1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
|
/******************************************************************************
* The MIT License
*
* Copyright (c) 2011 LeafLabs, LLC.
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy,
* modify, merge, publish, distribute, sublicense, and/or sell copies
* of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*****************************************************************************/
/**
* @file ring_buffer.h
* @brief Simple circular buffer
*
* This implementation is not thread-safe. In particular, none of
* these functions are guaranteed re-entrant.
*/
#ifndef _RING_BUFFER_H_
#define _RING_BUFFER_H_
#include "libmaple_types.h"
#ifdef __cplusplus
extern "C"{
#endif
/**
* Ring buffer type.
*
* The buffer is empty when head == tail.
*
* The buffer is full when the head is one byte in front of the tail,
* modulo buffer length.
*
* One byte is left free to distinguish empty from full. */
typedef struct ring_buffer {
volatile uint8 *buf; /**< Buffer items are stored into */
uint16 head; /**< Index of the next item to remove */
uint16 tail; /**< Index where the next item will get inserted */
uint16 size; /**< Buffer capacity minus one */
} ring_buffer;
/**
* Initialise a ring buffer.
*
* @param rb Instance to initialise
*
* @param size Number of items in buf. The ring buffer will always
* leave one element unoccupied, so the maximum number of
* elements it can store will be size - 1. Thus, size
* must be at least 2.
*
* @param buf Buffer to store items into
*/
static inline void rb_init(ring_buffer *rb, uint16 size, uint8 *buf) {
rb->head = 0;
rb->tail = 0;
rb->size = size - 1;
rb->buf = buf;
}
/**
* @brief Return the number of elements stored in the ring buffer.
* @param rb Buffer whose elements to count.
*/
static inline uint16 rb_full_count(ring_buffer *rb) {
__io ring_buffer *arb = rb;
int32 size = arb->tail - arb->head;
if (arb->tail < arb->head) {
size += arb->size + 1;
}
return (uint16)size;
}
/**
* @brief Returns true if and only if the ring buffer is full.
* @param rb Buffer to test.
*/
static inline int rb_is_full(ring_buffer *rb) {
return (rb->tail + 1 == rb->head) ||
(rb->tail == rb->size && rb->head == 0);
}
/**
* @brief Returns true if and only if the ring buffer is empty.
* @param rb Buffer to test.
*/
static inline int rb_is_empty(ring_buffer *rb) {
return rb->head == rb->tail;
}
/**
* Append element onto the end of a ring buffer.
* @param rb Buffer to append onto.
* @param element Value to append.
*/
static inline void rb_insert(ring_buffer *rb, uint8 element) {
rb->buf[rb->tail] = element;
rb->tail = (rb->tail == rb->size) ? 0 : rb->tail + 1;
}
/**
* @brief Remove and return the first item from a ring buffer.
* @param rb Buffer to remove from, must contain at least one element.
*/
static inline uint8 rb_remove(ring_buffer *rb) {
uint8 ch = rb->buf[rb->head];
rb->head = (rb->head == rb->size) ? 0 : rb->head + 1;
return ch;
}
/**
* @brief Attempt to remove the first item from a ring buffer.
*
* If the ring buffer is nonempty, removes and returns its first item.
* If it is empty, does nothing and returns a negative value.
*
* @param rb Buffer to attempt to remove from.
*/
static inline int16 rb_safe_remove(ring_buffer *rb) {
return rb_is_empty(rb) ? -1 : rb_remove(rb);
}
/**
* @brief Attempt to insert an element into a ring buffer.
*
* @param rb Buffer to insert into.
* @param element Value to insert into rb.
* @sideeffect If rb is not full, appends element onto buffer.
* @return If element was appended, then true; otherwise, false. */
static inline int rb_safe_insert(ring_buffer *rb, uint8 element) {
if (rb_is_full(rb)) {
return 0;
}
rb_insert(rb, element);
return 1;
}
/**
* @brief Append an item onto the end of a non-full ring buffer.
*
* If the buffer is full, removes its first item, then inserts the new
* element at the end.
*
* @param rb Ring buffer to insert into.
* @param element Value to insert into ring buffer.
* @return On success, returns -1. If an element was popped, returns
* the popped value.
*/
static inline int rb_push_insert(ring_buffer *rb, uint8 element) {
int ret = -1;
if (rb_is_full(rb)) {
ret = rb_remove(rb);
}
rb_insert(rb, element);
return ret;
}
/**
* @brief Discard all items from a ring buffer.
* @param rb Ring buffer to discard all items from.
*/
static inline void rb_reset(ring_buffer *rb) {
rb->tail = rb->head;
}
#ifdef __cplusplus
} // extern "C"
#endif
#endif
|
