util_filter.h revision d025a1bfef81af5c3a1e784762bf27971114b6e3
* The Apache Software License, Version 1.1 * Copyright (c) 2000 The Apache Software Foundation. All rights * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * 3. The end-user documentation included with the redistribution, * if any, must include the following acknowledgment: * "This product includes software developed by the * Alternately, this acknowledgment may appear in the software itself, * if and wherever such third-party acknowledgments normally appear. * 4. 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IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * ==================================================================== * This software consists of voluntary contributions made by many * individuals on behalf of the Apache Software Foundation. For more * information on the Apache Software Foundation, please see * @package Apache filter library * Filters operate using a "chaining" mechanism. The filters are chained * together into a sequence. When output is generated, it is passed through * each of the filters on this chain, until it reaches the end (or "bottom") * and is placed onto the network. * The top of the chain, the code generating the output, is typically called * a "content generator." The content generator's output is fed into the * filter chain using the standard Apache output mechanisms: ap_rputs(), * ap_rprintf(), ap_rwrite(), etc. * Each filter is defined by a callback. This callback takes the output from * the previous filter (or the content generator if there is no previous * filter), operates on it, and passes the result to the next filter in the * chain. This pass-off is performed using the ap_fc_* functions, such as * ap_fc_puts(), ap_fc_printf(), ap_fc_write(), etc. * When content generation is complete, the system will pass an "end of * stream" marker into the filter chain. The filters will use this to flush * out any internal state and to detect incomplete syntax (for example, an * unterminated SSI directive). /* forward declare the filter type */ * This function type is used for filter callbacks. It will be passed a * pointer to "this" filter, and a "bucket" containing the content to be * In filter->ctx, the callback will find its context. This context is * provided here, so that a filter may be installed multiple times, each * receiving its own per-install context pointer. * Callbacks are associated with a filter definition, which is specified * by name. See ap_register_input_filter() and ap_register_output_filter() * for setting the association between a name for a filter and its * associated callback (and other information). * The *bucket structure (and all those referenced by ->next and ->prev) * should be considered "const". The filter is allowed to modify the * the types and values of the individual buckets should not be altered. * The return value of a filter should be an APR status value. * and sort the filters to properly sequence their operation. * These filters are used to alter the content that is passed through * them. Examples are SSI or PHP. * These filters will alter the content, but in ways that are more * strongly associated with the output connection. Examples are * compression, character recoding, or chunked transfer coding. * It is important to note that these types of filters are not allowed * in a sub-request. A sub-requests output can certainly be filtered * by AP_FTYPE_CONTENT filters, but all of the "final processing" is * determined by the main request. * The types have a particular sort order, which allows us to insert them * into the filter chain in a determistic order. Within a particular grouping, * the ordering is equivalent to the order of calls to ap_add_*_filter(). * This is the request-time context structure for an installed filter (in * the output filter chain). It provides the callback to use for filtering, * the request this filter is associated with (which is important when * an output chain also includes sub-request filters), the context for this * Filter callbacks are free to use ->ctx as they please, to store context * during the filter process. Generally, this is superior over associating * the state directly with the request. A callback should not change any of * This structure is used for recording information about the * registered filters. It associates a name with the filter's callback * At the moment, these are simply linked in a chain, so a ->next pointer /** The registered name for this filter */ /** The function to call when this filter is invoked. */ /** The type of filter, either AP_FTYPE_CONTENT or AP_FTYPE_CONNECTION. * An AP_FTYPE_CONTENT filter modifies the data based on information * found in the content. An AP_FTYPE_CONNECTION filter modifies the * data based on the type of connection. /** The next filter_rec in the list */ * The representation of a filter chain. Each request has a list * of these structures which are called in turn to filter the data. Sub * requests get an exact copy of the main requests filter chain. /** The internal representation of this filter. This includes * the filter's name, type, and the actual function pointer. /** A place to store any data associated with the current filter */ /** The next filter in the chain */ /** The request_rec associated with the current filter. If a sub-request * adds filters, then the sub-request is the request associated with the /** The conn_rec associated with the current filter. This is analogous * to the request_rec, except that it is used for input filtering. /* This function just passes the current bucket brigade down to the next * filter on the filter stack. When a filter actually writes to the network * (usually either core or SSL), that filter should return the number of bytes * actually written and it will get propogated back up to the handler. If * nobody writes the data to the network, then this function will most likely * seg fault. I haven't come up with a good way to detect that case yet, and * it should never happen. Regardless, it's an unrecoverable error for the * current request. I would just rather it didn't take out the whole child * Get the current bucket brigade from the next filter on the filter * stack. The filter should return an apr_status_t value. If the bottom-most * filter doesn't write to the network, then AP_NOBODY_WROTE is returned. * @param filter The next filter in the chain * @param bucket The current bucket brigade * @return apr_status_t value * @deffunc apr_status_t ap_get_brigade(ap_filter_t *filter, ap_bucket_brigade *bucket) * Pass the current bucket brigade down to the next filter on the filter * stack. The filter should return an apr_status_t value. If the bottom-most * filter doesn't write to the network, then AP_NOBODY_WROTE is returned. * @param filter The next filter in the chain * @param bucket The current bucket brigade * @return apr_status_t value * @deffunc apr_status_t ap_pass_brigade(ap_filter_t *filter, ap_bucket_brigade *bucket) * ap_register_input_filter(): * This function is used to register an input filter with the system. * After this registration is performed, then a filter may be added * into the filter chain by using ap_add_input_filter() and simply * The filter's callback and type should be passed. * Register an input filter for later use. This allows modules to name their * filter functions for later addition to a specific request * @param name The name to attach to the filter function * @param filter_func The filter function to name * @param The type of filter function, either AP_FTYPE_CONTENT or AP_FTYPE_CONNECTION * @deffunc void ap_register_input_filter(const char *name, ap_filter_func filter_func, ap_filter_type ftype) * ap_register_output_filter(): * This function is used to register an output filter with the system. * After this registration is performed, then a filter may be added * into the filter chain by using ap_add_output_filter() and simply * The filter's callback and type should be passed. * Register an output filter for later use. This allows modules to name their * filter functions for later addition to a specific request * @param name The name to attach to the filter function * @param filter_func The filter function to name * @param The type of filter function, either AP_FTYPE_CONTENT or AP_FTYPE_CONNECTION * @deffunc void ap_register_output_filter(const char *name, ap_filter_func filter_func, ap_filter_type ftype) * Adds a named filter into the filter chain on the specified request record. * The filter will be installed with the specified context pointer. * Filters added in this way will always be placed at the end of the filters * that have the same type (thus, the filters have the same order as the * calls to ap_add_filter). If the current filter chain contains filters * from another request, then this filter will be added before those other * To re-iterate that last comment. This function is building a FIFO * list of filters. Take note of that when adding your filter to the chain. * Add a filter to the current connection. Filters are added in a FIFO manner. * The first filter added will be the first filter called. * @param name The name of the filter to add * @param c The connection to add the fillter for * @deffunc void ap_add_input_filter(const char *name, void *ctx, conn_rec *r) * Add a filter to the current request. Filters are added in a FIFO manner. * The first filter added will be the first filter called. * @param name The name of the filter to add * @param ctx Context data to set in the filter * @param r The request to add this filter for (or NULL if it isn't associated with a request) * @param c The connection to add this filter for * @deffunc void ap_add_output_filter(const char *name, void *ctx, request_rec *r, conn_rec *c) /* The next two filters are for abstraction purposes only. They could be * done away with, but that would require that we break modules if we ever * want to change our filter registration method. The basic idea, is that * all filters have a place to store data, the ctx pointer. These functions * fill out that pointer with a bucket brigade, and retrieve that data on * the next call. The nice thing about these functions, is that they * automatically concatenate the bucket brigades together for you. This means * that if you have already stored a brigade in the filters ctx pointer, then * when you add more it will be tacked onto the end of that brigade. When * you retrieve data, if you pass in a bucket brigade to the get function, * it will append the current brigade onto the one that you are retrieving. * prepare a bucket brigade to be setaside. If a different brigade was * set-aside earlier, then the two brigades are concatenated together. * @param f The current filter * @param save_to The brigade that was previously set-aside. Regardless, the * new bucket brigade is returned in this location. * @param b The bucket brigade to save aside. This brigade is always empty * @deffunc void ap_save_brigade(ap_filter_t *f, ap_bucket_brigade **save_to, ap_bucket_brigade **b) #
endif /* !AP_FILTER_H */