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<H1>Re: Writing Fujitsu M3091 backend</H1>
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<STRONG>From:</STRONG> mh (<A HREF="mailto:crapsite@gmx.net?Subject=Re:%20Writing%20Fujitsu%20M3091%20backend&In-Reply-To=&lt;01022720404600.00591@slowcrap&gt;"><EM>crapsite@gmx.net</EM></A>)<BR>
<STRONG>Date:</STRONG> Tue Feb 27 2001 - 11:04:30 PST
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Frederik Ramm, Die, 27 Feb 2001 :
<BR>
<EM>&gt; Hi,
</EM><BR>
<EM>&gt;
</EM><BR>
<EM>&gt; &gt; When scanning the first page, half the data goes in this large buffer,
</EM><BR>
<EM>&gt; &gt; then when the frontend asks for another page it comes out of the
</EM><BR>
<EM>&gt; &gt; buffer very quickly. The buffer can be discarded when the frontend
</EM><BR>
<EM>&gt; &gt; calls ..._close() so it won't take up RAM all the time.
</EM><BR>
<EM>&gt;
</EM><BR>
<EM>&gt; That sounds reasonable. But can I be sure that front-ends will support
</EM><BR>
<EM>&gt; reading multiple pages one after the other with no call to ..._close()
</EM><BR>
<EM>&gt; in between? This would not, for example, work with &quot;scanimage&quot;, would
</EM><BR>
<EM>&gt; it?
</EM><BR>
You can't be sure, but you can be quite sure that at least the graphical
<BR>
frontends won't call sane_close() between scans.
<BR>
On the whole, it's just an insufficiency in the current SANE Standard.
<BR>
Probably a simple
<BR>
SANE_Bool another_scan_follows
<BR>
in SANE_Parameters would be sufficient. If another_scan_follows is true
<BR>
and last_frame is true, the frontend knows, that the next frame belongs to a
<BR>
new image. This, of course, will only fly if the backend stores the
<BR>
following frames in RAM, like suggested by Nick Lamb.
<BR>
Another advantage is, that this doesn't break compatibilty with
<BR>
current frontends. They just read one image and call sane_cancel(); now
<BR>
the backend knows, that it can discard the following frames.
<BR>
<P>Just MHO
<BR>
Michael
<BR>
<P><PRE>
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