1 /* Licensed to the Apache Software Foundation (ASF) under one or more
2 * contributor license agreements. See the NOTICE file distributed with
3 * this work for additional information regarding copyright ownership.
4 * The ASF licenses this file to You under the Apache License, Version 2.0
5 * (the "License"); you may not use this file except in compliance with
6 * the License. You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
21 #include "apr_buckets.h"
35 * @brief Apache filter library
38 /** Returned by the bottom-most filter if no data was written.
39 * @see ap_pass_brigade(). */
40 #define AP_NOBODY_WROTE -1
41 /** Returned by the bottom-most filter if no data was read.
42 * @see ap_get_brigade(). */
43 #define AP_NOBODY_READ -2
44 /** Returned when?? @bug find out when! */
45 #define AP_FILTER_ERROR -3
48 * input filtering modes
51 /** The filter should return at most readbytes data. */
53 /** The filter should return at most one line of CRLF data.
54 * (If a potential line is too long or no CRLF is found, the
55 * filter may return partial data).
58 /** The filter should implicitly eat any CRLF pairs that it sees. */
60 /** The filter read should be treated as speculative and any returned
61 * data should be stored for later retrieval in another mode. */
63 /** The filter read should be exhaustive and read until it can not
65 * Use this mode with extreme caution.
68 /** The filter should initialize the connection if needed,
69 * NNTP or FTP over SSL for example.
75 * @defgroup filter FILTER CHAIN
77 * Filters operate using a "chaining" mechanism. The filters are chained
78 * together into a sequence. When output is generated, it is passed through
79 * each of the filters on this chain, until it reaches the end (or "bottom")
80 * and is placed onto the network.
82 * The top of the chain, the code generating the output, is typically called
83 * a "content generator." The content generator's output is fed into the
84 * filter chain using the standard Apache output mechanisms: ap_rputs(),
85 * ap_rprintf(), ap_rwrite(), etc.
87 * Each filter is defined by a callback. This callback takes the output from
88 * the previous filter (or the content generator if there is no previous
89 * filter), operates on it, and passes the result to the next filter in the
90 * chain. This pass-off is performed using the ap_fc_* functions, such as
91 * ap_fc_puts(), ap_fc_printf(), ap_fc_write(), etc.
93 * When content generation is complete, the system will pass an "end of
94 * stream" marker into the filter chain. The filters will use this to flush
95 * out any internal state and to detect incomplete syntax (for example, an
96 * unterminated SSI directive).
99 /* forward declare the filter type */
100 typedef struct ap_filter_t ap_filter_t;
103 * @name Filter callbacks
105 * This function type is used for filter callbacks. It will be passed a
106 * pointer to "this" filter, and a "bucket" containing the content to be
109 * In filter->ctx, the callback will find its context. This context is
110 * provided here, so that a filter may be installed multiple times, each
111 * receiving its own per-install context pointer.
113 * Callbacks are associated with a filter definition, which is specified
114 * by name. See ap_register_input_filter() and ap_register_output_filter()
115 * for setting the association between a name for a filter and its
116 * associated callback (and other information).
118 * If the initialization function argument passed to the registration
119 * functions is non-NULL, it will be called iff the filter is in the input
120 * or output filter chains and before any data is generated to allow the
121 * filter to prepare for processing.
123 * The *bucket structure (and all those referenced by ->next and ->prev)
124 * should be considered "const". The filter is allowed to modify the
125 * next/prev to insert/remove/replace elements in the bucket list, but
126 * the types and values of the individual buckets should not be altered.
128 * For the input and output filters, the return value of a filter should be
129 * an APR status value. For the init function, the return value should
130 * be an HTTP error code or OK if it was successful.
135 typedef apr_status_t (*ap_out_filter_func)(ap_filter_t *f,
136 apr_bucket_brigade *b);
137 typedef apr_status_t (*ap_in_filter_func)(ap_filter_t *f,
138 apr_bucket_brigade *b,
139 ap_input_mode_t mode,
140 apr_read_type_e block,
141 apr_off_t readbytes);
142 typedef int (*ap_init_filter_func)(ap_filter_t *f);
144 typedef union ap_filter_func {
145 ap_out_filter_func out_func;
146 ap_in_filter_func in_func;
152 * Filters have different types/classifications. These are used to group
153 * and sort the filters to properly sequence their operation.
155 * The types have a particular sort order, which allows us to insert them
156 * into the filter chain in a determistic order. Within a particular grouping,
157 * the ordering is equivalent to the order of calls to ap_add_*_filter().
160 /** These filters are used to alter the content that is passed through
161 * them. Examples are SSI or PHP. */
162 AP_FTYPE_RESOURCE = 10,
163 /** These filters are used to alter the content as a whole, but after all
164 * AP_FTYPE_RESOURCE filters are executed. These filters should not
165 * change the content-type. An example is deflate. */
166 AP_FTYPE_CONTENT_SET = 20,
167 /** These filters are used to handle the protocol between server and
168 * client. Examples are HTTP and POP. */
169 AP_FTYPE_PROTOCOL = 30,
170 /** These filters implement transport encodings (e.g., chunking). */
171 AP_FTYPE_TRANSCODE = 40,
172 /** These filters will alter the content, but in ways that are
173 * more strongly associated with the connection. Examples are
174 * splitting an HTTP connection into multiple requests and
175 * buffering HTTP responses across multiple requests.
177 * It is important to note that these types of filters are not
178 * allowed in a sub-request. A sub-request's output can certainly
179 * be filtered by ::AP_FTYPE_RESOURCE filters, but all of the "final
180 * processing" is determined by the main request. */
181 AP_FTYPE_CONNECTION = 50,
182 /** These filters don't alter the content. They are responsible for
183 * sending/receiving data to/from the client. */
184 AP_FTYPE_NETWORK = 60
188 * This is the request-time context structure for an installed filter (in
189 * the output filter chain). It provides the callback to use for filtering,
190 * the request this filter is associated with (which is important when
191 * an output chain also includes sub-request filters), the context for this
192 * installed filter, and the filter ordering/chaining fields.
194 * Filter callbacks are free to use ->ctx as they please, to store context
195 * during the filter process. Generally, this is superior over associating
196 * the state directly with the request. A callback should not change any of
200 typedef struct ap_filter_rec_t ap_filter_rec_t;
203 * This structure is used for recording information about the
204 * registered filters. It associates a name with the filter's callback
207 * At the moment, these are simply linked in a chain, so a ->next pointer
210 struct ap_filter_rec_t {
211 /** The registered name for this filter */
213 /** The function to call when this filter is invoked. */
214 ap_filter_func filter_func;
215 /** The function to call before the handlers are invoked. Notice
216 * that this function is called only for filters participating in
217 * the http protocol. Filters for other protocols are to be
218 * initiliazed by the protocols themselves. */
219 ap_init_filter_func filter_init_func;
220 /** The type of filter, either AP_FTYPE_CONTENT or AP_FTYPE_CONNECTION.
221 * An AP_FTYPE_CONTENT filter modifies the data based on information
222 * found in the content. An AP_FTYPE_CONNECTION filter modifies the
223 * data based on the type of connection.
225 ap_filter_type ftype;
227 /** The next filter_rec in the list */
228 struct ap_filter_rec_t *next;
232 * The representation of a filter chain. Each request has a list
233 * of these structures which are called in turn to filter the data. Sub
234 * requests get an exact copy of the main requests filter chain.
237 /** The internal representation of this filter. This includes
238 * the filter's name, type, and the actual function pointer.
240 ap_filter_rec_t *frec;
242 /** A place to store any data associated with the current filter */
245 /** The next filter in the chain */
248 /** The request_rec associated with the current filter. If a sub-request
249 * adds filters, then the sub-request is the request associated with the
254 /** The conn_rec associated with the current filter. This is analogous
255 * to the request_rec, except that it is used for input filtering.
261 * Get the current bucket brigade from the next filter on the filter
262 * stack. The filter returns an apr_status_t value. If the bottom-most
263 * filter doesn't read from the network, then ::AP_NOBODY_READ is returned.
264 * The bucket brigade will be empty when there is nothing left to get.
265 * @param filter The next filter in the chain
266 * @param bucket The current bucket brigade. The original brigade passed
267 * to ap_get_brigade() must be empty.
268 * @param mode The way in which the data should be read
269 * @param block How the operations should be performed
270 * ::APR_BLOCK_READ, ::APR_NONBLOCK_READ
271 * @param readbytes How many bytes to read from the next filter.
273 AP_DECLARE(apr_status_t) ap_get_brigade(ap_filter_t *filter,
274 apr_bucket_brigade *bucket,
275 ap_input_mode_t mode,
276 apr_read_type_e block,
277 apr_off_t readbytes);
280 * Pass the current bucket brigade down to the next filter on the filter
281 * stack. The filter returns an apr_status_t value. If the bottom-most
282 * filter doesn't write to the network, then ::AP_NOBODY_WROTE is returned.
283 * The caller relinquishes ownership of the brigade.
284 * @param filter The next filter in the chain
285 * @param bucket The current bucket brigade
287 AP_DECLARE(apr_status_t) ap_pass_brigade(ap_filter_t *filter,
288 apr_bucket_brigade *bucket);
291 * This function is used to register an input filter with the system.
292 * After this registration is performed, then a filter may be added
293 * into the filter chain by using ap_add_input_filter() and simply
294 * specifying the name.
296 * @param name The name to attach to the filter function
297 * @param filter_func The filter function to name
298 * @param filter_init The function to call before the filter handlers
300 * @param ftype The type of filter function, either ::AP_FTYPE_CONTENT or
301 * ::AP_FTYPE_CONNECTION
302 * @see add_input_filter()
304 AP_DECLARE(ap_filter_rec_t *) ap_register_input_filter(const char *name,
305 ap_in_filter_func filter_func,
306 ap_init_filter_func filter_init,
307 ap_filter_type ftype);
309 * This function is used to register an output filter with the system.
310 * After this registration is performed, then a filter may be added
311 * into the filter chain by using ap_add_output_filter() and simply
312 * specifying the name.
314 * @param name The name to attach to the filter function
315 * @param filter_func The filter function to name
316 * @param filter_init The function to call before the filter handlers
318 * @param ftype The type of filter function, either ::AP_FTYPE_CONTENT or
319 * ::AP_FTYPE_CONNECTION
320 * @see ap_add_output_filter()
322 AP_DECLARE(ap_filter_rec_t *) ap_register_output_filter(const char *name,
323 ap_out_filter_func filter_func,
324 ap_init_filter_func filter_init,
325 ap_filter_type ftype);
328 * Adds a named filter into the filter chain on the specified request record.
329 * The filter will be installed with the specified context pointer.
331 * Filters added in this way will always be placed at the end of the filters
332 * that have the same type (thus, the filters have the same order as the
333 * calls to ap_add_filter). If the current filter chain contains filters
334 * from another request, then this filter will be added before those other
337 * To re-iterate that last comment. This function is building a FIFO
338 * list of filters. Take note of that when adding your filter to the chain.
340 * @param name The name of the filter to add
341 * @param ctx Context data to provide to the filter
342 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
343 * @param c The connection to add the fillter for
345 AP_DECLARE(ap_filter_t *) ap_add_input_filter(const char *name, void *ctx,
346 request_rec *r, conn_rec *c);
349 * Variant of ap_add_input_filter() that accepts a registered filter handle
350 * (as returned by ap_register_input_filter()) rather than a filter name
352 * @param f The filter handle to add
353 * @param ctx Context data to provide to the filter
354 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
355 * @param c The connection to add the fillter for
357 AP_DECLARE(ap_filter_t *) ap_add_input_filter_handle(ap_filter_rec_t *f,
363 * Returns the filter handle for use with ap_add_input_filter_handle.
365 * @param name The filter name to look up
367 AP_DECLARE(ap_filter_rec_t *) ap_get_input_filter_handle(const char *name);
370 * Add a filter to the current request. Filters are added in a FIFO manner.
371 * The first filter added will be the first filter called.
372 * @param name The name of the filter to add
373 * @param ctx Context data to set in the filter
374 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
375 * @param c The connection to add this filter for
377 AP_DECLARE(ap_filter_t *) ap_add_output_filter(const char *name, void *ctx,
378 request_rec *r, conn_rec *c);
381 * Variant of ap_add_output_filter() that accepts a registered filter handle
382 * (as returned by ap_register_output_filter()) rather than a filter name
384 * @param f The filter handle to add
385 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
386 * @param c The connection to add the fillter for
388 AP_DECLARE(ap_filter_t *) ap_add_output_filter_handle(ap_filter_rec_t *f,
394 * Returns the filter handle for use with ap_add_output_filter_handle.
396 * @param name The filter name to look up
398 AP_DECLARE(ap_filter_rec_t *) ap_get_output_filter_handle(const char *name);
401 * Remove an input filter from either the request or connection stack
402 * it is associated with.
403 * @param f The filter to remove
406 AP_DECLARE(void) ap_remove_input_filter(ap_filter_t *f);
409 * Remove an output filter from either the request or connection stack
410 * it is associated with.
411 * @param f The filter to remove
414 AP_DECLARE(void) ap_remove_output_filter(ap_filter_t *f);
416 /* The next two filters are for abstraction purposes only. They could be
417 * done away with, but that would require that we break modules if we ever
418 * want to change our filter registration method. The basic idea, is that
419 * all filters have a place to store data, the ctx pointer. These functions
420 * fill out that pointer with a bucket brigade, and retrieve that data on
421 * the next call. The nice thing about these functions, is that they
422 * automatically concatenate the bucket brigades together for you. This means
423 * that if you have already stored a brigade in the filters ctx pointer, then
424 * when you add more it will be tacked onto the end of that brigade. When
425 * you retrieve data, if you pass in a bucket brigade to the get function,
426 * it will append the current brigade onto the one that you are retrieving.
430 * prepare a bucket brigade to be setaside. If a different brigade was
431 * set-aside earlier, then the two brigades are concatenated together.
432 * @param f The current filter
433 * @param save_to The brigade that was previously set-aside. Regardless, the
434 * new bucket brigade is returned in this location.
435 * @param b The bucket brigade to save aside. This brigade is always empty
437 * @param p Ensure that all data in the brigade lives as long as this pool
439 AP_DECLARE(apr_status_t) ap_save_brigade(ap_filter_t *f,
440 apr_bucket_brigade **save_to,
441 apr_bucket_brigade **b, apr_pool_t *p);
444 * Flush function for apr_brigade_* calls. This calls ap_pass_brigade
445 * to flush the brigade if the brigade buffer overflows.
446 * @param bb The brigade to flush
447 * @param ctx The filter to pass the brigade to
448 * @note this function has nothing to do with FLUSH buckets. It is simply
449 * a way to flush content out of a brigade and down a filter stack.
451 AP_DECLARE_NONSTD(apr_status_t) ap_filter_flush(apr_bucket_brigade *bb,
455 * Flush the current brigade down the filter stack.
456 * @param f The current filter
457 * @param bb The brigade to flush
459 AP_DECLARE(apr_status_t) ap_fflush(ap_filter_t *f, apr_bucket_brigade *bb);
462 * Write a buffer for the current filter, buffering if possible.
463 * @param f the filter doing the writing
464 * @param bb The brigade to buffer into
465 * @param data The data to write
466 * @param nbyte The number of bytes in the data
468 #define ap_fwrite(f, bb, data, nbyte) \
469 apr_brigade_write(bb, ap_filter_flush, f, data, nbyte)
472 * Write a buffer for the current filter, buffering if possible.
473 * @param f the filter doing the writing
474 * @param bb The brigade to buffer into
475 * @param str The string to write
477 #define ap_fputs(f, bb, str) \
478 apr_brigade_puts(bb, ap_filter_flush, f, str)
481 * Write a character for the current filter, buffering if possible.
482 * @param f the filter doing the writing
483 * @param bb The brigade to buffer into
484 * @param c The character to write
486 #define ap_fputc(f, bb, c) \
487 apr_brigade_putc(bb, ap_filter_flush, f, c)
490 * Write an unspecified number of strings to the current filter
491 * @param f the filter doing the writing
492 * @param bb The brigade to buffer into
493 * @param ... The strings to write
495 AP_DECLARE_NONSTD(apr_status_t) ap_fputstrs(ap_filter_t *f,
496 apr_bucket_brigade *bb,
500 * Output data to the filter in printf format
501 * @param f the filter doing the writing
502 * @param bb The brigade to buffer into
503 * @param fmt The format string
504 * @param ... The argumets to use to fill out the format string
506 AP_DECLARE_NONSTD(apr_status_t) ap_fprintf(ap_filter_t *f,
507 apr_bucket_brigade *bb,
510 __attribute__((format(printf,3,4)));
516 #endif /* !AP_FILTER_H */