filter.h

   1 /*
   2  * Copyright (C) 2005-2008 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 /**
  11  * Describes one running instance of a filter.
  12 */
  13 struct filter_node {
  14         /** The number in the array of available filters. */
  15         unsigned filter_num;
  16         /** The filter chain this filter node belongs to. */
  17         struct filter_chain *fc;
  18         /**
  19          * Each filter may store any filter-specific information about the particular
  20          * instance of the filter here.
  21          */
  22         void *private_data;
  23         /** The output buffer. */
  24         char *buf;
  25         /** The size of the output buffer. */
  26         size_t bufsize;
  27         /** The number of bytes currently loaded in \a buf. */
  28         size_t loaded;
  29         /** The list of registered callbacks. */
  30         struct list_head callbacks;
  31         /** A pointer to the configuration of this instance. */
  32         void *conf;
  33 };
  34
  35 /** Describes one running instance of a chain of filters */
  36 struct filter_chain {
  37         unsigned int num_filters;
  38         /**
  39          * The number of channels of the current stream.
  40          *
  41          * Set by the decoding filter.
  42          */
  43         unsigned int channels;
  44         /**
  45          * Current sample rate in Hz.
  46          *
  47          * Set by the decoding filter.
  48          */
  49         unsigned int samplerate;
  50         /** The list containing all filter nodes in this filter chain. */
  51         struct filter_node *filter_nodes;
  52         /**
  53          * The input buffer of the filter chain.
  54          *
  55          * This is set to point to the output buffer of the receiving application (the
  56          * buffer used to read from stdin for para_filter; the output buffer of the
  57          * current receiver for para_audiod).
  58          */
  59         char *inbuf;
  60         /**
  61          * The output buffer of the filter chain.
  62          *
  63          * Points to the output buffer of the last filter in the filter chain.
  64          */
  65         char *outbuf;
  66         /** Contains the number of bytes loaded in the input buffer. */
  67         size_t *in_loaded;
  68         /** Contains the number of bytes loaded in the output buffer. */
  69         size_t *out_loaded;
  70         /** Pointer to the error variable of the receiving application. */
  71         int *input_error;
  72         /** Pointer to the error variable of the writing application. */
  73         int *output_error;
  74         /** The task associated with the filter chain. */
  75         struct task task;
  76 };
  77
  78 #define FOR_EACH_FILTER_NODE(fn, fc, i) for (i = 0; i < (fc)->num_filters \
  79         && (fn = (fc)->filter_nodes + i); i++)
  80
  81
  82 /**
  83  * Used to manage grab clients.
  84  *
  85  * An application using paraslash's filter subsystem may register any number of
  86  * callbacks for each filter_node. It is possible to attach a filter callback
  87  * while the filter is running. This is used for stream grabbing in
  88  * para_audiod: Whenever a client sends the 'grab' command, para_audiod adds a
  89  * filter callback to the list of callbacks for the filter node specified in
  90  * the grab command.
  91  */
  92 struct filter_callback {
  93         /** All callbacks are organized in a doubly linked list. */
  94         struct list_head node;
  95         /**
  96          * Private data.
  97          *
  98          * May be initialized by the application before registering the callback. This
  99          * pointer is not used by the filter subsystem. It is provided for use within
 100          * the input/output/close callback functions.
 101          */
 102         void *data;
 103         /**
 104          * The input callback.
 105          *
 106          * In not \p NULL, the filter subsystem calls this function whenever the filter
 107          * consumed some or all of its input buffer. A pointer to the buffer of consumed
 108          * data, its length and a pointer to the own \a filter_callback structure are passed
 109          * to \a input_cb. The input callback is expected to return a negative value on errors.
 110          */
 111         int (*input_cb)(char *buf, size_t len, struct filter_callback *fc);
 112         /**
 113          * The output callback.
 114          *
 115          * If not NULL, this is called whenever the filter produces output. A pointer
 116          * to the output data, its length and a pointer to the own \a filter_callback
 117          * structure are passed to \a output_cb. Like the input callback, the output
 118          * callback is expected to return a negative value on errors.
 119          */
 120         int (*output_cb)(char *buf, size_t len, struct filter_callback *fc);
 121         /**
 122          * The callback close function.
 123          *
 124          * This gets called whenever the input/output callback returned an error, or if
 125          * the filter chain is going to be destroyed, e.g. because the end of the
 126          * stream was encountered. It is assumed to succeed.
 127          */
 128         void (*close)(struct filter_callback *fc);
 129 };
 130
 131
 132 /**
 133  * The structure associated with a paraslash filter.
 134  *
 135  * Paraslash filters are "modules" which are used to transform an audio stream.
 136  * struct filter contains pointers to functions that must be supplied by the
 137  * filter code in order to be used by the driving application (currently
 138  * para_audiod and para_filter).
 139  *
 140  * Note: As several instances of the same filter may be running at the same
 141  * time, all these filter functions must be reentrant; no static non-constant
 142  * variables may be used.
 143  * \sa mp3dec.c, oggdec.c, wav.c, compress.c, filter_node
 144  */
 145 struct filter {
 146         /** The name of the filter. */
 147         const char *name;
 148         /**
 149          * Pointer to the filter init routine.
 150          *
 151          * This function is only called once at startup. It must initialize the
 152          * other non-optional function pointers of this structure.
 153          */
 154         void (*init)(struct filter *f);
 155         /**
 156          * Open one instance of this filter.
 157          *
 158          * This should allocate the output buffer of the given filter node and do any
 159          * other filter-specific preparations like initializing the private_data member
 160          * of \a fn suitably. The open function is assumed to succeed.
 161          */
 162         void (*open)(struct filter_node *fn);
 163         /**
 164          * Convert (filter) the given data.
 165          *
 166          * Pointer to the converting function of the filter. It should convert the
 167          * given input buffer \a inbuf which is of length \a len to the previously
 168          * reserved output buffer of \a fn. On success, it must return the number of
 169          * bytes it consumed from \a inbuf. On errors, a negative number indicating the
 170          * kind of the error must be returned.
 171          *
 172          * A zero return value just means that nothing was converted (probably because
 173          * the input buffer was too small). This is not interpreted as an error.
 174          */
 175         ssize_t (*convert)(char *inbuf, size_t len, struct filter_node *fn);
 176         /**
 177          * Close one instance of this filter.
 178          *
 179          * Free all resources of associated with \a fn that were previously allocated
 180          * by the open() function.
 181          */
 182         void (*close)(struct filter_node *fn);
 183         /**
 184          * Print the help text for this filter and exit.
 185          *
 186          * This is optional and it is not necessary to initialize this pointer if
 187          * the filter does not have a help text.
 188          */
 189         void (*print_help)(void);
 190         /**
 191          * A pointer to the filter's command line parser.
 192          *
 193          * If this optional function pointer is not NULL, any filter options are passed
 194          * from the main program to this command line parser once at application
 195          * startup. The command line parser should check its command line options given
 196          * by \a argc and \a argv and abort on errors. On success, it should return a
 197          * pointer to the filter-specific configuration data determined by \a argc and
 198          * \a argv.
 199          */
 200         void *(*parse_config)(int argc, char **argv);
 201 };
 202
 203 void close_filters(struct filter_chain *fc);
 204 void filter_init(struct filter *all_filters);
 205 int check_filter_arg(char *filter_arg, void **conf);
 206 void filter_pre_select(__a_unused struct sched *s, struct task *t);
 207
 208
 209 static inline void write_int16_host_endian(char *buf, int val)
 210 {
 211 #ifdef WORDS_BIGENDIAN
 212         *buf = val >> 8;
 213         *(buf + 1) = val & 0xff;
 214 #else
 215         *buf = val & 0xff;
 216         *(buf + 1) = val >> 8;
 217 #endif
 218 }
 219
 220
 221 /** \cond */
 222 extern struct filter filters[];
 223 #define DECLARE_EXTERN_FILTER_INIT(name) \
 224         extern void name ## _init(struct filter *f)
 225
 226 #define FILTER_INIT(filter) { \
 227         .name = #filter, \
 228         .init = filter ## _init, \
 229         .parse_config = NULL, \
 230         .print_help = NULL \
 231 },
 232
 233 /* filters that are always present */
 234 DECLARE_EXTERN_FILTER_INIT(wav);
 235 /* wav is always the first filter */
 236 #define WAV_FILTER_NUM 0
 237 DECLARE_EXTERN_FILTER_INIT(compress);
 238
 239 /* next the optional filters */
 240 #ifdef HAVE_MAD
 241 DECLARE_EXTERN_FILTER_INIT(mp3dec);
 242 #define MP3DEC_FILTER FILTER_INIT(mp3dec)
 243 #else
 244 #define MP3DEC_FILTER
 245 #endif
 246
 247 #ifdef HAVE_FAAD
 248 DECLARE_EXTERN_FILTER_INIT(aacdec);
 249 #define AACDEC_FILTER FILTER_INIT(aacdec)
 250 #else
 251 #define AACDEC_FILTER
 252 #endif
 253
 254 #ifdef HAVE_OGGVORBIS
 255 DECLARE_EXTERN_FILTER_INIT(oggdec);
 256 #define OGGDEC_FILTER FILTER_INIT(oggdec)
 257 #else
 258 #define OGGDEC_FILTER
 259 #endif
 260 /** \endcond */
 261
 262 /** define an array of all available filters */
 263 #define DEFINE_FILTER_ARRAY(filters) struct filter filters[] = { \
 264         FILTER_INIT(wav) \
 265         FILTER_INIT(compress) \
 266         MP3DEC_FILTER \
 267         AACDEC_FILTER \
 268         OGGDEC_FILTER \
 269         { .name = NULL } };
 270
 271