Alc/alcRing.c

   1 /**
   2  * OpenAL cross platform audio library
   3  * Copyright (C) 1999-2007 by authors.
   4  * This library is free software; you can redistribute it and/or
   5  *  modify it under the terms of the GNU Library General Public
   6  *  License as published by the Free Software Foundation; either
   7  *  version 2 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  *  Library General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Library General Public
  15  *  License along with this library; if not, write to the
  16  *  Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17  *  Boston, MA  02111-1307, USA.
  18  * Or go to http://www.gnu.org/copyleft/lgpl.html
  19  */
  20
  21 #include "config.h"
  22
  23 #include <string.h>
  24 #include <stdlib.h>
  25
  26 #include "alMain.h"
  27
  28
  29 struct RingBuffer {
  30     ALubyte *mem;
  31
  32     ALsizei frame_size;
  33     ALsizei length;
  34     ALint read_pos;
  35     ALint write_pos;
  36
  37     CRITICAL_SECTION cs;
  38 };
  39
  40
  41 RingBuffer *CreateRingBuffer(ALsizei frame_size, ALsizei length)
  42 {
  43     RingBuffer *ring = calloc(1, sizeof(*ring) + ((length+1) * frame_size));
  44     if(ring)
  45     {
  46         ring->mem = (ALubyte*)(ring+1);
  47
  48         ring->frame_size = frame_size;
  49         ring->length = length+1;
  50         ring->read_pos = 0;
  51         ring->write_pos = 0;
  52
  53         InitializeCriticalSection(&ring->cs);
  54     }
  55     return ring;
  56 }
  57
  58 void DestroyRingBuffer(RingBuffer *ring)
  59 {
  60     if(ring)
  61     {
  62         DeleteCriticalSection(&ring->cs);
  63         free(ring);
  64     }
  65 }
  66
  67 ALsizei RingBufferSize(RingBuffer *ring)
  68 {
  69     ALsizei s;
  70
  71     EnterCriticalSection(&ring->cs);
  72     s = (ring->write_pos-ring->read_pos+ring->length) % ring->length;
  73     LeaveCriticalSection(&ring->cs);
  74
  75     return s;
  76 }
  77
  78 void WriteRingBuffer(RingBuffer *ring, const ALubyte *data, ALsizei len)
  79 {
  80     int remain;
  81
  82     EnterCriticalSection(&ring->cs);
  83
  84     remain = (ring->read_pos-ring->write_pos-1+ring->length) % ring->length;
  85     if(remain < len) len = remain;
  86
  87     if(len > 0)
  88     {
  89         remain = ring->length - ring->write_pos;
  90         if(remain < len)
  91         {
  92             memcpy(ring->mem+(ring->write_pos*ring->frame_size), data,
  93                    remain*ring->frame_size);
  94             memcpy(ring->mem, data+(remain*ring->frame_size),
  95                    (len-remain)*ring->frame_size);
  96         }
  97         else
  98             memcpy(ring->mem+(ring->write_pos*ring->frame_size), data,
  99                    len*ring->frame_size);
 100
 101         ring->write_pos += len;
 102         ring->write_pos %= ring->length;
 103     }
 104
 105     LeaveCriticalSection(&ring->cs);
 106 }
 107
 108 void ReadRingBuffer(RingBuffer *ring, ALubyte *data, ALsizei len)
 109 {
 110     int remain;
 111
 112     EnterCriticalSection(&ring->cs);
 113
 114     remain = ring->length - ring->read_pos;
 115     if(remain < len)
 116     {
 117         memcpy(data, ring->mem+(ring->read_pos*ring->frame_size), remain*ring->frame_size);
 118         memcpy(data+(remain*ring->frame_size), ring->mem, (len-remain)*ring->frame_size);
 119     }
 120     else
 121         memcpy(data, ring->mem+(ring->read_pos*ring->frame_size), len*ring->frame_size);
 122
 123     ring->read_pos += len;
 124     ring->read_pos %= ring->length;
 125
 126     LeaveCriticalSection(&ring->cs);
 127 }