2 * Copyright (C) 2005-2009 Andre Noll <maan@systemlinux.org>
4 * Licensed under the GPL v2. For licencing details see COPYING.
7 /** \file filter.h Filter-related structures and exported symbols from filter_common.c. */
9 /** The list of supported filters. */
10 enum filter_enum {FILTER_ENUM};
13 * Describes one running instance of a filter.
16 /** The number in the array of available filters. */
18 /** The filter chain this filter node belongs to. */
19 struct filter_chain *fc;
21 * Each filter may store any filter-specific information about the particular
22 * instance of the filter here.
25 /** The output buffer. */
27 /** The size of the output buffer. */
29 /** The number of bytes currently loaded in \a buf. */
31 /** The list of registered callbacks. */
32 struct list_head callbacks;
33 /** A pointer to the configuration of this instance. */
35 struct btr_node *btrn;
39 /** Describes one running instance of a chain of filters */
41 /** The length of the filter chain. */
42 unsigned int num_filters;
44 * The number of channels of the current stream.
46 * Set by the decoding filter.
48 unsigned int channels;
50 * Current sample rate in Hz.
52 * Set by the decoding filter.
54 unsigned int samplerate;
55 /** The list containing all filter nodes in this filter chain. */
56 struct filter_node *filter_nodes;
58 * The input buffer of the filter chain.
60 * This is set to point to the output buffer of the receiving application (the
61 * buffer used to read from stdin for para_filter; the output buffer of the
62 * current receiver for para_audiod).
66 * The output buffer of the filter chain.
68 * Points to the output buffer of the last filter in the filter chain.
71 /** Contains the number of bytes loaded in the input buffer. */
73 /** Contains the number of bytes loaded in the output buffer. */
75 /** Pointer to the error variable of the receiving application. */
77 /** Pointer to the error variable of the writing application. */
79 /** The task associated with the filter chain. */
83 #define FOR_EACH_FILTER_NODE(fn, fc, i) for (i = 0; i < (fc)->num_filters \
84 && (fn = (fc)->filter_nodes + i); i++)
88 * Used to manage grab clients.
90 * An application using paraslash's filter subsystem may register any number of
91 * callbacks for each filter_node. It is possible to attach a filter callback
92 * while the filter is running. This is used for stream grabbing in
93 * para_audiod: Whenever a client sends the 'grab' command, para_audiod adds a
94 * filter callback to the list of callbacks for the filter node specified in
97 struct filter_callback {
98 /** All callbacks are organized in a doubly linked list. */
99 struct list_head node;
101 * The input callback.
103 * If not \p NULL, the filter subsystem calls this function whenever the filter
104 * consumed some or all of its input buffer. A pointer to the buffer of consumed
105 * data, its length and a pointer to the own \a filter_callback structure are passed
106 * to \a input_cb. The input callback is expected to return a negative value on errors.
108 int (*input_cb)(char *buf, size_t len, struct filter_callback *fc);
110 * The output callback.
112 * If not NULL, this is called whenever the filter produces output. A pointer
113 * to the output data, its length and a pointer to the own \a filter_callback
114 * structure are passed to \a output_cb. Like the input callback, the output
115 * callback is expected to return a negative value on errors.
117 int (*output_cb)(char *buf, size_t len, struct filter_callback *fc);
119 * The callback close function.
121 * This gets called whenever the input/output callback returned an error, or if
122 * the filter chain is going to be destroyed, e.g. because the end of the
123 * stream was encountered. It is assumed to succeed.
125 void (*close)(struct filter_callback *fc);
130 * The structure associated with a paraslash filter.
132 * Paraslash filters are "modules" which are used to transform an audio stream.
133 * struct filter contains pointers to functions that must be supplied by the
134 * filter code in order to be used by the driving application (currently
135 * para_audiod and para_filter).
137 * Note: As several instances of the same filter may be running at the same
138 * time, all these filter functions must be reentrant; no static non-constant
139 * variables may be used.
140 * \sa mp3dec_filter.c, oggdec_filter.c, wav_filter.c, compress_filter.c, filter_node
143 /** The name of the filter. */
146 * Pointer to the filter init routine.
148 * This function is only called once at startup. It must initialize the
149 * other non-optional function pointers of this structure.
151 void (*init)(struct filter *f);
153 * Open one instance of this filter.
155 * This should allocate the output buffer of the given filter node and do any
156 * other filter-specific preparations like initializing the private_data member
157 * of \a fn suitably. The open function is assumed to succeed.
159 void (*open)(struct filter_node *fn);
161 * Convert (filter) the given data.
163 * Pointer to the converting function of the filter. It should convert the
164 * given input buffer \a inbuf which is of length \a len to the previously
165 * reserved output buffer of \a fn. On success, it must return the number of
166 * bytes it consumed from \a inbuf. On errors, a negative number indicating the
167 * kind of the error must be returned.
169 * A zero return value just means that nothing was converted (probably because
170 * the input buffer was too small). This is not interpreted as an error.
172 ssize_t (*convert)(char *inbuf, size_t len, struct filter_node *fn);
174 * Close one instance of this filter.
176 * Free all resources of associated with \a fn that were previously allocated
177 * by the open() function.
179 void (*close)(struct filter_node *fn);
181 * A pointer to the filter's command line parser.
183 * If this optional function pointer is not NULL, any filter options
184 * are passed from the main program to this command line parser once at
185 * application startup. The command line parser should check its
186 * command line options given by \a argc and \a argv and abort on
187 * errors. Success must be indicated by a non-negative return value. In
188 * this case the function should return a pointer to the
189 * filter-specific configuration data determined by \a argc and \a
190 * argv. On failure, a negative paraslash error code must be returned.
192 int (*parse_config)(int argc, char **argv, void **config);
194 /** The help texts for this filter. */
195 struct ggo_help help;
197 void (*pre_select)(struct sched *s, struct task *t);
198 void (*post_select)(struct sched *s, struct task *t);
199 btr_command_handler execute;
202 void close_filters(struct filter_chain *fc);
203 void filter_init(void);
204 int check_filter_arg(char *filter_arg, void **conf);
205 void filter_post_select(__a_unused struct sched *s, struct task *t);
206 void print_filter_helps(int detailed);
208 static inline void write_int16_host_endian(char *buf, int val)
210 #ifdef WORDS_BIGENDIAN
212 *(buf + 1) = val & 0xff;
215 *(buf + 1) = val >> 8;
221 #define FOR_EACH_SUPPORTED_FILTER(j) for (j = 0; j < NUM_SUPPORTED_FILTERS; j++)
223 /** The filter array, one structure for each supported filter. */
224 extern struct filter filters[NUM_SUPPORTED_FILTERS];