</A>) | Dallas, TX
<A HREF="http://home.sprynet.com/~cbagwell">http://home.sprynet.com/~cbagwell</A> | USA
<P>--
Source code, list archive, and docs: <A HREF="http://www.mostang.com/sane/">http://www.mostang.com/sane/</A>
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