src/buffer.c

   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 #include "config.h"
  21 #include "buffer.h"
  22 #include "chunk.h"
  23 #include "poison.h"
  24
  25 #include <glib.h>
  26
  27 #include <assert.h>
  28
  29 struct music_buffer {
  30         struct music_chunk *chunks;
  31         unsigned num_chunks;
  32
  33         struct music_chunk *available;
  34
  35         /** a mutex which protects #available */
  36         GMutex *mutex;
  37
  38 #ifndef NDEBUG
  39         unsigned num_allocated;
  40 #endif
  41 };
  42
  43 struct music_buffer *
  44 music_buffer_new(unsigned num_chunks)
  45 {
  46         struct music_buffer *buffer;
  47         struct music_chunk *chunk;
  48
  49         assert(num_chunks > 0);
  50
  51         buffer = g_new(struct music_buffer, 1);
  52
  53         buffer->chunks = g_new(struct music_chunk, num_chunks);
  54         buffer->num_chunks = num_chunks;
  55
  56         chunk = buffer->available = buffer->chunks;
  57         poison_undefined(chunk, sizeof(*chunk));
  58
  59         for (unsigned i = 1; i < num_chunks; ++i) {
  60                 chunk->next = &buffer->chunks[i];
  61                 chunk = chunk->next;
  62                 poison_undefined(chunk, sizeof(*chunk));
  63         }
  64
  65         chunk->next = NULL;
  66
  67         buffer->mutex = g_mutex_new();
  68
  69 #ifndef NDEBUG
  70         buffer->num_allocated = 0;
  71 #endif
  72
  73         return buffer;
  74 }
  75
  76 void
  77 music_buffer_free(struct music_buffer *buffer)
  78 {
  79         assert(buffer->chunks != NULL);
  80         assert(buffer->num_chunks > 0);
  81         assert(buffer->num_allocated == 0);
  82
  83         g_mutex_free(buffer->mutex);
  84         g_free(buffer->chunks);
  85         g_free(buffer);
  86 }
  87
  88 unsigned
  89 music_buffer_size(const struct music_buffer *buffer)
  90 {
  91         return buffer->num_chunks;
  92 }
  93
  94 struct music_chunk *
  95 music_buffer_allocate(struct music_buffer *buffer)
  96 {
  97         struct music_chunk *chunk;
  98
  99         g_mutex_lock(buffer->mutex);
 100
 101         chunk = buffer->available;
 102         if (chunk != NULL) {
 103                 buffer->available = chunk->next;
 104                 music_chunk_init(chunk);
 105
 106 #ifndef NDEBUG
 107                 ++buffer->num_allocated;
 108 #endif
 109         }
 110
 111         g_mutex_unlock(buffer->mutex);
 112         return chunk;
 113 }
 114
 115 void
 116 music_buffer_return(struct music_buffer *buffer, struct music_chunk *chunk)
 117 {
 118         assert(buffer != NULL);
 119         assert(chunk != NULL);
 120
 121         g_mutex_lock(buffer->mutex);
 122
 123         music_chunk_free(chunk);
 124         poison_undefined(chunk, sizeof(*chunk));
 125
 126         chunk->next = buffer->available;
 127         buffer->available = chunk;
 128
 129 #ifndef NDEBUG
 130         --buffer->num_allocated;
 131 #endif
 132
 133         g_mutex_unlock(buffer->mutex);
 134 }