1 /* ====================================================================
2 * The Apache Software License, Version 1.1
4 * Copyright (c) 2000 The Apache Software Foundation. All rights
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in
16 * the documentation and/or other materials provided with the
19 * 3. The end-user documentation included with the redistribution,
20 * if any, must include the following acknowledgment:
21 * "This product includes software developed by the
22 * Apache Software Foundation (http://www.apache.org/)."
23 * Alternately, this acknowledgment may appear in the software itself,
24 * if and wherever such third-party acknowledgments normally appear.
26 * 4. The names "Apache" and "Apache Software Foundation" must
27 * not be used to endorse or promote products derived from this
28 * software without prior written permission. For written
29 * permission, please contact apache@apache.org.
31 * 5. Products derived from this software may not be called "Apache",
32 * nor may "Apache" appear in their name, without prior written
33 * permission of the Apache Software Foundation.
35 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
36 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
37 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
38 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
39 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
40 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
41 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
42 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
43 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
44 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
45 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
47 * ====================================================================
49 * This software consists of voluntary contributions made by many
50 * individuals on behalf of the Apache Software Foundation. For more
51 * information on the Apache Software Foundation, please see
52 * <http://www.apache.org/>.
62 #ifdef APR_HAVE_STDARG_H
68 #include "ap_buckets.h"
71 * @package Apache filter library
74 #define AP_NOBODY_WROTE -1
75 #define AP_NOBODY_READ -2
76 #define AP_REQUEST_DONE -3
78 /* ap_input_mode_t - input filtering modes
82 * The filter shouldn't return until data is received or EOF is hit or an error
87 * The filter should process any available data/status as normal, but will not
88 * wait for additional data.
92 * The filter should return APR_SUCCESS if data is available or APR_EOF
93 * otherwise. The filter must not return any buckets of data. Data returned
94 * on a subsequent call, when mode is AP_MODE_BLOCKING or AP_MODE_NONBLOCKING.
105 * Filters operate using a "chaining" mechanism. The filters are chained
106 * together into a sequence. When output is generated, it is passed through
107 * each of the filters on this chain, until it reaches the end (or "bottom")
108 * and is placed onto the network.
110 * The top of the chain, the code generating the output, is typically called
111 * a "content generator." The content generator's output is fed into the
112 * filter chain using the standard Apache output mechanisms: ap_rputs(),
113 * ap_rprintf(), ap_rwrite(), etc.
115 * Each filter is defined by a callback. This callback takes the output from
116 * the previous filter (or the content generator if there is no previous
117 * filter), operates on it, and passes the result to the next filter in the
118 * chain. This pass-off is performed using the ap_fc_* functions, such as
119 * ap_fc_puts(), ap_fc_printf(), ap_fc_write(), etc.
121 * When content generation is complete, the system will pass an "end of
122 * stream" marker into the filter chain. The filters will use this to flush
123 * out any internal state and to detect incomplete syntax (for example, an
124 * unterminated SSI directive).
127 /* forward declare the filter type */
128 typedef struct ap_filter_t ap_filter_t;
133 * This function type is used for filter callbacks. It will be passed a
134 * pointer to "this" filter, and a "bucket" containing the content to be
137 * In filter->ctx, the callback will find its context. This context is
138 * provided here, so that a filter may be installed multiple times, each
139 * receiving its own per-install context pointer.
141 * Callbacks are associated with a filter definition, which is specified
142 * by name. See ap_register_input_filter() and ap_register_output_filter()
143 * for setting the association between a name for a filter and its
144 * associated callback (and other information).
146 * The *bucket structure (and all those referenced by ->next and ->prev)
147 * should be considered "const". The filter is allowed to modify the
148 * next/prev to insert/remove/replace elements in the bucket list, but
149 * the types and values of the individual buckets should not be altered.
151 * The return value of a filter should be an APR status value.
153 typedef apr_status_t (*ap_out_filter_func)(ap_filter_t *f, ap_bucket_brigade *b);
154 typedef apr_status_t (*ap_in_filter_func)(ap_filter_t *f, ap_bucket_brigade *b,
155 ap_input_mode_t mode);
156 typedef union ap_filter_func {
157 ap_out_filter_func out_func;
158 ap_in_filter_func in_func;
164 * Filters have different types/classifications. These are used to group
165 * and sort the filters to properly sequence their operation.
168 * These filters are used to alter the content that is passed through
169 * them. Examples are SSI or PHP.
171 * AP_FTYPE_HTTP_HEADER: (XXX somebody rename me or get rid of me please)
172 * This special type ensures that the HTTP header filter ends up in
173 * the proper location in the filter chain.
175 * AP_FTYPE_TRANSCODE:
176 * These filters implement transport encodings (e.g., chunking).
178 * AP_FTYPE_CONNECTION:
179 * These filters will alter the content, but in ways that are more
180 * strongly associated with the connection. Examples are splitting
181 * an HTTP connection into multiple requests and buffering HTTP
182 * responses across multiple requests.
184 * It is important to note that these types of filters are not allowed
185 * in a sub-request. A sub-request's output can certainly be filtered
186 * by AP_FTYPE_CONTENT filters, but all of the "final processing" is
187 * determined by the main request.
190 * These filters don't alter the content. They are responsible for
191 * sending/receiving data to/from the client.
193 * The types have a particular sort order, which allows us to insert them
194 * into the filter chain in a determistic order. Within a particular grouping,
195 * the ordering is equivalent to the order of calls to ap_add_*_filter().
198 AP_FTYPE_CONTENT = 10,
199 AP_FTYPE_HTTP_HEADER = 20,
200 AP_FTYPE_TRANSCODE = 30,
201 AP_FTYPE_CONNECTION = 40,
202 AP_FTYPE_NETWORK = 50
208 * This is the request-time context structure for an installed filter (in
209 * the output filter chain). It provides the callback to use for filtering,
210 * the request this filter is associated with (which is important when
211 * an output chain also includes sub-request filters), the context for this
212 * installed filter, and the filter ordering/chaining fields.
214 * Filter callbacks are free to use ->ctx as they please, to store context
215 * during the filter process. Generally, this is superior over associating
216 * the state directly with the request. A callback should not change any of
220 typedef struct ap_filter_rec_t ap_filter_rec_t;
223 * This structure is used for recording information about the
224 * registered filters. It associates a name with the filter's callback
227 * At the moment, these are simply linked in a chain, so a ->next pointer
230 struct ap_filter_rec_t {
231 /** The registered name for this filter */
233 /** The function to call when this filter is invoked. */
234 ap_filter_func filter_func;
235 /** The type of filter, either AP_FTYPE_CONTENT or AP_FTYPE_CONNECTION.
236 * An AP_FTYPE_CONTENT filter modifies the data based on information
237 * found in the content. An AP_FTYPE_CONNECTION filter modifies the
238 * data based on the type of connection.
240 ap_filter_type ftype;
242 /** The next filter_rec in the list */
243 struct ap_filter_rec_t *next;
247 * The representation of a filter chain. Each request has a list
248 * of these structures which are called in turn to filter the data. Sub
249 * requests get an exact copy of the main requests filter chain.
252 /** The internal representation of this filter. This includes
253 * the filter's name, type, and the actual function pointer.
255 ap_filter_rec_t *frec;
257 /** A place to store any data associated with the current filter */
260 /** The next filter in the chain */
263 /** The request_rec associated with the current filter. If a sub-request
264 * adds filters, then the sub-request is the request associated with the
269 /** The conn_rec associated with the current filter. This is analogous
270 * to the request_rec, except that it is used for input filtering.
276 * Get the current bucket brigade from the next filter on the filter
277 * stack. The filter should return an apr_status_t value. If the bottom-most
278 * filter doesn't write to the network, then AP_NOBODY_READ is returned.
279 * @param filter The next filter in the chain
280 * @param bucket The current bucket brigade
281 * @param mode AP_MODE_BLOCKING, AP_MODE_NONBLOCKING, or AP_MODE_PEEK
282 * @return apr_status_t value
283 * @deffunc apr_status_t ap_get_brigade(ap_filter_t *filter, ap_bucket_brigade *bucket, ap_input_mode_t mode)
285 AP_DECLARE(apr_status_t) ap_get_brigade(ap_filter_t *filter, ap_bucket_brigade *bucket,
286 ap_input_mode_t mode);
289 * Pass the current bucket brigade down to the next filter on the filter
290 * stack. The filter should return an apr_status_t value. If the bottom-most
291 * filter doesn't write to the network, then AP_NOBODY_WROTE is returned.
292 * @param filter The next filter in the chain
293 * @param bucket The current bucket brigade
294 * @return apr_status_t value
295 * @deffunc apr_status_t ap_pass_brigade(ap_filter_t *filter, ap_bucket_brigade *bucket)
297 AP_DECLARE(apr_status_t) ap_pass_brigade(ap_filter_t *filter, ap_bucket_brigade *bucket);
300 * ap_register_input_filter():
302 * This function is used to register an input filter with the system.
303 * After this registration is performed, then a filter may be added
304 * into the filter chain by using ap_add_input_filter() and simply
305 * specifying the name.
307 * The filter's callback and type should be passed.
310 * Register an input filter for later use. This allows modules to name their
311 * filter functions for later addition to a specific request
312 * @param name The name to attach to the filter function
313 * @param filter_func The filter function to name
314 * @param The type of filter function, either AP_FTYPE_CONTENT or AP_FTYPE_CONNECTION
315 * @deffunc void ap_register_input_filter(const char *name, ap_in_filter_func filter_func, ap_filter_type ftype)
317 AP_DECLARE(void) ap_register_input_filter(const char *name,
318 ap_in_filter_func filter_func,
319 ap_filter_type ftype);
321 * ap_register_output_filter():
323 * This function is used to register an output filter with the system.
324 * After this registration is performed, then a filter may be added
325 * into the filter chain by using ap_add_output_filter() and simply
326 * specifying the name.
328 * The filter's callback and type should be passed.
331 * Register an output filter for later use. This allows modules to name their
332 * filter functions for later addition to a specific request
333 * @param name The name to attach to the filter function
334 * @param filter_func The filter function to name
335 * @param The type of filter function, either AP_FTYPE_CONTENT or AP_FTYPE_CONNECTION
336 * @deffunc void ap_register_output_filter(const char *name, ap_out_filter_func filter_func, ap_filter_type ftype)
338 AP_DECLARE(void) ap_register_output_filter(const char *name,
339 ap_out_filter_func filter_func,
340 ap_filter_type ftype);
345 * Adds a named filter into the filter chain on the specified request record.
346 * The filter will be installed with the specified context pointer.
348 * Filters added in this way will always be placed at the end of the filters
349 * that have the same type (thus, the filters have the same order as the
350 * calls to ap_add_filter). If the current filter chain contains filters
351 * from another request, then this filter will be added before those other
354 * To re-iterate that last comment. This function is building a FIFO
355 * list of filters. Take note of that when adding your filter to the chain.
358 * Add a filter to the current connection. Filters are added in a FIFO manner.
359 * The first filter added will be the first filter called.
360 * @param name The name of the filter to add
361 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
362 * @param c The connection to add the fillter for
363 * @deffunc void ap_add_input_filter(const char *name, void *ctx, request_rec *r, conn_rec *c)
365 AP_DECLARE(void) ap_add_input_filter(const char *name, void *ctx, request_rec *r, conn_rec *c);
368 * Add a filter to the current request. Filters are added in a FIFO manner.
369 * The first filter added will be the first filter called.
370 * @param name The name of the filter to add
371 * @param ctx Context data to set in the filter
372 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
373 * @param c The connection to add this filter for
374 * @deffunc void ap_add_output_filter(const char *name, void *ctx, request_rec *r, conn_rec *c)
376 AP_DECLARE(void) ap_add_output_filter(const char *name, void *ctx,
377 request_rec *r, conn_rec *c);
379 AP_DECLARE(void) ap_remove_output_filter(ap_filter_t *f);
381 /* The next two filters are for abstraction purposes only. They could be
382 * done away with, but that would require that we break modules if we ever
383 * want to change our filter registration method. The basic idea, is that
384 * all filters have a place to store data, the ctx pointer. These functions
385 * fill out that pointer with a bucket brigade, and retrieve that data on
386 * the next call. The nice thing about these functions, is that they
387 * automatically concatenate the bucket brigades together for you. This means
388 * that if you have already stored a brigade in the filters ctx pointer, then
389 * when you add more it will be tacked onto the end of that brigade. When
390 * you retrieve data, if you pass in a bucket brigade to the get function,
391 * it will append the current brigade onto the one that you are retrieving.
395 * prepare a bucket brigade to be setaside. If a different brigade was
396 * set-aside earlier, then the two brigades are concatenated together.
397 * @param f The current filter
398 * @param save_to The brigade that was previously set-aside. Regardless, the
399 * new bucket brigade is returned in this location.
400 * @param b The bucket brigade to save aside. This brigade is always empty
402 * @deffunc void ap_save_brigade(ap_filter_t *f, ap_bucket_brigade **save_to, ap_bucket_brigade **b)
404 AP_DECLARE(void) ap_save_brigade(ap_filter_t *f, ap_bucket_brigade **save_to,
405 ap_bucket_brigade **b);
411 #endif /* !AP_FILTER_H */