mod_expires.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。

        }
        else if (!strncasecmp(word, "weeks", 1)) {
            factor = 60 * 60 * 24 * 7;
        }
        else if (!strncasecmp(word, "days", 1)) {
            factor = 60 * 60 * 24;
        }
        else if (!strncasecmp(word, "hours", 1)) {
            factor = 60 * 60;
        }
        else if (!strncasecmp(word, "minutes", 2)) {
            factor = 60;
        }
        else if (!strncasecmp(word, "seconds", 1)) {
            factor = 1;
        }
        else {
            return apr_pstrcat(p, "bad expires code, unrecognised <type>",
                           "'", word, "'", NULL);
        }

        modifier = modifier + factor * num;

        /* next <num>
         */
        word = ap_getword_conf(p, &code);
    }

    *real_code = apr_psprintf(p, "%c%d", base, modifier);

    return NULL;
}

static const char *set_expiresbytype(cmd_parms *cmd, void *in_dir_config,
                                     const char *mime, const char *code)
{
    expires_dir_config *dir_config = in_dir_config;
    char *response, *real_code;
    const char *check;

    check = ap_strrchr_c(mime, '/');
    if ((strlen(++check) == 1) && (*check == '*')) {
        dir_config->wildcards = 1;
    }
    
    if ((response = check_code(cmd->pool, code, &real_code)) == NULL) {
        apr_table_setn(dir_config->expiresbytype, mime, real_code);
        return NULL;
    }
    return apr_pstrcat(cmd->pool,
                 "'ExpiresByType ", mime, " ", code, "': ", response, NULL);
}

static const char *set_expiresdefault(cmd_parms *cmd, void *in_dir_config,
                                      const char *code)
{
    expires_dir_config * dir_config = in_dir_config;
    char *response, *real_code;

    if ((response = check_code(cmd->pool, code, &real_code)) == NULL) {
        dir_config->expiresdefault = real_code;
        return NULL;
    }
    return apr_pstrcat(cmd->pool,
                   "'ExpiresDefault ", code, "': ", response, NULL);
}

static const command_rec expires_cmds[] =
{
    AP_INIT_FLAG("ExpiresActive", set_expiresactive, NULL, DIR_CMD_PERMS,
                 "Limited to 'on' or 'off'"),
    AP_INIT_TAKE2("ExpiresByType", set_expiresbytype, NULL, DIR_CMD_PERMS,
                  "a MIME type followed by an expiry date code"),
    AP_INIT_TAKE1("ExpiresDefault", set_expiresdefault, NULL, DIR_CMD_PERMS,
                  "an expiry date code"),
    {NULL}
};

static void *merge_expires_dir_configs(apr_pool_t *p, void *basev, void *addv)
{
    expires_dir_config *new = (expires_dir_config *) apr_pcalloc(p, sizeof(expires_dir_config));
    expires_dir_config *base = (expires_dir_config *) basev;
    expires_dir_config *add = (expires_dir_config *) addv;

    if (add->active == ACTIVE_DONTCARE) {
        new->active = base->active;
    }
    else {
        new->active = add->active;
    }

    if (add->expiresdefault != NULL) {
        new->expiresdefault = add->expiresdefault;
    }
    else {
	new->expiresdefault = base->expiresdefault;
    }
    new->wildcards = add->wildcards;
    new->expiresbytype = apr_table_overlay(p, add->expiresbytype,
                                        base->expiresbytype);
    return new;
}

/*
 * Handle the setting of the expiration response header fields according
 * to our criteria.
 */

static int set_expiration_fields(request_rec *r, const char *code,
                                 apr_table_t *t)
{
    apr_time_t base;
    apr_time_t additional;
    apr_time_t expires;
    int additional_sec;
    char *timestr;

    switch (code[0]) {
    case 'M':
	if (r->finfo.filetype == 0) { 
	    /* file doesn't exist on disk, so we can't do anything based on
	     * modification time.  Note that this does _not_ log an error.
	     */
	    return DECLINED;
	}
	base = r->finfo.mtime;
        additional_sec = atoi(&code[1]);
        additional = apr_time_from_sec(additional_sec);
        break;
    case 'A':
        /* there's been some discussion and it's possible that 
         * 'access time' will be stored in request structure
         */
        base = r->request_time;
        additional_sec = atoi(&code[1]);
        additional = apr_time_from_sec(additional_sec);
        break;
    default:
        /* expecting the add_* routines to be case-hardened this 
         * is just a reminder that module is beta
         */
        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
                    "internal error: bad expires code: %s", r->filename);
        return HTTP_INTERNAL_SERVER_ERROR;
    }

    expires = base + additional;
    apr_table_mergen(t, "Cache-Control",
                     apr_psprintf(r->pool, "max-age=%" APR_TIME_T_FMT,
                                  apr_time_sec(expires - r->request_time)));
    timestr = apr_palloc(r->pool, APR_RFC822_DATE_LEN);
    apr_rfc822_date(timestr, expires);
    apr_table_setn(t, "Expires", timestr);
    return OK;
}

/*
 * Output filter to set the Expires response header field
 * according to the content-type of the response -- if it hasn't
 * already been set.
 */
static apr_status_t expires_filter(ap_filter_t *f,
                                   apr_bucket_brigade *b)
{
    request_rec *r;
    expires_dir_config *conf;
    const char *expiry;
    apr_table_t *t;

    r = f->r;
    conf = (expires_dir_config *) ap_get_module_config(r->per_dir_config,
                                                       &expires_module);

    /*
     * Check to see which output header table we should use;
     * mod_cgi loads script fields into r->err_headers_out,
     * for instance.
     */
    expiry = apr_table_get(r->err_headers_out, "Expires");
    if (expiry != NULL) {
        t = r->err_headers_out;
    }
    else {
        expiry = apr_table_get(r->headers_out, "Expires");
        t = r->headers_out;
    }
    if (expiry == NULL) {
        /*
         * No expiration has been set, so we can apply any managed by
         * this module.  First, check to see if there is an applicable
         * ExpiresByType directive.
         */
        expiry = apr_table_get(conf->expiresbytype, 
                               ap_field_noparam(r->pool, r->content_type));
        if (expiry == NULL) {
            int usedefault = 1;
            /*
             * See if we have a wildcard entry for the major type.
             */
            if (conf->wildcards) {
                char *checkmime;
                char *spos;
                checkmime = apr_pstrdup(r->pool, r->content_type);
                spos = checkmime ? ap_strchr(checkmime, '/') : NULL;
                if (spos != NULL) {
                    /*
                     * Without a '/' character, nothing we have will match.
                     * However, we have one.
                     */
                    if (strlen(++spos) > 0) {
                        *spos++ = '*';
                        *spos = '\0';
                    }
                    else {
                        checkmime = apr_pstrcat(r->pool, checkmime, "*", NULL);
                    }
                    expiry = apr_table_get(conf->expiresbytype, checkmime);
                    usedefault = (expiry == NULL);
                }
            }
            if (usedefault) {
                /*
                 * Use the ExpiresDefault directive
                 */
                expiry = conf->expiresdefault;
            }
        }
        if (expiry != NULL) {
            set_expiration_fields(r, expiry, t);
        }
    }
    ap_remove_output_filter(f);
    return ap_pass_brigade(f->next, b);
}

static void expires_insert_filter(request_rec *r)
{
    expires_dir_config *conf;

    /* Don't add Expires headers to errors */
    if (ap_is_HTTP_ERROR(r->status)) {
        return;
    }
    /* Say no to subrequests */
    if (r->main != NULL) {
        return;
    }
    conf = (expires_dir_config *) ap_get_module_config(r->per_dir_config,
                                                       &expires_module);

    /* Check to see if the filter is enabled and if there are any applicable 
     * config directives for this directory scope
     */
    if (conf->active != ACTIVE_ON ||
        (apr_is_empty_table(conf->expiresbytype) && !conf->expiresdefault)) {
        return;
    }
    ap_add_output_filter("MOD_EXPIRES", NULL, r, r->connection);
    return;
}
static void register_hooks(apr_pool_t *p)
{
    /* mod_expires needs to run *before* the cache save filter which is
     * AP_FTYPE_CONTENT_SET-1.  Otherwise, our expires won't be honored.
     */
    ap_register_output_filter("MOD_EXPIRES", expires_filter, NULL,
                              AP_FTYPE_CONTENT_SET-2);
    ap_hook_insert_error_filter(expires_insert_filter, NULL, NULL, APR_HOOK_MIDDLE);
    ap_hook_insert_filter(expires_insert_filter, NULL, NULL, APR_HOOK_MIDDLE);
}

module AP_MODULE_DECLARE_DATA expires_module =
{
    STANDARD20_MODULE_STUFF,
    create_dir_expires_config,  /* dir config creater */
    merge_expires_dir_configs,  /* dir merger --- default is to override */
    NULL,                       /* server config */
    NULL,                       /* merge server configs */
    expires_cmds,               /* command apr_table_t */
    register_hooks		/* register hooks */
};