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/* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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* Andrew Wilson <Andrew.Wilson@cm.cf.ac.uk> 26.Jan.96
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* This module allows you to control the form of the Expires: header
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* that Apache issues for each access. Directives can appear in
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* configuration files or in .htaccess files so expiry semantics can
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* be defined on a per-directory basis.
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* Valid directives are:
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* ExpiresActive on | off
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* ExpiresDefault <code><seconds>
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* ExpiresByType type/encoding <code><seconds>
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* Valid values for <code> are:
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* 'M' expires header shows file modification date + <seconds>
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* 'A' expires header shows access time + <seconds>
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* [I'm not sure which of these is best under different
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* circumstances, I guess it's for other people to explore.
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* The effects may be indistinguishable for a number of cases]
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* <seconds> should be an integer value [acceptable to atoi()]
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* There is NO space between the <code> and <seconds>.
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* For example, a directory which contains information which changes
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* frequently might contain:
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* # reports generated by cron every hour. don't let caches
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* # hold onto stale information
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* ExpiresDefault M3600
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* Another example, our html pages can change all the time, the gifs
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* tend not to change often:
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* # pages are hot (1 week), images are cold (1 month)
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* ExpiresByType text/html A604800
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* ExpiresByType image/gif A2592000
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* Expires can be turned on for all URLs on the server by placing the
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* following directive in a conf file:
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* ExpiresActive can also appear in .htaccess files, enabling the
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* behaviour to be turned on or off for each chosen directory.
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* # turn off Expires behaviour in this directory
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* # and subdirectories
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* Directives defined for a directory are valid in subdirectories
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* unless explicitly overridden by new directives in the subdirectory
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* ALTERNATIVE DIRECTIVE SYNTAX
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* Directives can also be defined in a more readable syntax of the form:
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* ExpiresDefault "<base> [plus] {<num> <type>}*"
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* ExpiresByType type/encoding "<base> [plus] {<num> <type>}*"
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* where <base> is one of:
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* now equivalent to 'access'
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* where the 'plus' keyword is optional
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* where <num> should be an integer value [acceptable to atoi()]
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* where <type> is one of:
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* For example, any of the following directives can be used to make
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* documents expire 1 month after being accessed, by default:
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* ExpiresDefault "access plus 1 month"
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* ExpiresDefault "access plus 4 weeks"
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* ExpiresDefault "access plus 30 days"
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* The expiry time can be fine-tuned by adding several '<num> <type>'
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* ExpiresByType text/html "access plus 1 month 15 days 2 hours"
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* ExpiresByType image/gif "modification plus 5 hours 3 minutes"
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* 29.Jan.96 Hardened the add_* functions. Server will now bail out
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* if bad directives are given in the conf files.
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* 02.Feb.96 Returns DECLINED if not 'ExpiresActive on', giving other
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* expires-aware modules a chance to play with the same
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* directives. [Michael Rutman]
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* 03.Feb.96 Call tzset() before localtime(). Trying to get the module
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* to work properly in non GMT timezones.
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* 12.Feb.96 Modified directive syntax to allow more readable commands:
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* ExpiresDefault "now plus 10 days 20 seconds"
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* ExpiresDefault "access plus 30 days"
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* ExpiresDefault "modification plus 1 year 10 months 30 days"
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* 13.Feb.96 Fix call to table_get() with NULL 2nd parameter [Rob Hartill]
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* 19.Feb.96 Call gm_timestr_822() to get time formatted correctly, can't
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* rely on presence of HTTP_TIME_FORMAT in Apache 1.1+.
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* 21.Feb.96 This version (0.0.9) reverses assumptions made in 0.0.8
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* about star/star handlers. Reverting to 0.0.7 behaviour.
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* 08.Jun.96 allows ExpiresDefault to be used with responses that use
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* the DefaultType by not DECLINING, but instead skipping
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* the table_get check and then looking for an ExpiresDefault.
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* 04.Nov.96 'const' definitions added.
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* add support for Cache-Control: max-age=20 from the HTTP/1.1
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* proposal (in this case, a ttl of 20 seconds) [ask roy]
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* add per-file expiry and explicit expiry times - duplicates some
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* of the mod_cern_meta.c functionality. eg:
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* ExpiresExplicit index.html "modification plus 30 days"
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* Hi, welcome to the internet.
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#include "apr_strings.h"
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#define APR_WANT_STRFUNC
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#include "apr_want.h"
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#include "ap_config.h"
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#include "http_config.h"
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#include "http_log.h"
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#include "http_request.h"
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#include "http_protocol.h"
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char *expiresdefault;
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apr_table_t *expiresbytype;
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} expires_dir_config;
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/* from mod_dir, why is this alias used?
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#define DIR_CMD_PERMS OR_INDEXES
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#define ACTIVE_DONTCARE 2
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module AP_MODULE_DECLARE_DATA expires_module;
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static void *create_dir_expires_config(apr_pool_t *p, char *dummy)
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expires_dir_config *new =
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(expires_dir_config *) apr_pcalloc(p, sizeof(expires_dir_config));
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new->active = ACTIVE_DONTCARE;
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new->expiresdefault = NULL;
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new->expiresbytype = apr_table_make(p, 4);
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static const char *set_expiresactive(cmd_parms *cmd, void *in_dir_config, int arg)
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expires_dir_config *dir_config = in_dir_config;
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/* if we're here at all it's because someone explicitly
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* set the active flag
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dir_config->active = ACTIVE_ON;
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dir_config->active = ACTIVE_OFF;
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/* check_code() parse 'code' and return NULL or an error response
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* string. If we return NULL then real_code contains code converted
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* to the cnnnn format.
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static char *check_code(apr_pool_t *p, const char *code, char **real_code)
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/* 0.0.4 compatibility?
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if ((code[0] == 'A') || (code[0] == 'M')) {
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*real_code = (char *)code;
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/* <base> [plus] {<num> <type>}*
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word = ap_getword_conf(p, &code);
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if (!strncasecmp(word, "now", 1) ||
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!strncasecmp(word, "access", 1)) {
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else if (!strncasecmp(word, "modification", 1)) {
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return apr_pstrcat(p, "bad expires code, unrecognised <base> '",
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word = ap_getword_conf(p, &code);
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if (!strncasecmp(word, "plus", 1)) {
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word = ap_getword_conf(p, &code);
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if (apr_isdigit(word[0])) {
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return apr_pstrcat(p, "bad expires code, numeric value expected <num> '",
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word = ap_getword_conf(p, &code);
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return apr_pstrcat(p, "bad expires code, missing <type>", NULL);
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if (!strncasecmp(word, "years", 1)) {
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factor = 60 * 60 * 24 * 365;
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else if (!strncasecmp(word, "months", 2)) {
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factor = 60 * 60 * 24 * 30;
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else if (!strncasecmp(word, "weeks", 1)) {
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factor = 60 * 60 * 24 * 7;
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else if (!strncasecmp(word, "days", 1)) {
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factor = 60 * 60 * 24;
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else if (!strncasecmp(word, "hours", 1)) {
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else if (!strncasecmp(word, "minutes", 2)) {
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else if (!strncasecmp(word, "seconds", 1)) {
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return apr_pstrcat(p, "bad expires code, unrecognised <type>",
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"'", word, "'", NULL);
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modifier = modifier + factor * num;
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word = ap_getword_conf(p, &code);
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*real_code = apr_psprintf(p, "%c%d", base, modifier);
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static const char *set_expiresbytype(cmd_parms *cmd, void *in_dir_config,
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const char *mime, const char *code)
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expires_dir_config *dir_config = in_dir_config;
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char *response, *real_code;
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check = ap_strrchr_c(mime, '/');
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if ((strlen(++check) == 1) && (*check == '*')) {
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dir_config->wildcards = 1;
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if ((response = check_code(cmd->pool, code, &real_code)) == NULL) {
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apr_table_setn(dir_config->expiresbytype, mime, real_code);
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return apr_pstrcat(cmd->pool,
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"'ExpiresByType ", mime, " ", code, "': ", response, NULL);
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static const char *set_expiresdefault(cmd_parms *cmd, void *in_dir_config,
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expires_dir_config * dir_config = in_dir_config;
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char *response, *real_code;
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if ((response = check_code(cmd->pool, code, &real_code)) == NULL) {
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dir_config->expiresdefault = real_code;
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return apr_pstrcat(cmd->pool,
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"'ExpiresDefault ", code, "': ", response, NULL);
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static const command_rec expires_cmds[] =
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AP_INIT_FLAG("ExpiresActive", set_expiresactive, NULL, DIR_CMD_PERMS,
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"Limited to 'on' or 'off'"),
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AP_INIT_TAKE2("ExpiresByType", set_expiresbytype, NULL, DIR_CMD_PERMS,
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"a MIME type followed by an expiry date code"),
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AP_INIT_TAKE1("ExpiresDefault", set_expiresdefault, NULL, DIR_CMD_PERMS,
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"an expiry date code"),
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static void *merge_expires_dir_configs(apr_pool_t *p, void *basev, void *addv)
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expires_dir_config *new = (expires_dir_config *) apr_pcalloc(p, sizeof(expires_dir_config));
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expires_dir_config *base = (expires_dir_config *) basev;
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expires_dir_config *add = (expires_dir_config *) addv;
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if (add->active == ACTIVE_DONTCARE) {
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new->active = base->active;
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new->active = add->active;
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if (add->expiresdefault != NULL) {
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new->expiresdefault = add->expiresdefault;
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new->expiresdefault = base->expiresdefault;
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new->wildcards = add->wildcards;
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new->expiresbytype = apr_table_overlay(p, add->expiresbytype,
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base->expiresbytype);
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* Handle the setting of the expiration response header fields according
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static int set_expiration_fields(request_rec *r, const char *code,
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apr_time_t additional;
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if (r->finfo.filetype == 0) {
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/* file doesn't exist on disk, so we can't do anything based on
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* modification time. Note that this does _not_ log an error.
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base = r->finfo.mtime;
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additional_sec = atoi(&code[1]);
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additional = apr_time_from_sec(additional_sec);
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/* there's been some discussion and it's possible that
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* 'access time' will be stored in request structure
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base = r->request_time;
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additional_sec = atoi(&code[1]);
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additional = apr_time_from_sec(additional_sec);
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/* expecting the add_* routines to be case-hardened this
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* is just a reminder that module is beta
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ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
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"internal error: bad expires code: %s", r->filename);
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return HTTP_INTERNAL_SERVER_ERROR;
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expires = base + additional;
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apr_table_mergen(t, "Cache-Control",
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apr_psprintf(r->pool, "max-age=%" APR_TIME_T_FMT,
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apr_time_sec(expires - r->request_time)));
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timestr = apr_palloc(r->pool, APR_RFC822_DATE_LEN);
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apr_rfc822_date(timestr, expires);
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apr_table_setn(t, "Expires", timestr);
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* Output filter to set the Expires response header field
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* according to the content-type of the response -- if it hasn't
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static apr_status_t expires_filter(ap_filter_t *f,
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apr_bucket_brigade *b)
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expires_dir_config *conf;
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conf = (expires_dir_config *) ap_get_module_config(r->per_dir_config,
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* Check to see which output header table we should use;
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* mod_cgi loads script fields into r->err_headers_out,
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expiry = apr_table_get(r->err_headers_out, "Expires");
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if (expiry != NULL) {
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t = r->err_headers_out;
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expiry = apr_table_get(r->headers_out, "Expires");
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if (expiry == NULL) {
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* No expiration has been set, so we can apply any managed by
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* this module. First, check to see if there is an applicable
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* ExpiresByType directive.
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expiry = apr_table_get(conf->expiresbytype,
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ap_field_noparam(r->pool, r->content_type));
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if (expiry == NULL) {
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* See if we have a wildcard entry for the major type.
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if (conf->wildcards) {
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checkmime = apr_pstrdup(r->pool, r->content_type);
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spos = checkmime ? ap_strchr(checkmime, '/') : NULL;
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* Without a '/' character, nothing we have will match.
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* However, we have one.
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if (strlen(++spos) > 0) {
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checkmime = apr_pstrcat(r->pool, checkmime, "*", NULL);
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expiry = apr_table_get(conf->expiresbytype, checkmime);
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usedefault = (expiry == NULL);
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* Use the ExpiresDefault directive
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expiry = conf->expiresdefault;
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if (expiry != NULL) {
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set_expiration_fields(r, expiry, t);
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ap_remove_output_filter(f);
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return ap_pass_brigade(f->next, b);
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static void expires_insert_filter(request_rec *r)
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expires_dir_config *conf;
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/* Don't add Expires headers to errors */
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if (ap_is_HTTP_ERROR(r->status)) {
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/* Say no to subrequests */
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if (r->main != NULL) {
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conf = (expires_dir_config *) ap_get_module_config(r->per_dir_config,
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/* Check to see if the filter is enabled and if there are any applicable
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* config directives for this directory scope
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if (conf->active != ACTIVE_ON ||
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(apr_is_empty_table(conf->expiresbytype) && !conf->expiresdefault)) {
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ap_add_output_filter("MOD_EXPIRES", NULL, r, r->connection);
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static void register_hooks(apr_pool_t *p)
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/* mod_expires needs to run *before* the cache save filter which is
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* AP_FTYPE_CONTENT_SET-1. Otherwise, our expires won't be honored.
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ap_register_output_filter("MOD_EXPIRES", expires_filter, NULL,
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AP_FTYPE_CONTENT_SET-2);
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ap_hook_insert_error_filter(expires_insert_filter, NULL, NULL, APR_HOOK_MIDDLE);
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ap_hook_insert_filter(expires_insert_filter, NULL, NULL, APR_HOOK_MIDDLE);
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module AP_MODULE_DECLARE_DATA expires_module =
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STANDARD20_MODULE_STUFF,
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create_dir_expires_config, /* dir config creater */
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merge_expires_dir_configs, /* dir merger --- default is to override */
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NULL, /* server config */
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NULL, /* merge server configs */
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expires_cmds, /* command apr_table_t */
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register_hooks /* register hooks */