modules/examples/mod_case_filter.c

/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "httpd.h"
#include "http_config.h"
#include "apr_buckets.h"
#include "apr_general.h"
#include "apr_lib.h"
#include "util_filter.h"
#include "http_request.h"

#include <ctype.h>

static const char s_szCaseFilterName[] = "CaseFilter";
module AP_MODULE_DECLARE_DATA case_filter_module;

typedef struct
{
    int bEnabled;
} CaseFilterConfig;

static void *CaseFilterCreateServerConfig(apr_pool_t *p, server_rec *s)
{
    CaseFilterConfig *pConfig = apr_pcalloc(p,sizeof *pConfig);

    pConfig->bEnabled = 0;

    return pConfig;
}

static void CaseFilterInsertFilter(request_rec *r)
{
    CaseFilterConfig *pConfig = ap_get_module_config(r->server->module_config,
                                                     &case_filter_module);

    if (!pConfig->bEnabled)
        return;

    ap_add_output_filter(s_szCaseFilterName, NULL, r, r->connection);
}

static apr_status_t CaseFilterOutFilter(ap_filter_t *f,
                                        apr_bucket_brigade *pbbIn)
{
    request_rec *r = f->r;
    conn_rec *c = r->connection;
    apr_bucket *pbktIn;
    apr_bucket_brigade *pbbOut;

    pbbOut = apr_brigade_create(r->pool, c->bucket_alloc);
    for (pbktIn = APR_BRIGADE_FIRST(pbbIn);
         pbktIn != APR_BRIGADE_SENTINEL(pbbIn);
         pbktIn = APR_BUCKET_NEXT(pbktIn))
    {
        const char *data;
        apr_size_t len;
        char *buf;
        apr_size_t n;
        apr_bucket *pbktOut;

        if (APR_BUCKET_IS_EOS(pbktIn)) {
            apr_bucket *pbktEOS = apr_bucket_eos_create(c->bucket_alloc);
            APR_BRIGADE_INSERT_TAIL(pbbOut, pbktEOS);
            continue;
        }

        /* read */
        apr_bucket_read(pbktIn, &data, &len, APR_BLOCK_READ);

        /* write */
        buf = apr_bucket_alloc(len, c->bucket_alloc);
        for (n=0 ; n < len ; ++n) {
            buf[n] = apr_toupper(data[n]);
        }

        pbktOut = apr_bucket_heap_create(buf, len, apr_bucket_free,
                                         c->bucket_alloc);
        APR_BRIGADE_INSERT_TAIL(pbbOut, pbktOut);
    }

    /* Q: is there any advantage to passing a brigade for each bucket?
     * A: obviously, it can cut down server resource consumption, if this
     * experimental module was fed a file of 4MB, it would be using 8MB for
     * the 'read' buckets and the 'write' buckets.
     *
     * Note it is more efficient to consume (destroy) each bucket as it's
     * processed above than to do a single cleanup down here.  In any case,
     * don't let our caller pass the same buckets to us, twice;
     */
    apr_brigade_cleanup(pbbIn);
    return ap_pass_brigade(f->next, pbbOut);
}

static const char *CaseFilterEnable(cmd_parms *cmd, void *dummy, int arg)
{
    CaseFilterConfig *pConfig = ap_get_module_config(cmd->server->module_config,
                                                     &case_filter_module);
    pConfig->bEnabled = arg;

    return NULL;
}

static const command_rec CaseFilterCmds[] =
{
    AP_INIT_FLAG("CaseFilter", CaseFilterEnable, NULL, RSRC_CONF,
                 "Run a case filter on this host"),
    { NULL }
};

static void CaseFilterRegisterHooks(apr_pool_t *p)
{
    ap_hook_insert_filter(CaseFilterInsertFilter, NULL, NULL, APR_HOOK_MIDDLE);
    ap_register_output_filter(s_szCaseFilterName, CaseFilterOutFilter, NULL,
                              AP_FTYPE_RESOURCE);
}

AP_DECLARE_MODULE(case_filter) =
{
    STANDARD20_MODULE_STUFF,
    NULL,
    NULL,
    CaseFilterCreateServerConfig,
    NULL,
    CaseFilterCmds,
    CaseFilterRegisterHooks
};