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         /**
  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         struct btr_node *btrn;
  34         struct task task;
  35         size_t min_iqs;
  36 };
  37
  38 /**
  39  * The structure associated with a paraslash filter.
  40  *
  41  * Paraslash filters are "modules" which are used to transform an audio stream.
  42  * struct filter contains pointers to functions that must be supplied by the
  43  * filter code in order to be used by the driving application (currently
  44  * para_audiod and para_filter).
  45  *
  46  * Note: As several instances of the same filter may be running at the same
  47  * time, all these filter functions must be reentrant; no static non-constant
  48  * variables may be used.
  49  * \sa mp3dec_filter.c, oggdec_filter.c, wav_filter.c, compress_filter.c, filter_node
  50  */
  51 struct filter {
  52         /** The name of the filter. */
  53         const char *name;
  54         /**
  55          * Pointer to the filter init routine.
  56          *
  57          * This function is only called once at startup. It must initialize the
  58          * other non-optional function pointers of this structure.
  59          */
  60         void (*init)(struct filter *f);
  61         /**
  62          * Open one instance of this filter.
  63          *
  64          * This should allocate the output buffer of the given filter node and do any
  65          * other filter-specific preparations like initializing the private_data member
  66          * of \a fn suitably. The open function is assumed to succeed.
  67          */
  68         void (*open)(struct filter_node *fn);
  69         /**
  70          * Close one instance of this filter.
  71          *
  72          * Free all resources of associated with \a fn that were previously allocated
  73          * by the open() function.
  74          */
  75         void (*close)(struct filter_node *fn);
  76         /**
  77          * A pointer to the filter's command line parser.
  78          *
  79          * If this optional function pointer is not NULL, any filter options
  80          * are passed from the main program to this command line parser once at
  81          * application startup. The command line parser should check its
  82          * command line options given by \a argc and \a argv and abort on
  83          * errors. Success must be indicated by a non-negative return value. In
  84          * this case the function should return a pointer to the
  85          * filter-specific configuration data determined by \a argc and \a
  86          * argv. On failure, a negative paraslash error code must be returned.
  87          */
  88         int (*parse_config)(int argc, char **argv, void **config);
  89         void (*free_config)(void *conf);
  90
  91         /** The help texts for this filter. */
  92         struct ggo_help help;
  93         void (*pre_select)(struct sched *s, struct task *t);
  94         /**
  95          * Convert (filter) the given data.
  96          *
  97          * Pointer to the converting function of the filter. It should convert as
  98          * input data as possible. On errors, the post_select function is supposed
  99          * to set t->error to a (negative) error code.
 100          */
 101         void (*post_select)(struct sched *s, struct task *t);
 102         btr_command_handler execute;
 103 };
 104
 105 void filter_init(void);
 106 int check_filter_arg(char *filter_arg, void **conf);
 107 void print_filter_helps(int detailed);
 108 void generic_filter_pre_select(struct sched *s, struct task *t);
 109
 110 static inline void write_int16_host_endian(char *buf, int val)
 111 {
 112 #ifdef WORDS_BIGENDIAN
 113         *buf = val >> 8;
 114         *(buf + 1) = val & 0xff;
 115 #else
 116         *buf = val & 0xff;
 117         *(buf + 1) = val >> 8;
 118 #endif
 119 }
 120
 121 DECLARE_FILTER_INITS
 122
 123 #define FOR_EACH_SUPPORTED_FILTER(j)  for (j = 0; j < NUM_SUPPORTED_FILTERS; j++)
 124
 125 /** The filter array, one structure for each supported filter. */
 126 extern struct filter filters[NUM_SUPPORTED_FILTERS];