server/util_filter.c

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2000 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
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 *    distribution.
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 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
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 * 4. The names "Apache" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
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 * 5. Products derived from this software may not be called "Apache",
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 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

#include "util_filter.h"

/*
 * ap_filter_rec_t:
 *
 * This (internal) structure is used for recording information about the
 * registered filters. It associates a name with the filter's callback
 * and filter type.
 *
 * At the moment, these are simply linked in a chain, so a ->next pointer
 * is available.
 */
typedef struct ap_filter_rec_t {
    const char *name;
    ap_filter_func filter_func;
    ap_filter_type ftype;

    struct ap_filter_rec_t *next;
} ap_filter_rec_t;

/* ### make this visible for direct manipulation?
   ### use a hash table
*/
static ap_filter_rec_t *registered_filters = NULL;

/* NOTE: Apache's current design doesn't allow a pool to be passed thu,
   so we depend on a global to hold the correct pool
*/
#define FILTER_POOL     ap_global_hook_pool
#include "ap_hooks.h"   /* for ap_global_hook_pool */

/*
** This macro returns true/false if a given filter should be inserted BEFORE
** another filter. This will happen when one of: 1) there isn't another
** filter; 2) that filter has a higher filter type (class); 3) that filter
** corresponds to a different request.
*/
#define INSERT_BEFORE(f, before_this) ((before_this) == NULL \
                                       || (before_this)->ftype > (f)->ftype)


static ap_status_t filter_cleanup(void *ctx)
{
    registered_filters = NULL;
    return APR_SUCCESS;
}

API_EXPORT(void) ap_register_filter(const char *name,
                                    ap_filter_func filter_func,
                                    ap_filter_type ftype)
{
    ap_filter_rec_t *frec = ap_palloc(FILTER_POOL, sizeof(*frec));

    frec->name = name;
    frec->filter_func = filter_func;
    frec->ftype = ftype;

    frec->next = registered_filters;
    registered_filters = frec;

    ap_register_cleanup(FILTER_POOL, NULL, filter_cleanup, NULL);
}

API_EXPORT(void) ap_add_filter(const char *name, void *ctx, request_rec *r)
{
    ap_filter_rec_t *frec = registered_filters;

    for (; frec != NULL; frec = frec->next) {
        if (!strcasecmp(name, frec->name)) {
            ap_filter_t *f = ap_pcalloc(r->pool, sizeof(*f));

            f->filter_func = frec->filter_func;
            f->ctx = ctx;
            f->ftype = frec->ftype;

            if (INSERT_BEFORE(f, r->filters)) {
                f->next = r->filters;
                r->filters = f;
            }
            else {
                ap_filter_t *fscan = r->filters;
                while (!INSERT_BEFORE(f, fscan->next))
                    fscan = fscan->next;
                f->next = fscan->next;
                fscan->next = f;
            }

            break;
        }
    }
}