src/chunk.h

   1 /*
   2  * Copyright (C) 2003-2010 The Music Player Daemon Project
   3  * http://www.musicpd.org
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18  */
  19
  20 #ifndef MPD_CHUNK_H
  21 #define MPD_CHUNK_H
  22
  23 #include "replay_gain_info.h"
  24
  25 #ifndef NDEBUG
  26 #include "audio_format.h"
  27 #endif
  28
  29 #include <stdbool.h>
  30 #include <stdint.h>
  31 #include <stddef.h>
  32
  33 enum {
  34         CHUNK_SIZE = 4096,
  35 };
  36
  37 struct audio_format;
  38
  39 /**
  40  * A chunk of music data.  Its format is defined by the
  41  * music_pipe_append() caller.
  42  */
  43 struct music_chunk {
  44         /** the next chunk in a linked list */
  45         struct music_chunk *next;
  46
  47         /** number of bytes stored in this chunk */
  48         uint16_t length;
  49
  50         /** current bit rate of the source file */
  51         uint16_t bit_rate;
  52
  53         /** the time stamp within the song */
  54         float times;
  55
  56         /**
  57          * An optional tag associated with this chunk (and the
  58          * following chunks); appears at song boundaries.  The tag
  59          * object is owned by this chunk, and must be freed when this
  60          * chunk is deinitialized in music_chunk_free()
  61          */
  62         struct tag *tag;
  63
  64         /**
  65          * Replay gain information associated with this chunk.
  66          * Only valid if the serial is not 0.
  67          */
  68         struct replay_gain_info replay_gain_info;
  69
  70         /**
  71          * A serial number for checking if replay gain info has
  72          * changed since the last chunk.  The magic value 0 indicates
  73          * that there is no replay gain info available.
  74          */
  75         unsigned replay_gain_serial;
  76
  77         /** the data (probably PCM) */
  78         char data[CHUNK_SIZE];
  79
  80 #ifndef NDEBUG
  81         struct audio_format audio_format;
  82 #endif
  83 };
  84
  85 void
  86 music_chunk_init(struct music_chunk *chunk);
  87
  88 void
  89 music_chunk_free(struct music_chunk *chunk);
  90
  91 static inline bool
  92 music_chunk_is_empty(const struct music_chunk *chunk)
  93 {
  94         return chunk->length == 0 && chunk->tag == NULL;
  95 }
  96
  97 #ifndef NDEBUG
  98 /**
  99  * Checks if the audio format if the chunk is equal to the specified
 100  * audio_format.
 101  */
 102 bool
 103 music_chunk_check_format(const struct music_chunk *chunk,
 104                          const struct audio_format *audio_format);
 105 #endif
 106
 107 /**
 108  * Prepares appending to the music chunk.  Returns a buffer where you
 109  * may write into.  After you are finished, call music_chunk_expand().
 110  *
 111  * @param chunk the music_chunk object
 112  * @param audio_format the audio format for the appended data; must
 113  * stay the same for the life cycle of this chunk
 114  * @param data_time the time within the song
 115  * @param bit_rate the current bit rate of the source file
 116  * @param max_length_r the maximum write length is returned here
 117  * @return a writable buffer, or NULL if the chunk is full
 118  */
 119 void *
 120 music_chunk_write(struct music_chunk *chunk,
 121                   const struct audio_format *audio_format,
 122                   float data_time, uint16_t bit_rate,
 123                   size_t *max_length_r);
 124
 125 /**
 126  * Increases the length of the chunk after the caller has written to
 127  * the buffer returned by music_chunk_write().
 128  *
 129  * @param chunk the music_chunk object
 130  * @param audio_format the audio format for the appended data; must
 131  * stay the same for the life cycle of this chunk
 132  * @param length the number of bytes which were appended
 133  * @return true if the chunk is full
 134  */
 135 bool
 136 music_chunk_expand(struct music_chunk *chunk,
 137                    const struct audio_format *audio_format, size_t length);
 138
 139 #endif