Documentation updates for 0.4.
[paraslash.git] / filter.h
1 /*
2 * Copyright (C) 2005-2009 Andre Noll <maan@systemlinux.org>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6
7 /** \file filter.h Filter-related structures and exported symbols from filter_common.c. */
8
9 /** The list of supported filters. */
10 enum filter_enum {FILTER_ENUM};
11
12 /**
13 * Describes one running instance of a filter.
14 */
15 struct filter_node {
16 /** The number in the array of available filters. */
17 unsigned filter_num;
18 /** The filter chain this filter node belongs to. */
19 struct filter_chain *fc;
20 /**
21 * Each filter may store any filter-specific information about the particular
22 * instance of the filter here.
23 */
24 void *private_data;
25 /** The output buffer. */
26 char *buf;
27 /** The size of the output buffer. */
28 size_t bufsize;
29 /** The number of bytes currently loaded in \a buf. */
30 size_t loaded;
31 /** The list of registered callbacks. */
32 struct list_head callbacks;
33 /** A pointer to the configuration of this instance. */
34 void *conf;
35 };
36
37 /** Describes one running instance of a chain of filters */
38 struct filter_chain {
39 /** The length of the filter chain. */
40 unsigned int num_filters;
41 /**
42 * The number of channels of the current stream.
43 *
44 * Set by the decoding filter.
45 */
46 unsigned int channels;
47 /**
48 * Current sample rate in Hz.
49 *
50 * Set by the decoding filter.
51 */
52 unsigned int samplerate;
53 /** The list containing all filter nodes in this filter chain. */
54 struct filter_node *filter_nodes;
55 /**
56 * The input buffer of the filter chain.
57 *
58 * This is set to point to the output buffer of the receiving application (the
59 * buffer used to read from stdin for para_filter; the output buffer of the
60 * current receiver for para_audiod).
61 */
62 char **inbufp;
63 /**
64 * The output buffer of the filter chain.
65 *
66 * Points to the output buffer of the last filter in the filter chain.
67 */
68 char **outbufp;
69 /** Contains the number of bytes loaded in the input buffer. */
70 size_t *in_loaded;
71 /** Contains the number of bytes loaded in the output buffer. */
72 size_t *out_loaded;
73 /** Pointer to the error variable of the receiving application. */
74 int *input_error;
75 /** Pointer to the error variable of the writing application. */
76 int *output_error;
77 /** The task associated with the filter chain. */
78 struct task task;
79 };
80
81 #define FOR_EACH_FILTER_NODE(fn, fc, i) for (i = 0; i < (fc)->num_filters \
82 && (fn = (fc)->filter_nodes + i); i++)
83
84
85 /**
86 * Used to manage grab clients.
87 *
88 * An application using paraslash's filter subsystem may register any number of
89 * callbacks for each filter_node. It is possible to attach a filter callback
90 * while the filter is running. This is used for stream grabbing in
91 * para_audiod: Whenever a client sends the 'grab' command, para_audiod adds a
92 * filter callback to the list of callbacks for the filter node specified in
93 * the grab command.
94 */
95 struct filter_callback {
96 /** All callbacks are organized in a doubly linked list. */
97 struct list_head node;
98 /**
99 * Private data.
100 *
101 * May be initialized by the application before registering the callback. This
102 * pointer is not used by the filter subsystem. It is provided for use within
103 * the input/output/close callback functions.
104 */
105 void *data;
106 /**
107 * The input callback.
108 *
109 * In not \p NULL, the filter subsystem calls this function whenever the filter
110 * consumed some or all of its input buffer. A pointer to the buffer of consumed
111 * data, its length and a pointer to the own \a filter_callback structure are passed
112 * to \a input_cb. The input callback is expected to return a negative value on errors.
113 */
114 int (*input_cb)(char *buf, size_t len, struct filter_callback *fc);
115 /**
116 * The output callback.
117 *
118 * If not NULL, this is called whenever the filter produces output. A pointer
119 * to the output data, its length and a pointer to the own \a filter_callback
120 * structure are passed to \a output_cb. Like the input callback, the output
121 * callback is expected to return a negative value on errors.
122 */
123 int (*output_cb)(char *buf, size_t len, struct filter_callback *fc);
124 /**
125 * The callback close function.
126 *
127 * This gets called whenever the input/output callback returned an error, or if
128 * the filter chain is going to be destroyed, e.g. because the end of the
129 * stream was encountered. It is assumed to succeed.
130 */
131 void (*close)(struct filter_callback *fc);
132 };
133
134
135 /**
136 * The structure associated with a paraslash filter.
137 *
138 * Paraslash filters are "modules" which are used to transform an audio stream.
139 * struct filter contains pointers to functions that must be supplied by the
140 * filter code in order to be used by the driving application (currently
141 * para_audiod and para_filter).
142 *
143 * Note: As several instances of the same filter may be running at the same
144 * time, all these filter functions must be reentrant; no static non-constant
145 * variables may be used.
146 * \sa mp3dec_filter.c, oggdec_filter.c, wav_filter.c, compress_filter.c, filter_node
147 */
148 struct filter {
149 /** The name of the filter. */
150 const char *name;
151 /**
152 * Pointer to the filter init routine.
153 *
154 * This function is only called once at startup. It must initialize the
155 * other non-optional function pointers of this structure.
156 */
157 void (*init)(struct filter *f);
158 /**
159 * Open one instance of this filter.
160 *
161 * This should allocate the output buffer of the given filter node and do any
162 * other filter-specific preparations like initializing the private_data member
163 * of \a fn suitably. The open function is assumed to succeed.
164 */
165 void (*open)(struct filter_node *fn);
166 /**
167 * Convert (filter) the given data.
168 *
169 * Pointer to the converting function of the filter. It should convert the
170 * given input buffer \a inbuf which is of length \a len to the previously
171 * reserved output buffer of \a fn. On success, it must return the number of
172 * bytes it consumed from \a inbuf. On errors, a negative number indicating the
173 * kind of the error must be returned.
174 *
175 * A zero return value just means that nothing was converted (probably because
176 * the input buffer was too small). This is not interpreted as an error.
177 */
178 ssize_t (*convert)(char *inbuf, size_t len, struct filter_node *fn);
179 /**
180 * Close one instance of this filter.
181 *
182 * Free all resources of associated with \a fn that were previously allocated
183 * by the open() function.
184 */
185 void (*close)(struct filter_node *fn);
186 /**
187 * A pointer to the filter's command line parser.
188 *
189 * If this optional function pointer is not NULL, any filter options
190 * are passed from the main program to this command line parser once at
191 * application startup. The command line parser should check its
192 * command line options given by \a argc and \a argv and abort on
193 * errors. Success must be indicated by a non-negative return value. In
194 * this case the function should return a pointer to the
195 * filter-specific configuration data determined by \a argc and \a
196 * argv. On failure, a negative paraslash error code must be returned.
197 */
198 int (*parse_config)(int argc, char **argv, void **config);
199
200 /** The help texts for this filter. */
201 struct ggo_help help;
202 };
203
204 void close_filters(struct filter_chain *fc);
205 void filter_init(void);
206 int check_filter_arg(char *filter_arg, void **conf);
207 void filter_pre_select(__a_unused struct sched *s, struct task *t);
208 void print_filter_helps(int detailed);
209
210 static inline void write_int16_host_endian(char *buf, int val)
211 {
212 #ifdef WORDS_BIGENDIAN
213 *buf = val >> 8;
214 *(buf + 1) = val & 0xff;
215 #else
216 *buf = val & 0xff;
217 *(buf + 1) = val >> 8;
218 #endif
219 }
220
221 DECLARE_FILTER_INITS
222
223 #define FOR_EACH_SUPPORTED_FILTER(j) for (j = 0; j < NUM_SUPPORTED_FILTERS; j++)
224
225 /** The filter array, one structure for each supported filter. */
226 extern struct filter filters[NUM_SUPPORTED_FILTERS];