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.,
  17  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 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 #include "threads.h"
  28 #include "almalloc.h"
  29 #include "compat.h"
  30
  31
  32 /* NOTE: This lockless ringbuffer implementation is copied from JACK, extended
  33  * to include an element size. Consequently, parameters and return values for a
  34  * size or count is in 'elements', not bytes. Additionally, it only supports
  35  * single-consumer/single-provider operation. */
  36 struct ll_ringbuffer {
  37     volatile size_t write_ptr;
  38     volatile size_t read_ptr;
  39     size_t size;
  40     size_t size_mask;
  41     size_t elem_size;
  42     int mlocked;
  43
  44     alignas(16) char buf[];
  45 };
  46
  47 /* Create a new ringbuffer to hold at least `sz' elements of `elem_sz' bytes.
  48  * The number of elements is rounded up to the next power of two. */
  49 ll_ringbuffer_t *ll_ringbuffer_create(size_t sz, size_t elem_sz)
  50 {
  51     ll_ringbuffer_t *rb;
  52     ALuint power_of_two;
  53
  54     power_of_two = NextPowerOf2(sz);
  55     if(power_of_two < sz)
  56         return NULL;
  57
  58     rb = al_malloc(16, sizeof(*rb) + power_of_two*elem_sz);
  59     if(!rb) return NULL;
  60
  61     rb->size = power_of_two;
  62     rb->size_mask = rb->size - 1;
  63     rb->elem_size = elem_sz;
  64     rb->write_ptr = 0;
  65     rb->read_ptr = 0;
  66     rb->mlocked = 0;
  67     return rb;
  68 }
  69
  70 /* Free all data associated with the ringbuffer `rb'. */
  71 void ll_ringbuffer_free(ll_ringbuffer_t *rb)
  72 {
  73     if(rb)
  74     {
  75 #ifdef USE_MLOCK
  76         if(rb->mlocked)
  77             munlock(rb, sizeof(*rb) + rb->size*rb->elem_size);
  78 #endif /* USE_MLOCK */
  79         al_free(rb);
  80     }
  81 }
  82
  83 /* Lock the data block of `rb' using the system call 'mlock'. */
  84 int ll_ringbuffer_mlock(ll_ringbuffer_t *rb)
  85 {
  86 #ifdef USE_MLOCK
  87     if(!rb->locked && mlock(rb, sizeof(*rb) + rb->size*rb->elem_size))
  88         return -1;
  89 #endif /* USE_MLOCK */
  90     rb->mlocked = 1;
  91     return 0;
  92 }
  93
  94 /* Reset the read and write pointers to zero. This is not thread safe. */
  95 void ll_ringbuffer_reset(ll_ringbuffer_t *rb)
  96 {
  97     rb->read_ptr = 0;
  98     rb->write_ptr = 0;
  99     memset(rb->buf, 0, rb->size*rb->elem_size);
 100 }
 101
 102 /* Return the number of elements available for reading. This is the number of
 103  * elements in front of the read pointer and behind the write pointer. */
 104 size_t ll_ringbuffer_read_space(const ll_ringbuffer_t *rb)
 105 {
 106     size_t w = rb->write_ptr;
 107     size_t r = rb->read_ptr;
 108     return (rb->size+w-r) & rb->size_mask;
 109 }
 110 /* Return the number of elements available for writing. This is the number of
 111  * elements in front of the write pointer and behind the read pointer. */
 112 size_t ll_ringbuffer_write_space(const ll_ringbuffer_t *rb)
 113 {
 114     size_t w = rb->write_ptr;
 115     size_t r = rb->read_ptr;
 116     return (rb->size+r-w-1) & rb->size_mask;
 117 }
 118
 119 /* The copying data reader. Copy at most `cnt' elements from `rb' to `dest'.
 120  * Returns the actual number of elements copied. */
 121 size_t ll_ringbuffer_read(ll_ringbuffer_t *rb, char *dest, size_t cnt)
 122 {
 123     size_t free_cnt;
 124     size_t cnt2;
 125     size_t to_read;
 126     size_t n1, n2;
 127
 128     free_cnt = ll_ringbuffer_read_space(rb);
 129     if(free_cnt == 0) return 0;
 130
 131     to_read = (cnt > free_cnt) ? free_cnt : cnt;
 132     cnt2 = rb->read_ptr + to_read;
 133     if(cnt2 > rb->size)
 134     {
 135         n1 = rb->size - rb->read_ptr;
 136         n2 = cnt2 & rb->size_mask;
 137     }
 138     else
 139     {
 140         n1 = to_read;
 141         n2 = 0;
 142     }
 143
 144     memcpy(dest, &(rb->buf[rb->read_ptr*rb->elem_size]), n1*rb->elem_size);
 145     rb->read_ptr = (rb->read_ptr + n1) & rb->size_mask;
 146     if(n2)
 147     {
 148         memcpy(dest + n1*rb->elem_size, &(rb->buf[rb->read_ptr*rb->elem_size]), n2*rb->elem_size);
 149         rb->read_ptr = (rb->read_ptr + n2) & rb->size_mask;
 150     }
 151     return to_read;
 152 }
 153
 154 /* The copying data reader w/o read pointer advance. Copy at most `cnt'
 155  * elements from `rb' to `dest'. Returns the actual number of elements copied.
 156  */
 157 size_t ll_ringbuffer_peek(ll_ringbuffer_t *rb, char *dest, size_t cnt)
 158 {
 159     size_t free_cnt;
 160     size_t cnt2;
 161     size_t to_read;
 162     size_t n1, n2;
 163     size_t tmp_read_ptr;
 164
 165     tmp_read_ptr = rb->read_ptr;
 166     free_cnt = ll_ringbuffer_read_space(rb);
 167     if(free_cnt == 0) return 0;
 168
 169     to_read = (cnt > free_cnt) ? free_cnt : cnt;
 170     cnt2 = tmp_read_ptr + to_read;
 171     if(cnt2 > rb->size)
 172     {
 173         n1 = rb->size - tmp_read_ptr;
 174         n2 = cnt2 & rb->size_mask;
 175     }
 176     else
 177     {
 178         n1 = to_read;
 179         n2 = 0;
 180     }
 181
 182     memcpy(dest, &(rb->buf[tmp_read_ptr*rb->elem_size]), n1*rb->elem_size);
 183     tmp_read_ptr = (tmp_read_ptr + n1) & rb->size_mask;
 184     if(n2)
 185         memcpy(dest + n1*rb->elem_size, &(rb->buf[tmp_read_ptr*rb->elem_size]), n2*rb->elem_size);
 186     return to_read;
 187 }
 188
 189 /* The copying data writer. Copy at most `cnt' elements to `rb' from `src'.
 190  * Returns the actual number of elements copied. */
 191 size_t ll_ringbuffer_write(ll_ringbuffer_t *rb, const char *src, size_t cnt)
 192 {
 193     size_t free_cnt;
 194     size_t cnt2;
 195     size_t to_write;
 196     size_t n1, n2;
 197
 198     free_cnt = ll_ringbuffer_write_space(rb);
 199     if(free_cnt == 0) return 0;
 200
 201     to_write = (cnt > free_cnt) ? free_cnt : cnt;
 202     cnt2 = rb->write_ptr + to_write;
 203     if(cnt2 > rb->size)
 204     {
 205         n1 = rb->size - rb->write_ptr;
 206         n2 = cnt2 & rb->size_mask;
 207     }
 208     else
 209     {
 210         n1 = to_write;
 211         n2 = 0;
 212     }
 213
 214     memcpy(&(rb->buf[rb->write_ptr*rb->elem_size]), src, n1*rb->elem_size);
 215     rb->write_ptr = (rb->write_ptr + n1) & rb->size_mask;
 216     if(n2)
 217     {
 218         memcpy(&(rb->buf[rb->write_ptr*rb->elem_size]), src + n1*rb->elem_size, n2*rb->elem_size);
 219         rb->write_ptr = (rb->write_ptr + n2) & rb->size_mask;
 220     }
 221     return to_write;
 222 }
 223
 224 /* Advance the read pointer `cnt' places. */
 225 void ll_ringbuffer_read_advance(ll_ringbuffer_t *rb, size_t cnt)
 226 {
 227     size_t tmp = (rb->read_ptr + cnt) & rb->size_mask;
 228     rb->read_ptr = tmp;
 229 }
 230
 231 /* Advance the write pointer `cnt' places. */
 232 void ll_ringbuffer_write_advance(ll_ringbuffer_t *rb, size_t cnt)
 233 {
 234     size_t tmp = (rb->write_ptr + cnt) & rb->size_mask;
 235     rb->write_ptr = tmp;
 236 }
 237
 238 /* The non-copying data reader. `vec' is an array of two places. Set the values
 239  * at `vec' to hold the current readable data at `rb'. If the readable data is
 240  * in one segment the second segment has zero length. */
 241 void ll_ringbuffer_get_read_vector(const ll_ringbuffer_t *rb, ll_ringbuffer_data_t * vec)
 242 {
 243     size_t free_cnt;
 244     size_t cnt2;
 245     size_t w, r;
 246
 247     w = rb->write_ptr;
 248     r = rb->read_ptr;
 249     free_cnt = (rb->size+w-r) & rb->size_mask;
 250
 251     cnt2 = r + free_cnt;
 252     if(cnt2 > rb->size)
 253     {
 254         /* Two part vector: the rest of the buffer after the current write ptr,
 255          * plus some from the start of the buffer. */
 256         vec[0].buf = (char*)&(rb->buf[r*rb->elem_size]);
 257         vec[0].len = rb->size - r;
 258         vec[1].buf = (char*)rb->buf;
 259         vec[1].len = cnt2 & rb->size_mask;
 260     }
 261     else
 262     {
 263         /* Single part vector: just the rest of the buffer */
 264         vec[0].buf = (char*)&(rb->buf[r*rb->elem_size]);
 265         vec[0].len = free_cnt;
 266         vec[1].buf = NULL;
 267         vec[1].len = 0;
 268     }
 269 }
 270
 271 /* The non-copying data writer. `vec' is an array of two places. Set the values
 272  * at `vec' to hold the current writeable data at `rb'. If the writeable data
 273  * is in one segment the second segment has zero length. */
 274 void ll_ringbuffer_get_write_vector(const ll_ringbuffer_t *rb, ll_ringbuffer_data_t *vec)
 275 {
 276     size_t free_cnt;
 277     size_t cnt2;
 278     size_t w, r;
 279
 280     w = rb->write_ptr;
 281     r = rb->read_ptr;
 282     free_cnt = (rb->size+r-w-1) & rb->size_mask;
 283
 284     cnt2 = w + free_cnt;
 285     if(cnt2 > rb->size)
 286     {
 287         /* Two part vector: the rest of the buffer after the current write ptr,
 288          * plus some from the start of the buffer. */
 289         vec[0].buf = (char*)&(rb->buf[w*rb->elem_size]);
 290         vec[0].len = rb->size - w;
 291         vec[1].buf = (char*)rb->buf;
 292         vec[1].len = cnt2 & rb->size_mask;
 293     }
 294     else
 295     {
 296         vec[0].buf = (char*)&(rb->buf[w*rb->elem_size]);
 297         vec[0].len = free_cnt;
 298         vec[1].buf = NULL;
 299         vec[1].len = 0;
 300     }
 301 }