filter.h

   1 /*
   2  * Copyright (C) 2005-2007 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_chain.c */
   8
   9 /**
  10  * describes one running instance of a chain of filters
  11  *
  12  */
  13 struct filter_chain {
  14         /**
  15          *
  16          *
  17          * the number of channels of the current stream
  18          *
  19          * Set by the decoding filter
  20          */
  21                 unsigned int channels;
  22         /**
  23          *
  24          *
  25          * current samplerate in Hz
  26          *
  27          * Set by the decoding filter
  28          */
  29                 unsigned int samplerate;
  30         /**
  31          *
  32          *
  33          * the list containing all filter nodes in this filter chain
  34          */
  35                 struct list_head filters;
  36         /**
  37          *
  38          *
  39          * the input buffer of the filter chain
  40          *
  41          * This is set to point to the output buffer of the receiving application (the
  42          * buffer used to read from stdin for para_filter; the output buffer of the
  43          * current receiver for para_audiod)
  44          */
  45                 char *inbuf;
  46         /**
  47          *
  48          *
  49          * the output buffer of the filter chain
  50          *
  51          * Points to the output buffer of the last filter in the filter chain
  52         **/
  53                 char *outbuf;
  54         /**
  55          *
  56          *
  57          * pointer to variable containing the number of bytes loaded in the input buffer
  58          */
  59                 size_t *in_loaded;
  60         /**
  61          *
  62          *
  63          * pointer to variable containing the number of bytes loaded in the output buffer
  64          */
  65                 size_t *out_loaded;
  66         /** Non-zero if this filter wont' produce any more output. */
  67         int error;
  68         /** Pointer to the error variable of the receiving application. */
  69         int *input_error;
  70         /** Pointer to the eof flag of the writing application. */
  71         int *output_error;
  72         /** the task associated with the filter chain */
  73         struct task task;
  74 };
  75
  76 /**
  77  * describes one running instance of a filter
  78 */
  79 struct filter_node {
  80 /**
  81  *
  82  *
  83  * a pointer to the corresponding filter struct
  84  */
  85         struct filter *filter;
  86 /**
  87  *
  88  *
  89  * the filter chain this filter node belongs to
  90  */
  91         struct filter_chain *fc;
  92 /**
  93  *
  94  *
  95  * the position of the filter in the corresponding filter chain
  96  *
  97  * all filters that make up the filter chains are organized in a doubly
  98  * linked list.
  99  */
 100         struct list_head node;
 101 /**
 102  *
 103  *
 104  * each filter may store any filter-specific information about the particular
 105  * instance of the filter here.
 106  */
 107         void *private_data;
 108 /**
 109  *
 110  *
 111  * the output buffer
 112  */
 113         char *buf;
 114 /**
 115  * the size of the output buffer
 116  */
 117         size_t bufsize;
 118 /**
 119  *
 120  *
 121  * the number of bytes currently loaded in \a buf
 122  */
 123         size_t loaded;
 124 /**
 125  *
 126  *
 127  * the list of registered callbacks
 128  */
 129         struct list_head callbacks;
 130 /**
 131  *
 132  * a pointer to the configuration of this instance
 133  */
 134         void *conf;
 135 };
 136
 137 /**
 138  * used to manage grab clients
 139  *
 140  * An application using paraslash's filter subsystem may register any number of
 141  * callbacks for each filter_node. It is possible to attach a filter callback
 142  * while the filter is running. This is used for stream grabbing in
 143  * para_audiod: Whenever a client sends the 'grab' command, para_audiod adds a
 144  * filter callback to the list of callbacks for the filter node specified in
 145  * the grab command.
 146  */
 147 struct filter_callback {
 148 /**
 149  *
 150  *
 151  * all callbacks are organized in a doubly linked list
 152  */
 153         struct list_head node;
 154 /**
 155  *
 156  *
 157  * private data
 158  *
 159  * May be initialized by the application before registering the callback. This
 160  * pointer is not used by the filter subsystem. It is provided for use within
 161  * the input/ouput/close callback functions.
 162  */
 163         void *data;
 164 /**
 165  *
 166  *
 167  * the input callback
 168  *
 169  * In not \p NULL, the filter subsystem calls this function whenever the filter
 170  * consumed some or all of its input buffer. A pointer to the buffer of consumed
 171  * data, its length and a pointer to the own \a filter_callback structure are passed
 172  * to \a input_cb. The input callback is expected to return a negative value on errors.
 173  */
 174         int (*input_cb)(char *buf, size_t len, struct filter_callback *fc);
 175 /**
 176  *
 177  *
 178  * the output callback
 179  *
 180  * If not NULL, this is called whenever the filter produces output. A pointer
 181  * to the output data, its length and a pointer to the own \a filter_callback
 182  * structure are passed to \a output_cb. Like the input callback, the output
 183  * callback is expected to return a negative value on errors.
 184  */
 185         int (*output_cb)(char *buf, size_t len, struct filter_callback *fc);
 186 /**
 187  *
 188  *
 189  * the callback close function
 190  *
 191  * This gets called whenever the input/ouput callback returned an error, or if
 192  * the filter chain is going to be destroyed, e.g. because the end of the
 193  * stream was encounterd. It is assumed to succeed.
 194  */
 195         void (*close)(struct filter_callback *fc);
 196 };
 197
 198
 199 void close_filters(struct filter_chain *fc);
 200 void filter_init(struct filter *all_filters);
 201 int check_filter_arg(char *filter_arg, void **conf);
 202 void filter_pre_select(__a_unused struct sched *s, struct task *t);
 203
 204 /**
 205  * the structure associated with a paraslash filter
 206  *
 207  * Paraslash filters are "modules" which are used to transform an audio stream.
 208  * struct filter contains pointers to functions that must be supplied by the
 209  * filter code in order to be used by the driving application (currently
 210  * para_audiod and para_filter).
 211  *
 212  * Note: As several instances of the same filter may be running at the same
 213  * time, all these filter functions must be reentrant; no static non-constant
 214  * variables may be used.
 215  * \sa mp3dec.c, oggdec.c, wav.c, compress.c, filter_node
 216  */
 217 struct filter {
 218 /**
 219  *
 220  *
 221  * the name of the filter
 222  */
 223 const char *name;
 224 /**
 225  *
 226  *
 227  * pointer to the filter init routine
 228  *
 229  * This function is only called once at startup. It must initialize the
 230  * other non-optional function pointers of \a f.
 231  */
 232 void (*init)(struct filter *f);
 233 /**
 234  *
 235  *
 236  * open one instance of this filter
 237  *
 238  * This should allocate the output buffer of the given filter node and do any
 239  * other filter-specific preparations like initializing the private_data member
 240  * of \a fn suitably. The open function is assumed to succeed.
 241  */
 242 void (*open)(struct filter_node *fn);
 243 /**
 244  *
 245  *
 246  * convert (filter) the given data
 247  *
 248  * Pointer to the converting function of the filter. It should convert the
 249  * given input buffer \a inbuf which is of length \a len to the previoulsy
 250  * reserved output buffer of \a fn. On success, it must return the number of
 251  * bytes it consumed from \a inbuf. On errors, a negative number indicating the
 252  * kind of the error must be returned.
 253  *
 254  * A zero return value just means that nothing was converted (probably because
 255  * the input buffer was too small). This is not interpreted as an error.
 256  */
 257 ssize_t (*convert)(char *inbuf, size_t len, struct filter_node *fn);
 258 /**
 259  *
 260  *
 261  * close one instance of this filter
 262  *
 263  * Free all resources of associated with \a fn that were previously allocated
 264  * by the open() function.
 265  */
 266 void (*close)(struct filter_node *fn);
 267 /**
 268  *
 269  *
 270  * print the help text for this filter and exit
 271  *
 272  * This is optional and it is not necessary to initialize this pointer if
 273  * the filter does not have a help text.
 274  */
 275 void (*print_help)(void);
 276 /**
 277  *
 278  *
 279  * a pointer to the filter's command line parser
 280  *
 281  * If this optional function pointer is not NULL, any filter options are passed
 282  * from the main propgram to this command line parser once at application
 283  * startup. The command line parser should check its command line options given
 284  * by \a argc and \a argv and abort on errors. On success, it should return a
 285  * pointer to the filter-specific configuration data determined by \a argc and
 286  * \a argv.
 287  */
 288 void *(*parse_config)(int argc, char **argv);
 289 };
 290
 291
 292 static inline void write_int16_host_endian(char *buf, int val)
 293 {
 294 #ifdef WORDS_BIGENDIAN
 295         *buf = val >> 8;
 296         *(buf + 1) = val & 0xff;
 297 #else
 298         *buf = val & 0xff;
 299         *(buf + 1) = val >> 8;
 300 #endif
 301 }
 302
 303
 304 /** \cond */
 305 extern struct filter filters[];
 306 #define DECLARE_EXTERN_FILTER_INIT(name) \
 307         extern void name ## _init(struct filter *f)
 308
 309 #define FILTER_INIT(filter) { \
 310         .name = #filter, \
 311         .init = filter ## _init, \
 312         .parse_config = NULL, \
 313         .print_help = NULL \
 314 },
 315
 316 /* filters that are always present */
 317 DECLARE_EXTERN_FILTER_INIT(wav);
 318 /* wav is always the first filter */
 319 #define WAV_FILTER_NUM 0
 320 DECLARE_EXTERN_FILTER_INIT(compress);
 321
 322 /* next the optional filters */
 323 #ifdef HAVE_MAD
 324 DECLARE_EXTERN_FILTER_INIT(mp3dec);
 325 #define MP3DEC_FILTER FILTER_INIT(mp3dec)
 326 #else
 327 #define MP3DEC_FILTER
 328 #endif
 329
 330 #ifdef HAVE_FAAD
 331 DECLARE_EXTERN_FILTER_INIT(aacdec);
 332 #define AACDEC_FILTER FILTER_INIT(aacdec)
 333 #else
 334 #define AACDEC_FILTER
 335 #endif
 336
 337 #ifdef HAVE_OGGVORBIS
 338 DECLARE_EXTERN_FILTER_INIT(oggdec);
 339 #define OGGDEC_FILTER FILTER_INIT(oggdec)
 340 #else
 341 #define OGGDEC_FILTER
 342 #endif
 343 /** \endcond */
 344
 345 /** define an array of all available filters */
 346 #define DEFINE_FILTER_ARRAY(filters) struct filter filters[] = { \
 347         FILTER_INIT(wav) \
 348         FILTER_INIT(compress) \
 349         MP3DEC_FILTER \
 350         AACDEC_FILTER \
 351         OGGDEC_FILTER \
 352         { .name = NULL } };
 353
 354