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+<div class='body'>
<!--
- "$Id: api-filter.shtml 6649 2007-07-11 21:46:42Z mike $"
+ "$Id: api-cups.header 7279 2008-01-31 01:50:44Z mike $"
- Filter and backend API introduction for the Common UNIX Printing System (CUPS).
+ Filter and backend programming header for the Common UNIX Printing System
+ (CUPS).
- Copyright 2007 by Apple Inc.
- Copyright 1997-2006 by Easy Software Products, all rights reserved.
+ Copyright 2008 by Apple Inc.
These coded instructions, statements, and computer programs are the
property of Apple Inc. and are protected by Federal copyright
file is missing or damaged, see the license at "http://www.cups.org/".
-->
-<h2 class='title'>Introduction</h2>
+<h1 class="title">Filter and Backend Programming</h1>
-<p>The CUPS filter and backend APIs define standard exit codes
-and provide access to the backchannel data stream. They are only
-used when writing backends, filters, and port monitors.</p>
+<div class='summary'><table summary='General Information'>
+<thead>
+<tr>
+ <th>Header</th>
+ <th>cups/backend.h<br>
+ cups/sidechannel.h</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+ <th>Library</th>
+ <td>-lcups</td>
+</tr>
+<tr>
+ <th>See Also</th>
+ <td>Programming: <a href='api-overview.html' target='_top'>Introduction to CUPS Programming</a><br>
+ Programming: <a href='api-cups.html' target='_top'>CUPS API</a><br>
+ Programming: <a href='api-ppd.html' target='_top'>PPD API</a><br>
+ Programming: <a href='api-raster.html' target='_top'>Raster API</a></td>
+</tr>
+</tbody>
+</table></div>
+<h2 class="title">Contents</h2>
+<ul class="contents">
+</li>
+<li><a href="#OVERVIEW">Overview</a><ul class="subcontents">
+<li><a href="#EXITCODES">Exit Codes</a></li>
+<li><a href="#ENVIRONMENT">Environment Variables</a></li>
+<li><a href="#MESSAGES">Communicating with the Scheduler</a></li>
+<li><a href="#COMMUNICATING">Communicating with the Backend</a></li>
+</ul></li>
+<li><a href="#FUNCTIONS">Functions</a><ul class="code">
+<li><a href="#cupsBackChannelRead" title="Read data from the backchannel.">cupsBackChannelRead</a></li>
+<li><a href="#cupsBackChannelWrite" title="Write data to the backchannel.">cupsBackChannelWrite</a></li>
+<li><a href="#cupsSideChannelDoRequest" title="Send a side-channel command to a backend and wait for a response.">cupsSideChannelDoRequest</a></li>
+<li><a href="#cupsSideChannelRead" title="Read a side-channel message.">cupsSideChannelRead</a></li>
+<li><a href="#cupsSideChannelWrite" title="Write a side-channel message.">cupsSideChannelWrite</a></li>
+</ul>
+<li><a href="#TYPES">Data Types</a><ul class="code">
+ <li><a href="#cups_backend_t" title="Backend exit codes">cups_backend_t</a></li>
+ <li><a href="#cups_sc_bidi_t" title="Bidirectional capabilities">cups_sc_bidi_t</a></li>
+ <li><a href="#cups_sc_command_t" title="Request command codes">cups_sc_command_t</a></li>
+ <li><a href="#cups_sc_state_t" title="Printer state bits">cups_sc_state_t</a></li>
+ <li><a href="#cups_sc_status_t" title="Response status codes">cups_sc_status_t</a></li>
+</ul></li>
+<li><a href="#ENUMERATIONS">Constants</a><ul class="code">
+ <li><a href="#cups_backend_e" title="Backend exit codes">cups_backend_e</a></li>
+ <li><a href="#cups_sc_bidi_e" title="Bidirectional capabilities">cups_sc_bidi_e</a></li>
+ <li><a href="#cups_sc_command_e" title="Request command codes">cups_sc_command_e</a></li>
+ <li><a href="#cups_sc_state_e" title="Printer state bits">cups_sc_state_e</a></li>
+ <li><a href="#cups_sc_status_e" title="Response status codes">cups_sc_status_e</a></li>
+</ul></li>
+</ul>
+<!--
+ "$Id: api-filter.shtml 6649 2007-07-11 21:46:42Z mike $"
-<h2 class='title'>General Usage</h2>
+ Filter and backend programming introduction for the Common UNIX Printing
+ System (CUPS).
-<p>The <var><cups/backend.h></var> and
-<var><cups/cups.h></var> header files must be included to
-use the <tt>CUPS_BACKEND_</tt> constants and
-<tt>cupsBackChannel</tt> functions, respectively.</p>
+ Copyright 2007-2008 by Apple Inc.
+ Copyright 1997-2006 by Easy Software Products, all rights reserved.
-<p>The <var><cups/sidechannel.h></var> header file must be
-included to use the <tt>CUPS_SC_</tt> constants and <tt>cupsSideChannel</tt> functions.</p>
+ These coded instructions, statements, and computer programs are the
+ property of Apple Inc. and are protected by Federal copyright
+ law. Distribution and use rights are outlined in the file "LICENSE.txt"
+ which should have been included with this file. If this file is
+ file is missing or damaged, see the license at "http://www.cups.org/".
+-->
-<p>Programs using these functions must be linked to the CUPS
-library: <var>libcups.a</var>, <var>libcups.so.2</var>,
-<var>libcups.2.dylib</var>, <var>libcups_s.a</var>, or
-<var>libcups2.lib</var> depending on the platform. The following
-command compiles <var>myprogram.c</var> using GCC and the CUPS
-library:</p>
+<h2 class='title'><a name="OVERVIEW">Overview</a></h2>
-<pre class='command'>
-<kbd>gcc -o myprogram myprogram.c -lcups</kbd>
-</pre>
+<p>Filters, printer drivers, port monitors, and backends use a common interface
+for processing print jobs and communicating status information to the scheduler.
+Each filter is run with a standard set of command-line arguments:<p>
+<dl class="code">
-<h2 class='title'>Compatibility</h2>
+ <dt>argv[1]</dt>
+ <dd>The job ID</dd>
-<p>The <tt>cupsBackChannel</tt> functions require CUPS 1.2 or higher. The <tt>cupsSideChannel</tt> functions require CUPS 1.3 or higher.</p>
+ <dt>argv[2]</dt>
+ <dd>The user printing the job</dd>
+ <dt>argv[3]</dt>
+ <dd>The job name/title</dd>
-<h2 class='title'>Using the cupsBackChannel APIs</h2>
+ <dt>argv[4]</dt>
+ <dd>The number of copies to print</dd>
-<p>The <tt>cupsBackChannel</tt> APIs allow your filters, drivers, and port monitors to read data back from a printer and your backends to send data from a printer to the filters, drivers, and port monitors associated with the current job. Back-channel data is normally sent by the printer in response to a command sent from your program to the printer via <tt>stdout</tt>.</p>
+ <dt>argv[5]</dt>
+ <dd>The options that were provided when the job was submitted</dd>
-<p>The <tt>cupsBackChannelRead()</tt> function reads data from the printer via the backend. You provide a timeout in seconds along with a buffer pointer and the size of that buffer. It returns the number of bytes or -1 if there was an error. The following code example shows how to poll for back-channel data in your program:</p>
+ <dt>argv[6]</dt>
+ <dd>The file to print (first filter only)</dd>
+</dl>
-<pre class='command'>
-#include <cups/cups.h>
+<p>The scheduler runs one or more of these programs to print any given job. The
+first filter reads from the print file and writes to the standard output, while
+the remaining filters read from the standard input and write to the standard
+output. The backend is the last filter in the chain and writes to the
+device.</p>
-char buffer[8192];
-ssize_t bytes;
+<h3><a name="EXITCODES">Exit Codes</a></h3>
-/* Use a timeout of 0.0 seconds to poll for back-channel data */
-bytes = cupsBackChannelRead(buffer, sizeof(buffer), 0.0);
-</pre>
+<p>Filters must exit with status 0 when they successfully generate print data
+or 1 when they encounter an error. Backends can return any of the
+<a href="#cups_backend_t"><code>cups_backend_t</code></a> constants.</p>
-<p>If you are writing a backend, the <tt>cupsBackChannelWrite()</tt> function sends any back-channel data you have received from the printer to upstream filters in the print filter chain. We recommend using a timeout of 1.0 seconds:</p>
+<h3><a name="ENVIRONMENT">Environment Variables</a></h3>
-<pre class='command'>
-#include <cups/cups.h>
+<p>The following environment variables are defined by the printing system:</p>
-char buffer[8192];
-ssize_t bytes;
+<dl class="code">
-/* Use a timeout of 1.0 seconds to give filters a chance to read */
-cupsBackChannelWrite(buffer, bytes, 1.0);
-</pre>
+ <dt>APPLE_LANGUAGES</dt>
+ <dd>The Apple language identifier associated with the job
+ (Mac OS X only).</dd>
+ <dt>CHARSET</dt>
+ <dd>The job character set, typically "utf-8".</dd>
-<h2 class='title'>Using the cupsSideChannel APIs</h2>
+ <dt>CLASS</dt>
+ <dd>When a job is submitted to a printer class, contains the name of
+ the destination printer class. Otherwise this environment
+ variable will not be set.</dd>
-<p>The <tt>cupsSideChannel</tt> APIs allow your filters, drivers, port monitors, and backend to send and receive the following out-of-band commands:</p>
+ <dt>CONTENT_TYPE</dt>
+ <dd>The MIME type associated with the file (e.g.
+ application/postscript).</dd>
-<ul>
+ <dt>CUPS_CACHEDIR</dt>
+ <dd>The directory where cache files can be stored.</dd>
- <li><tt>CUPS_SC_CMD_SOFT_RESET</tt> - Do a soft reset</li>
- <li><tt>CUPS_SC_CMD_DRAIN_OUTPUT</tt> - Drain all pending output</li>
- <li><tt>CUPS_SC_CMD_GET_BIDI</tt> - Return bidirectional capabilities</li>
- <li><tt>CUPS_SC_CMD_GET_DEVICE_ID</tt> - Return the IEEE-1284 device ID</li>
- <li><tt>CUPS_SC_CMD_GET_STATE</tt> - Return the device state</li>
+ <dt>CUPS_DATADIR</dt>
+ <dd>The directory where data files can be found.</dd>
-</ul>
+ <dt>CUPS_SERVERROOT</dt>
+ <dd>The root directory of the server.</dd>
+ <dt>DEVICE_URI</dt>
+ <dd>The device-uri associated with the printer.</dd>
-<h3>Sending Commands from a Filter, Driver, or Port Monitor</h3>
+ <dt>FINAL_CONTENT_TYPE</dt>
+ <dd>The MIME type associated with the printer (e.g.
+ application/vnd.cups-postscript).</dd>
-<p>The <tt>cupsSideChannelDoRequest()</tt> function is used by filters, drivers, and port monitors to send a command to the backend and read back a response:</p>
+ <dt>LANG</dt>
+ <dd>The language locale associated with the job.</dd>
-<pre class='command'>
-cups_sc_status_t cupsSideChannelDoRequest(cups_sc_command_t command,
- char *data, int *datalen,
- double timeout);
-</pre>
+ <dt>PPD</dt>
+ <dd>The full pathname of the PostScript Printer Description (PPD)
+ file for this printer.</dd>
-<p>The <tt>CUPS_SC_CMD_SOFT_RESET</tt> and <tt>CUPS_SC_CMD_DRAIN_OUTPUT</tt> commands do not return any data values, while the others return one or more bytes. The <tt>timeout</tt> parameter allows your program to poll or wait for the command to complete - use a timeout of 30 seconds for <tt>CUPS_SC_CMD_SOFT_RESET</tt> and <tt>CUPS_SC_CMD_DRAIN_OUTPUT</tt> and a timeout of 1 second for all other commands.</p>
+ <dt>PRINTER</dt>
+ <dd>The name of the printer.</dd>
-<p><tt>CUPS_SC_CMD_GET_BIDI</tt> returns a single <tt>char</tt> value that tells you whether the backend supports bidirectional communications:</p>
+ <dt>RIP_CACHE</dt>
+ <dd>The recommended amount of memory to use for Raster Image
+ Processors (RIPs).</dd>
-<pre class='command'>
-#include <cups/sidechannel.h>
+</dl>
-char data;
-int datalen;
-cups_sc_bidi_t bidi;
-cups_sc_status_t status;
+<h3><a name="MESSAGES">Communicating with the Scheduler</a></h3>
-/* Tell cupsSideChannelDoRequest() how big our buffer is... */
-datalen = 1;
+<p>Filters and backends communicate wih the scheduler by writing messages
+to the standard error file. For example, the following code sets the current
+printer state message to "Printing page 5":</p>
-/* Get the bidirectional capabilities, waiting for up to 1 second */
-status = cupsSideChannelDoRequest(CUPS_SC_CMD_GET_BIDI, &data, &datalen, 1.0);
+<pre class="example">
+int page = 5;
-/* Use the returned value if OK was returned and the length is still 1 */
-if (status == CUPS_SC_STATUS_OK && datalen == 1)
- bidi = (cups_sc_bidi_t)data;
-else
- bidi = CUPS_SC_BIDI_NOT_SUPPORTED;
+fprintf(stderr, "INFO: Printing page %d\n", page);
</pre>
-<p><tt>CUPS_SC_CMD_GET_DEVICE_ID</tt> returns a string of characters containing the IEEE-1284 device ID for the connected printer:</p>
+<p>Each message is a single line of text starting with one of the following
+prefix strings:</p>
+
+<dl class="code">
+
+ <dt>ALERT: message</dt>
+ <dd>Sets the printer-state-message attribute and adds the specified
+ message to the current error log file using the "alert" log level.</dd>
+
+ <dt>ATTR: attribute=value [attribute=value]</dt>
+ <dd>Sets the named printer or job attribute(s). Typically this is used
+ to set the <code>marker-colors</code>, <code>marker-levels</code>,
+ <code>marker-names</code>, <code>marker-types</code>,
+ <code>printer-alert</code>, and <code>printer-alert-description</code>
+ printer attributes.</dd>
+
+ <dt>CRIT: message</dt>
+ <dd>Sets the printer-state-message attribute and adds the specified
+ message to the current error log file using the "critical" log
+ level.</dd>
+
+ <dt>DEBUG: message</dt>
+ <dd>Sets the printer-state-message attribute and adds the specified
+ message to the current error log file using the "debug" log level.</dd>
+
+ <dt>DEBUG2: message</dt>
+ <dd>Sets the printer-state-message attribute and adds the specified
+ message to the current error log file using the "debug2" log level.</dd>
+
+ <dt>EMERG: message</dt>
+ <dd>Sets the printer-state-message attribute and adds the specified
+ message to the current error log file using the "emergency" log
+ level.</dd>
+
+ <dt>ERROR: message</dt>
+ <dd>Sets the printer-state-message attribute and adds the specified
+ message to the current error log file using the "error" log level.</dd>
+
+ <dt>INFO: message</dt>
+ <dd>Sets the printer-state-message attribute. If the current log level
+ is set to "debug2", also adds the specified message to the current error
+ log file using the "info" log level.</dd>
+
+ <dt>NOTICE: message</dt>
+ <dd>Sets the printer-state-message attribute and adds the specified
+ message to the current error log file using the "notice" log level.</dd>
+
+ <dt>PAGE: page-number #-copies</dt>
+ <dt>PAGE: total #-pages</dt>
+ <dd>Adds an entry to the current page log file. The first form adds
+ #-copies to the job-media-sheets-completed attribute. The second
+ form sets the job-media-sheets-completed attribute to #-pages.</dd>
+
+ <dt>STATE: printer-state-reason [printer-state-reason ...]</dt>
+ <dt>STATE: + printer-state-reason [printer-state-reason ...]</dt>
+ <dt>STATE: - printer-state-reason [printer-state-reason ...]</dt>
+ <dd>Sets, adds, or removes printer-state-reason keywords to the
+ current queue. Typically this is used to indicate media, ink, and
+ toner conditions on a printer.</dd>
+
+ <dt>WARNING: message</dt>
+ <dd>Sets the printer-state-message attribute and adds the specified
+ message to the current error log file using the "warning" log
+ level.</dd>
+
+</dl>
+
+<p>Messages without one of these prefixes are treated as if they began with
+the "DEBUG:" prefix string.</p>
+
+<h3><a name="COMMUNICATING">Communicating with the Backend</a></h3>
+
+<p>Filters can communicate with the backend via the
+<a href="#cupsBackChannelRead"><code>cupsBackChannelRead</code></a> and
+<a href="#cupsSideChannelDoRequest"><code>cupsSideChannelDoRequest</code></a>
+functions. The
+<a href="#cupsBackChannelRead"><code>cupsBackChannelRead</code></a> function
+reads data that has been sent back from the device and is typically used to
+obtain status and configuration information. For example, the following code
+polls the backend for back-channel data:</p>
+
+<pre class="example">
+#include <cups/cups.h>
+
+char buffer[8192];
+ssize_t bytes;
+
+/* Use a timeout of 0.0 seconds to poll for back-channel data */
+bytes = cupsBackChannelRead(buffer, sizeof(buffer), 0.0);
+</pre>
-<pre class='command'>
+The
+<a href="#cupsSideChannelDoRequest"><code>cupsSideChannelDoRequest</code></a>
+function allows you to get out-of-band status information and do synchronization
+with the device. For example, the following code gets the current IEEE-1284
+device ID string from the backend:</p>
+
+<pre class="example">
#include <cups/sidechannel.h>
char data[2049];
int datalen;
-cups_sc_status_t status;
+<a href="#cups_sc_status_t">cups_sc_status_t</a> status;
/* Tell cupsSideChannelDoRequest() how big our buffer is, less 1 byte for nul-termination... */
datalen = sizeof(data) - 1;
/* Get the IEEE-1284 device ID, waiting for up to 1 second */
-status = cupsSideChannelDoRequest(CUPS_SC_CMD_GET_DEVICE_ID, data, &datalen, 1.0);
+status = <a href="#cupsSideChannelDoRequest">cupsSideChannelDoRequest</a>(CUPS_SC_CMD_GET_DEVICE_ID, data, &datalen, 1.0);
/* Use the returned value if OK was returned and the length is non-zero */
if (status == CUPS_SC_STATUS_OK && datalen > 0)
data[0] = '\0';
</pre>
-<p><tt>CUPS_SC_CMD_GET_STATE</tt> returns a single <tt>char</tt> value that tells you the current device state:</p>
-
-<pre class='command'>
-#include <cups/sidechannel.h>
-
-char data;
-int datalen;
-cups_sc_state_t state;
-cups_sc_status_t status;
-
-/* Tell cupsSideChannelDoRequest() how big our buffer is... */
-datalen = 1;
-
-/* Get the bidirectional capabilities, waiting for up to 1 second */
-status = cupsSideChannelDoRequest(CUPS_SC_CMD_GET_STATE, &data, &datalen, 1.0);
-
-/* Use the returned value if OK was returned and the length is still 1 */
-if (status == CUPS_SC_STATUS_OK && datalen == 1)
- state = (cups_sc_state_t)data;
-else
- state = CUPS_SC_STATE_OFFLINE;
-</pre>
-
+<p>Backends communicate with filters using the reciprocal functions
+<a href="#cupsBackChannelWrite"><code>cupsBackChannelWrite</code></a>,
+<a href="#cupsSideChannelRead"><code>cupsSideChannelRead</code></a>, and
+<a href="#cupsSideChannelWrite"><code>cupsSideChannelWrite</code></a>. We
+recommend writing back-channel data using a timeout of 1.0 seconds:</p>
-<h3>Handling Commands in your Backend</h3>
+<pre class="example">
+#include <cups/cups.h>
-<p>The <tt>cupsSideChannelRead()</tt> function is used by backends to read a command from a filter, driver, or port monitor:</p>
+char buffer[8192];
+ssize_t bytes;
-<pre class='command'>
-int cupsSideChannelRead(cups_sc_command_t &command,
- cups_sc_status_t &status,
- char *data, int *datalen, double timeout);
+/* Use a timeout of 1.0 seconds to give filters a chance to read */
+cupsBackChannelWrite(buffer, bytes, 1.0);
</pre>
-<p>Backends can either poll for commands using a <tt>timeout</tt> of 0.0, wait indefinitely for commands using a <tt>timeout</tt> of -1.0 (probably in a separate thread for that purpose), or use <tt>select()</tt> or <tt>poll()</tt> on the <tt>CUPS_SC_FD</tt> file descriptor (4) to handle input and output on several file descriptors at the same time. Backends can pass <tt>NULL</tt> for the <tt>data</tt> and <tt>datalen</tt> parameters, since none of the commands sent by upstream filters contain any data at this time.</p>
-
-<p>Once a command is processed, the backend uses the <tt>cupsSideChannelWrite()</tt> function to send its response:</p>
-
-<pre class='command'>
+<p>The <a href="#cupsSideChannelRead"><code>cupsSideChannelRead</code></a>
+function reads a side-channel command from a filter, driver, or port monitor.
+Backends can either poll for commands using a <code>timeout</code> of 0.0, wait
+indefinitely for commands using a <code>timeout</code> of -1.0 (probably in a
+separate thread for that purpose), or use <code>select</code> or
+<code>poll</code> on the <code>CUPS_SC_FD</code> file descriptor (4) to handle
+input and output on several file descriptors at the same time. Backends can pass
+<code>NULL</code> for the <code>data</code> and <code>datalen</code> parameters
+since none of the commands sent by upstream filters contain any data at this
+time.</p>
+
+<p>Once a command is processed, the backend uses the
+<a href="#cupsSideChannelWrite"><code>cupsSideChannelWrite</code></a> function
+to send its response. For example, the following code shows how to poll for a
+side-channel command and respond to it:</p>
+
+<pre class="example">
#include <cups/sidechannel.h>
-cups_sc_command_t command;
-cups_sc_status_t status;
+<a href="#cups_sc_command_t">cups_sc_command_t</a> command;
+<a href="#cups_sc_status_t">cups_sc_status_t</a> status;
/* Poll for a command... */
-if (!cupsSideChannelRead(&command, &status, NULL, NULL, 0.0))
+if (!<a href="#cupsSideChannelRead">cupsSideChannelRead</a>(&command, &status, NULL, NULL, 0.0))
{
char data[2048];
int datalen;
switch (command)
{
- ... handle supported commands, file data/datalen/status with values as needed ...
+ /* handle supported commands, file data/datalen/status with values as needed */
default :
status = CUPS_SC_STATUS_NOT_IMPLEMENTED;
}
/* Send a response... */
- cupsSideChannelWrite(command, status, data, datalen, 1.0);
+ <a href="#cupsSideChannelWrite">cupsSideChannelWrite</a>(command, status, data, datalen, 1.0);
}
</pre>
-<h2 class='title'>Contents</h2>
-<ul>
- <li><a href='#FUNCTIONS'>Functions</a></li>
-</ul>
-<!-- NEW PAGE -->
-<h2 class='title'><a name='FUNCTIONS'>Functions</a></h2>
-<ul>
- <li><a href='#cupsBackChannelRead'><tt>cupsBackChannelRead()</tt></a> <span class='info'> CUPS 1.2 </span></li>
- <li><a href='#cupsBackChannelWrite'><tt>cupsBackChannelWrite()</tt></a> <span class='info'> CUPS 1.2 </span></li>
- <li><a href='#cupsSideChannelDoRequest'><tt>cupsSideChannelDoRequest()</tt></a> <span class='info'> CUPS 1.3 </span></li>
- <li><a href='#cupsSideChannelRead'><tt>cupsSideChannelRead()</tt></a> <span class='info'> CUPS 1.3 </span></li>
- <li><a href='#cupsSideChannelWrite'><tt>cupsSideChannelWrite()</tt></a> <span class='info'> CUPS 1.3 </span></li>
-</ul>
-<!-- NEW PAGE -->
-<h3 class='title'><span class='info'> CUPS 1.2 </span><a name='cupsBackChannelRead'>cupsBackChannelRead()</a></h3>
-<h4>Description</h4>
-<p>Read data from the backchannel.
-<p>Reads up to "bytes" bytes from the backchannel. The "timeout"
+<h2 class="title"><a name="FUNCTIONS">Functions</a></h2>
+<h3 class="function"><span class="info"> CUPS 1.2 </span><a name="cupsBackChannelRead">cupsBackChannelRead</a></h3>
+<p class="description">Read data from the backchannel.</p>
+<p class="code">
+ssize_t cupsBackChannelRead (<br>
+ char *buffer,<br>
+ size_t bytes,<br>
+ double timeout<br>
+);</p>
+<h4 class="parameters">Parameters</h4>
+<dl>
+<dt>buffer</dt>
+<dd class="description">Buffer to read</dd>
+<dt>bytes</dt>
+<dd class="description">Bytes to read</dd>
+<dt>timeout</dt>
+<dd class="description">Timeout in seconds</dd>
+</dl>
+<h4 class="returnvalue">Return Value</h4>
+<p class="description">Bytes read or -1 on error</p>
+<h4 class="discussion">Discussion</h4>
+<p class="discussion">Reads up to "bytes" bytes from the backchannel. The "timeout"
parameter controls how many seconds to wait for the data - use
0.0 to return immediately if there is no data, -1.0 to wait
for data indefinitely.
-
-<h4>Syntax</h4>
-<p><tt>
-ssize_t<br>
-cupsBackChannelRead(
- char * buffer,
- size_t bytes,
- double timeout);
-</tt></p>
-<h4>Arguments</h4>
-<div class='table'><table align='center' border='1' width='80%' cellpadding='5' cellspacing='0' summary='Arguments'>
-<thead><tr><th>Name</th><th>Description</th></tr></thead>
-<tbody>
-<tr><td><tt>buffer</tt></td><td>Buffer to read</td></tr>
-<tr><td><tt>bytes</tt></td><td>Bytes to read</td></tr>
-<tr><td><tt>timeout</tt></td><td>Timeout in seconds</td></tr>
-</tbody></table></div>
-<h4>Returns</h4>
-<p>Bytes read or -1 on error</p>
-<!-- NEW PAGE -->
-<h3 class='title'><span class='info'> CUPS 1.2 </span><a name='cupsBackChannelWrite'>cupsBackChannelWrite()</a></h3>
-<h4>Description</h4>
-<p>Write data to the backchannel.
-<p>Writes "bytes" bytes to the backchannel. The "timeout" parameter
+</p>
+<h3 class="function"><span class="info"> CUPS 1.2 </span><a name="cupsBackChannelWrite">cupsBackChannelWrite</a></h3>
+<p class="description">Write data to the backchannel.</p>
+<p class="code">
+ssize_t cupsBackChannelWrite (<br>
+ const char *buffer,<br>
+ size_t bytes,<br>
+ double timeout<br>
+);</p>
+<h4 class="parameters">Parameters</h4>
+<dl>
+<dt>buffer</dt>
+<dd class="description">Buffer to write</dd>
+<dt>bytes</dt>
+<dd class="description">Bytes to write</dd>
+<dt>timeout</dt>
+<dd class="description">Timeout in seconds</dd>
+</dl>
+<h4 class="returnvalue">Return Value</h4>
+<p class="description">Bytes written or -1 on error</p>
+<h4 class="discussion">Discussion</h4>
+<p class="discussion">Writes "bytes" bytes to the backchannel. The "timeout" parameter
controls how many seconds to wait for the data to be written - use
0.0 to return immediately if the data cannot be written, -1.0 to wait
indefinitely.
-
-<h4>Syntax</h4>
-<p><tt>
-ssize_t<br>
-cupsBackChannelWrite(
- const char * buffer,
- size_t bytes,
- double timeout);
-</tt></p>
-<h4>Arguments</h4>
-<div class='table'><table align='center' border='1' width='80%' cellpadding='5' cellspacing='0' summary='Arguments'>
-<thead><tr><th>Name</th><th>Description</th></tr></thead>
-<tbody>
-<tr><td><tt>buffer</tt></td><td>Buffer to write</td></tr>
-<tr><td><tt>bytes</tt></td><td>Bytes to write</td></tr>
-<tr><td><tt>timeout</tt></td><td>Timeout in seconds</td></tr>
-</tbody></table></div>
-<h4>Returns</h4>
-<p>Bytes written or -1 on error</p>
-<!-- NEW PAGE -->
-<h3 class='title'><span class='info'> CUPS 1.3 </span><a name='cupsSideChannelDoRequest'>cupsSideChannelDoRequest()</a></h3>
-<h4>Description</h4>
-<p>Send a side-channel command to a backend and wait for a response.
-<p>This function is normally only called by filters, drivers, or port
+</p>
+<h3 class="function"><span class="info"> CUPS 1.3 </span><a name="cupsSideChannelDoRequest">cupsSideChannelDoRequest</a></h3>
+<p class="description">Send a side-channel command to a backend and wait for a response.</p>
+<p class="code">
+<a href="#cups_sc_status_t">cups_sc_status_t</a> cupsSideChannelDoRequest (<br>
+ <a href="#cups_sc_command_t">cups_sc_command_t</a> command,<br>
+ char *data,<br>
+ int *datalen,<br>
+ double timeout<br>
+);</p>
+<h4 class="parameters">Parameters</h4>
+<dl>
+<dt>command</dt>
+<dd class="description">Command to send</dd>
+<dt>data</dt>
+<dd class="description">Response data buffer pointer</dd>
+<dt>datalen</dt>
+<dd class="description">Size of data buffer on entry, number of bytes in buffer on return</dd>
+<dt>timeout</dt>
+<dd class="description">Timeout in seconds</dd>
+</dl>
+<h4 class="returnvalue">Return Value</h4>
+<p class="description">Status of command</p>
+<h4 class="discussion">Discussion</h4>
+<p class="discussion">This function is normally only called by filters, drivers, or port
monitors in order to communicate with the backend used by the current
printer. Programs must be prepared to handle timeout or "not
implemented" status codes, which indicate that the backend or device
-do not support the specified side-channel command.
-<p>The "datalen" parameter must be initialized to the size of the buffer
+do not support the specified side-channel command.<br>
+<br>
+The "datalen" parameter must be initialized to the size of the buffer
pointed to by the "data" parameter. cupsSideChannelDoRequest() will
update the value to contain the number of data bytes in the buffer.
-
-<h4>Syntax</h4>
-<p><tt>
-<a href='#cups_sc_status_t'>cups_sc_status_t</a><br>
-cupsSideChannelDoRequest(
- cups_sc_command_t command,
- char * data,
- int * datalen,
- double timeout);
-</tt></p>
-<h4>Arguments</h4>
-<div class='table'><table align='center' border='1' width='80%' cellpadding='5' cellspacing='0' summary='Arguments'>
-<thead><tr><th>Name</th><th>Description</th></tr></thead>
-<tbody>
-<tr><td><tt>command</tt></td><td>Command to send</td></tr>
-<tr><td><tt>data</tt></td><td>Response data buffer pointer</td></tr>
-<tr><td><tt>datalen</tt></td><td>Size of data buffer on entry, number of bytes in buffer on return</td></tr>
-<tr><td><tt>timeout</tt></td><td>Timeout in seconds</td></tr>
-</tbody></table></div>
-<h4>Returns</h4>
-<p>Status of command</p>
-<!-- NEW PAGE -->
-<h3 class='title'><span class='info'> CUPS 1.3 </span><a name='cupsSideChannelRead'>cupsSideChannelRead()</a></h3>
-<h4>Description</h4>
-<p>Read a side-channel message.
-<p>This function is normally only called by backend programs to read
+</p>
+<h3 class="function"><span class="info"> CUPS 1.3 </span><a name="cupsSideChannelRead">cupsSideChannelRead</a></h3>
+<p class="description">Read a side-channel message.</p>
+<p class="code">
+int cupsSideChannelRead (<br>
+ <a href="#cups_sc_command_t">cups_sc_command_t</a> *command,<br>
+ <a href="#cups_sc_status_t">cups_sc_status_t</a> *status,<br>
+ char *data,<br>
+ int *datalen,<br>
+ double timeout<br>
+);</p>
+<h4 class="parameters">Parameters</h4>
+<dl>
+<dt>command</dt>
+<dd class="description">Command code</dd>
+<dt>status</dt>
+<dd class="description">Status code</dd>
+<dt>data</dt>
+<dd class="description">Data buffer pointer</dd>
+<dt>datalen</dt>
+<dd class="description">Size of data buffer on entry, number of bytes in buffer on return</dd>
+<dt>timeout</dt>
+<dd class="description">Timeout in seconds</dd>
+</dl>
+<h4 class="returnvalue">Return Value</h4>
+<p class="description">0 on success, -1 on error</p>
+<h4 class="discussion">Discussion</h4>
+<p class="discussion">This function is normally only called by backend programs to read
commands from a filter, driver, or port monitor program. The
caller must be prepared to handle incomplete or invalid messages
-and return the corresponding status codes.
-<p>The "datalen" parameter must be initialized to the size of the buffer
+and return the corresponding status codes.<br>
+<br>
+The "datalen" parameter must be initialized to the size of the buffer
pointed to by the "data" parameter. cupsSideChannelDoRequest() will
update the value to contain the number of data bytes in the buffer.
-
-<h4>Syntax</h4>
-<p><tt>
-int<br>
-cupsSideChannelRead(
- cups_sc_command_t * command,
- <a href='#cups_sc_status_t'>cups_sc_status_t</a> * status,
- char * data,
- int * datalen,
- double timeout);
-</tt></p>
-<h4>Arguments</h4>
-<div class='table'><table align='center' border='1' width='80%' cellpadding='5' cellspacing='0' summary='Arguments'>
-<thead><tr><th>Name</th><th>Description</th></tr></thead>
-<tbody>
-<tr><td><tt>command</tt></td><td>Command code</td></tr>
-<tr><td><tt>status</tt></td><td>Status code</td></tr>
-<tr><td><tt>data</tt></td><td>Data buffer pointer</td></tr>
-<tr><td><tt>datalen</tt></td><td>Size of data buffer on entry, number of bytes in buffer on return</td></tr>
-<tr><td><tt>timeout</tt></td><td>Timeout in seconds</td></tr>
-</tbody></table></div>
-<h4>Returns</h4>
-<p>0 on success, -1 on error</p>
-<!-- NEW PAGE -->
-<h3 class='title'><span class='info'> CUPS 1.3 </span><a name='cupsSideChannelWrite'>cupsSideChannelWrite()</a></h3>
-<h4>Description</h4>
-<p>Write a side-channel message.
-<p>This function is normally only called by backend programs to send
+</p>
+<h3 class="function"><span class="info"> CUPS 1.3 </span><a name="cupsSideChannelWrite">cupsSideChannelWrite</a></h3>
+<p class="description">Write a side-channel message.</p>
+<p class="code">
+int cupsSideChannelWrite (<br>
+ <a href="#cups_sc_command_t">cups_sc_command_t</a> command,<br>
+ <a href="#cups_sc_status_t">cups_sc_status_t</a> status,<br>
+ const char *data,<br>
+ int datalen,<br>
+ double timeout<br>
+);</p>
+<h4 class="parameters">Parameters</h4>
+<dl>
+<dt>command</dt>
+<dd class="description">Command code</dd>
+<dt>status</dt>
+<dd class="description">Status code</dd>
+<dt>data</dt>
+<dd class="description">Data buffer pointer</dd>
+<dt>datalen</dt>
+<dd class="description">Number of bytes of data</dd>
+<dt>timeout</dt>
+<dd class="description">Timeout in seconds</dd>
+</dl>
+<h4 class="returnvalue">Return Value</h4>
+<p class="description">0 on success, -1 on error</p>
+<h4 class="discussion">Discussion</h4>
+<p class="discussion">This function is normally only called by backend programs to send
responses to a filter, driver, or port monitor program.
-
-<h4>Syntax</h4>
-<p><tt>
-int<br>
-cupsSideChannelWrite(
- cups_sc_command_t command,
- <a href='#cups_sc_status_t'>cups_sc_status_t</a> status,
- const char * data,
- int datalen,
- double timeout);
-</tt></p>
-<h4>Arguments</h4>
-<div class='table'><table align='center' border='1' width='80%' cellpadding='5' cellspacing='0' summary='Arguments'>
-<thead><tr><th>Name</th><th>Description</th></tr></thead>
-<tbody>
-<tr><td><tt>command</tt></td><td>Command code</td></tr>
-<tr><td><tt>status</tt></td><td>Status code</td></tr>
-<tr><td><tt>data</tt></td><td>Data buffer pointer</td></tr>
-<tr><td><tt>datalen</tt></td><td>Number of bytes of data</td></tr>
-<tr><td><tt>timeout</tt></td><td>Timeout in seconds</td></tr>
-</tbody></table></div>
-<h4>Returns</h4>
-<p>0 on success, -1 on error</p>
+</p>
+<h2 class="title"><a name="TYPES">Data Types</a></h2>
+<h3 class="typedef"><a name="cups_backend_t">cups_backend_t</a></h3>
+<p class="description">Backend exit codes</p>
+<p class="code">
+typedef enum <a href="#cups_backend_e">cups_backend_e</a> cups_backend_t;
+</p>
+<h3 class="typedef"><a name="cups_sc_bidi_t">cups_sc_bidi_t</a></h3>
+<p class="description">Bidirectional capabilities</p>
+<p class="code">
+typedef enum <a href="#cups_sc_bidi_e">cups_sc_bidi_e</a> cups_sc_bidi_t;
+</p>
+<h3 class="typedef"><a name="cups_sc_command_t">cups_sc_command_t</a></h3>
+<p class="description">Request command codes</p>
+<p class="code">
+typedef enum <a href="#cups_sc_command_e">cups_sc_command_e</a> cups_sc_command_t;
+</p>
+<h3 class="typedef"><a name="cups_sc_state_t">cups_sc_state_t</a></h3>
+<p class="description">Printer state bits</p>
+<p class="code">
+typedef enum <a href="#cups_sc_state_e">cups_sc_state_e</a> cups_sc_state_t;
+</p>
+<h3 class="typedef"><a name="cups_sc_status_t">cups_sc_status_t</a></h3>
+<p class="description">Response status codes</p>
+<p class="code">
+typedef enum <a href="#cups_sc_status_e">cups_sc_status_e</a> cups_sc_status_t;
+</p>
+<h2 class="title"><a name="ENUMERATIONS">Constants</a></h2>
+<h3 class="enumeration"><a name="cups_backend_e">cups_backend_e</a></h3>
+<p class="description">Backend exit codes</p>
+<h4 class="constants">Constants</h4>
+<dl>
+<dt>CUPS_BACKEND_AUTH_REQUIRED </dt>
+<dd class="description">Job failed, authentication required</dd>
+<dt>CUPS_BACKEND_CANCEL </dt>
+<dd class="description">Job failed, cancel job</dd>
+<dt>CUPS_BACKEND_FAILED </dt>
+<dd class="description">Job failed, use error-policy</dd>
+<dt>CUPS_BACKEND_HOLD </dt>
+<dd class="description">Job failed, hold job</dd>
+<dt>CUPS_BACKEND_OK </dt>
+<dd class="description">Job completed successfully</dd>
+<dt>CUPS_BACKEND_STOP </dt>
+<dd class="description">Job failed, stop queue</dd>
+</dl>
+<h3 class="enumeration"><a name="cups_sc_bidi_e">cups_sc_bidi_e</a></h3>
+<p class="description">Bidirectional capabilities</p>
+<h4 class="constants">Constants</h4>
+<dl>
+<dt>CUPS_SC_BIDI_NOT_SUPPORTED </dt>
+<dd class="description">Bidirectional I/O is not supported</dd>
+<dt>CUPS_SC_BIDI_SUPPORTED </dt>
+<dd class="description">Bidirectional I/O is supported</dd>
+</dl>
+<h3 class="enumeration"><a name="cups_sc_command_e">cups_sc_command_e</a></h3>
+<p class="description">Request command codes</p>
+<h4 class="constants">Constants</h4>
+<dl>
+<dt>CUPS_SC_CMD_DRAIN_OUTPUT </dt>
+<dd class="description">Drain all pending output</dd>
+<dt>CUPS_SC_CMD_GET_BIDI </dt>
+<dd class="description">Return bidirectional capabilities</dd>
+<dt>CUPS_SC_CMD_GET_DEVICE_ID </dt>
+<dd class="description">Return the IEEE-1284 device ID</dd>
+<dt>CUPS_SC_CMD_GET_STATE </dt>
+<dd class="description">Return the device state</dd>
+<dt>CUPS_SC_CMD_SOFT_RESET </dt>
+<dd class="description">Do a soft reset</dd>
+</dl>
+<h3 class="enumeration"><a name="cups_sc_state_e">cups_sc_state_e</a></h3>
+<p class="description">Printer state bits</p>
+<h4 class="constants">Constants</h4>
+<dl>
+<dt>CUPS_SC_STATE_BUSY </dt>
+<dd class="description">Device is busy</dd>
+<dt>CUPS_SC_STATE_ERROR </dt>
+<dd class="description">Other error condition</dd>
+<dt>CUPS_SC_STATE_MARKER_EMPTY </dt>
+<dd class="description">Toner/ink out condition</dd>
+<dt>CUPS_SC_STATE_MARKER_LOW </dt>
+<dd class="description">Toner/ink low condition</dd>
+<dt>CUPS_SC_STATE_MEDIA_EMPTY </dt>
+<dd class="description">Paper out condition</dd>
+<dt>CUPS_SC_STATE_MEDIA_LOW </dt>
+<dd class="description">Paper low condition</dd>
+<dt>CUPS_SC_STATE_OFFLINE </dt>
+<dd class="description">Device is off-line</dd>
+<dt>CUPS_SC_STATE_ONLINE </dt>
+<dd class="description">Device is on-line</dd>
+</dl>
+<h3 class="enumeration"><a name="cups_sc_status_e">cups_sc_status_e</a></h3>
+<p class="description">Response status codes</p>
+<h4 class="constants">Constants</h4>
+<dl>
+<dt>CUPS_SC_STATUS_BAD_MESSAGE </dt>
+<dd class="description">The command/response message was invalid</dd>
+<dt>CUPS_SC_STATUS_IO_ERROR </dt>
+<dd class="description">An I/O error occurred</dd>
+<dt>CUPS_SC_STATUS_NONE </dt>
+<dd class="description">No status</dd>
+<dt>CUPS_SC_STATUS_NOT_IMPLEMENTED </dt>
+<dd class="description">Command not implemented</dd>
+<dt>CUPS_SC_STATUS_NO_RESPONSE </dt>
+<dd class="description">The device did not respond</dd>
+<dt>CUPS_SC_STATUS_OK </dt>
+<dd class="description">Operation succeeded</dd>
+<dt>CUPS_SC_STATUS_TIMEOUT </dt>
+<dd class="description">The backend did not respond</dd>
+<dt>CUPS_SC_STATUS_TOO_BIG </dt>
+<dd class="description">Response too big</dd>
+</dl>
+</div>
</body>
</html>
projects / thirdparty / cups.git / blobdiff