Thank you for such quick response, allan. Do you mean to say that the value of maxlen is determined by the frontend? On xsane application, maxlen value is 8192 when using acquire preview and then value of maxlen is 65536 when using scan function. Our external backend currently reads images by row on sane_read(). Issue occurs when using acquire preview on colored A3 original because the number of bytes per row is more than the value of maxlen. If I reallocate the argument buf to a much bigger size, xsane closes and I get this error message below: *** stack smashing detected ***: xsane terminated Aborted (core dumped)
Since our external backend currently reads images by row on sane_read(), is it better to just change our implementation on sane_read() ? On Wed, Mar 9, 2016 at 9:39 AM, m. allan noah <[email protected]> wrote: > Because different frontends have different requirements. Some try to > save memory, some try to maximize speed by using large buffers, some > try to fill a network packet exactly. You can (and should expect) to > get any value of maxlen from 1 byte to perhaps a 1M, maybe more. > > allan > > On Tue, Mar 8, 2016 at 8:23 PM, ky gcp <[email protected]> wrote: > > why does the value of maxlen vary from various frontends? > > > > On Tue, Mar 8, 2016 at 9:06 PM, m. allan noah <[email protected]> > wrote: > >> > >> maxlen is provided by the caller of the function, to tell the backend > >> how much memory the caller has allocated for image data. > >> > >> allan > >> > >> On Tue, Mar 8, 2016 at 3:09 AM, ky gcp <[email protected]> wrote: > >> > hi, > >> > > >> > how is the argument maxlen determined in sane_read() function? > >> > > >> > SANE_Status sane_read (SANE_Handle h, SANE_Byte * buf, SANE_Int > maxlen, > >> > SANE_Int * len); > >> > > >> > Thanks for your help. > >> > > >> > -- > >> > sane-devel mailing list: [email protected] > >> > http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/sane-devel > >> > Unsubscribe: Send mail with subject "unsubscribe your_password" > >> > to [email protected] > >> > >> > >> > >> -- > >> "well, I stand up next to a mountain- and I chop it down with the edge > >> of my hand" > > > > > > > > -- > "well, I stand up next to a mountain- and I chop it down with the edge > of my hand" >
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