2 * Copyright (c) 2016 Tilman Sauerbeck (tilman at code-monkey de)
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files (the
6 * "Software"), to deal in the Software without restriction, including
7 * without limitation the rights to use, copy, modify, merge, publish,
8 * distribute, sublicense, and/or sell copies of the Software, and to
9 * permit persons to whom the Software is furnished to do so, subject to
10 * the following conditions:
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
19 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
20 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
21 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
26 #define __ACCESS_ONCE(x) ({ \
27 __attribute__ ((__unused__)) typeof(x) __var = ( typeof(x)) 0; \
28 (volatile typeof(x) *) &(x); })
29 #define ACCESS_ONCE(x) (*__ACCESS_ONCE(x))
32 ringbuf_is_empty (struct ringbuf *rb)
34 uint32_t read_index = ACCESS_ONCE (rb->read_index);
35 uint32_t write_index = ACCESS_ONCE (rb->write_index);
37 return read_index == write_index;
41 ringbuf_is_full (struct ringbuf *rb)
43 uint32_t read_index = ACCESS_ONCE (rb->read_index);
44 uint32_t write_index = ACCESS_ONCE (rb->write_index);
46 return (write_index - read_index) == (rb->size_minus_1 + 1);
50 ringbuf_write (struct ringbuf *rb, uint8_t value)
52 uint32_t write_index = ACCESS_ONCE (rb->write_index);
54 rb->buffer[write_index & rb->size_minus_1] = value;
56 /* Ensure we only update rb->write_index _after_ we stored
57 * the data in the array.
59 __sync_synchronize ();
61 ACCESS_ONCE (rb->write_index) = write_index + 1;
65 ringbuf_read (struct ringbuf *rb)
67 uint32_t read_index = ACCESS_ONCE (rb->read_index);
68 uint8_t value = rb->buffer[read_index & rb->size_minus_1];
70 /* Ensure we only update rb->read_index _after_ we read
71 * the data from the array.
73 __sync_synchronize ();
75 ACCESS_ONCE (rb->read_index) = read_index + 1;