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62 #ifdef APR_HAVE_STDARG_H
68 #include "apr_buckets.h"
71 * @package Apache filter library
74 #define AP_NOBODY_WROTE -1
75 #define AP_NOBODY_READ -2
76 #define AP_FILTER_ERROR -3
79 * @heading ap_input_mode_t - input filtering modes
83 * The filter shouldn't return until data is received or EOF is hit
88 * The filter should process any available data/status as normal,
89 * but will not wait for additional data.
93 * The filter should return APR_SUCCESS if data is available or
94 * APR_EOF otherwise. The filter must not return any buckets of
95 * data. Data returned on a subsequent call, when mode is
96 * AP_MODE_BLOCKING or AP_MODE_NONBLOCKING.
107 * Filters operate using a "chaining" mechanism. The filters are chained
108 * together into a sequence. When output is generated, it is passed through
109 * each of the filters on this chain, until it reaches the end (or "bottom")
110 * and is placed onto the network.
112 * The top of the chain, the code generating the output, is typically called
113 * a "content generator." The content generator's output is fed into the
114 * filter chain using the standard Apache output mechanisms: ap_rputs(),
115 * ap_rprintf(), ap_rwrite(), etc.
117 * Each filter is defined by a callback. This callback takes the output from
118 * the previous filter (or the content generator if there is no previous
119 * filter), operates on it, and passes the result to the next filter in the
120 * chain. This pass-off is performed using the ap_fc_* functions, such as
121 * ap_fc_puts(), ap_fc_printf(), ap_fc_write(), etc.
123 * When content generation is complete, the system will pass an "end of
124 * stream" marker into the filter chain. The filters will use this to flush
125 * out any internal state and to detect incomplete syntax (for example, an
126 * unterminated SSI directive).
129 /* forward declare the filter type */
130 typedef struct ap_filter_t ap_filter_t;
135 * This function type is used for filter callbacks. It will be passed a
136 * pointer to "this" filter, and a "bucket" containing the content to be
139 * In filter->ctx, the callback will find its context. This context is
140 * provided here, so that a filter may be installed multiple times, each
141 * receiving its own per-install context pointer.
143 * Callbacks are associated with a filter definition, which is specified
144 * by name. See ap_register_input_filter() and ap_register_output_filter()
145 * for setting the association between a name for a filter and its
146 * associated callback (and other information).
148 * The *bucket structure (and all those referenced by ->next and ->prev)
149 * should be considered "const". The filter is allowed to modify the
150 * next/prev to insert/remove/replace elements in the bucket list, but
151 * the types and values of the individual buckets should not be altered.
153 * The return value of a filter should be an APR status value.
155 typedef apr_status_t (*ap_out_filter_func)(ap_filter_t *f, apr_bucket_brigade *b);
156 typedef apr_status_t (*ap_in_filter_func)(ap_filter_t *f, apr_bucket_brigade *b,
157 ap_input_mode_t mode);
158 typedef union ap_filter_func {
159 ap_out_filter_func out_func;
160 ap_in_filter_func in_func;
164 * @heading Filter Types
168 * Filters have different types/classifications. These are used to group
169 * and sort the filters to properly sequence their operation.
172 * These filters are used to alter the content that is passed through
173 * them. Examples are SSI or PHP.
175 * AP_FTYPE_HTTP_HEADER: (XXX somebody rename me or get rid of me please)
176 * This special type ensures that the HTTP header filter ends up in
177 * the proper location in the filter chain.
179 * AP_FTYPE_TRANSCODE:
180 * These filters implement transport encodings (e.g., chunking).
182 * AP_FTYPE_CONNECTION:
183 * These filters will alter the content, but in ways that are more
184 * strongly associated with the connection. Examples are splitting
185 * an HTTP connection into multiple requests and buffering HTTP
186 * responses across multiple requests.
188 * It is important to note that these types of filters are not allowed
189 * in a sub-request. A sub-request's output can certainly be filtered
190 * by AP_FTYPE_CONTENT filters, but all of the "final processing" is
191 * determined by the main request.
194 * These filters don't alter the content. They are responsible for
195 * sending/receiving data to/from the client.
197 * The types have a particular sort order, which allows us to insert them
198 * into the filter chain in a determistic order. Within a particular grouping,
199 * the ordering is equivalent to the order of calls to ap_add_*_filter().
202 AP_FTYPE_CONTENT = 10,
203 AP_FTYPE_HTTP_HEADER = 20,
204 AP_FTYPE_TRANSCODE = 30,
205 AP_FTYPE_CONNECTION = 40,
206 AP_FTYPE_NETWORK = 50
212 * This is the request-time context structure for an installed filter (in
213 * the output filter chain). It provides the callback to use for filtering,
214 * the request this filter is associated with (which is important when
215 * an output chain also includes sub-request filters), the context for this
216 * installed filter, and the filter ordering/chaining fields.
218 * Filter callbacks are free to use ->ctx as they please, to store context
219 * during the filter process. Generally, this is superior over associating
220 * the state directly with the request. A callback should not change any of
224 typedef struct ap_filter_rec_t ap_filter_rec_t;
227 * This structure is used for recording information about the
228 * registered filters. It associates a name with the filter's callback
231 * At the moment, these are simply linked in a chain, so a ->next pointer
234 struct ap_filter_rec_t {
235 /** The registered name for this filter */
237 /** The function to call when this filter is invoked. */
238 ap_filter_func filter_func;
239 /** The type of filter, either AP_FTYPE_CONTENT or AP_FTYPE_CONNECTION.
240 * An AP_FTYPE_CONTENT filter modifies the data based on information
241 * found in the content. An AP_FTYPE_CONNECTION filter modifies the
242 * data based on the type of connection.
244 ap_filter_type ftype;
246 /** The next filter_rec in the list */
247 struct ap_filter_rec_t *next;
251 * The representation of a filter chain. Each request has a list
252 * of these structures which are called in turn to filter the data. Sub
253 * requests get an exact copy of the main requests filter chain.
256 /** The internal representation of this filter. This includes
257 * the filter's name, type, and the actual function pointer.
259 ap_filter_rec_t *frec;
261 /** A place to store any data associated with the current filter */
264 /** The next filter in the chain */
267 /** The request_rec associated with the current filter. If a sub-request
268 * adds filters, then the sub-request is the request associated with the
273 /** The conn_rec associated with the current filter. This is analogous
274 * to the request_rec, except that it is used for input filtering.
280 * Get the current bucket brigade from the next filter on the filter
281 * stack. The filter should return an apr_status_t value. If the bottom-most
282 * filter doesn't write to the network, then AP_NOBODY_READ is returned.
283 * @param filter The next filter in the chain
284 * @param bucket The current bucket brigade
285 * @param mode AP_MODE_BLOCKING, AP_MODE_NONBLOCKING, or AP_MODE_PEEK
286 * @return apr_status_t value
287 * @deffunc apr_status_t ap_get_brigade(ap_filter_t *filter, apr_bucket_brigade *bucket, ap_input_mode_t mode)
289 AP_DECLARE(apr_status_t) ap_get_brigade(ap_filter_t *filter, apr_bucket_brigade *bucket,
290 ap_input_mode_t mode);
293 * Pass the current bucket brigade down to the next filter on the filter
294 * stack. The filter should return an apr_status_t value. If the bottom-most
295 * filter doesn't write to the network, then AP_NOBODY_WROTE is returned.
296 * @param filter The next filter in the chain
297 * @param bucket The current bucket brigade
298 * @return apr_status_t value
299 * @deffunc apr_status_t ap_pass_brigade(ap_filter_t *filter, apr_bucket_brigade *bucket)
301 AP_DECLARE(apr_status_t) ap_pass_brigade(ap_filter_t *filter, apr_bucket_brigade *bucket);
304 * This function is used to register an input filter with the system.
305 * After this registration is performed, then a filter may be added
306 * into the filter chain by using ap_add_input_filter() and simply
307 * specifying the name.
309 * @param name The name to attach to the filter function
310 * @param filter_func The filter function to name
311 * @param ftype The type of filter function, either AP_FTYPE_CONTENT or AP_FTYPE_CONNECTION
313 AP_DECLARE(void) ap_register_input_filter(const char *name,
314 ap_in_filter_func filter_func,
315 ap_filter_type ftype);
317 * This function is used to register an output filter with the system.
318 * After this registration is performed, then a filter may be added
319 * into the filter chain by using ap_add_output_filter() and simply
320 * specifying the name.
322 * @param name The name to attach to the filter function
323 * @param filter_func The filter function to name
324 * @param ftype The type of filter function, either AP_FTYPE_CONTENT or AP_FTYPE_CONNECTION
325 * @see ::ap_add_output_filter
327 AP_DECLARE(void) ap_register_output_filter(const char *name,
328 ap_out_filter_func filter_func,
329 ap_filter_type ftype);
334 * Adds a named filter into the filter chain on the specified request record.
335 * The filter will be installed with the specified context pointer.
337 * Filters added in this way will always be placed at the end of the filters
338 * that have the same type (thus, the filters have the same order as the
339 * calls to ap_add_filter). If the current filter chain contains filters
340 * from another request, then this filter will be added before those other
343 * To re-iterate that last comment. This function is building a FIFO
344 * list of filters. Take note of that when adding your filter to the chain.
347 * Add a filter to the current connection. Filters are added in a FIFO manner.
348 * The first filter added will be the first filter called.
349 * @param name The name of the filter to add
350 * @param r The request to add this filter for (or NULL if it isn't associated with a request)
351 * @param c The connection to add the fillter for
352 * @deffunc void ap_add_input_filter(const char *name, void *ctx, request_rec *r, conn_rec *c)
354 AP_DECLARE(void) ap_add_input_filter(const char *name, void *ctx, request_rec *r, conn_rec *c);
357 * Add a filter to the current request. Filters are added in a FIFO manner.
358 * The first filter added will be the first filter called.
359 * @param name The name of the filter to add
360 * @param ctx Context data to set in the filter
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 this filter for
363 * @deffunc void ap_add_output_filter(const char *name, void *ctx, request_rec *r, conn_rec *c)
365 AP_DECLARE(void) ap_add_output_filter(const char *name, void *ctx,
366 request_rec *r, conn_rec *c);
368 AP_DECLARE(void) ap_remove_output_filter(ap_filter_t *f);
370 /* The next two filters are for abstraction purposes only. They could be
371 * done away with, but that would require that we break modules if we ever
372 * want to change our filter registration method. The basic idea, is that
373 * all filters have a place to store data, the ctx pointer. These functions
374 * fill out that pointer with a bucket brigade, and retrieve that data on
375 * the next call. The nice thing about these functions, is that they
376 * automatically concatenate the bucket brigades together for you. This means
377 * that if you have already stored a brigade in the filters ctx pointer, then
378 * when you add more it will be tacked onto the end of that brigade. When
379 * you retrieve data, if you pass in a bucket brigade to the get function,
380 * it will append the current brigade onto the one that you are retrieving.
384 * prepare a bucket brigade to be setaside. If a different brigade was
385 * set-aside earlier, then the two brigades are concatenated together.
386 * @param f The current filter
387 * @param save_to The brigade that was previously set-aside. Regardless, the
388 * new bucket brigade is returned in this location.
389 * @param b The bucket brigade to save aside. This brigade is always empty
391 * @deffunc apr_status_t ap_save_brigade(ap_filter_t *f, apr_bucket_brigade **save_to, apr_bucket_brigade **b)
393 AP_DECLARE(apr_status_t) ap_save_brigade(ap_filter_t *f, apr_bucket_brigade **save_to,
394 apr_bucket_brigade **b);
397 * Flush function for apr_brigade_* calls. This calls ap_pass_brigade
398 * to flush the brigade if the brigade buffer overflows.
399 * @param bb The brigade to flush
400 * @param ctx The filter to pass the brigade to
401 * @deffunc apr_status_t ap_filter_flush(apr_bucket_brigade *bb, void *ctx)
403 AP_DECLARE(apr_status_t) ap_filter_flush(apr_bucket_brigade *bb, void *ctx);
406 * Flush the current brigade down the filter stack
407 * @param f the next filter in the stack
408 * @param bb The brigade to flush
409 * @deffunc apr_status_t ap_fflush(ap_filter_t *f, apr_bucket_brigade *bb)
411 AP_DECLARE(apr_status_t) ap_fflush(ap_filter_t *f, apr_bucket_brigade *bb);
414 * Write a buffer for the current filter, buffering if possible.
415 * @param f the filter doing the writing
416 * @param bb The brigade to buffer into
417 * @param data The data to write
418 * @param nbyte The number of bytes in the data
419 * @deffunc int ap_fwrite(ap_filter_t *f, apr_bucket_brigade *bb, const char *data, apr_ssize_t nbyte);
421 #define ap_fwrite(f, bb, data, nbyte) \
422 apr_brigade_write(bb, ap_filter_flush, (f)->next, data, nbyte)
425 * Write a buffer for the current filter, buffering if possible.
426 * @param f the filter doing the writing
427 * @param bb The brigade to buffer into
428 * @param str The string to write
429 * @deffunc int ap_fputs(ap_filter_t *f, apr_bucket_brigade *bb, const char *str);
431 #define ap_fputs(f, bb, str) \
432 apr_brigade_puts(bb, ap_filter_flush, (f)->next, str)
435 * Write a character for the current filter, buffering if possible.
436 * @param f the filter doing the writing
437 * @param bb The brigade to buffer into
438 * @param c The character to write
439 * @deffunc int ap_fputc(ap_filter_t *f, apr_bucket_brigade *bb, char c);
441 #define ap_fputc(f, bb, c) \
442 apr_brigade_putc(bb, ap_filter_flush, (f)->next, c)
445 * Write an unspecified number of strings to the current filter
446 * @param f the filter doing the writing
447 * @param bb The brigade to buffer into
448 * @param ... The strings to write
449 * @deffunc int ap_fputs(ap_filter_t *f, apr_bucket_brigade *bb, ...);
451 #define ap_fvputs(f, bb, args...) \
452 apr_brigade_putstrs(bb, ap_filter_flush, (f)->next, ##args)
455 * Output data to the filter in printf format
456 * @param f the filter doing the writing
457 * @param bb The brigade to buffer into
458 * @param fmt The format string
459 * @param ... The argumets to use to fill out the format string
460 * @deffunc int ap_fputs(ap_filter_t *f, apr_bucket_brigade *bb, const char *fmt, ...);
462 #define ap_fprintf(f, bb, fmt, args...) \
463 apr_brigade_printf(bb, ap_filter_flush, (f)->next, fmt, ##args)
469 #endif /* !AP_FILTER_H */