util_filter.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。

/* Copyright 2000-2005 The Apache Software Foundation or its licensors, as
 * applicable.
 *
 * Licensed 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.
 */

#define APR_WANT_STRFUNC
#include "apr_want.h"
#include "apr_lib.h"
#include "apr_hash.h"
#include "apr_strings.h"

#include "httpd.h"
#include "http_log.h"
#include "util_filter.h"

/* NOTE: Apache's current design doesn't allow a pool to be passed thru,
   so we depend on a global to hold the correct pool
*/
#define FILTER_POOL     apr_hook_global_pool
#include "apr_hooks.h"   /* for apr_hook_global_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)->frec->ftype > (f)->frec->ftype \
                           || (before_this)->r != (f)->r)

/* Trie structure to hold the mapping from registered
 * filter names to filters
 */

typedef struct filter_trie_node filter_trie_node;

typedef struct {
    int c;
    filter_trie_node *child;
} filter_trie_child_ptr;

/* Each trie node has an array of pointers to its children.
 * The array is kept in sorted order so that add_any_filter()
 * can do a binary search
 */
struct filter_trie_node {
    ap_filter_rec_t *frec;
    filter_trie_child_ptr *children;
    int nchildren;
    int size;
};

#define TRIE_INITIAL_SIZE 4

/* Link a trie node to its parent
 */
static void trie_node_link(apr_pool_t *p, filter_trie_node *parent,
                           filter_trie_node *child, int c)
{
    int i, j;

    if (parent->nchildren == parent->size) {
        filter_trie_child_ptr *new;
        parent->size *= 2;
        new = (filter_trie_child_ptr *)apr_palloc(p, parent->size *
                                             sizeof(filter_trie_child_ptr));
        memcpy(new, parent->children, parent->nchildren *
               sizeof(filter_trie_child_ptr));
        parent->children = new;
    }

    for (i = 0; i < parent->nchildren; i++) {
        if (c == parent->children[i].c) {
            return;
        }
        else if (c < parent->children[i].c) {
            break;
        }
    }
    for (j = parent->nchildren; j > i; j--) {
        parent->children[j].c = parent->children[j - 1].c;
        parent->children[j].child = parent->children[j - 1].child;
    }
    parent->children[i].c = c;
    parent->children[i].child = child;

    parent->nchildren++;
}

/* Allocate a new node for a trie.
 * If parent is non-NULL, link the new node under the parent node with
 * key 'c' (or, if an existing child node matches, return that one)
 */
static filter_trie_node *trie_node_alloc(apr_pool_t *p,
                                         filter_trie_node *parent, char c)
{
    filter_trie_node *new_node;
    if (parent) {
        int i;
        for (i = 0; i < parent->nchildren; i++) {
            if (c == parent->children[i].c) {
                return parent->children[i].child;
            }
            else if (c < parent->children[i].c) {
                break;
            }
        }
        new_node =
            (filter_trie_node *)apr_palloc(p, sizeof(filter_trie_node));
        trie_node_link(p, parent, new_node, c);
    }
    else { /* No parent node */
        new_node = (filter_trie_node *)apr_palloc(p,
                                                  sizeof(filter_trie_node));
    }

    new_node->frec = NULL;
    new_node->nchildren = 0;
    new_node->size = TRIE_INITIAL_SIZE;
    new_node->children = (filter_trie_child_ptr *)apr_palloc(p,
                             new_node->size * sizeof(filter_trie_child_ptr));
    return new_node;
}

static filter_trie_node *registered_output_filters = NULL;
static filter_trie_node *registered_input_filters = NULL;


static apr_status_t filter_cleanup(void *ctx)
{
    registered_output_filters = NULL;
    registered_input_filters = NULL;
    return APR_SUCCESS;
}

static ap_filter_rec_t *get_filter_handle(const char *name,
                                          const filter_trie_node *filter_set)
{
    if (filter_set) {
        const char *n;
        const filter_trie_node *node;

        node = filter_set;
        for (n = name; *n; n++) {
            int start, end;
            start = 0;
            end = node->nchildren - 1;
            while (end >= start) {
                int middle = (end + start) / 2;
                char ch = node->children[middle].c;
                if (*n == ch) {
                    node = node->children[middle].child;
                    break;
                }
                else if (*n < ch) {
                    end = middle - 1;
                }
                else {
                    start = middle + 1;
                }
            }
            if (end < start) {
                node = NULL;
                break;
            }
        }

        if (node && node->frec) {
            return node->frec;
        }
    }
    return NULL;
}

AP_DECLARE(ap_filter_rec_t *)ap_get_output_filter_handle(const char *name)
{
    return get_filter_handle(name, registered_output_filters);
}

AP_DECLARE(ap_filter_rec_t *)ap_get_input_filter_handle(const char *name)
{
    return get_filter_handle(name, registered_input_filters);
}

static ap_filter_rec_t *register_filter(const char *name,
                            ap_filter_func filter_func,
                            ap_init_filter_func filter_init,
                            ap_filter_type ftype,
                            filter_trie_node **reg_filter_set)
{
    ap_filter_rec_t *frec;
    char *normalized_name;
    const char *n;
    filter_trie_node *node;

    if (!*reg_filter_set) {
        *reg_filter_set = trie_node_alloc(FILTER_POOL, NULL, 0);
    }

    normalized_name = apr_pstrdup(FILTER_POOL, name);
    ap_str_tolower(normalized_name);

    node = *reg_filter_set;
    for (n = normalized_name; *n; n++) {
        filter_trie_node *child = trie_node_alloc(FILTER_POOL, node, *n);
        if (apr_isalpha(*n)) {
            trie_node_link(FILTER_POOL, node, child, apr_toupper(*n));
        }
        node = child;
    }
    if (node->frec) {
        frec = node->frec;
    }
    else {
        frec = apr_palloc(FILTER_POOL, sizeof(*frec));
        node->frec = frec;
        frec->name = normalized_name;
    }
    frec->filter_func = filter_func;
    frec->filter_init_func = filter_init;
    frec->ftype = ftype;
    
    apr_pool_cleanup_register(FILTER_POOL, NULL, filter_cleanup, 
                              apr_pool_cleanup_null);
    return frec;
}

AP_DECLARE(ap_filter_rec_t *) ap_register_input_filter(const char *name,
                                          ap_in_filter_func filter_func,
                                          ap_init_filter_func filter_init,
                                          ap_filter_type ftype)
{
    ap_filter_func f;
    f.in_func = filter_func;
    return register_filter(name, f, filter_init, ftype,
                           &registered_input_filters);
}                                                                    

AP_DECLARE(ap_filter_rec_t *) ap_register_output_filter(const char *name,
                                           ap_out_filter_func filter_func,
                                           ap_init_filter_func filter_init,
                                           ap_filter_type ftype)
{
    ap_filter_func f;
    f.out_func = filter_func;
    return register_filter(name, f, filter_init, ftype,
                           &registered_output_filters);
}

static ap_filter_t *add_any_filter_handle(ap_filter_rec_t *frec, void *ctx, 
                                          request_rec *r, conn_rec *c, 
                                          ap_filter_t **r_filters,
                                          ap_filter_t **p_filters,
                                          ap_filter_t **c_filters)
{
    apr_pool_t* p = r ? r->pool : c->pool;
    ap_filter_t *f = apr_palloc(p, sizeof(*f));
    ap_filter_t **outf;

    if (frec->ftype < AP_FTYPE_PROTOCOL) {
        if (r) {
            outf = r_filters;
        }
        else {
            ap_log_error(APLOG_MARK, APLOG_ERR, 0, NULL,
                      "a content filter was added without a request: %s", frec->name);
            return NULL;
        }
    }
    else if (frec->ftype < AP_FTYPE_CONNECTION) {
        if (r) {
            outf = p_filters;
        }
        else {
            ap_log_error(APLOG_MARK, APLOG_ERR, 0, NULL,
                         "a protocol filter was added without a request: %s", frec->name);
            return NULL;
        }
    }
    else {
        outf = c_filters;
    }

    f->frec = frec;
    f->ctx = ctx;
    f->r = r;
    f->c = c;
    f->next = NULL;