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59 #include "apr_buckets.h"
73 * @brief Apache filter library
76 /** Returned by the bottom-most filter if no data was written.
77 * @see ap_pass_brigade(). */
78 #define AP_NOBODY_WROTE -1
79 /** Returned by the bottom-most filter if no data was read.
80 * @see ap_get_brigade(). */
81 #define AP_NOBODY_READ -2
82 /** Returned when?? @bug find out when! */
83 #define AP_FILTER_ERROR -3
86 * input filtering modes
89 /** The filter should return at most readbytes data. */
91 /** The filter should return at most one line of CRLF data.
92 * (If a potential line is too long or no CRLF is found, the
93 * filter may return partial data).
96 /** The filter should implicitly eat any CRLF pairs that it sees. */
98 /** The filter read should be treated as speculative and any returned
99 * data should be stored for later retrieval in another mode. */
101 /** The filter read should be exhaustive and read until it can not
103 * Use this mode with extreme caution.
106 /** The filter should initialize the connection if needed,
107 * NNTP or FTP over SSL for example.
113 * @defgroup filter FILTER CHAIN
115 * Filters operate using a "chaining" mechanism. The filters are chained
116 * together into a sequence. When output is generated, it is passed through
117 * each of the filters on this chain, until it reaches the end (or "bottom")
118 * and is placed onto the network.
120 * The top of the chain, the code generating the output, is typically called
121 * a "content generator." The content generator's output is fed into the
122 * filter chain using the standard Apache output mechanisms: ap_rputs(),
123 * ap_rprintf(), ap_rwrite(), etc.
125 * Each filter is defined by a callback. This callback takes the output from
126 * the previous filter (or the content generator if there is no previous
127 * filter), operates on it, and passes the result to the next filter in the
128 * chain. This pass-off is performed using the ap_fc_* functions, such as
129 * ap_fc_puts(), ap_fc_printf(), ap_fc_write(), etc.
131 * When content generation is complete, the system will pass an "end of
132 * stream" marker into the filter chain. The filters will use this to flush
133 * out any internal state and to detect incomplete syntax (for example, an
134 * unterminated SSI directive).
137 /* forward declare the filter type */
138 typedef struct ap_filter_t ap_filter_t;
141 * @name Filter callbacks
143 * This function type is used for filter callbacks. It will be passed a
144 * pointer to "this" filter, and a "bucket" containing the content to be
147 * In filter->ctx, the callback will find its context. This context is
148 * provided here, so that a filter may be installed multiple times, each
149 * receiving its own per-install context pointer.
151 * Callbacks are associated with a filter definition, which is specified
152 * by name. See ap_register_input_filter() and ap_register_output_filter()
153 * for setting the association between a name for a filter and its
154 * associated callback (and other information).
156 * The *bucket structure (and all those referenced by ->next and ->prev)
157 * should be considered "const". The filter is allowed to modify the
158 * next/prev to insert/remove/replace elements in the bucket list, but
159 * the types and values of the individual buckets should not be altered.
161 * The return value of a filter should be an APR status value.
166 typedef apr_status_t (*ap_out_filter_func)(ap_filter_t *f, apr_bucket_brigade *b);
167 typedef apr_status_t (*ap_in_filter_func)(ap_filter_t *f, apr_bucket_brigade *b,
168 ap_input_mode_t mode, apr_read_type_e block, apr_off_t readbytes);
170 typedef union ap_filter_func {
171 ap_out_filter_func out_func;
172 ap_in_filter_func in_func;
178 * Filters have different types/classifications. These are used to group
179 * and sort the filters to properly sequence their operation.
181 * The types have a particular sort order, which allows us to insert them
182 * into the filter chain in a determistic order. Within a particular grouping,
183 * the ordering is equivalent to the order of calls to ap_add_*_filter().
186 /** These filters are used to alter the content that is passed through
187 * them. Examples are SSI or PHP. */
188 AP_FTYPE_CONTENT = 10,
189 /** (XXX somebody rename me or get rid of me please)
190 * This special type ensures that the HTTP header filter ends up in
191 * the proper location in the filter chain. */
192 AP_FTYPE_HTTP_HEADER = 20,
193 /** These filters implement transport encodings (e.g., chunking). */
194 AP_FTYPE_TRANSCODE = 30,
195 /** These filters will alter the content, but in ways that are
196 * more strongly associated with the connection. Examples are
197 * splitting * an HTTP connection into multiple requests and
198 * buffering HTTP * responses across multiple requests.
200 * It is important to note that these types of filters are not
201 * allowed in a sub-request. A sub-request's output can certainly
202 * be filtered by ::AP_FTYPE_CONTENT filters, but all of the "final
203 * processing" is determined by the main request. */
204 AP_FTYPE_CONNECTION = 40,
205 /** These filters don't alter the content. They are responsible for
206 * sending/receiving data to/from the client. */
207 AP_FTYPE_NETWORK = 50
211 * This is the request-time context structure for an installed filter (in
212 * the output filter chain). It provides the callback to use for filtering,
213 * the request this filter is associated with (which is important when
214 * an output chain also includes sub-request filters), the context for this
215 * installed filter, and the filter ordering/chaining fields.
217 * Filter callbacks are free to use ->ctx as they please, to store context
218 * during the filter process. Generally, this is superior over associating
219 * the state directly with the request. A callback should not change any of
223 typedef struct ap_filter_rec_t ap_filter_rec_t;
226 * This structure is used for recording information about the
227 * registered filters. It associates a name with the filter's callback
230 * At the moment, these are simply linked in a chain, so a ->next pointer
233 struct ap_filter_rec_t {
234 /** The registered name for this filter */
236 /** The function to call when this filter is invoked. */
237 ap_filter_func filter_func;
238 /** The type of filter, either AP_FTYPE_CONTENT or AP_FTYPE_CONNECTION.
239 * An AP_FTYPE_CONTENT filter modifies the data based on information
240 * found in the content. An AP_FTYPE_CONNECTION filter modifies the
241 * data based on the type of connection.
243 ap_filter_type ftype;
245 /** The next filter_rec in the list */
246 struct ap_filter_rec_t *next;
250 * The representation of a filter chain. Each request has a list
251 * of these structures which are called in turn to filter the data. Sub
252 * requests get an exact copy of the main requests filter chain.
255 /** The internal representation of this filter. This includes
256 * the filter's name, type, and the actual function pointer.
258 ap_filter_rec_t *frec;
260 /** A place to store any data associated with the current filter */
263 /** The next filter in the chain */
266 /** The previous filter in the chain */
269 /** The request_rec associated with the current filter. If a sub-request
270 * adds filters, then the sub-request is the request associated with the
275 /** The conn_rec associated with the current filter. This is analogous
276 * to the request_rec, except that it is used for input filtering.
282 * Get the current bucket brigade from the next filter on the filter
283 * stack. The filter returns an apr_status_t value. If the bottom-most
284 * filter doesn't read from the network, then ::AP_NOBODY_READ is returned.
285 * @param filter The next filter in the chain
286 * @param bucket The current bucket brigade
287 * @param mode The way in which the data should be read
288 * @param block How the operations should be performed
289 * ::APR_BLOCK_READ, ::APR_NONBLOCK_READ
290 * @param readbytes How many bytes to read from the next filter.
292 AP_DECLARE(apr_status_t) ap_get_brigade(ap_filter_t *filter,
293 apr_bucket_brigade *bucket,
294 ap_input_mode_t mode,
295 apr_read_type_e block,
296 apr_off_t readbytes);
299 * Pass the current bucket brigade down to the next filter on the filter
300 * stack. The filter returns an apr_status_t value. If the bottom-most
301 * filter doesn't write to the network, then ::AP_NOBODY_WROTE is returned.
302 * @param filter The next filter in the chain
303 * @param bucket The current bucket brigade
305 AP_DECLARE(apr_status_t) ap_pass_brigade(ap_filter_t *filter, apr_bucket_brigade *bucket);
308 * This function is used to register an input 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_input_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 ftype The type of filter function, either ::AP_FTYPE_CONTENT or ::
316 * AP_FTYPE_CONNECTION
317 * @see add_input_filter()
319 AP_DECLARE(ap_filter_rec_t *) ap_register_input_filter(const char *name,
320 ap_in_filter_func filter_func,
321 ap_filter_type ftype);
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 * @param name The name to attach to the filter function
329 * @param filter_func The filter function to name
330 * @param ftype The type of filter function, either ::AP_FTYPE_CONTENT or
331 * ::AP_FTYPE_CONNECTION
332 * @see ap_add_output_filter()
334 AP_DECLARE(ap_filter_rec_t *) ap_register_output_filter(const char *name,
335 ap_out_filter_func filter_func,
336 ap_filter_type ftype);
339 * Adds a named filter into the filter chain on the specified request record.
340 * The filter will be installed with the specified context pointer.
342 * Filters added in this way will always be placed at the end of the filters
343 * that have the same type (thus, the filters have the same order as the
344 * calls to ap_add_filter). If the current filter chain contains filters
345 * from another request, then this filter will be added before those other
348 * To re-iterate that last comment. This function is building a FIFO
349 * list of filters. Take note of that when adding your filter to the chain.
351 * @param name The name of the filter 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(const char *name, void *ctx,
357 request_rec *r, conn_rec *c);
360 * Variant of ap_add_input_filter() that accepts a registered filter handle
361 * (as returned by ap_register_input_filter()) rather than a filter name
363 * @param name The filter to add
364 * @param ctx Context data to provide to the filter
365 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
366 * @param c The connection to add the fillter for
368 AP_DECLARE(ap_filter_t *) ap_add_input_filter_handle(ap_filter_rec_t *f,
374 * Returns the filter handle for use with ap_add_input_filter_handle.
376 * @param name The filter name to look up
378 AP_DECLARE(ap_filter_rec_t *) ap_get_input_filter_handle(const char *name);
381 * Add a filter to the current request. Filters are added in a FIFO manner.
382 * The first filter added will be the first filter called.
383 * @param name The name of the filter to add
384 * @param ctx Context data to set in the filter
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 this filter for
388 AP_DECLARE(ap_filter_t *) ap_add_output_filter(const char *name, void *ctx,
389 request_rec *r, conn_rec *c);
392 * Variant of ap_add_output_filter() that accepts a registered filter handle
393 * (as returned by ap_register_output_filter()) rather than a filter name
395 * @param name The filter to add
396 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
397 * @param c The connection to add the fillter for
399 AP_DECLARE(ap_filter_t *) ap_add_output_filter_handle(ap_filter_rec_t *f,
404 * Returns the filter handle for use with ap_add_output_filter_handle.
406 * @param name The filter name to look up
408 AP_DECLARE(ap_filter_rec_t *) ap_get_output_filter_handle(const char *name);
411 * Remove an input filter from either the request or connection stack
412 * it is associated with.
413 * @param f The filter to remove
416 AP_DECLARE(void) ap_remove_input_filter(ap_filter_t *f);
419 * Remove an output filter from either the request or connection stack
420 * it is associated with.
421 * @param f The filter to remove
424 AP_DECLARE(void) ap_remove_output_filter(ap_filter_t *f);
426 /* The next two filters are for abstraction purposes only. They could be
427 * done away with, but that would require that we break modules if we ever
428 * want to change our filter registration method. The basic idea, is that
429 * all filters have a place to store data, the ctx pointer. These functions
430 * fill out that pointer with a bucket brigade, and retrieve that data on
431 * the next call. The nice thing about these functions, is that they
432 * automatically concatenate the bucket brigades together for you. This means
433 * that if you have already stored a brigade in the filters ctx pointer, then
434 * when you add more it will be tacked onto the end of that brigade. When
435 * you retrieve data, if you pass in a bucket brigade to the get function,
436 * it will append the current brigade onto the one that you are retrieving.
440 * prepare a bucket brigade to be setaside. If a different brigade was
441 * set-aside earlier, then the two brigades are concatenated together.
442 * @param f The current filter
443 * @param save_to The brigade that was previously set-aside. Regardless, the
444 * new bucket brigade is returned in this location.
445 * @param b The bucket brigade to save aside. This brigade is always empty
447 * @param p Ensure that all data in the brigade lives as long as this pool
449 AP_DECLARE(apr_status_t) ap_save_brigade(ap_filter_t *f, apr_bucket_brigade **save_to,
450 apr_bucket_brigade **b, apr_pool_t *p);
453 * Flush function for apr_brigade_* calls. This calls ap_pass_brigade
454 * to flush the brigade if the brigade buffer overflows.
455 * @param bb The brigade to flush
456 * @param ctx The filter to pass the brigade to
458 AP_DECLARE_NONSTD(apr_status_t) ap_filter_flush(apr_bucket_brigade *bb, void *ctx);
461 * Flush the current brigade down the filter stack.
462 * @param f The current filter
463 * @param bb The brigade to flush
465 AP_DECLARE(apr_status_t) ap_fflush(ap_filter_t *f, apr_bucket_brigade *bb);
468 * Write a buffer for the current filter, buffering if possible.
469 * @param f the filter doing the writing
470 * @param bb The brigade to buffer into
471 * @param data The data to write
472 * @param nbyte The number of bytes in the data
474 #define ap_fwrite(f, bb, data, nbyte) \
475 apr_brigade_write(bb, ap_filter_flush, f, data, nbyte)
478 * Write a buffer for the current filter, buffering if possible.
479 * @param f the filter doing the writing
480 * @param bb The brigade to buffer into
481 * @param str The string to write
483 #define ap_fputs(f, bb, str) \
484 apr_brigade_puts(bb, ap_filter_flush, f, str)
487 * Write a character for the current filter, buffering if possible.
488 * @param f the filter doing the writing
489 * @param bb The brigade to buffer into
490 * @param c The character to write
492 #define ap_fputc(f, bb, c) \
493 apr_brigade_putc(bb, ap_filter_flush, f, c)
496 * Write an unspecified number of strings to the current filter
497 * @param f the filter doing the writing
498 * @param bb The brigade to buffer into
499 * @param ... The strings to write
501 AP_DECLARE_NONSTD(apr_status_t) ap_fputstrs(ap_filter_t *f,
502 apr_bucket_brigade *bb,
506 * Output data to the filter in printf format
507 * @param f the filter doing the writing
508 * @param bb The brigade to buffer into
509 * @param fmt The format string
510 * @param ... The argumets to use to fill out the format string
512 AP_DECLARE_NONSTD(apr_status_t) ap_fprintf(ap_filter_t *f,
513 apr_bucket_brigade *bb,
516 __attribute__((format(printf,3,4)));
522 #endif /* !AP_FILTER_H */