mod_example.c

Apache HTTP Server 是一个功能强大的灵活的与HTTP/1.1相兼容的web服务器.这里给出的是Apache HTTP服务器的源码。

    const char *sofar;
    char *addon;
    char *where;
    apr_pool_t *p;
    const char *trace_copy;

    /*
     * Make sure our pools and tables are set up - we need 'em.
     */
    setup_module_cells();
    /*
     * Now, if we're in request-context, we use the request pool.
     */
    if (r != NULL) {
        p = r->pool;
        if ((trace_copy = apr_table_get(r->notes, TRACE_NOTE)) == NULL) {
            trace_copy = "";
        }
    }
    else {
        /*
         * We're not in request context, so the trace gets attached to our
         * module-wide pool.  We do the create/destroy every time we're called
         * in non-request context; this avoids leaking memory in some of
         * the subsequent calls that allocate memory only once (such as the
         * key formation below).
         *
         * Make a new sub-pool and copy any existing trace to it.  Point the
         * trace cell at the copied value.
         */
        apr_pool_create(&p, x_pool);
        if (trace != NULL) {
            trace = apr_pstrdup(p, trace);
        }
        /*
         * Now, if we have a sub-pool from before, nuke it and replace with
         * the one we just allocated.
         */
        if (x_subpool != NULL) {
            apr_pool_destroy(x_subpool);
        }
        x_subpool = p;
        trace_copy = trace;
    }
    /*
     * If we weren't passed a configuration record, we can't figure out to
     * what location this call applies.  This only happens for co-routines
     * that don't operate in a particular directory or server context.  If we
     * got a valid record, extract the location (directory or server) to which
     * it applies.
     */
    where = (mconfig != NULL) ? mconfig->loc : "nowhere";
    where = (where != NULL) ? where : "";
    /*
     * Now, if we're not in request context, see if we've been called with
     * this particular combination before.  The apr_table_t is allocated in the
     * module's private pool, which doesn't get destroyed.
     */
    if (r == NULL) {
        char *key;

        key = apr_pstrcat(p, note, ":", where, NULL);
        if (apr_table_get(static_calls_made, key) != NULL) {
            /*
             * Been here, done this.
             */
            return;
        }
        else {
            /*
             * First time for this combination of routine and environment -
             * log it so we don't do it again.
             */
            apr_table_set(static_calls_made, key, "been here");
        }
    }
    addon = apr_pstrcat(p,
                        "   <li>\n"
                        "    <dl>\n"
                        "     <dt><samp>", note, "</samp></dt>\n"
                        "     <dd><samp>[", where, "]</samp></dd>\n"
                        "    </dl>\n"
                        "   </li>\n",
                        NULL);
    sofar = (trace_copy == NULL) ? "" : trace_copy;
    trace_copy = apr_pstrcat(p, sofar, addon, NULL);
    if (r != NULL) {
        apr_table_set(r->notes, TRACE_NOTE, trace_copy);
    }
    else {
        trace = trace_copy;
    }
    /*
     * You *could* change the following if you wanted to see the calling
     * sequence reported in the server's error_log, but beware - almost all of
     * these co-routines are called for every single request, and the impact
     * on the size (and readability) of the error_log is considerable.
     */
#define EXAMPLE_LOG_EACH 0
    if (EXAMPLE_LOG_EACH && (s != NULL)) {
        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s, "mod_example: %s", note);
    }
}

/*--------------------------------------------------------------------------*/
/* We prototyped the various syntax for command handlers (routines that     */
/* are called when the configuration parser detects a directive declared    */
/* by our module) earlier.  Now we actually declare a "real" routine that   */
/* will be invoked by the parser when our "real" directive is               */
/* encountered.                                                             */
/*                                                                          */
/* If a command handler encounters a problem processing the directive, it   */
/* signals this fact by returning a non-NULL pointer to a string            */
/* describing the problem.                                                  */
/*                                                                          */
/* The magic return value DECLINE_CMD is used to deal with directives       */
/* that might be declared by multiple modules.  If the command handler      */
/* returns NULL, the directive was processed; if it returns DECLINE_CMD,    */
/* the next module (if any) that declares the directive is given a chance   */
/* at it.  If it returns any other value, it's treated as the text of an    */
/* error message.                                                           */
/*--------------------------------------------------------------------------*/
/* 
 * Command handler for the NO_ARGS "Example" directive.  All we do is mark the
 * call in the trace log, and flag the applicability of the directive to the
 * current location in that location's configuration record.
 */
static const char *cmd_example(cmd_parms *cmd, void *mconfig)
{
    x_cfg *cfg = (x_cfg *) mconfig;

    /*
     * "Example Wuz Here"
     */
    cfg->local = 1;
    trace_add(cmd->server, NULL, cfg, "cmd_example()");
    return NULL;
}

/*--------------------------------------------------------------------------*/
/*                                                                          */
/* Now we declare our content handlers, which are invoked when the server   */
/* encounters a document which our module is supposed to have a chance to   */
/* see.  (See mod_mime's SetHandler and AddHandler directives, and the      */
/* mod_info and mod_status examples, for more details.)                     */
/*                                                                          */
/* Since content handlers are dumping data directly into the connection     */
/* (using the r*() routines, such as rputs() and rprintf()) without         */
/* intervention by other parts of the server, they need to make             */
/* sure any accumulated HTTP headers are sent first.  This is done by       */
/* calling send_http_header().  Otherwise, no header will be sent at all,   */
/* and the output sent to the client will actually be HTTP-uncompliant.     */
/*--------------------------------------------------------------------------*/
/* 
 * Sample content handler.  All this does is display the call list that has
 * been built up so far.
 *
 * The return value instructs the caller concerning what happened and what to
 * do next:
 *  OK ("we did our thing")
 *  DECLINED ("this isn't something with which we want to get involved")
 *  HTTP_mumble ("an error status should be reported")
 */
static int x_handler(request_rec *r)
{
    x_cfg *dcfg;

    if (strcmp(r->handler, "example-handler")) {
        return DECLINED;
    }

    dcfg = our_dconfig(r);
    trace_add(r->server, r, dcfg, "x_handler()");
    /*
     * We're about to start sending content, so we need to force the HTTP
     * headers to be sent at this point.  Otherwise, no headers will be sent
     * at all.  We can set any we like first, of course.  **NOTE** Here's
     * where you set the "Content-type" header, and you do so by putting it in
     * r->content_type, *not* r->headers_out("Content-type").  If you don't
     * set it, it will be filled in with the server's default type (typically
     * "text/plain").  You *must* also ensure that r->content_type is lower
     * case.
     *
     * We also need to start a timer so the server can know if the connexion
     * is broken.
     */
    ap_set_content_type(r, "text/html");
    /*
     * If we're only supposed to send header information (HEAD request), we're
     * already there.
     */
    if (r->header_only) {
        return OK;
    }

    /*
     * Now send our actual output.  Since we tagged this as being
     * "text/html", we need to embed any HTML.
     */
    ap_rputs(DOCTYPE_HTML_3_2, r);
    ap_rputs("<HTML>\n", r);
    ap_rputs(" <HEAD>\n", r);
    ap_rputs("  <TITLE>mod_example Module Content-Handler Output\n", r);
    ap_rputs("  </TITLE>\n", r);
    ap_rputs(" </HEAD>\n", r);
    ap_rputs(" <BODY>\n", r);
    ap_rputs("  <H1><SAMP>mod_example</SAMP> Module Content-Handler Output\n", r);
    ap_rputs("  </H1>\n", r);
    ap_rputs("  <P>\n", r);
    ap_rprintf(r, "  Apache HTTP Server version: \"%s\"\n",
	    ap_get_server_version());
    ap_rputs("  <BR>\n", r);
    ap_rprintf(r, "  Server built: \"%s\"\n", ap_get_server_built());
    ap_rputs("  </P>\n", r);;
    ap_rputs("  <P>\n", r);
    ap_rputs("  The format for the callback trace is:\n", r);
    ap_rputs("  </P>\n", r);
    ap_rputs("  <DL>\n", r);
    ap_rputs("   <DT><EM>n</EM>.<SAMP>&lt;routine-name&gt;", r);
    ap_rputs("(&lt;routine-data&gt;)</SAMP>\n", r);
    ap_rputs("   </DT>\n", r);
    ap_rputs("   <DD><SAMP>[&lt;applies-to&gt;]</SAMP>\n", r);
    ap_rputs("   </DD>\n", r);
    ap_rputs("  </DL>\n", r);
    ap_rputs("  <P>\n", r);
    ap_rputs("  The <SAMP>&lt;routine-data&gt;</SAMP> is supplied by\n", r);
    ap_rputs("  the routine when it requests the trace,\n", r);
    ap_rputs("  and the <SAMP>&lt;applies-to&gt;</SAMP> is extracted\n", r);
    ap_rputs("  from the configuration record at the time of the trace.\n", r);
    ap_rputs("  <STRONG>SVR()</STRONG> indicates a server environment\n", r);
    ap_rputs("  (blank means the main or default server, otherwise it's\n", r);
    ap_rputs("  the name of the VirtualHost); <STRONG>DIR()</STRONG>\n", r);
    ap_rputs("  indicates a location in the URL or filesystem\n", r);
    ap_rputs("  namespace.\n", r);
    ap_rputs("  </P>\n", r);
    ap_rprintf(r, "  <H2>Static callbacks so far:</H2>\n  <OL>\n%s  </OL>\n",
            trace);
    ap_rputs("  <H2>Request-specific callbacks so far:</H2>\n", r);
    ap_rprintf(r, "  <OL>\n%s  </OL>\n", apr_table_get(r->notes, TRACE_NOTE));
    ap_rputs("  <H2>Environment for <EM>this</EM> call:</H2>\n", r);
    ap_rputs("  <UL>\n", r);
    ap_rprintf(r, "   <LI>Applies-to: <SAMP>%s</SAMP>\n   </LI>\n", dcfg->loc);
    ap_rprintf(r, "   <LI>\"Example\" directive declared here: %s\n   </LI>\n",
            (dcfg->local ? "YES" : "NO"));
    ap_rprintf(r, "   <LI>\"Example\" inherited: %s\n   </LI>\n",
            (dcfg->congenital ? "YES" : "NO"));
    ap_rputs("  </UL>\n", r);
    ap_rputs(" </BODY>\n", r);
    ap_rputs("</HTML>\n", r);
    /*
     * We're all done, so cancel the timeout we set.  Since this is probably
     * the end of the request we *could* assume this would be done during
     * post-processing - but it's possible that another handler might be
     * called and inherit our outstanding timer.  Not good; to each its own.
     */
    /*
     * We did what we wanted to do, so tell the rest of the server we
     * succeeded.
     */
    return OK;
}

/*--------------------------------------------------------------------------*/
/*                                                                          */
/* Now let's declare routines for each of the callback phase in order.      */
/* (That's the order in which they're listed in the callback list, *not     */
/* the order in which the server calls them!  See the command_rec           */
/* declaration near the bottom of this file.)  Note that these may be       */
/* called for situations that don't relate primarily to our function - in   */
/* other words, the fixup handler shouldn't assume that the request has     */
/* to do with "example" stuff.                                              */
/*                                                                          */
/* With the exception of the content handler, all of our routines will be   */
/* called for each request, unless an earlier handler from another module   */
/* aborted the sequence.                                                    */
/*                                                                          */
/* Handlers that are declared as "int" can return the following:            */
/*                                                                          */
/*  OK          Handler accepted the request and did its thing with it.     */
/*  DECLINED    Handler took no action.                                     */
/*  HTTP_mumble Handler looked at request and found it wanting.             */
/*                                                                          */
/* What the server does after calling a module handler depends upon the     */
/* handler's return value.  In all cases, if the handler returns            */
/* DECLINED, the server will continue to the next module with an handler    */
/* for the current phase.  However, if the handler return a non-OK,         */
/* non-DECLINED status, the server aborts the request right there.  If      */
/* the handler returns OK, the server's next action is phase-specific;      */
/* see the individual handler comments below for details.                   */
/*                                                                          */
/*--------------------------------------------------------------------------*/
/* 
 * This function is called during server initialisation.  Any information
 * that needs to be recorded must be in static cells, since there's no
 * configuration record.
 *
 * There is no return value.
 */

/* 
 * This function is called when an heavy-weight process (such as a child) is
 * being run down or destroyed.  As with the child initialisation function,
 * any information that needs to be recorded must be in static cells, since
 * there's no configuration record.
 *
 * There is no return value.
 */

/* 
 * This function is called during server initialisation when an heavy-weight
 * process (such as a child) is being initialised.  As with the
 * module initialisation function, any information that needs to be recorded
 * must be in static cells, since there's no configuration record.
 *
 * There is no return value.
 */

/*
 * This function gets called to create a per-directory configuration
 * record.  This will be called for the "default" server environment, and for
 * each directory for which the parser finds any of our directives applicable.
 * If a directory doesn't have any of our directives involved (i.e., they
 * aren't in the .htaccess file, or a <Location>, <Directory>, or related
 * block), this routine will *not* be called - the configuration for the
 * closest ancestor is used.
 *
 * The return value is a pointer to the created module-specific
 * structure.
 */