2 Copyright (C) 2000 Paul Davis & Benno Senoner
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2 of the License, or
7 (at your option) any later version.
9 This program 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
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software
16 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
25 #include <pbd/atomic.h>
31 RingBuffer (size_t sz) {
34 for (power_of_two = 1; 1U<<power_of_two < sz; power_of_two++);
36 size = 1<<power_of_two;
44 virtual ~RingBuffer() {
49 /* !!! NOT THREAD SAFE !!! */
50 atomic_set (&write_ptr, 0);
51 atomic_set (&read_ptr, 0);
54 void set (size_t r, size_t w) {
55 /* !!! NOT THREAD SAFE !!! */
56 atomic_set (&write_ptr, w);
57 atomic_set (&read_ptr, r);
60 size_t read (T *dest, size_t cnt);
61 size_t write (T *src, size_t cnt);
68 void get_read_vector (rw_vector *);
69 void get_write_vector (rw_vector *);
71 void decrement_read_ptr (size_t cnt) {
72 atomic_set (&read_ptr, (atomic_read(&read_ptr) - cnt) & size_mask);
75 void increment_read_ptr (size_t cnt) {
76 atomic_set (&read_ptr, (atomic_read(&read_ptr) + cnt) & size_mask);
79 void increment_write_ptr (size_t cnt) {
80 atomic_set (&write_ptr, (atomic_read(&write_ptr) + cnt) & size_mask);
83 size_t write_space () {
86 w = atomic_read (&write_ptr);
87 r = atomic_read (&read_ptr);
90 return ((r - w + size) & size_mask) - 1;
98 size_t read_space () {
101 w = atomic_read (&write_ptr);
102 r = atomic_read (&read_ptr);
107 return (w - r + size) & size_mask;
111 T *buffer () { return buf; }
112 size_t get_write_ptr () const { return atomic_read (&write_ptr); }
113 size_t get_read_ptr () const { return atomic_read (&read_ptr); }
114 size_t bufsize () const { return size; }
124 template<class T> size_t
125 RingBuffer<T>::read (T *dest, size_t cnt)
131 size_t priv_read_ptr;
133 priv_read_ptr=atomic_read(&read_ptr);
135 if ((free_cnt = read_space ()) == 0) {
139 to_read = cnt > free_cnt ? free_cnt : cnt;
141 cnt2 = priv_read_ptr + to_read;
144 n1 = size - priv_read_ptr;
145 n2 = cnt2 & size_mask;
151 memcpy (dest, &buf[priv_read_ptr], n1 * sizeof (T));
152 priv_read_ptr = (priv_read_ptr + n1) & size_mask;
155 memcpy (dest+n1, buf, n2 * sizeof (T));
159 atomic_set(&read_ptr, priv_read_ptr);
163 template<class T> size_t
164 RingBuffer<T>::write (T *src, size_t cnt)
171 size_t priv_write_ptr;
173 priv_write_ptr=atomic_read(&write_ptr);
175 if ((free_cnt = write_space ()) == 0) {
179 to_write = cnt > free_cnt ? free_cnt : cnt;
181 cnt2 = priv_write_ptr + to_write;
184 n1 = size - priv_write_ptr;
185 n2 = cnt2 & size_mask;
191 memcpy (&buf[priv_write_ptr], src, n1 * sizeof (T));
192 priv_write_ptr = (priv_write_ptr + n1) & size_mask;
195 memcpy (buf, src+n1, n2 * sizeof (T));
199 atomic_set(&write_ptr, priv_write_ptr);
203 template<class T> void
204 RingBuffer<T>::get_read_vector (RingBuffer<T>::rw_vector *vec)
211 w = atomic_read (&write_ptr);
212 r = atomic_read (&read_ptr);
217 free_cnt = (w - r + size) & size_mask;
223 /* Two part vector: the rest of the buffer after the
224 current write ptr, plus some from the start of
228 vec->buf[0] = &buf[r];
229 vec->len[0] = size - r;
231 vec->len[1] = cnt2 & size_mask;
235 /* Single part vector: just the rest of the buffer */
237 vec->buf[0] = &buf[r];
238 vec->len[0] = free_cnt;
243 template<class T> void
244 RingBuffer<T>::get_write_vector (RingBuffer<T>::rw_vector *vec)
251 w = atomic_read (&write_ptr);
252 r = atomic_read (&read_ptr);
255 free_cnt = ((r - w + size) & size_mask) - 1;
257 free_cnt = (r - w) - 1;
266 /* Two part vector: the rest of the buffer after the
267 current write ptr, plus some from the start of
271 vec->buf[0] = &buf[w];
272 vec->len[0] = size - w;
274 vec->len[1] = cnt2 & size_mask;
276 vec->buf[0] = &buf[w];
277 vec->len[0] = free_cnt;
283 #endif /* __ringbuffer_h__ */