kopia lustrzana https://gitlab.com/sane-project/website
461 wiersze
19 KiB
HTML
461 wiersze
19 KiB
HTML
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<a href="doc018.html"><img src=../icons/next.gif alt="Next"></a>
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<a href="doc000.html"><img src=../icons/up.gif alt="Up"></a>
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<a href="doc016.html"><img src=../icons/previous.gif alt="Previous"></a>
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<a href="doc000.html"><img src=../icons/contents.gif alt="Contents"></a>
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<a href="doc019.html"><img src=../icons/index.gif alt="Index"></a>
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<hr>
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<title>Remote Procedure Call Requests</title>
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<h2><a name="s5.2">5.2 Remote Procedure Call Requests</a></h2>
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<p>The SANE network protocol is a client/server-style remote procedure
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call (RPC) protocol. This means that all activity is initiated by the
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client side (the network backend)---a server is restricted to
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answering request by the client.
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<p><h3><a name="s5.2.1">5.2.1 <tt>SANE_NET_INIT<a name="i150"></tt></a></h3>
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<p>This RPC establishes a connection to a particular SANE network daemon.
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It must be the first call in a SANE network session. The parameter
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and reply arguments for this call are shown in the table below:
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<center>
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<table cellpadding=0 cellspacing=0>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<b>request:</b> </td>
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<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<tt>SANE_Word version_code</tt> </td>
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<td colspan=1 align=left nowrap> <tt>SANE_Word status</tt> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<tt>SANE_String user_name</tt> </td>
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<td colspan=1 align=left nowrap> <tt>SANE_Word version_code</tt> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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</td></tr>
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</table>
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</center>
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The <tt>version_code</tt> argument in the request is the SANE
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version-code of the network backend that is contacting the network
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daemon (see Section <a href="doc010.html#s4.1">4.1</a>). The
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``build-revision'' in the version code is used to hold the network
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protocol version. The SANE network daemon receiving such a request
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must make sure that the network protocol version corresponds to a
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supported version since otherwise the encoding of the network stream
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may be incompatible (even though the SANE interface itself may be
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compatible). The <tt>user_name</tt> argument is the name of the user
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on whose behalf this call is being performed. If the network backend
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cannot determine a user-name, it passes a <tt>NULL</tt> pointer for this
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argument. No trust should be placed in the authenticity of this
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user-name. The intent of this string is to provide more convenience
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to the user. E.g., it could be used as the default-user name in
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subsequent authentication calls.
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<p>In the reply, <tt>status</tt> indicates the completion status. If the
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value is anything other than <tt>SANE_STATUS_SUCCESS</tt>, the
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remainder of the reply has undefined values.<a name="F2"><a href="footnotes.html#000002"><sup><fontsize=-2>2</font></sup></a></a> The <tt>version_code</tt> argument returns the
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SANE version-code that the network daemon supports. See the comments
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in the previous paragraph on the meaning of the build-revision in this
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version code.
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<p><h3><a name="s5.2.2">5.2.2 <tt>SANE_NET_GET_DEVICES<a name="i152"></tt></a></h3>
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<p>This RPC is used to obtain the list of devices accessible by the SANE
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daemon.
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<center>
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<table cellpadding=0 cellspacing=0>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<b>request:</b> </td>
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<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<tt>void</tt> </td>
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<td colspan=1 align=left nowrap> <tt>SANE_Word status</tt> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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</td>
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<td colspan=1 align=left nowrap> <tt>SANE_Device ***device_list</tt> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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</td></tr>
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</table>
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</center>
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There are no arguments in the request for this call.
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<p>In the reply, <tt>status</tt> indicates the completion status. If the
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value is anything other than <tt>SANE_STATUS_SUCCESS</tt>, the
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remainder of the reply has undefined values. The <tt>device_list</tt>
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argument is a pointer to a <tt>NULL</tt>-terminated array of
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<tt>SANE_Device</tt> pointers.
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<p><h3><a name="s5.2.3">5.2.3 <tt>SANE_NET_OPEN<a name="i154"></tt></a></h3>
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<p>This RPC is used to open a connection to a remote SANE device.
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<center>
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<table cellpadding=0 cellspacing=0>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<b>request:</b> </td>
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<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<tt>SANE_String device_name</tt> </td>
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<td colspan=1 align=left nowrap> <tt>SANE_Word status</tt> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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</td>
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<td colspan=1 align=left nowrap> <tt>SANE_Word handle</tt> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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</td>
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<td colspan=1 align=left nowrap> <tt>SANE_String resource</tt> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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</td></tr>
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</table>
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</center>
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The <tt>device_name</tt> argument specifies the name of the device to
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open.
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<p>In the reply, <tt>status</tt> indicates the completion status. If the
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value is anything other than <tt>SANE_STATUS_SUCCESS</tt>, the
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remainder of the reply has undefined values. The <tt>handle</tt>
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argument specifies the device handle that uniquely identifies the
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connection. The <tt>resource</tt> argument is used to request
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authentication. If it has a non-<tt>NULL</tt> value, the network
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backend should authenticate the specified resource and then retry this
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operation (see Section <a href="doc017.html#s5.2.10">5.2.10</a> for details on how to
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authorize a resource).
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<p><h3><a name="s5.2.4">5.2.4 <tt>SANE_NET_CLOSE<a name="i156"></tt></a></h3>
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<p>This RPC is used to close a connection to a remote SANE device.
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<center>
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<table cellpadding=0 cellspacing=0>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<b>request:</b> </td>
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<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<tt>SANE_Word handle</tt> </td>
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<td colspan=1 align=left nowrap> <tt>SANE_Word dummy</tt> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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</td></tr>
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</table>
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</center>
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The <tt>handle</tt> argument identifies the connection that should be
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closed.
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<p>In the reply, the <tt>dummy</tt> argument is unused. Its purpose is to
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ensure proper synchronization (without it, a net client would not be
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able to determine when the RPC has completed).
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<p><h3><a name="s5.2.5">5.2.5 <tt>SANE_NET_GET_OPTION_DESCRIPTORS<a name="i158"></tt></a></h3>
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<p>This RPC is used to obtain <em>all</em> the option descriptors for a
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remote SANE device.
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<center>
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<table cellpadding=0 cellspacing=0>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<b>request:</b> </td>
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<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<tt>SANE_Word handle</tt> </td>
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<td colspan=1 align=left nowrap> <tt>Option_Descriptor_Array odesc</tt> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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</td></tr>
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</table>
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</center>
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The <tt>handle</tt> argument identifies the remote device whose option
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descriptors should be obtained.
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<p>In the reply, the <tt>odesc</tt> argument is used to return the array of
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option descriptors. The option descriptor array has the following
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structure:
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<blockquote><a name="i160">
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<pre>
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struct Option_Descriptor_Array
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{
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SANE_Word num_options;
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SANE_Option_Descriptor **desc;
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};
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</pre>
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</blockquote>
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<p><h3><a name="s5.2.6">5.2.6 <tt>SANE_NET_CONTROL_OPTION<a name="i161"></tt></a></h3>
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<p>This RPC is used to control (inquire, set, or set to automatic) a
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specific option of a remote SANE device.
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<center>
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<table cellpadding=0 cellspacing=0>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<b>request:</b> </td>
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<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<tt>SANE_Word handle</tt> </td>
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<td colspan=1 align=left nowrap> <tt>SANE_Status status</tt> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<tt>SANE_Word option</tt> </td>
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<td colspan=1 align=left nowrap> <tt>SANE_Word info</tt> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<tt>SANE_Word action</tt> </td>
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<td colspan=1 align=left nowrap> <tt>SANE_Word value_type</tt> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<tt>SANE_Word value_type</tt> </td>
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<td colspan=1 align=left nowrap> <tt>SANE_Word value_size</tt> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<tt>SANE_Word value_size</tt> </td>
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<td colspan=1 align=left nowrap> <tt>void *value</tt> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<tt>void *value</tt> </td>
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<td colspan=1 align=left nowrap> <tt>SANE_String *resource</tt> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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</td></tr>
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</table>
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</center>
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The <tt>handle</tt> argument identifies the remote device whose option
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should be controlled. Argument <tt>option</tt> is the number (index) of
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the option that should be controlled. Argument <tt>action</tt>
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specifies what action should be taken (get, set, or set automatic).
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Argument <tt>value_type</tt> specifies the type of the option value
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(must be one of <tt>SANE_TYPE_BOOL</tt>, <tt>SANE_TYPE_INT</tt>,
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<tt>SANE_TYPE_FIXED</tt>, <tt>SANE_TYPE_STRING</tt>,
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<tt>SANE_TYPE_BUTTON</tt>). Argument <tt>value_size</tt> specifies
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the size of the option value in number of bytes (see
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Section <a href="doc011.html#s4.2.9.6">4.2.9.6</a> for the precise meaning of this value).
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Finally, argument <tt>value</tt> is a pointer to the option value. It
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must be a writeable area that is at least <tt>value_size</tt> bytes
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large. (Note that this area must be writable even if the action is to
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set the option value. This is because the backend may not be able to
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set the exact option value, in which case the option value is used to
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return the next best value that the backend has chosen.)
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<p>In the reply, argument <tt>resource</tt> is set to the name of the
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resource that must be authorized before this call can be retried. If
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this value is non-<tt>NULL</tt>, all other arguments have undefined
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values (see Section <a href="doc017.html#s5.2.10">5.2.10</a> for details on how to
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authorize a resource). Argument <tt>status</tt> indicates the
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completion status. If the value is anything other than
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<tt>SANE_STATUS_SUCCESS</tt>, the remainder of the reply has undefined
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values. The <tt>info</tt> argument returns the information on how well
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the backend was able to satisfy the request. For details, see the
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description of the corresponding argument in
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Section <a href="doc012.html#s4.3.7">4.3.7</a>. Arguments <tt>value_type</tt> and
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<tt>value_size</tt> have the same values as the arguments by the same
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name in corresponding request. The values are repeated here to ensure
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that both the request and the reply are self-contained (i.e., they can
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be encoded and decoded independently). Argument <tt>value</tt> is holds
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the value of the option that has become effective as a result of this
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RPC.
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<p><h3><a name="s5.2.7">5.2.7 <tt>SANE_NET_GET_PARAMETERS<a name="i163"></tt></a></h3>
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<p>This RPC is used to obtain the scan parameters of a remote SANE
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device.
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<center>
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<table cellpadding=0 cellspacing=0>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<b>request:</b> </td>
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<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<tt>SANE_Word handle</tt> </td>
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<td colspan=1 align=left nowrap> <tt>SANE_Status status</tt> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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</td>
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<td colspan=1 align=left nowrap> <tt>SANE_Parameters params</tt> </td></tr>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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</td></tr>
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</table>
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</center>
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The <tt>handle</tt> argument identifies the connection to the remote
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device whose scan parameters should be returned.
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<p>In the reply, <tt>status</tt> indicates the completion status. If the
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value is anything other than <tt>SANE_STATUS_SUCCESS</tt>, the
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remainder of the reply has undefined values. The argument
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<tt>params</tt> is used to return the scan parameters.
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<p><h3><a name="s5.2.8">5.2.8 <tt>SANE_NET_START<a name="i165"></tt></a></h3>
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<p>This RPC is used to start image acquisition (scanning).
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<center>
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<table cellpadding=0 cellspacing=0>
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<tr valign=top>
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<td colspan=1 align=left nowrap>
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<b>request:</b> </td>
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<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
|
||
|
|
<tr valign=top>
|
||
|
|
<td colspan=1 align=left nowrap>
|
||
|
|
<tt>SANE_Word handle</tt> </td>
|
||
|
|
<td colspan=1 align=left nowrap> <tt>SANE_Status status</tt> </td></tr>
|
||
|
|
<tr valign=top>
|
||
|
|
<td colspan=1 align=left nowrap>
|
||
|
|
</td>
|
||
|
|
<td colspan=1 align=left nowrap> <tt>SANE_Word port</tt> </td></tr>
|
||
|
|
<tr valign=top>
|
||
|
|
<td colspan=1 align=left nowrap>
|
||
|
|
</td>
|
||
|
|
<td colspan=1 align=left nowrap> <tt>SANE_Word byte_order</tt> </td></tr>
|
||
|
|
<tr valign=top>
|
||
|
|
<td colspan=1 align=left nowrap>
|
||
|
|
</td>
|
||
|
|
<td colspan=1 align=left nowrap> <tt>SANE_String resource</tt> </td></tr>
|
||
|
|
<tr valign=top>
|
||
|
|
<td colspan=1 align=left nowrap>
|
||
|
|
</td></tr>
|
||
|
|
</table>
|
||
|
|
</center>
|
||
|
|
The <tt>handle</tt> argument identifies the connection to the remote
|
||
|
|
device from which the image should be acquired.
|
||
|
|
|
||
|
|
<p>In the reply, argument <tt>resource</tt> is set to the name of the
|
||
|
|
resource that must be authorized before this call can be retried. If
|
||
|
|
this value is non-<tt>NULL</tt>, all other arguments have undefined
|
||
|
|
values (see Section <a href="doc017.html#s5.2.10">5.2.10</a> for details on how to
|
||
|
|
authorize a resource). Argument, <tt>status</tt> indicates the
|
||
|
|
completion status. If the value is anything other than
|
||
|
|
<tt>SANE_STATUS_SUCCESS</tt>, the remainder of the reply has
|
||
|
|
undefined values. The argument <tt>port</tt> returns the port number
|
||
|
|
from which the image data will be available. To read the image data,
|
||
|
|
a network client must connect to the remote host at the indicated port
|
||
|
|
number. Through this port, the image data is transmitted as a
|
||
|
|
sequence of data records. Each record starts with the data length in
|
||
|
|
bytes. The data length is transmitted as a sequence of four bytes.
|
||
|
|
These bytes should be interpreted as an unsigned integer in big-endian
|
||
|
|
format. The four length bytes are followed by the number of data
|
||
|
|
bytes indicated by the length. Except for byte-order, the data is in
|
||
|
|
the same format as defined for <tt>sane_read()</tt>. Since some
|
||
|
|
records may contain no data at all, a length value of zero is
|
||
|
|
perfectly valid. The special length value of <tt>0xffffffff</tt> is
|
||
|
|
used to indicate the end of the data stream. That is, after receiving
|
||
|
|
a record length of <tt>0xffffffff</tt>, the network client should close
|
||
|
|
the data connection and stop reading data.
|
||
|
|
|
||
|
|
<p>Argument <tt>byte_order</tt> specifies the byte-order of the image
|
||
|
|
data. A value of 0x1234 indicates little-endian format, a value of
|
||
|
|
0x4321 indicates big-endian format. All other values are presently
|
||
|
|
undefined and reserved for future enhancements of this protocol. The
|
||
|
|
intent is that a network server sends data in its own byte-order and
|
||
|
|
the client is responsible for adjusting the byte-order, if necessary.
|
||
|
|
This approach causes no unnecessary overheads in the case where the
|
||
|
|
server and client byte-order match and puts the extra burden on the
|
||
|
|
client side when there is a byte-order mismatch. Putting the burden
|
||
|
|
on the client-side improves the scalability properties of this
|
||
|
|
protocol.
|
||
|
|
|
||
|
|
<p><h3><a name="s5.2.9">5.2.9 <tt>SANE_NET_CANCEL<a name="i167"></tt></a></h3>
|
||
|
|
|
||
|
|
<p>This RPC is used to cancel the current operation of a remote SANE
|
||
|
|
device.
|
||
|
|
<center>
|
||
|
|
<table cellpadding=0 cellspacing=0>
|
||
|
|
<tr valign=top>
|
||
|
|
<td colspan=1 align=left nowrap>
|
||
|
|
<b>request:</b> </td>
|
||
|
|
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
|
||
|
|
<tr valign=top>
|
||
|
|
<td colspan=1 align=left nowrap>
|
||
|
|
<tt>SANE_Word handle</tt> </td>
|
||
|
|
<td colspan=1 align=left nowrap> <tt>SANE_Word dummy</tt> </td></tr>
|
||
|
|
<tr valign=top>
|
||
|
|
<td colspan=1 align=left nowrap>
|
||
|
|
</td></tr>
|
||
|
|
</table>
|
||
|
|
</center>
|
||
|
|
The <tt>handle</tt> argument identifies the connection whose operation
|
||
|
|
should be cancelled.
|
||
|
|
|
||
|
|
<p>In the reply, the <tt>dummy</tt> argument is unused. Its purpose is to
|
||
|
|
ensure proper synchronization (without it, a net client would not be
|
||
|
|
able to determine when the RPC has completed).
|
||
|
|
|
||
|
|
<p><h3><a name="s5.2.10">5.2.10 <tt>SANE_NET_AUTHORIZE<a name="i169"></tt></a></h3>
|
||
|
|
<a name="i171">
|
||
|
|
|
||
|
|
<p>This RPC is used to pass authorization data from the net client to the
|
||
|
|
net server.
|
||
|
|
<center>
|
||
|
|
<table cellpadding=0 cellspacing=0>
|
||
|
|
<tr valign=top>
|
||
|
|
<td colspan=1 align=left nowrap>
|
||
|
|
<b>request:</b> </td>
|
||
|
|
<td colspan=1 align=left nowrap> <b>reply:</b> </td></tr>
|
||
|
|
<tr valign=top>
|
||
|
|
<td colspan=1 align=left nowrap>
|
||
|
|
<tt>SANE_String resource</tt> </td>
|
||
|
|
<td colspan=1 align=left nowrap> <tt>SANE_Word dummy</tt> </td></tr>
|
||
|
|
<tr valign=top>
|
||
|
|
<td colspan=1 align=left nowrap>
|
||
|
|
<tt>SANE_String username</tt> </td>
|
||
|
|
<td colspan=1 align=left nowrap> </td></tr>
|
||
|
|
<tr valign=top>
|
||
|
|
<td colspan=1 align=left nowrap>
|
||
|
|
<tt>SANE_String password</tt> </td>
|
||
|
|
<td colspan=1 align=left nowrap> </td></tr>
|
||
|
|
<tr valign=top>
|
||
|
|
<td colspan=1 align=left nowrap>
|
||
|
|
</td></tr>
|
||
|
|
</table>
|
||
|
|
</center>
|
||
|
|
The <tt>resource</tt> argument specifies the name of the resource to be
|
||
|
|
authorized. This argument should be set to the string returned in the
|
||
|
|
<tt>resource</tt> argument of the RPC reply that required this
|
||
|
|
authorization call. The <tt>username</tt> and <tt>password</tt> are the
|
||
|
|
name of the user that is accessing the resource and the password for
|
||
|
|
the specified resource/user pair.
|
||
|
|
|
||
|
|
<p>Since the password is not encrypted during network transmission, it is
|
||
|
|
recommended to use the following extension:
|
||
|
|
|
||
|
|
<p>If the server adds the string `<tt>$MD5$</tt>' to the resource-name followed
|
||
|
|
by a random string not longer then 128 bytes, the client may answer with the
|
||
|
|
MD5 digest of the concatenation of the password and the random string. To
|
||
|
|
differentiate between the MD5 digest and a strange password the client prepends
|
||
|
|
the MD5 digest with the string `<tt>$MD5$</tt>'.
|
||
|
|
|
||
|
|
<p>In the reply, <tt>dummy</tt> is completely unused. Note that there is
|
||
|
|
no direct failure indication. This is unnecessary since a net client
|
||
|
|
will retry the RPC that resulted in the authorization request until
|
||
|
|
that call succeeds (or until the request is cancelled). The RPC that resulted
|
||
|
|
in the authorization request continues after the reply from the client and may
|
||
|
|
fail with <tt>SANE_STATUS_ACCESS_DENIED</tt>.
|
||
|
|
|
||
|
|
<p><h3><a name="s5.2.11">5.2.11 <tt>SANE_NET_EXIT<a name="i172"></tt></a></h3>
|
||
|
|
|
||
|
|
<p>This RPC is used to disconnect a net client from a net server. There
|
||
|
|
are no request or reply arguments in this call. As a result of this
|
||
|
|
call, the connection between the client and the server that was
|
||
|
|
established by the <tt>SANE_NET_INIT</tt> call will be closed.
|
||
|
|
|
||
|
|
<p>
|
||
|
|
|
||
|
|
<p><p><hr>
|
||
|
|
<a href="doc018.html"><img src=../icons/next.gif alt="Next"></a>
|
||
|
|
<a href="doc000.html"><img src=../icons/up.gif alt="Up"></a>
|
||
|
|
<a href="doc016.html"><img src=../icons/previous.gif alt="Previous"></a>
|
||
|
|
<a href="doc000.html"><img src=../icons/contents.gif alt="Contents"></a>
|
||
|
|
<a href="doc019.html"><img src=../icons/index.gif alt="Index"></a>
|
||
|
|
<hr>
|
||
|
|
</body></html>
|