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 254 <div class='body'>
 255 <!--
 256   "$Id: api-filter.header 7285 2008-02-01 23:57:39Z mike $"
 257
 258   Filter and backend programming header for the Common UNIX Printing System
 259   (CUPS).
 260
 261   Copyright 2008 by Apple Inc.
 262
 263   These coded instructions, statements, and computer programs are the
 264   property of Apple Inc. and are protected by Federal copyright
 265   law.  Distribution and use rights are outlined in the file "LICENSE.txt"
 266   which should have been included with this file.  If this file is
 267   file is missing or damaged, see the license at "http://www.cups.org/".
 268 -->
 269
 270 <h1 class="title">Filter and Backend Programming</h1>
 271
 272 <div class='summary'><table summary='General Information'>
 273 <thead>
 274 <tr>
 275         <th>Headers</th>
 276         <th>cups/backend.h<br>
 277         cups/sidechannel.h<br>
 278         cups/snmp.h</th>
 279 </tr>
 280 </thead>
 281 <tbody>
 282 <tr>
 283         <th>Library</th>
 284         <td>-lcups</td>
 285 </tr>
 286 <tr>
 287         <th>See Also</th>
 288         <td>Programming: <a href='api-overview.html' target='_top'>Introduction to CUPS Programming</a><br>
 289         Programming: <a href='api-cups.html' target='_top'>CUPS API</a><br>
 290         Programming: <a href='api-ppd.html' target='_top'>PPD API</a><br>
 291         Programming: <a href='api-raster.html' target='_top'>Raster API</a></td>
 292 </tr>
 293 </tbody>
 294 </table></div>
 295 <h2 class="title">Contents</h2>
 296 <ul class="contents">
 297 </li>
 298 <li><a href="#OVERVIEW">Overview</a><ul class="subcontents">
 299 <li><a href="#SECURITY">Security Considerations</a></li>
 300 <li><a href="#TEMPFILES">Temporary Files</a></li>
 301 <li><a href="#COPIES">Copy Generation</a></li>
 302 <li><a href="#EXITCODES">Exit Codes</a></li>
 303 <li><a href="#ENVIRONMENT">Environment Variables</a></li>
 304 <li><a href="#MESSAGES">Communicating with the Scheduler</a></li>
 305 <li><a href="#COMMUNICATING">Communicating with the Backend</a></li>
 306 <li><a href="#SNMP">Doing SNMP Queries with Network Printers</a></li>
 307 </ul></li>
 308 <li><a href="#FUNCTIONS">Functions</a><ul class="code">
 309 <li><a href="#cupsBackChannelRead" title="Read data from the backchannel.">cupsBackChannelRead</a></li>
 310 <li><a href="#cupsBackChannelWrite" title="Write data to the backchannel.">cupsBackChannelWrite</a></li>
 311 <li><a href="#cupsBackendDeviceURI" title="Get the device URI for a backend.">cupsBackendDeviceURI</a></li>
 312 <li><a href="#cupsSNMPClose" title="Close a SNMP socket.">cupsSNMPClose</a></li>
 313 <li><a href="#cupsSNMPCopyOID" title="Copy an OID.">cupsSNMPCopyOID</a></li>
 314 <li><a href="#cupsSNMPDefaultCommunity" title="Get the default SNMP community name.">cupsSNMPDefaultCommunity</a></li>
 315 <li><a href="#cupsSNMPIsOID" title="Test whether a SNMP response contains the specified OID.">cupsSNMPIsOID</a></li>
 316 <li><a href="#cupsSNMPIsOIDPrefixed" title="Test whether a SNMP response uses the specified
 317 OID prefix.">cupsSNMPIsOIDPrefixed</a></li>
 318 <li><a href="#cupsSNMPOpen" title="Open a SNMP socket.">cupsSNMPOpen</a></li>
 319 <li><a href="#cupsSNMPRead" title="Read and parse a SNMP response.">cupsSNMPRead</a></li>
 320 <li><a href="#cupsSNMPSetDebug" title="Enable/disable debug logging to stderr.">cupsSNMPSetDebug</a></li>
 321 <li><a href="#cupsSNMPWalk" title="Enumerate a group of OIDs.">cupsSNMPWalk</a></li>
 322 <li><a href="#cupsSNMPWrite" title="Send an SNMP query packet.">cupsSNMPWrite</a></li>
 323 <li><a href="#cupsSideChannelDoRequest" title="Send a side-channel command to a backend and wait for a response.">cupsSideChannelDoRequest</a></li>
 324 <li><a href="#cupsSideChannelRead" title="Read a side-channel message.">cupsSideChannelRead</a></li>
 325 <li><a href="#cupsSideChannelWrite" title="Write a side-channel message.">cupsSideChannelWrite</a></li>
 326 </ul>
 327 <li><a href="#TYPES">Data Types</a><ul class="code">
 328         <li><a href="#cups_asn1_t" title="ASN1 request/object types">cups_asn1_t</a></li>
 329         <li><a href="#cups_backend_t" title="Backend exit codes">cups_backend_t</a></li>
 330         <li><a href="#cups_sc_bidi_t" title="Bidirectional capabilities">cups_sc_bidi_t</a></li>
 331         <li><a href="#cups_sc_command_t" title="Request command codes">cups_sc_command_t</a></li>
 332         <li><a href="#cups_sc_state_t" title="Printer state bits">cups_sc_state_t</a></li>
 333         <li><a href="#cups_sc_status_t" title="Response status codes">cups_sc_status_t</a></li>
 334         <li><a href="#cups_snmp_cb_t" title="Prototypes...">cups_snmp_cb_t</a></li>
 335         <li><a href="#cups_snmp_t" title="SNMP data packet">cups_snmp_t</a></li>
 336 </ul></li>
 337 <li><a href="#STRUCTURES">Structures</a><ul class="code">
 338         <li><a href="#cups_snmp_hexstring_s" title="Hex-STRING value">cups_snmp_hexstring_s</a></li>
 339         <li><a href="#cups_snmp_s" title="SNMP data packet">cups_snmp_s</a></li>
 340 </ul></li>
 341 <li><a href="#UNIONS">Unions</a><ul class="code">
 342         <li><a href="#cups_snmp_value_u" title="Object value">cups_snmp_value_u</a></li>
 343 </ul></li>
 344 <li><a href="#ENUMERATIONS">Constants</a><ul class="code">
 345         <li><a href="#cups_asn1_e" title="ASN1 request/object types">cups_asn1_e</a></li>
 346         <li><a href="#cups_backend_e" title="Backend exit codes">cups_backend_e</a></li>
 347         <li><a href="#cups_sc_bidi_e" title="Bidirectional capabilities">cups_sc_bidi_e</a></li>
 348         <li><a href="#cups_sc_command_e" title="Request command codes">cups_sc_command_e</a></li>
 349         <li><a href="#cups_sc_state_e" title="Printer state bits">cups_sc_state_e</a></li>
 350         <li><a href="#cups_sc_status_e" title="Response status codes">cups_sc_status_e</a></li>
 351 </ul></li>
 352 </ul>
 353 <!--
 354   "$Id: api-filter.shtml 7288 2008-02-06 01:39:05Z mike $"
 355
 356   Filter and backend programming introduction for the Common UNIX Printing
 357   System (CUPS).
 358
 359   Copyright 2007-2008 by Apple Inc.
 360   Copyright 1997-2006 by Easy Software Products, all rights reserved.
 361
 362   These coded instructions, statements, and computer programs are the
 363   property of Apple Inc. and are protected by Federal copyright
 364   law.  Distribution and use rights are outlined in the file "LICENSE.txt"
 365   which should have been included with this file.  If this file is
 366   file is missing or damaged, see the license at "http://www.cups.org/".
 367 -->
 368
 369 <h2 class='title'><a name="OVERVIEW">Overview</a></h2>
 370
 371 <p>Filters, printer drivers, port monitors, and backends use a common interface
 372 for processing print jobs and communicating status information to the scheduler.
 373 Each filter is run with a standard set of command-line arguments:<p>
 374
 375 <dl class="code">
 376
 377         <dt>argv[1]</dt>
 378         <dd>The job ID</dd>
 379
 380         <dt>argv[2]</dt>
 381         <dd>The user printing the job</dd>
 382
 383         <dt>argv[3]</dt>
 384         <dd>The job name/title</dd>
 385
 386         <dt>argv[4]</dt>
 387         <dd>The number of copies to print</dd>
 388
 389         <dt>argv[5]</dt>
 390         <dd>The options that were provided when the job was submitted</dd>
 391
 392         <dt>argv[6]</dt>
 393         <dd>The file to print (first filter only)</dd>
 394 </dl>
 395
 396 <p>The scheduler runs one or more of these programs to print any given job. The
 397 first filter reads from the print file and writes to the standard output, while
 398 the remaining filters read from the standard input and write to the standard
 399 output. The backend is the last filter in the chain and writes to the
 400 device.</p>
 401
 402 <h3><a name="SECURITY">Security Considerations</a></h3>
 403
 404 <p>It is always important to use security programming practices. Filters and
 405 most backends are run as a non-priviledged user, so the major security
 406 consideration is resource utilization - filters should not depend on unlimited
 407 amounts of CPU, memory, or disk space, and should protect against conditions
 408 that could lead to excess usage of any resource like infinite loops and
 409 unbounded recursion. In addition, filters must <em>never</em> allow the user to
 410 specify an arbitrary file path to a separator page, template, or other file
 411 used by the filter since that can lead to an unauthorized disclosure of
 412 information. <em>Always</em> treat input as suspect and validate it!</p>
 413
 414 <p>If you are developing a backend that runs as root, make sure to check for
 415 potential buffer overflows, integer under/overflow conditions, and file
 416 accesses since these can lead to privilege escalations. When writing files,
 417 always validate the file path and <em>never</em> allow a user to determine
 418 where to store a file.</p>
 419
 420 <blockquote><b>Note:</b>
 421
 422 <p><em>Never</em> write files to a user's home directory. Aside from the
 423 security implications, CUPS is a network print service and as such the network
 424 user may not be the same as the local user and/or there may not be a local home
 425 directory to write to.</p>
 426
 427 <p>In addition, some operating systems provide additional security mechanisms
 428 that further limit file system access, even for backends running as root.  On
 429 Mac OS X, for example, no backend may write to a user's home directory.</p>
 430 </blockquote>
 431
 432 <h3><a name="TEMPFILES">Temporary Files</a></h3>
 433
 434 <p>Temporary files should be created in the directory specified by the
 435 "TMPDIR" environment variable. The
 436 <a href="#cupsTempFile2"><code>cupsTempFile2</code></a> function can be
 437 used to safely create temporary files in this directory.</p>
 438
 439 <h3><a name="COPIES">Copy Generation</a></h3>
 440
 441 <p>The <code>argv[4]</code> argument specifies the number of copies to produce
 442 of the input file. In general, you should only generate copies if the
 443 <em>filename</em> argument is supplied. The only exception to this are
 444 filters that produce device-independent PostScript output, since the PostScript
 445 filter <var>pstops</var> is responsible for generating copies of PostScript
 446 files.</p>
 447
 448 <h3><a name="EXITCODES">Exit Codes</a></h3>
 449
 450 <p>Filters must exit with status 0 when they successfully generate print data
 451 or 1 when they encounter an error. Backends can return any of the
 452 <a href="#cups_backend_t"><code>cups_backend_t</code></a> constants.</p>
 453
 454 <h3><a name="ENVIRONMENT">Environment Variables</a></h3>
 455
 456 <p>The following environment variables are defined by the printing system:</p>
 457
 458 <dl class="code">
 459
 460         <dt>APPLE_LANGUAGES</dt>
 461         <dd>The Apple language identifier associated with the job
 462         (Mac OS X only).</dd>
 463
 464         <dt>CHARSET</dt>
 465         <dd>The job character set, typically "utf-8".</dd>
 466
 467         <dt>CLASS</dt>
 468         <dd>When a job is submitted to a printer class, contains the name of
 469         the destination printer class. Otherwise this environment
 470         variable will not be set.</dd>
 471
 472         <dt>CONTENT_TYPE</dt>
 473         <dd>The MIME type associated with the file (e.g.
 474         application/postscript).</dd>
 475
 476         <dt>CUPS_CACHEDIR</dt>
 477         <dd>The directory where cache files can be stored.</dd>
 478
 479         <dt>CUPS_DATADIR</dt>
 480         <dd>The directory where data files can be found.</dd>
 481
 482         <dt>CUPS_SERVERROOT</dt>
 483         <dd>The root directory of the server.</dd>
 484
 485         <dt>DEVICE_URI</dt>
 486         <dd>The device-uri associated with the printer.</dd>
 487
 488         <dt>FINAL_CONTENT_TYPE</dt>
 489         <dd>The MIME type associated with the printer (e.g.
 490         application/vnd.cups-postscript).</dd>
 491
 492         <dt>LANG</dt>
 493         <dd>The language locale associated with the job.</dd>
 494
 495         <dt>PPD</dt>
 496         <dd>The full pathname of the PostScript Printer Description (PPD)
 497         file for this printer.</dd>
 498
 499         <dt>PRINTER</dt>
 500         <dd>The name of the printer.</dd>
 501
 502         <dt>RIP_CACHE</dt>
 503         <dd>The recommended amount of memory to use for Raster Image
 504         Processors (RIPs).</dd>
 505
 506 </dl>
 507
 508 <h3><a name="MESSAGES">Communicating with the Scheduler</a></h3>
 509
 510 <p>Filters and backends communicate wih the scheduler by writing messages
 511 to the standard error file. For example, the following code sets the current
 512 printer state message to "Printing page 5":</p>
 513
 514 <pre class="example">
 515 int page = 5;
 516
 517 fprintf(stderr, "INFO: Printing page %d\n", page);
 518 </pre>
 519
 520 <p>Each message is a single line of text starting with one of the following
 521 prefix strings:</p>
 522
 523 <dl class="code">
 524
 525         <dt>ALERT: message</dt>
 526         <dd>Sets the printer-state-message attribute and adds the specified
 527         message to the current error log file using the "alert" log level.</dd>
 528
 529         <dt>ATTR: attribute=value [attribute=value]</dt>
 530         <dd>Sets the named printer or job attribute(s). Typically this is used
 531         to set the <code>marker-colors</code>, <code>marker-levels</code>,
 532         <code>marker-names</code>, <code>marker-types</code>,
 533         <code>printer-alert</code>, and <code>printer-alert-description</code>
 534         printer attributes.</dd>
 535
 536         <dt>CRIT: message</dt>
 537         <dd>Sets the printer-state-message attribute and adds the specified
 538         message to the current error log file using the "critical" log
 539         level.</dd>
 540
 541         <dt>DEBUG: message</dt>
 542         <dd>Sets the printer-state-message attribute and adds the specified
 543         message to the current error log file using the "debug" log level.</dd>
 544
 545         <dt>DEBUG2: message</dt>
 546         <dd>Sets the printer-state-message attribute and adds the specified
 547         message to the current error log file using the "debug2" log level.</dd>
 548
 549         <dt>EMERG: message</dt>
 550         <dd>Sets the printer-state-message attribute and adds the specified
 551         message to the current error log file using the "emergency" log
 552         level.</dd>
 553
 554         <dt>ERROR: message</dt>
 555         <dd>Sets the printer-state-message attribute and adds the specified
 556         message to the current error log file using the "error" log level.</dd>
 557
 558         <dt>INFO: message</dt>
 559         <dd>Sets the printer-state-message attribute. If the current log level
 560         is set to "debug2", also adds the specified message to the current error
 561         log file using the "info" log level.</dd>
 562
 563         <dt>NOTICE: message</dt>
 564         <dd>Sets the printer-state-message attribute and adds the specified
 565         message to the current error log file using the "notice" log level.</dd>
 566
 567         <dt>PAGE: page-number #-copies</dt>
 568         <dt>PAGE: total #-pages</dt>
 569         <dd>Adds an entry to the current page log file. The first form adds
 570         #-copies to the job-media-sheets-completed attribute. The second
 571         form sets the job-media-sheets-completed attribute to #-pages.</dd>
 572
 573         <dt>STATE: printer-state-reason [printer-state-reason ...]</dt>
 574         <dt>STATE: + printer-state-reason [printer-state-reason ...]</dt>
 575         <dt>STATE: - printer-state-reason [printer-state-reason ...]</dt>
 576         <dd>Sets, adds, or removes printer-state-reason keywords to the
 577         current queue. Typically this is used to indicate media, ink, and
 578         toner conditions on a printer.</dd>
 579
 580         <dt>WARNING: message</dt>
 581         <dd>Sets the printer-state-message attribute and adds the specified
 582         message to the current error log file using the "warning" log
 583         level.</dd>
 584
 585 </dl>
 586
 587 <p>Messages without one of these prefixes are treated as if they began with
 588 the "DEBUG:" prefix string.</p>
 589
 590 <h3><a name="COMMUNICATING">Communicating with the Backend</a></h3>
 591
 592 <p>Filters can communicate with the backend via the
 593 <a href="#cupsBackChannelRead"><code>cupsBackChannelRead</code></a> and
 594 <a href="#cupsSideChannelDoRequest"><code>cupsSideChannelDoRequest</code></a>
 595 functions. The
 596 <a href="#cupsBackChannelRead"><code>cupsBackChannelRead</code></a> function
 597 reads data that has been sent back from the device and is typically used to
 598 obtain status and configuration information. For example, the following code
 599 polls the backend for back-channel data:</p>
 600
 601 <pre class="example">
 602 #include &lt;cups/cups.h&gt;
 603
 604 char buffer[8192];
 605 ssize_t bytes;
 606
 607 /* Use a timeout of 0.0 seconds to poll for back-channel data */
 608 bytes = cupsBackChannelRead(buffer, sizeof(buffer), 0.0);
 609 </pre>
 610
 611 The
 612 <a href="#cupsSideChannelDoRequest"><code>cupsSideChannelDoRequest</code></a>
 613 function allows you to get out-of-band status information and do synchronization
 614 with the device. For example, the following code gets the current IEEE-1284
 615 device ID string from the backend:</p>
 616
 617 <pre class="example">
 618 #include &lt;cups/sidechannel.h&gt;
 619
 620 char data[2049];
 621 int datalen;
 622 <a href="#cups_sc_status_t">cups_sc_status_t</a> status;
 623
 624 /* Tell cupsSideChannelDoRequest() how big our buffer is, less 1 byte for nul-termination... */
 625 datalen = sizeof(data) - 1;
 626
 627 /* Get the IEEE-1284 device ID, waiting for up to 1 second */
 628 status = <a href="#cupsSideChannelDoRequest">cupsSideChannelDoRequest</a>(CUPS_SC_CMD_GET_DEVICE_ID, data, &amp;datalen, 1.0);
 629
 630 /* Use the returned value if OK was returned and the length is non-zero */
 631 if (status == CUPS_SC_STATUS_OK && datalen > 0)
 632   data[datalen] = '\0';
 633 else
 634   data[0] = '\0';
 635 </pre>
 636
 637 <p>Backends communicate with filters using the reciprocal functions
 638 <a href="#cupsBackChannelWrite"><code>cupsBackChannelWrite</code></a>,
 639 <a href="#cupsSideChannelRead"><code>cupsSideChannelRead</code></a>, and
 640 <a href="#cupsSideChannelWrite"><code>cupsSideChannelWrite</code></a>. We
 641 recommend writing back-channel data using a timeout of 1.0 seconds:</p>
 642
 643 <pre class="example">
 644 #include &lt;cups/cups.h&gt;
 645
 646 char buffer[8192];
 647 ssize_t bytes;
 648
 649 /* Use a timeout of 1.0 seconds to give filters a chance to read */
 650 cupsBackChannelWrite(buffer, bytes, 1.0);
 651 </pre>
 652
 653 <p>The <a href="#cupsSideChannelRead"><code>cupsSideChannelRead</code></a>
 654 function reads a side-channel command from a filter, driver, or port monitor.
 655 Backends can either poll for commands using a <code>timeout</code> of 0.0, wait
 656 indefinitely for commands using a <code>timeout</code> of -1.0 (probably in a
 657 separate thread for that purpose), or use <code>select</code> or
 658 <code>poll</code> on the <code>CUPS_SC_FD</code> file descriptor (4) to handle
 659 input and output on several file descriptors at the same time. Backends can pass
 660 <code>NULL</code> for the <code>data</code> and <code>datalen</code> parameters
 661 since none of the commands sent by upstream filters contain any data at this
 662 time.</p>
 663
 664 <p>Once a command is processed, the backend uses the
 665 <a href="#cupsSideChannelWrite"><code>cupsSideChannelWrite</code></a> function
 666 to send its response. For example, the following code shows how to poll for a
 667 side-channel command and respond to it:</p>
 668
 669 <pre class="example">
 670 #include &lt;cups/sidechannel.h&gt;
 671
 672 <a href="#cups_sc_command_t">cups_sc_command_t</a> command;
 673 <a href="#cups_sc_status_t">cups_sc_status_t</a> status;
 674
 675 /* Poll for a command... */
 676 if (!<a href="#cupsSideChannelRead">cupsSideChannelRead</a>(&amp;command, &amp;status, NULL, NULL, 0.0))
 677 {
 678   char data[2048];
 679   int datalen;
 680
 681   switch (command)
 682   {
 683     /* handle supported commands, file data/datalen/status with values as needed */
 684
 685     default :
 686         status  = CUPS_SC_STATUS_NOT_IMPLEMENTED;
 687         datalen = 0;
 688         break;
 689   }
 690
 691   /* Send a response... */
 692   <a href="#cupsSideChannelWrite">cupsSideChannelWrite</a>(command, status, data, datalen, 1.0);
 693 }
 694 </pre>
 695
 696 <h3><a name="SNMP">Doing SNMP Queries with Network Printers</a></h3>
 697
 698 <p>The Simple Network Management Protocol (SNMP) allows you to get the current
 699 status, page counter, and supply levels from most network printers. Every
 700 piece of information is associated with an Object Identifier (OID), and
 701 every printer has a <em>community</em> name associated with it. OIDs can be
 702 queried directly or by "walking" over a range of OIDs with a common prefix.</p>
 703
 704 <p>The CUPS SNMP functions provide a simple API for querying network printers.
 705 Queries are made using a datagram socket that is created using
 706 <a href="#cupsSNMPOpen"><code>cupsSNMPOpen</code></a> and destroyed using
 707 <a href="#cupsSNMPClose"><code>cupsSNMPClose</code></a>:</p>
 708
 709 <pre class="example">
 710 #include &lt;cups/snmp.h&gt;
 711
 712 int snmp = <a href="#cupsSNMPOpen">cupsSNMPOpen</a>(AF_INET);
 713
 714 /* do some queries */
 715
 716 <a href="#cupsSNMPClose">cupsSNMPClose</a>(snmp);
 717 </pre>
 718
 719 <p>OIDs are simple C arrays of integers, terminated by a value of -1. For
 720 example, the page counter OID .1.3.6.1.2.1.43.10.2.1.4.1.1 would be:</p>
 721
 722 <pre class="example">
 723 int page_counter_oid[] = { 1, 3, 6, 1, 2, 1, 43, 10, 2, 1, 4, 1, 1, -1 };
 724 </pre>
 725
 726 <p>You send a query using
 727 <a href="#cupsSNMPWrite"><code>cupsSNMPWrite</code></a> and read the value back
 728 using <a href="#cupsSNMPRead"><code>cupsSNMPRead</code></a>. The value is read
 729 into a structure called <a href="#cups_snmp_t"><code>cups_snmp_t</code></a>:</p>
 730
 731 <pre class="example">
 732 #include &lt;cups/snmp.h&gt;
 733
 734 int page_counter_oid[] = { 1, 3, 6, 1, 2, 1, 43, 10, 2, 1, 4, 1, 1, -1 };
 735 http_addrlist_t *host = httpAddrGetList("myprinter", AF_UNSPEC, "161");
 736 int snmp = <a href="#cupsSNMPOpen">cupsSNMPOpen</a>(host->addr.addr.sa_family);
 737 <a href="#cups_snmp_t">cups_snmp_t</a> packet;
 738
 739 <a href="#cupsSNMPWrite">cupsSNMPWrite</a>(snmp, &amp;(host->addr), CUPS_SNMP_VERSION_1,
 740                 <a href="#cupsSNMPDefaultCommunity">cupsSNMPDefaultCommunity</a>(), CUPS_ASN1_GET_REQUEST, 1,
 741                 page_counter_oid);
 742 if (<a href="#cupsSNMPRead">cupsSNMPRead</a>(snmp, &amp;packet, 5000))
 743 {
 744   /* Do something with the value */
 745   printf("Page counter is: %d\n", packet.object_value.integer);
 746 }
 747 </pre>
 748
 749 <p>The <a href="#cupsSNMPWalk"><code>cupsSNMPWalk</code></a> function allows you
 750 to query a whole group of OIDs, calling a function of your choice for each OID
 751 that is found:</p>
 752
 753 <pre class="example">
 754 #include &lt;cups/snmp.h&gt;
 755
 756 void
 757 my_callback(<a href="#cups_snmp_t">cups_snmp_t</a> *packet, void *data)
 758 {
 759   /* Do something with the value */
 760 }
 761
 762 int printer_mib_oid[] = { 1, 3, 6, 1, 2, 1, 43, -1 };
 763 http_addrlist_t *host = httpAddrGetList("myprinter", AF_UNSPEC, "161");
 764 int snmp = <a href="#cupsSNMPOpen">cupsSNMPOpen</a>(host->addr.addr.sa_family);
 765 void *my_data;
 766
 767 <a href="#cupsSNMPWalk">cupsSNMPWalk</a>(snmp, &amp;(host->addr), CUPS_SNMP_VERSION_1,
 768                <a href="#cupsSNMPDefaultCommunity">cupsSNMPDefaultCommunity</a>(), printer_mib_oid, my_callback, my_data);
 769 </pre>
 770 <h2 class="title"><a name="FUNCTIONS">Functions</a></h2>
 771 <h3 class="function"><span class="info">&nbsp;CUPS 1.2&nbsp;</span><a name="cupsBackChannelRead">cupsBackChannelRead</a></h3>
 772 <p class="description">Read data from the backchannel.</p>
 773 <p class="code">
 774 ssize_t cupsBackChannelRead (<br>
 775 &nbsp;&nbsp;&nbsp;&nbsp;char *buffer,<br>
 776 &nbsp;&nbsp;&nbsp;&nbsp;size_t bytes,<br>
 777 &nbsp;&nbsp;&nbsp;&nbsp;double timeout<br>
 778 );</p>
 779 <h4 class="parameters">Parameters</h4>
 780 <dl>
 781 <dt>buffer</dt>
 782 <dd class="description">Buffer to read</dd>
 783 <dt>bytes</dt>
 784 <dd class="description">Bytes to read</dd>
 785 <dt>timeout</dt>
 786 <dd class="description">Timeout in seconds</dd>
 787 </dl>
 788 <h4 class="returnvalue">Return Value</h4>
 789 <p class="description">Bytes read or -1 on error</p>
 790 <h4 class="discussion">Discussion</h4>
 791 <p class="discussion">Reads up to &quot;bytes&quot; bytes from the backchannel. The &quot;timeout&quot;
 792 parameter controls how many seconds to wait for the data - use
 793 0.0 to return immediately if there is no data, -1.0 to wait
 794 for data indefinitely.
 795
 796 </p>
 797 <h3 class="function"><span class="info">&nbsp;CUPS 1.2&nbsp;</span><a name="cupsBackChannelWrite">cupsBackChannelWrite</a></h3>
 798 <p class="description">Write data to the backchannel.</p>
 799 <p class="code">
 800 ssize_t cupsBackChannelWrite (<br>
 801 &nbsp;&nbsp;&nbsp;&nbsp;const char *buffer,<br>
 802 &nbsp;&nbsp;&nbsp;&nbsp;size_t bytes,<br>
 803 &nbsp;&nbsp;&nbsp;&nbsp;double timeout<br>
 804 );</p>
 805 <h4 class="parameters">Parameters</h4>
 806 <dl>
 807 <dt>buffer</dt>
 808 <dd class="description">Buffer to write</dd>
 809 <dt>bytes</dt>
 810 <dd class="description">Bytes to write</dd>
 811 <dt>timeout</dt>
 812 <dd class="description">Timeout in seconds</dd>
 813 </dl>
 814 <h4 class="returnvalue">Return Value</h4>
 815 <p class="description">Bytes written or -1 on error</p>
 816 <h4 class="discussion">Discussion</h4>
 817 <p class="discussion">Writes &quot;bytes&quot; bytes to the backchannel. The &quot;timeout&quot; parameter
 818 controls how many seconds to wait for the data to be written - use
 819 0.0 to return immediately if the data cannot be written, -1.0 to wait
 820 indefinitely.
 821
 822 </p>
 823 <h3 class="function"><a name="cupsBackendDeviceURI">cupsBackendDeviceURI</a></h3>
 824 <p class="description">Get the device URI for a backend.</p>
 825 <p class="code">
 826 const char *cupsBackendDeviceURI (<br>
 827 &nbsp;&nbsp;&nbsp;&nbsp;char **argv<br>
 828 );</p>
 829 <h4 class="parameters">Parameters</h4>
 830 <dl>
 831 <dt>argv</dt>
 832 <dd class="description">Command-line arguments</dd>
 833 </dl>
 834 <h4 class="returnvalue">Return Value</h4>
 835 <p class="description">Device URI or <code>NULL</code></p>
 836 <h4 class="discussion">Discussion</h4>
 837 <p class="discussion">The &quot;argv&quot; argument is the argv argument passed to main(). This
 838 function returns the device URI passed in the DEVICE_URI environment
 839 variable or the device URI passed in argv[0], whichever is found
 840 first.</p>
 841 <h3 class="function"><span class="info">&nbsp;CUPS 1.4&nbsp;</span><a name="cupsSNMPClose">cupsSNMPClose</a></h3>
 842 <p class="description">Close a SNMP socket.</p>
 843 <p class="code">
 844 void cupsSNMPClose (<br>
 845 &nbsp;&nbsp;&nbsp;&nbsp;int fd<br>
 846 );</p>
 847 <h4 class="parameters">Parameters</h4>
 848 <dl>
 849 <dt>fd</dt>
 850 <dd class="description">SNMP socket file descriptor</dd>
 851 </dl>
 852 <h3 class="function"><span class="info">&nbsp;CUPS 1.4&nbsp;</span><a name="cupsSNMPCopyOID">cupsSNMPCopyOID</a></h3>
 853 <p class="description">Copy an OID.</p>
 854 <p class="code">
 855 int *cupsSNMPCopyOID (<br>
 856 &nbsp;&nbsp;&nbsp;&nbsp;int *dst,<br>
 857 &nbsp;&nbsp;&nbsp;&nbsp;const int *src,<br>
 858 &nbsp;&nbsp;&nbsp;&nbsp;int dstsize<br>
 859 );</p>
 860 <h4 class="parameters">Parameters</h4>
 861 <dl>
 862 <dt>dst</dt>
 863 <dd class="description">Destination OID</dd>
 864 <dt>src</dt>
 865 <dd class="description">Source OID</dd>
 866 <dt>dstsize</dt>
 867 <dd class="description">Number of integers in dst</dd>
 868 </dl>
 869 <h4 class="returnvalue">Return Value</h4>
 870 <p class="description">New OID</p>
 871 <h4 class="discussion">Discussion</h4>
 872 <p class="discussion">The array pointed to by &quot;src&quot; is terminated by the value -1.
 873
 874 </p>
 875 <h3 class="function"><span class="info">&nbsp;CUPS 1.4&nbsp;</span><a name="cupsSNMPDefaultCommunity">cupsSNMPDefaultCommunity</a></h3>
 876 <p class="description">Get the default SNMP community name.</p>
 877 <p class="code">
 878 const char *cupsSNMPDefaultCommunity (void);</p>
 879 <h4 class="returnvalue">Return Value</h4>
 880 <p class="description">Default community name</p>
 881 <h4 class="discussion">Discussion</h4>
 882 <p class="discussion">The default community name is the first community name found in the
 883 snmp.conf file. If no community name is defined there, &quot;public&quot; is used.
 884
 885 </p>
 886 <h3 class="function"><span class="info">&nbsp;CUPS 1.4&nbsp;</span><a name="cupsSNMPIsOID">cupsSNMPIsOID</a></h3>
 887 <p class="description">Test whether a SNMP response contains the specified OID.</p>
 888 <p class="code">
 889 int cupsSNMPIsOID (<br>
 890 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#cups_snmp_t">cups_snmp_t</a> *packet,<br>
 891 &nbsp;&nbsp;&nbsp;&nbsp;const int *oid<br>
 892 );</p>
 893 <h4 class="parameters">Parameters</h4>
 894 <dl>
 895 <dt>packet</dt>
 896 <dd class="description">Response packet</dd>
 897 <dt>oid</dt>
 898 <dd class="description">OID</dd>
 899 </dl>
 900 <h4 class="returnvalue">Return Value</h4>
 901 <p class="description">1 if equal, 0 if not equal</p>
 902 <h4 class="discussion">Discussion</h4>
 903 <p class="discussion">The array pointed to by &quot;oid&quot; is terminated by the value -1.
 904
 905 </p>
 906 <h3 class="function"><span class="info">&nbsp;CUPS 1.4&nbsp;</span><a name="cupsSNMPIsOIDPrefixed">cupsSNMPIsOIDPrefixed</a></h3>
 907 <p class="description">Test whether a SNMP response uses the specified
 908 OID prefix.</p>
 909 <p class="code">
 910 int cupsSNMPIsOIDPrefixed (<br>
 911 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#cups_snmp_t">cups_snmp_t</a> *packet,<br>
 912 &nbsp;&nbsp;&nbsp;&nbsp;const int *prefix<br>
 913 );</p>
 914 <h4 class="parameters">Parameters</h4>
 915 <dl>
 916 <dt>packet</dt>
 917 <dd class="description">Response packet</dd>
 918 <dt>prefix</dt>
 919 <dd class="description">OID prefix</dd>
 920 </dl>
 921 <h4 class="returnvalue">Return Value</h4>
 922 <p class="description">1 if prefixed, 0 if not prefixed</p>
 923 <h4 class="discussion">Discussion</h4>
 924 <p class="discussion">The array pointed to by &quot;prefix&quot; is terminated by the value -1.
 925
 926 </p>
 927 <h3 class="function"><span class="info">&nbsp;CUPS 1.4&nbsp;</span><a name="cupsSNMPOpen">cupsSNMPOpen</a></h3>
 928 <p class="description">Open a SNMP socket.</p>
 929 <p class="code">
 930 int cupsSNMPOpen (<br>
 931 &nbsp;&nbsp;&nbsp;&nbsp;int family<br>
 932 );</p>
 933 <h4 class="parameters">Parameters</h4>
 934 <dl>
 935 <dt>family</dt>
 936 <dd class="description">Address family - <code>AF_INET</code> or <code>AF_INET6</code></dd>
 937 </dl>
 938 <h4 class="returnvalue">Return Value</h4>
 939 <p class="description">SNMP socket file descriptor</p>
 940 <h3 class="function"><span class="info">&nbsp;CUPS 1.4&nbsp;</span><a name="cupsSNMPRead">cupsSNMPRead</a></h3>
 941 <p class="description">Read and parse a SNMP response.</p>
 942 <p class="code">
 943 <a href="#cups_snmp_t">cups_snmp_t</a> *cupsSNMPRead (<br>
 944 &nbsp;&nbsp;&nbsp;&nbsp;int fd,<br>
 945 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#cups_snmp_t">cups_snmp_t</a> *packet,<br>
 946 &nbsp;&nbsp;&nbsp;&nbsp;double timeout<br>
 947 );</p>
 948 <h4 class="parameters">Parameters</h4>
 949 <dl>
 950 <dt>fd</dt>
 951 <dd class="description">SNMP socket file descriptor</dd>
 952 <dt>packet</dt>
 953 <dd class="description">SNMP packet buffer</dd>
 954 <dt>timeout</dt>
 955 <dd class="description">Timeout in seconds</dd>
 956 </dl>
 957 <h4 class="returnvalue">Return Value</h4>
 958 <p class="description">SNMP packet or <code>NULL</code> if none</p>
 959 <h4 class="discussion">Discussion</h4>
 960 <p class="discussion">If &quot;timeout&quot; is negative, <code>cupsSNMPRead</code> will wait for a response
 961 indefinitely.
 962
 963 </p>
 964 <h3 class="function"><span class="info">&nbsp;CUPS 1.4&nbsp;</span><a name="cupsSNMPSetDebug">cupsSNMPSetDebug</a></h3>
 965 <p class="description">Enable/disable debug logging to stderr.</p>
 966 <p class="code">
 967 void cupsSNMPSetDebug (<br>
 968 &nbsp;&nbsp;&nbsp;&nbsp;int level<br>
 969 );</p>
 970 <h4 class="parameters">Parameters</h4>
 971 <dl>
 972 <dt>level</dt>
 973 <dd class="description">1 to enable debug output, 0 otherwise</dd>
 974 </dl>
 975 <h3 class="function"><span class="info">&nbsp;CUPS 1.4&nbsp;</span><a name="cupsSNMPWalk">cupsSNMPWalk</a></h3>
 976 <p class="description">Enumerate a group of OIDs.</p>
 977 <p class="code">
 978 int cupsSNMPWalk (<br>
 979 &nbsp;&nbsp;&nbsp;&nbsp;int fd,<br>
 980 &nbsp;&nbsp;&nbsp;&nbsp;http_addr_t *address,<br>
 981 &nbsp;&nbsp;&nbsp;&nbsp;int version,<br>
 982 &nbsp;&nbsp;&nbsp;&nbsp;const char *community,<br>
 983 &nbsp;&nbsp;&nbsp;&nbsp;const int *prefix,<br>
 984 &nbsp;&nbsp;&nbsp;&nbsp;double timeout,<br>
 985 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#cups_snmp_cb_t">cups_snmp_cb_t</a> cb,<br>
 986 &nbsp;&nbsp;&nbsp;&nbsp;void *data<br>
 987 );</p>
 988 <h4 class="parameters">Parameters</h4>
 989 <dl>
 990 <dt>fd</dt>
 991 <dd class="description">SNMP socket</dd>
 992 <dt>address</dt>
 993 <dd class="description">Address to query</dd>
 994 <dt>version</dt>
 995 <dd class="description">SNMP version</dd>
 996 <dt>community</dt>
 997 <dd class="description">Community name</dd>
 998 <dt>prefix</dt>
 999 <dd class="description">OID prefix</dd>
1000 <dt>timeout</dt>
1001 <dd class="description">Timeout for each response in seconds</dd>
1002 <dt>cb</dt>
1003 <dd class="description">Function to call for each response</dd>
1004 <dt>data</dt>
1005 <dd class="description">User data pointer that is passed to the callback function</dd>
1006 </dl>
1007 <h4 class="returnvalue">Return Value</h4>
1008 <p class="description">Number of OIDs found or -1 on error</p>
1009 <h4 class="discussion">Discussion</h4>
1010 <p class="discussion">This function queries all of the OIDs with the specified OID prefix,
1011 calling the &quot;cb&quot; function for every response that is received.<br>
1012 <br>
1013 The array pointed to by &quot;prefix&quot; is terminated by the value -1.<br>
1014 <br>
1015 If &quot;timeout&quot; is negative, <code>cupsSNMPWalk</code> will wait for a response
1016 indefinitely.
1017
1018 </p>
1019 <h3 class="function"><span class="info">&nbsp;CUPS 1.4&nbsp;</span><a name="cupsSNMPWrite">cupsSNMPWrite</a></h3>
1020 <p class="description">Send an SNMP query packet.</p>
1021 <p class="code">
1022 int cupsSNMPWrite (<br>
1023 &nbsp;&nbsp;&nbsp;&nbsp;int fd,<br>
1024 &nbsp;&nbsp;&nbsp;&nbsp;http_addr_t *address,<br>
1025 &nbsp;&nbsp;&nbsp;&nbsp;int version,<br>
1026 &nbsp;&nbsp;&nbsp;&nbsp;const char *community,<br>
1027 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#cups_asn1_t">cups_asn1_t</a> request_type,<br>
1028 &nbsp;&nbsp;&nbsp;&nbsp;const unsigned request_id,<br>
1029 &nbsp;&nbsp;&nbsp;&nbsp;const int *oid<br>
1030 );</p>
1031 <h4 class="parameters">Parameters</h4>
1032 <dl>
1033 <dt>fd</dt>
1034 <dd class="description">SNMP socket</dd>
1035 <dt>address</dt>
1036 <dd class="description">Address to send to</dd>
1037 <dt>version</dt>
1038 <dd class="description">SNMP version</dd>
1039 <dt>community</dt>
1040 <dd class="description">Community name</dd>
1041 <dt>request_type</dt>
1042 <dd class="description">Request type</dd>
1043 <dt>request_id</dt>
1044 <dd class="description">Request ID</dd>
1045 <dt>oid</dt>
1046 <dd class="description">OID</dd>
1047 </dl>
1048 <h4 class="returnvalue">Return Value</h4>
1049 <p class="description">1 on success, 0 on error</p>
1050 <h4 class="discussion">Discussion</h4>
1051 <p class="discussion">The array pointed to by &quot;oid&quot; is terminated by the value -1.
1052
1053 </p>
1054 <h3 class="function"><span class="info">&nbsp;CUPS 1.3&nbsp;</span><a name="cupsSideChannelDoRequest">cupsSideChannelDoRequest</a></h3>
1055 <p class="description">Send a side-channel command to a backend and wait for a response.</p>
1056 <p class="code">
1057 <a href="#cups_sc_status_t">cups_sc_status_t</a> cupsSideChannelDoRequest (<br>
1058 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#cups_sc_command_t">cups_sc_command_t</a> command,<br>
1059 &nbsp;&nbsp;&nbsp;&nbsp;char *data,<br>
1060 &nbsp;&nbsp;&nbsp;&nbsp;int *datalen,<br>
1061 &nbsp;&nbsp;&nbsp;&nbsp;double timeout<br>
1062 );</p>
1063 <h4 class="parameters">Parameters</h4>
1064 <dl>
1065 <dt>command</dt>
1066 <dd class="description">Command to send</dd>
1067 <dt>data</dt>
1068 <dd class="description">Response data buffer pointer</dd>
1069 <dt>datalen</dt>
1070 <dd class="description">Size of data buffer on entry, number of bytes in buffer on return</dd>
1071 <dt>timeout</dt>
1072 <dd class="description">Timeout in seconds</dd>
1073 </dl>
1074 <h4 class="returnvalue">Return Value</h4>
1075 <p class="description">Status of command</p>
1076 <h4 class="discussion">Discussion</h4>
1077 <p class="discussion">This function is normally only called by filters, drivers, or port
1078 monitors in order to communicate with the backend used by the current
1079 printer.  Programs must be prepared to handle timeout or &quot;not
1080 implemented&quot; status codes, which indicate that the backend or device
1081 do not support the specified side-channel command.<br>
1082 <br>
1083 The &quot;datalen&quot; parameter must be initialized to the size of the buffer
1084 pointed to by the &quot;data&quot; parameter.  cupsSideChannelDoRequest() will
1085 update the value to contain the number of data bytes in the buffer.
1086
1087 </p>
1088 <h3 class="function"><span class="info">&nbsp;CUPS 1.3&nbsp;</span><a name="cupsSideChannelRead">cupsSideChannelRead</a></h3>
1089 <p class="description">Read a side-channel message.</p>
1090 <p class="code">
1091 int cupsSideChannelRead (<br>
1092 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#cups_sc_command_t">cups_sc_command_t</a> *command,<br>
1093 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#cups_sc_status_t">cups_sc_status_t</a> *status,<br>
1094 &nbsp;&nbsp;&nbsp;&nbsp;char *data,<br>
1095 &nbsp;&nbsp;&nbsp;&nbsp;int *datalen,<br>
1096 &nbsp;&nbsp;&nbsp;&nbsp;double timeout<br>
1097 );</p>
1098 <h4 class="parameters">Parameters</h4>
1099 <dl>
1100 <dt>command</dt>
1101 <dd class="description">Command code</dd>
1102 <dt>status</dt>
1103 <dd class="description">Status code</dd>
1104 <dt>data</dt>
1105 <dd class="description">Data buffer pointer</dd>
1106 <dt>datalen</dt>
1107 <dd class="description">Size of data buffer on entry, number of bytes in buffer on return</dd>
1108 <dt>timeout</dt>
1109 <dd class="description">Timeout in seconds</dd>
1110 </dl>
1111 <h4 class="returnvalue">Return Value</h4>
1112 <p class="description">0 on success, -1 on error</p>
1113 <h4 class="discussion">Discussion</h4>
1114 <p class="discussion">This function is normally only called by backend programs to read
1115 commands from a filter, driver, or port monitor program.  The
1116 caller must be prepared to handle incomplete or invalid messages
1117 and return the corresponding status codes.<br>
1118 <br>
1119 The &quot;datalen&quot; parameter must be initialized to the size of the buffer
1120 pointed to by the &quot;data&quot; parameter.  cupsSideChannelDoRequest() will
1121 update the value to contain the number of data bytes in the buffer.
1122
1123 </p>
1124 <h3 class="function"><span class="info">&nbsp;CUPS 1.3&nbsp;</span><a name="cupsSideChannelWrite">cupsSideChannelWrite</a></h3>
1125 <p class="description">Write a side-channel message.</p>
1126 <p class="code">
1127 int cupsSideChannelWrite (<br>
1128 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#cups_sc_command_t">cups_sc_command_t</a> command,<br>
1129 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#cups_sc_status_t">cups_sc_status_t</a> status,<br>
1130 &nbsp;&nbsp;&nbsp;&nbsp;const char *data,<br>
1131 &nbsp;&nbsp;&nbsp;&nbsp;int datalen,<br>
1132 &nbsp;&nbsp;&nbsp;&nbsp;double timeout<br>
1133 );</p>
1134 <h4 class="parameters">Parameters</h4>
1135 <dl>
1136 <dt>command</dt>
1137 <dd class="description">Command code</dd>
1138 <dt>status</dt>
1139 <dd class="description">Status code</dd>
1140 <dt>data</dt>
1141 <dd class="description">Data buffer pointer</dd>
1142 <dt>datalen</dt>
1143 <dd class="description">Number of bytes of data</dd>
1144 <dt>timeout</dt>
1145 <dd class="description">Timeout in seconds</dd>
1146 </dl>
1147 <h4 class="returnvalue">Return Value</h4>
1148 <p class="description">0 on success, -1 on error</p>
1149 <h4 class="discussion">Discussion</h4>
1150 <p class="discussion">This function is normally only called by backend programs to send
1151 responses to a filter, driver, or port monitor program.
1152
1153 </p>
1154 <h2 class="title"><a name="TYPES">Data Types</a></h2>
1155 <h3 class="typedef"><a name="cups_asn1_t">cups_asn1_t</a></h3>
1156 <p class="description">ASN1 request/object types</p>
1157 <p class="code">
1158 typedef enum <a href="#cups_asn1_e">cups_asn1_e</a> cups_asn1_t;
1159 </p>
1160 <h3 class="typedef"><a name="cups_backend_t">cups_backend_t</a></h3>
1161 <p class="description">Backend exit codes</p>
1162 <p class="code">
1163 typedef enum <a href="#cups_backend_e">cups_backend_e</a> cups_backend_t;
1164 </p>
1165 <h3 class="typedef"><a name="cups_sc_bidi_t">cups_sc_bidi_t</a></h3>
1166 <p class="description">Bidirectional capabilities</p>
1167 <p class="code">
1168 typedef enum <a href="#cups_sc_bidi_e">cups_sc_bidi_e</a> cups_sc_bidi_t;
1169 </p>
1170 <h3 class="typedef"><a name="cups_sc_command_t">cups_sc_command_t</a></h3>
1171 <p class="description">Request command codes</p>
1172 <p class="code">
1173 typedef enum <a href="#cups_sc_command_e">cups_sc_command_e</a> cups_sc_command_t;
1174 </p>
1175 <h3 class="typedef"><a name="cups_sc_state_t">cups_sc_state_t</a></h3>
1176 <p class="description">Printer state bits</p>
1177 <p class="code">
1178 typedef enum <a href="#cups_sc_state_e">cups_sc_state_e</a> cups_sc_state_t;
1179 </p>
1180 <h3 class="typedef"><a name="cups_sc_status_t">cups_sc_status_t</a></h3>
1181 <p class="description">Response status codes</p>
1182 <p class="code">
1183 typedef enum <a href="#cups_sc_status_e">cups_sc_status_e</a> cups_sc_status_t;
1184 </p>
1185 <h3 class="typedef"><a name="cups_snmp_cb_t">cups_snmp_cb_t</a></h3>
1186 <p class="description">Prototypes...</p>
1187 <p class="code">
1188 typedef void (*cups_snmp_cb_t)(<a href="#cups_snmp_t">cups_snmp_t</a> *packet, void *data);
1189 </p>
1190 <h3 class="typedef"><a name="cups_snmp_t">cups_snmp_t</a></h3>
1191 <p class="description">SNMP data packet</p>
1192 <p class="code">
1193 typedef struct <a href="#cups_snmp_s">cups_snmp_s</a> cups_snmp_t;
1194 </p>
1195 <h2 class="title"><a name="STRUCTURES">Structures</a></h2>
1196 <h3 class="struct"><a name="cups_snmp_hexstring_s">cups_snmp_hexstring_s</a></h3>
1197 <p class="description">Hex-STRING value</p>
1198 <p class="code">struct cups_snmp_hexstring_s {<br>
1199 &nbsp;&nbsp;&nbsp;&nbsp;unsigned char bytes[CUPS_SNMP_MAX_STRING];<br>
1200 &nbsp;&nbsp;&nbsp;&nbsp;int num_bytes;<br>
1201 };</p>
1202 <h4 class="members">Members</h4>
1203 <dl>
1204 <dt>bytes[CUPS_SNMP_MAX_STRING] </dt>
1205 <dd class="description">Bytes in string</dd>
1206 <dt>num_bytes </dt>
1207 <dd class="description">Number of bytes</dd>
1208 </dl>
1209 <h3 class="struct"><a name="cups_snmp_s">cups_snmp_s</a></h3>
1210 <p class="description">SNMP data packet</p>
1211 <p class="code">struct cups_snmp_s {<br>
1212 &nbsp;&nbsp;&nbsp;&nbsp;http_addr_t address;<br>
1213 &nbsp;&nbsp;&nbsp;&nbsp;char community[CUPS_SNMP_MAX_STRING];<br>
1214 &nbsp;&nbsp;&nbsp;&nbsp;const char *error;<br>
1215 &nbsp;&nbsp;&nbsp;&nbsp;int error_index;<br>
1216 &nbsp;&nbsp;&nbsp;&nbsp;int error_status;<br>
1217 &nbsp;&nbsp;&nbsp;&nbsp;int object_name[CUPS_SNMP_MAX_OID];<br>
1218 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#cups_asn1_t">cups_asn1_t</a> object_type;<br>
1219 &nbsp;&nbsp;&nbsp;&nbsp;union <a href="#cups_snmp_value_u">cups_snmp_value_u</a> object_value;<br>
1220 &nbsp;&nbsp;&nbsp;&nbsp;int request_id;<br>
1221 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#cups_asn1_t">cups_asn1_t</a> request_type;<br>
1222 &nbsp;&nbsp;&nbsp;&nbsp;int version;<br>
1223 };</p>
1224 <h4 class="members">Members</h4>
1225 <dl>
1226 <dt>address </dt>
1227 <dd class="description">Source address</dd>
1228 <dt>community[CUPS_SNMP_MAX_STRING] </dt>
1229 <dd class="description">Community name</dd>
1230 <dt>error </dt>
1231 <dd class="description">Encode/decode error</dd>
1232 <dt>error_index </dt>
1233 <dd class="description">error-index value</dd>
1234 <dt>error_status </dt>
1235 <dd class="description">error-status value</dd>
1236 <dt>object_name[CUPS_SNMP_MAX_OID] </dt>
1237 <dd class="description">object-name value</dd>
1238 <dt>object_type </dt>
1239 <dd class="description">object-value type</dd>
1240 <dt>object_value </dt>
1241 <dd class="description">object-value value</dd>
1242 <dt>request_id </dt>
1243 <dd class="description">request-id value</dd>
1244 <dt>request_type </dt>
1245 <dd class="description">Request type</dd>
1246 <dt>version </dt>
1247 <dd class="description">Version number</dd>
1248 </dl>
1249 <h2 class="title"><a name="UNIONS">Unions</a></h2>
1250 <h3 class="union"><a name="cups_snmp_value_u">cups_snmp_value_u</a></h3>
1251 <p class="description">Object value</p>
1252 <p class="code">union cups_snmp_value_u {<br>
1253 &nbsp;&nbsp;&nbsp;&nbsp;int boolean;<br>
1254 &nbsp;&nbsp;&nbsp;&nbsp;unsigned counter;<br>
1255 &nbsp;&nbsp;&nbsp;&nbsp;unsigned gauge;<br>
1256 &nbsp;&nbsp;&nbsp;&nbsp;struct <a href="#cups_snmp_hexstring_s">cups_snmp_hexstring_s</a> hex_string;<br>
1257 &nbsp;&nbsp;&nbsp;&nbsp;int integer;<br>
1258 &nbsp;&nbsp;&nbsp;&nbsp;int oid[CUPS_SNMP_MAX_OID];<br>
1259 &nbsp;&nbsp;&nbsp;&nbsp;char string[CUPS_SNMP_MAX_STRING];<br>
1260 &nbsp;&nbsp;&nbsp;&nbsp;unsigned timeticks;<br>
1261 };</p>
1262 <h4 class="members">Members</h4>
1263 <dl>
1264 <dt>boolean </dt>
1265 <dd class="description">Boolean value</dd>
1266 <dt>counter </dt>
1267 <dd class="description">Counter value</dd>
1268 <dt>gauge </dt>
1269 <dd class="description">Gauge value</dd>
1270 <dt>hex_string </dt>
1271 <dd class="description">Hex string value</dd>
1272 <dt>integer </dt>
1273 <dd class="description">Integer value</dd>
1274 <dt>oid[CUPS_SNMP_MAX_OID] </dt>
1275 <dd class="description">OID value</dd>
1276 <dt>string[CUPS_SNMP_MAX_STRING] </dt>
1277 <dd class="description">String value</dd>
1278 <dt>timeticks </dt>
1279 <dd class="description">Timeticks  value</dd>
1280 </dl>
1281 <h2 class="title"><a name="ENUMERATIONS">Constants</a></h2>
1282 <h3 class="enumeration"><a name="cups_asn1_e">cups_asn1_e</a></h3>
1283 <p class="description">ASN1 request/object types</p>
1284 <h4 class="constants">Constants</h4>
1285 <dl>
1286 <dt>CUPS_ASN1_BIT_STRING </dt>
1287 <dd class="description">BIT STRING</dd>
1288 <dt>CUPS_ASN1_BOOLEAN </dt>
1289 <dd class="description">BOOLEAN</dd>
1290 <dt>CUPS_ASN1_COUNTER </dt>
1291 <dd class="description">32-bit unsigned aka Counter32</dd>
1292 <dt>CUPS_ASN1_END_OF_CONTENTS </dt>
1293 <dd class="description">End-of-contents</dd>
1294 <dt>CUPS_ASN1_GAUGE </dt>
1295 <dd class="description">32-bit unsigned aka Gauge32</dd>
1296 <dt>CUPS_ASN1_GET_NEXT_REQUEST </dt>
1297 <dd class="description">GetNextRequest-PDU</dd>
1298 <dt>CUPS_ASN1_GET_REQUEST </dt>
1299 <dd class="description">GetRequest-PDU</dd>
1300 <dt>CUPS_ASN1_GET_RESPONSE </dt>
1301 <dd class="description">GetResponse-PDU</dd>
1302 <dt>CUPS_ASN1_HEX_STRING </dt>
1303 <dd class="description">Binary string aka Hex-STRING</dd>
1304 <dt>CUPS_ASN1_INTEGER </dt>
1305 <dd class="description">INTEGER or ENUMERATION</dd>
1306 <dt>CUPS_ASN1_NULL_VALUE </dt>
1307 <dd class="description">NULL VALUE</dd>
1308 <dt>CUPS_ASN1_OCTET_STRING </dt>
1309 <dd class="description">OCTET STRING</dd>
1310 <dt>CUPS_ASN1_OID </dt>
1311 <dd class="description">OBJECT IDENTIFIER</dd>
1312 <dt>CUPS_ASN1_SEQUENCE </dt>
1313 <dd class="description">SEQUENCE</dd>
1314 <dt>CUPS_ASN1_TIMETICKS </dt>
1315 <dd class="description">32-bit unsigned aka Timeticks32</dd>
1316 </dl>
1317 <h3 class="enumeration"><a name="cups_backend_e">cups_backend_e</a></h3>
1318 <p class="description">Backend exit codes</p>
1319 <h4 class="constants">Constants</h4>
1320 <dl>
1321 <dt>CUPS_BACKEND_AUTH_REQUIRED </dt>
1322 <dd class="description">Job failed, authentication required</dd>
1323 <dt>CUPS_BACKEND_CANCEL </dt>
1324 <dd class="description">Job failed, cancel job</dd>
1325 <dt>CUPS_BACKEND_FAILED </dt>
1326 <dd class="description">Job failed, use error-policy</dd>
1327 <dt>CUPS_BACKEND_HOLD </dt>
1328 <dd class="description">Job failed, hold job</dd>
1329 <dt>CUPS_BACKEND_OK </dt>
1330 <dd class="description">Job completed successfully</dd>
1331 <dt>CUPS_BACKEND_STOP </dt>
1332 <dd class="description">Job failed, stop queue</dd>
1333 </dl>
1334 <h3 class="enumeration"><a name="cups_sc_bidi_e">cups_sc_bidi_e</a></h3>
1335 <p class="description">Bidirectional capabilities</p>
1336 <h4 class="constants">Constants</h4>
1337 <dl>
1338 <dt>CUPS_SC_BIDI_NOT_SUPPORTED </dt>
1339 <dd class="description">Bidirectional I/O is not supported</dd>
1340 <dt>CUPS_SC_BIDI_SUPPORTED </dt>
1341 <dd class="description">Bidirectional I/O is supported</dd>
1342 </dl>
1343 <h3 class="enumeration"><a name="cups_sc_command_e">cups_sc_command_e</a></h3>
1344 <p class="description">Request command codes</p>
1345 <h4 class="constants">Constants</h4>
1346 <dl>
1347 <dt>CUPS_SC_CMD_DRAIN_OUTPUT </dt>
1348 <dd class="description">Drain all pending output</dd>
1349 <dt>CUPS_SC_CMD_GET_BIDI </dt>
1350 <dd class="description">Return bidirectional capabilities</dd>
1351 <dt>CUPS_SC_CMD_GET_DEVICE_ID </dt>
1352 <dd class="description">Return the IEEE-1284 device ID</dd>
1353 <dt>CUPS_SC_CMD_GET_STATE </dt>
1354 <dd class="description">Return the device state</dd>
1355 <dt>CUPS_SC_CMD_SOFT_RESET </dt>
1356 <dd class="description">Do a soft reset</dd>
1357 </dl>
1358 <h3 class="enumeration"><a name="cups_sc_state_e">cups_sc_state_e</a></h3>
1359 <p class="description">Printer state bits</p>
1360 <h4 class="constants">Constants</h4>
1361 <dl>
1362 <dt>CUPS_SC_STATE_BUSY </dt>
1363 <dd class="description">Device is busy</dd>
1364 <dt>CUPS_SC_STATE_ERROR </dt>
1365 <dd class="description">Other error condition</dd>
1366 <dt>CUPS_SC_STATE_MARKER_EMPTY </dt>
1367 <dd class="description">Toner/ink out condition</dd>
1368 <dt>CUPS_SC_STATE_MARKER_LOW </dt>
1369 <dd class="description">Toner/ink low condition</dd>
1370 <dt>CUPS_SC_STATE_MEDIA_EMPTY </dt>
1371 <dd class="description">Paper out condition</dd>
1372 <dt>CUPS_SC_STATE_MEDIA_LOW </dt>
1373 <dd class="description">Paper low condition</dd>
1374 <dt>CUPS_SC_STATE_OFFLINE </dt>
1375 <dd class="description">Device is off-line</dd>
1376 <dt>CUPS_SC_STATE_ONLINE </dt>
1377 <dd class="description">Device is on-line</dd>
1378 </dl>
1379 <h3 class="enumeration"><a name="cups_sc_status_e">cups_sc_status_e</a></h3>
1380 <p class="description">Response status codes</p>
1381 <h4 class="constants">Constants</h4>
1382 <dl>
1383 <dt>CUPS_SC_STATUS_BAD_MESSAGE </dt>
1384 <dd class="description">The command/response message was invalid</dd>
1385 <dt>CUPS_SC_STATUS_IO_ERROR </dt>
1386 <dd class="description">An I/O error occurred</dd>
1387 <dt>CUPS_SC_STATUS_NONE </dt>
1388 <dd class="description">No status</dd>
1389 <dt>CUPS_SC_STATUS_NOT_IMPLEMENTED </dt>
1390 <dd class="description">Command not implemented</dd>
1391 <dt>CUPS_SC_STATUS_NO_RESPONSE </dt>
1392 <dd class="description">The device did not respond</dd>
1393 <dt>CUPS_SC_STATUS_OK </dt>
1394 <dd class="description">Operation succeeded</dd>
1395 <dt>CUPS_SC_STATUS_TIMEOUT </dt>
1396 <dd class="description">The backend did not respond</dd>
1397 <dt>CUPS_SC_STATUS_TOO_BIG </dt>
1398 <dd class="description">Response too big</dd>
1399 </dl>
1400 </div>
1401 </body>
1402 </html>