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。

    if (INSERT_BEFORE(f, *outf)) {
        f->next = *outf;

        if (*outf) {
            ap_filter_t *first = NULL;

            if (r) {
                /* If we are adding our first non-connection filter,
                 * Then don't try to find the right location, it is
                 * automatically first.
                 */
                if (*r_filters != *c_filters) {
                    first = *r_filters;
                    while (first && (first->next != (*outf))) {
                        first = first->next;
                    }
                }
            }
            if (first && first != (*outf)) {
                first->next = f;
            }
        }
        *outf = f;
    }
    else {
        ap_filter_t *fscan = *outf;
        while (!INSERT_BEFORE(f, fscan->next))
            fscan = fscan->next;

        f->next = fscan->next;
	fscan->next = f;
    }

    if (frec->ftype < AP_FTYPE_CONNECTION && (*r_filters == *c_filters)) {
        *r_filters = *p_filters;
    }
    return f;
}

static ap_filter_t *add_any_filter(const char *name, void *ctx, 
                                   request_rec *r, conn_rec *c, 
                                   const filter_trie_node *reg_filter_set,
                                   ap_filter_t **r_filters, 
                                   ap_filter_t **p_filters,
                                   ap_filter_t **c_filters)
{
    if (reg_filter_set) {
        const char *n;
        const filter_trie_node *node;

        node = reg_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 add_any_filter_handle(node->frec, ctx, r, c, r_filters, 
                                         p_filters, c_filters);
        }
    }

    ap_log_error(APLOG_MARK, APLOG_ERR, 0, NULL,
                 "an unknown filter was not added: %s", name);
    return NULL;
}

AP_DECLARE(ap_filter_t *) ap_add_input_filter(const char *name, void *ctx,
                                              request_rec *r, conn_rec *c)
{
    return add_any_filter(name, ctx, r, c, registered_input_filters,
                          r ? &r->input_filters : NULL, 
                          r ? &r->proto_input_filters : NULL, &c->input_filters);
}

AP_DECLARE(ap_filter_t *) ap_add_input_filter_handle(ap_filter_rec_t *f,
                                                     void *ctx,
                                                     request_rec *r,
                                                     conn_rec *c)
{
    return add_any_filter_handle(f, ctx, r, c, r ? &r->input_filters : NULL,
                                 r ? &r->proto_input_filters : NULL, 
                                 &c->input_filters);
}

AP_DECLARE(ap_filter_t *) ap_add_output_filter(const char *name, void *ctx,
                                               request_rec *r, conn_rec *c)
{
    return add_any_filter(name, ctx, r, c, registered_output_filters,
                          r ? &r->output_filters : NULL, 
                          r ? &r->proto_output_filters : NULL, &c->output_filters);
}

AP_DECLARE(ap_filter_t *) ap_add_output_filter_handle(ap_filter_rec_t *f,
                                                      void *ctx,
                                                      request_rec *r,
                                                      conn_rec *c)
{
    return add_any_filter_handle(f, ctx, r, c, r ? &r->output_filters : NULL,
                                 r ? &r->proto_output_filters : NULL,
                                 &c->output_filters);
}

static void remove_any_filter(ap_filter_t *f, ap_filter_t **r_filt, ap_filter_t **p_filt,
                              ap_filter_t **c_filt)
{
    ap_filter_t **curr = r_filt ? r_filt : c_filt;
    ap_filter_t *fscan = *curr;

    if (p_filt && *p_filt == f)
        *p_filt = (*p_filt)->next;

    if (*curr == f) {
        *curr = (*curr)->next;
        return;
    }

    while (fscan->next != f) {
        if (!(fscan = fscan->next)) {
            return;
        }
    }

    fscan->next = f->next;
}

AP_DECLARE(void) ap_remove_input_filter(ap_filter_t *f)
{
    remove_any_filter(f, f->r ? &f->r->input_filters : NULL, 
                      f->r ? &f->r->proto_input_filters : NULL, 
                      &f->c->input_filters);
}

AP_DECLARE(void) ap_remove_output_filter(ap_filter_t *f)
{
    remove_any_filter(f, f->r ? &f->r->output_filters : NULL, 
                      f->r ? &f->r->proto_output_filters : NULL, 
                      &f->c->output_filters);
}

/* 
 * Read data from the next filter in the filter stack.  Data should be 
 * modified in the bucket brigade that is passed in.  The core allocates the
 * bucket brigade, modules that wish to replace large chunks of data or to
 * save data off to the side should probably create their own temporary
 * brigade especially for that use.
 */
AP_DECLARE(apr_status_t) ap_get_brigade(ap_filter_t *next,
                                        apr_bucket_brigade *bb, 
                                        ap_input_mode_t mode,
                                        apr_read_type_e block,
                                        apr_off_t readbytes)
{
    if (next) {
        return next->frec->filter_func.in_func(next, bb, mode, block, 
                                               readbytes);
    }
    return AP_NOBODY_READ;
}

/* Pass the buckets to the next filter in the filter stack.  If the
 * current filter is a handler, we should get NULL passed in instead of
 * the current filter.  At that point, we can just call the first filter in
 * the stack, or r->output_filters.
 */
AP_DECLARE(apr_status_t) ap_pass_brigade(ap_filter_t *next, 
                                         apr_bucket_brigade *bb)
{
    if (next) {
        apr_bucket *e;
        if ((e = APR_BRIGADE_LAST(bb)) && APR_BUCKET_IS_EOS(e) && next->r) {
            /* This is only safe because HTTP_HEADER filter is always in
             * the filter stack.   This ensures that there is ALWAYS a
             * request-based filter that we can attach this to.  If the
             * HTTP_FILTER is removed, and another filter is not put in its
             * place, then handlers like mod_cgi, which attach their own
             * EOS bucket to the brigade will be broken, because we will
             * get two EOS buckets on the same request.
             */
            next->r->eos_sent = 1;

            /* remember the eos for internal redirects, too */
            if (next->r->prev) {
                request_rec *prev = next->r->prev;

                while (prev) {
                    prev->eos_sent = 1;
                    prev = prev->prev;
                }
            }
        }
        return next->frec->filter_func.out_func(next, bb);
    }
    return AP_NOBODY_WROTE;
}

AP_DECLARE(apr_status_t) ap_save_brigade(ap_filter_t *f, 
                                         apr_bucket_brigade **saveto,
                                         apr_bucket_brigade **b, apr_pool_t *p)
{
    apr_bucket *e;
    apr_status_t rv, srv = APR_SUCCESS;

    /* If have never stored any data in the filter, then we had better
     * create an empty bucket brigade so that we can concat.
     */
    if (!(*saveto)) {
        *saveto = apr_brigade_create(p, f->c->bucket_alloc);
    }
    
    APR_RING_FOREACH(e, &(*b)->list, apr_bucket, link) {
        rv = apr_bucket_setaside(e, p);

        /* If the bucket type does not implement setaside, then
         * (hopefully) morph it into a bucket type which does, and set
         * *that* aside... */
        if (rv == APR_ENOTIMPL) {
            const char *s;
            apr_size_t n;

            rv = apr_bucket_read(e, &s, &n, APR_BLOCK_READ);
            if (rv == APR_SUCCESS) {
                rv = apr_bucket_setaside(e, p);
            }
        }

        if (rv != APR_SUCCESS) {
            srv = rv;
            /* Return an error but still save the brigade if
             * ->setaside() is really not implemented. */
            if (rv != APR_ENOTIMPL) {
                return rv;
            }
        }
    }
    APR_BRIGADE_CONCAT(*saveto, *b);
    return srv;
}

AP_DECLARE_NONSTD(apr_status_t) ap_filter_flush(apr_bucket_brigade *bb, 
                                                void *ctx)
{
    ap_filter_t *f = ctx;

    return ap_pass_brigade(f, bb);
}

AP_DECLARE(apr_status_t) ap_fflush(ap_filter_t *f, apr_bucket_brigade *bb)
{
    apr_bucket *b;

    b = apr_bucket_flush_create(f->c->bucket_alloc);
    APR_BRIGADE_INSERT_TAIL(bb, b);
    return ap_pass_brigade(f, bb);
}

AP_DECLARE_NONSTD(apr_status_t) ap_fputstrs(ap_filter_t *f,
                                            apr_bucket_brigade *bb, ...)
{
    va_list args;
    apr_status_t rv;

    va_start(args, bb);
    rv = apr_brigade_vputstrs(bb, ap_filter_flush, f, args);
    va_end(args);
    return rv;
}

AP_DECLARE_NONSTD(apr_status_t) ap_fprintf(ap_filter_t *f,
                                           apr_bucket_brigade *bb,
                                           const char *fmt,
                                           ...)
{
    va_list args;
    apr_status_t rv;

    va_start(args, fmt);
    rv = apr_brigade_vprintf(bb, ap_filter_flush, f, fmt, args);
    va_end(args);
    return rv;
}