1 /* Copyright 2000-2004 The Apache Software Foundation
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at
7 * http://www.apache.org/licenses/LICENSE-2.0
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
20 #include "apr_buckets.h"
34 * @brief Apache filter library
37 /** Returned by the bottom-most filter if no data was written.
38 * @see ap_pass_brigade(). */
39 #define AP_NOBODY_WROTE -1
40 /** Returned by the bottom-most filter if no data was read.
41 * @see ap_get_brigade(). */
42 #define AP_NOBODY_READ -2
43 /** Returned when?? @bug find out when! */
44 #define AP_FILTER_ERROR -3
47 * input filtering modes
50 /** The filter should return at most readbytes data. */
52 /** The filter should return at most one line of CRLF data.
53 * (If a potential line is too long or no CRLF is found, the
54 * filter may return partial data).
57 /** The filter should implicitly eat any CRLF pairs that it sees. */
59 /** The filter read should be treated as speculative and any returned
60 * data should be stored for later retrieval in another mode. */
62 /** The filter read should be exhaustive and read until it can not
64 * Use this mode with extreme caution.
67 /** The filter should initialize the connection if needed,
68 * NNTP or FTP over SSL for example.
74 * @defgroup filter FILTER CHAIN
76 * Filters operate using a "chaining" mechanism. The filters are chained
77 * together into a sequence. When output is generated, it is passed through
78 * each of the filters on this chain, until it reaches the end (or "bottom")
79 * and is placed onto the network.
81 * The top of the chain, the code generating the output, is typically called
82 * a "content generator." The content generator's output is fed into the
83 * filter chain using the standard Apache output mechanisms: ap_rputs(),
84 * ap_rprintf(), ap_rwrite(), etc.
86 * Each filter is defined by a callback. This callback takes the output from
87 * the previous filter (or the content generator if there is no previous
88 * filter), operates on it, and passes the result to the next filter in the
89 * chain. This pass-off is performed using the ap_fc_* functions, such as
90 * ap_fc_puts(), ap_fc_printf(), ap_fc_write(), etc.
92 * When content generation is complete, the system will pass an "end of
93 * stream" marker into the filter chain. The filters will use this to flush
94 * out any internal state and to detect incomplete syntax (for example, an
95 * unterminated SSI directive).
98 /* forward declare the filter type */
99 typedef struct ap_filter_t ap_filter_t;
102 * @name Filter callbacks
104 * This function type is used for filter callbacks. It will be passed a
105 * pointer to "this" filter, and a "bucket" containing the content to be
108 * In filter->ctx, the callback will find its context. This context is
109 * provided here, so that a filter may be installed multiple times, each
110 * receiving its own per-install context pointer.
112 * Callbacks are associated with a filter definition, which is specified
113 * by name. See ap_register_input_filter() and ap_register_output_filter()
114 * for setting the association between a name for a filter and its
115 * associated callback (and other information).
117 * If the initialization function argument passed to the registration
118 * functions is non-NULL, it will be called iff the filter is in the input
119 * or output filter chains and before any data is generated to allow the
120 * filter to prepare for processing.
122 * The *bucket structure (and all those referenced by ->next and ->prev)
123 * should be considered "const". The filter is allowed to modify the
124 * next/prev to insert/remove/replace elements in the bucket list, but
125 * the types and values of the individual buckets should not be altered.
127 * For the input and output filters, the return value of a filter should be
128 * an APR status value. For the init function, the return value should
129 * be an HTTP error code or OK if it was successful.
134 typedef apr_status_t (*ap_out_filter_func)(ap_filter_t *f,
135 apr_bucket_brigade *b);
136 typedef apr_status_t (*ap_in_filter_func)(ap_filter_t *f,
137 apr_bucket_brigade *b,
138 ap_input_mode_t mode,
139 apr_read_type_e block,
140 apr_off_t readbytes);
141 typedef int (*ap_init_filter_func)(ap_filter_t *f);
143 typedef union ap_filter_func {
144 ap_out_filter_func out_func;
145 ap_in_filter_func in_func;
151 * Filters have different types/classifications. These are used to group
152 * and sort the filters to properly sequence their operation.
154 * The types have a particular sort order, which allows us to insert them
155 * into the filter chain in a determistic order. Within a particular grouping,
156 * the ordering is equivalent to the order of calls to ap_add_*_filter().
159 /** These filters are used to alter the content that is passed through
160 * them. Examples are SSI or PHP. */
161 AP_FTYPE_RESOURCE = 10,
162 /** These filters are used to alter the content as a whole, but after all
163 * AP_FTYPE_RESOURCE filters are executed. These filters should not
164 * change the content-type. An example is deflate. */
165 AP_FTYPE_CONTENT_SET = 20,
166 /** These filters are used to handle the protocol between server and
167 * client. Examples are HTTP and POP. */
168 AP_FTYPE_PROTOCOL = 30,
169 /** These filters implement transport encodings (e.g., chunking). */
170 AP_FTYPE_TRANSCODE = 40,
171 /** These filters will alter the content, but in ways that are
172 * more strongly associated with the connection. Examples are
173 * splitting an HTTP connection into multiple requests and
174 * buffering HTTP responses across multiple requests.
176 * It is important to note that these types of filters are not
177 * allowed in a sub-request. A sub-request's output can certainly
178 * be filtered by ::AP_FTYPE_RESOURCE filters, but all of the "final
179 * processing" is determined by the main request. */
180 AP_FTYPE_CONNECTION = 50,
181 /** These filters don't alter the content. They are responsible for
182 * sending/receiving data to/from the client. */
183 AP_FTYPE_NETWORK = 60
187 * This is the request-time context structure for an installed filter (in
188 * the output filter chain). It provides the callback to use for filtering,
189 * the request this filter is associated with (which is important when
190 * an output chain also includes sub-request filters), the context for this
191 * installed filter, and the filter ordering/chaining fields.
193 * Filter callbacks are free to use ->ctx as they please, to store context
194 * during the filter process. Generally, this is superior over associating
195 * the state directly with the request. A callback should not change any of
199 typedef struct ap_filter_rec_t ap_filter_rec_t;
202 * This structure is used for recording information about the
203 * registered filters. It associates a name with the filter's callback
206 * At the moment, these are simply linked in a chain, so a ->next pointer
209 struct ap_filter_rec_t {
210 /** The registered name for this filter */
212 /** The function to call when this filter is invoked. */
213 ap_filter_func filter_func;
214 /** The function to call before the handlers are invoked. Notice
215 * that this function is called only for filters participating in
216 * the http protocol. Filters for other protocols are to be
217 * initiliazed by the protocols themselves. */
218 ap_init_filter_func filter_init_func;
219 /** The type of filter, either AP_FTYPE_CONTENT or AP_FTYPE_CONNECTION.
220 * An AP_FTYPE_CONTENT filter modifies the data based on information
221 * found in the content. An AP_FTYPE_CONNECTION filter modifies the
222 * data based on the type of connection.
224 ap_filter_type ftype;
226 /** The next filter_rec in the list */
227 struct ap_filter_rec_t *next;
231 * The representation of a filter chain. Each request has a list
232 * of these structures which are called in turn to filter the data. Sub
233 * requests get an exact copy of the main requests filter chain.
236 /** The internal representation of this filter. This includes
237 * the filter's name, type, and the actual function pointer.
239 ap_filter_rec_t *frec;
241 /** A place to store any data associated with the current filter */
244 /** The next filter in the chain */
247 /** The request_rec associated with the current filter. If a sub-request
248 * adds filters, then the sub-request is the request associated with the
253 /** The conn_rec associated with the current filter. This is analogous
254 * to the request_rec, except that it is used for input filtering.
260 * Get the current bucket brigade from the next filter on the filter
261 * stack. The filter returns an apr_status_t value. If the bottom-most
262 * filter doesn't read from the network, then ::AP_NOBODY_READ is returned.
263 * The bucket brigade will be empty when there is nothing left to get.
264 * @param filter The next filter in the chain
265 * @param bucket The current bucket brigade. The original brigade passed
266 * to ap_get_brigade() must be empty.
267 * @param mode The way in which the data should be read
268 * @param block How the operations should be performed
269 * ::APR_BLOCK_READ, ::APR_NONBLOCK_READ
270 * @param readbytes How many bytes to read from the next filter.
272 AP_DECLARE(apr_status_t) ap_get_brigade(ap_filter_t *filter,
273 apr_bucket_brigade *bucket,
274 ap_input_mode_t mode,
275 apr_read_type_e block,
276 apr_off_t readbytes);
279 * Pass the current bucket brigade down to the next filter on the filter
280 * stack. The filter returns an apr_status_t value. If the bottom-most
281 * filter doesn't write to the network, then ::AP_NOBODY_WROTE is returned.
282 * The caller relinquishes ownership of the brigade.
283 * @param filter The next filter in the chain
284 * @param bucket The current bucket brigade
286 AP_DECLARE(apr_status_t) ap_pass_brigade(ap_filter_t *filter,
287 apr_bucket_brigade *bucket);
290 * This function is used to register an input filter with the system.
291 * After this registration is performed, then a filter may be added
292 * into the filter chain by using ap_add_input_filter() and simply
293 * specifying the name.
295 * @param name The name to attach to the filter function
296 * @param filter_func The filter function to name
297 * @param filter_init The function to call before the filter handlers
299 * @param ftype The type of filter function, either ::AP_FTYPE_CONTENT or
300 * ::AP_FTYPE_CONNECTION
301 * @see add_input_filter()
303 AP_DECLARE(ap_filter_rec_t *) ap_register_input_filter(const char *name,
304 ap_in_filter_func filter_func,
305 ap_init_filter_func filter_init,
306 ap_filter_type ftype);
308 * This function is used to register an output filter with the system.
309 * After this registration is performed, then a filter may be added
310 * into the filter chain by using ap_add_output_filter() and simply
311 * specifying the name.
313 * @param name The name to attach to the filter function
314 * @param filter_func The filter function to name
315 * @param filter_init The function to call before the filter handlers
317 * @param ftype The type of filter function, either ::AP_FTYPE_CONTENT or
318 * ::AP_FTYPE_CONNECTION
319 * @see ap_add_output_filter()
321 AP_DECLARE(ap_filter_rec_t *) ap_register_output_filter(const char *name,
322 ap_out_filter_func filter_func,
323 ap_init_filter_func filter_init,
324 ap_filter_type ftype);
327 * Adds a named filter into the filter chain on the specified request record.
328 * The filter will be installed with the specified context pointer.
330 * Filters added in this way will always be placed at the end of the filters
331 * that have the same type (thus, the filters have the same order as the
332 * calls to ap_add_filter). If the current filter chain contains filters
333 * from another request, then this filter will be added before those other
336 * To re-iterate that last comment. This function is building a FIFO
337 * list of filters. Take note of that when adding your filter to the chain.
339 * @param name The name of the filter to add
340 * @param ctx Context data to provide to the filter
341 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
342 * @param c The connection to add the fillter for
344 AP_DECLARE(ap_filter_t *) ap_add_input_filter(const char *name, void *ctx,
345 request_rec *r, conn_rec *c);
348 * Variant of ap_add_input_filter() that accepts a registered filter handle
349 * (as returned by ap_register_input_filter()) rather than a filter name
351 * @param f The filter handle to add
352 * @param ctx Context data to provide to the filter
353 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
354 * @param c The connection to add the fillter for
356 AP_DECLARE(ap_filter_t *) ap_add_input_filter_handle(ap_filter_rec_t *f,
362 * Returns the filter handle for use with ap_add_input_filter_handle.
364 * @param name The filter name to look up
366 AP_DECLARE(ap_filter_rec_t *) ap_get_input_filter_handle(const char *name);
369 * Add a filter to the current request. Filters are added in a FIFO manner.
370 * The first filter added will be the first filter called.
371 * @param name The name of the filter to add
372 * @param ctx Context data to set in the filter
373 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
374 * @param c The connection to add this filter for
376 AP_DECLARE(ap_filter_t *) ap_add_output_filter(const char *name, void *ctx,
377 request_rec *r, conn_rec *c);
380 * Variant of ap_add_output_filter() that accepts a registered filter handle
381 * (as returned by ap_register_output_filter()) rather than a filter name
383 * @param f The filter handle to add
384 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
385 * @param c The connection to add the fillter for
387 AP_DECLARE(ap_filter_t *) ap_add_output_filter_handle(ap_filter_rec_t *f,
393 * Returns the filter handle for use with ap_add_output_filter_handle.
395 * @param name The filter name to look up
397 AP_DECLARE(ap_filter_rec_t *) ap_get_output_filter_handle(const char *name);
400 * Remove an input filter from either the request or connection stack
401 * it is associated with.
402 * @param f The filter to remove
405 AP_DECLARE(void) ap_remove_input_filter(ap_filter_t *f);
408 * Remove an output filter from either the request or connection stack
409 * it is associated with.
410 * @param f The filter to remove
413 AP_DECLARE(void) ap_remove_output_filter(ap_filter_t *f);
415 /* The next two filters are for abstraction purposes only. They could be
416 * done away with, but that would require that we break modules if we ever
417 * want to change our filter registration method. The basic idea, is that
418 * all filters have a place to store data, the ctx pointer. These functions
419 * fill out that pointer with a bucket brigade, and retrieve that data on
420 * the next call. The nice thing about these functions, is that they
421 * automatically concatenate the bucket brigades together for you. This means
422 * that if you have already stored a brigade in the filters ctx pointer, then
423 * when you add more it will be tacked onto the end of that brigade. When
424 * you retrieve data, if you pass in a bucket brigade to the get function,
425 * it will append the current brigade onto the one that you are retrieving.
429 * prepare a bucket brigade to be setaside. If a different brigade was
430 * set-aside earlier, then the two brigades are concatenated together.
431 * @param f The current filter
432 * @param save_to The brigade that was previously set-aside. Regardless, the
433 * new bucket brigade is returned in this location.
434 * @param b The bucket brigade to save aside. This brigade is always empty
436 * @param p Ensure that all data in the brigade lives as long as this pool
438 AP_DECLARE(apr_status_t) ap_save_brigade(ap_filter_t *f,
439 apr_bucket_brigade **save_to,
440 apr_bucket_brigade **b, apr_pool_t *p);
443 * Flush function for apr_brigade_* calls. This calls ap_pass_brigade
444 * to flush the brigade if the brigade buffer overflows.
445 * @param bb The brigade to flush
446 * @param ctx The filter to pass the brigade to
447 * @note this function has nothing to do with FLUSH buckets. It is simply
448 * a way to flush content out of a brigade and down a filter stack.
450 AP_DECLARE_NONSTD(apr_status_t) ap_filter_flush(apr_bucket_brigade *bb,
454 * Flush the current brigade down the filter stack.
455 * @param f The current filter
456 * @param bb The brigade to flush
458 AP_DECLARE(apr_status_t) ap_fflush(ap_filter_t *f, apr_bucket_brigade *bb);
461 * Write a buffer for the current filter, buffering if possible.
462 * @param f the filter doing the writing
463 * @param bb The brigade to buffer into
464 * @param data The data to write
465 * @param nbyte The number of bytes in the data
467 #define ap_fwrite(f, bb, data, nbyte) \
468 apr_brigade_write(bb, ap_filter_flush, f, data, nbyte)
471 * Write a buffer for the current filter, buffering if possible.
472 * @param f the filter doing the writing
473 * @param bb The brigade to buffer into
474 * @param str The string to write
476 #define ap_fputs(f, bb, str) \
477 apr_brigade_puts(bb, ap_filter_flush, f, str)
480 * Write a character for the current filter, buffering if possible.
481 * @param f the filter doing the writing
482 * @param bb The brigade to buffer into
483 * @param c The character to write
485 #define ap_fputc(f, bb, c) \
486 apr_brigade_putc(bb, ap_filter_flush, f, c)
489 * Write an unspecified number of strings to the current filter
490 * @param f the filter doing the writing
491 * @param bb The brigade to buffer into
492 * @param ... The strings to write
494 AP_DECLARE_NONSTD(apr_status_t) ap_fputstrs(ap_filter_t *f,
495 apr_bucket_brigade *bb,
499 * Output data to the filter in printf format
500 * @param f the filter doing the writing
501 * @param bb The brigade to buffer into
502 * @param fmt The format string
503 * @param ... The argumets to use to fill out the format string
505 AP_DECLARE_NONSTD(apr_status_t) ap_fprintf(ap_filter_t *f,
506 apr_bucket_brigade *bb,
509 __attribute__((format(printf,3,4)));
515 #endif /* !AP_FILTER_H */