forked from dhess/c-ringbuf
-
Notifications
You must be signed in to change notification settings - Fork 1
/
ringbuf.c
348 lines (297 loc) · 8.2 KB
/
ringbuf.c
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
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
/*
* ringbuf.c - C ring buffer (FIFO) implementation.
*
* Written in 2011 by Drew Hess <[email protected]>.
*
* To the extent possible under law, the author(s) have dedicated all
* copyright and related and neighboring rights to this software to
* the public domain worldwide. This software is distributed without
* any warranty.
*
* You should have received a copy of the CC0 Public Domain Dedication
* along with this software. If not, see
* <http://creativecommons.org/publicdomain/zero/1.0/>.
*/
#include "ringbuf.h"
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>
#include <sys/param.h>
#include <assert.h>
/*
* The code is written for clarity, not cleverness or performance, and
* contains many assert()s to enforce invariant assumptions and catch
* bugs. Feel free to optimize the code and to remove asserts for use
* in your own projects, once you're comfortable that it functions as
* intended.
*/
struct ringbuf_t
{
uint8_t *buf;
uint8_t *head, *tail;
size_t size;
};
ringbuf_t
ringbuf_new(size_t capacity)
{
ringbuf_t rb = malloc(sizeof(struct ringbuf_t));
if (rb) {
/* One byte is used for detecting the full condition. */
rb->size = capacity + 1;
rb->buf = malloc(rb->size);
if (rb->buf)
ringbuf_reset(rb);
else {
free(rb);
return 0;
}
}
return rb;
}
size_t
ringbuf_buffer_size(const struct ringbuf_t *rb)
{
return rb->size;
}
void
ringbuf_reset(ringbuf_t rb)
{
rb->head = rb->tail = rb->buf;
}
void
ringbuf_free(ringbuf_t *rb)
{
assert(rb && *rb);
free((*rb)->buf);
free(*rb);
*rb = 0;
}
size_t
ringbuf_capacity(const struct ringbuf_t *rb)
{
return ringbuf_buffer_size(rb) - 1;
}
/*
* Return a pointer to one-past-the-end of the ring buffer's
* contiguous buffer. You shouldn't normally need to use this function
* unless you're writing a new ringbuf_* function.
*/
static const uint8_t *
ringbuf_end(const struct ringbuf_t *rb)
{
return rb->buf + ringbuf_buffer_size(rb);
}
size_t
ringbuf_bytes_free(const struct ringbuf_t *rb)
{
if (rb->head >= rb->tail)
return ringbuf_capacity(rb) - (rb->head - rb->tail);
else
return rb->tail - rb->head - 1;
}
size_t
ringbuf_bytes_used(const struct ringbuf_t *rb)
{
return ringbuf_capacity(rb) - ringbuf_bytes_free(rb);
}
int
ringbuf_is_full(const struct ringbuf_t *rb)
{
return ringbuf_bytes_free(rb) == 0;
}
int
ringbuf_is_empty(const struct ringbuf_t *rb)
{
return ringbuf_bytes_free(rb) == ringbuf_capacity(rb);
}
const void *
ringbuf_tail(const struct ringbuf_t *rb)
{
return rb->tail;
}
const void *
ringbuf_head(const struct ringbuf_t *rb)
{
return rb->head;
}
/*
* Given a ring buffer rb and a pointer to a location within its
* contiguous buffer, return the a pointer to the next logical
* location in the ring buffer.
*/
static uint8_t *
ringbuf_nextp(ringbuf_t rb, const uint8_t *p)
{
/*
* The assert guarantees the expression (++p - rb->buf) is
* non-negative; therefore, the modulus operation is safe and
* portable.
*/
assert((p >= rb->buf) && (p < ringbuf_end(rb)));
return rb->buf + ((++p - rb->buf) % ringbuf_buffer_size(rb));
}
size_t
ringbuf_findchr(const struct ringbuf_t *rb, int c, size_t offset)
{
const uint8_t *bufend = ringbuf_end(rb);
size_t bytes_used = ringbuf_bytes_used(rb);
if (offset >= bytes_used)
return bytes_used;
const uint8_t *start = rb->buf +
(((rb->tail - rb->buf) + offset) % ringbuf_buffer_size(rb));
assert(bufend > start);
size_t n = MIN(bufend - start, bytes_used - offset);
const uint8_t *found = memchr(start, c, n);
if (found)
return offset + (found - start);
else
return ringbuf_findchr(rb, c, offset + n);
}
size_t
ringbuf_memset(ringbuf_t dst, int c, size_t len)
{
const uint8_t *bufend = ringbuf_end(dst);
size_t nwritten = 0;
size_t count = MIN(len, ringbuf_buffer_size(dst));
int overflow = count > ringbuf_bytes_free(dst);
while (nwritten != count) {
/* don't copy beyond the end of the buffer */
assert(bufend > dst->head);
size_t n = MIN(bufend - dst->head, count - nwritten);
memset(dst->head, c, n);
dst->head += n;
nwritten += n;
/* wrap? */
if (dst->head == bufend)
dst->head = dst->buf;
}
if (overflow) {
dst->tail = ringbuf_nextp(dst, dst->head);
assert(ringbuf_is_full(dst));
}
return nwritten;
}
void *
ringbuf_memcpy_into(ringbuf_t dst, const void *src, size_t count)
{
const uint8_t *u8src = src;
const uint8_t *bufend = ringbuf_end(dst);
int overflow = count > ringbuf_bytes_free(dst);
size_t nread = 0;
while (nread != count) {
/* don't copy beyond the end of the buffer */
assert(bufend > dst->head);
size_t n = MIN(bufend - dst->head, count - nread);
memcpy(dst->head, u8src + nread, n);
dst->head += n;
nread += n;
/* wrap? */
if (dst->head == bufend)
dst->head = dst->buf;
}
if (overflow) {
dst->tail = ringbuf_nextp(dst, dst->head);
assert(ringbuf_is_full(dst));
}
return dst->head;
}
ssize_t
ringbuf_read(int fd, ringbuf_t rb, size_t count)
{
const uint8_t *bufend = ringbuf_end(rb);
size_t nfree = ringbuf_bytes_free(rb);
/* don't write beyond the end of the buffer */
assert(bufend > rb->head);
count = MIN(bufend - rb->head, count);
ssize_t n = read(fd, rb->head, count);
if (n > 0) {
assert(rb->head + n <= bufend);
rb->head += n;
/* wrap? */
if (rb->head == bufend)
rb->head = rb->buf;
/* fix up the tail pointer if an overflow occurred */
if (n > nfree) {
rb->tail = ringbuf_nextp(rb, rb->head);
assert(ringbuf_is_full(rb));
}
}
return n;
}
void *
ringbuf_memcpy_from(void *dst, ringbuf_t src, size_t count)
{
size_t bytes_used = ringbuf_bytes_used(src);
if (count > bytes_used)
return 0;
uint8_t *u8dst = dst;
const uint8_t *bufend = ringbuf_end(src);
size_t nwritten = 0;
while (nwritten != count) {
assert(bufend > src->tail);
size_t n = MIN(bufend - src->tail, count - nwritten);
memcpy(u8dst + nwritten, src->tail, n);
src->tail += n;
nwritten += n;
/* wrap ? */
if (src->tail == bufend)
src->tail = src->buf;
}
assert(count + ringbuf_bytes_used(src) == bytes_used);
return src->tail;
}
ssize_t
ringbuf_write(int fd, ringbuf_t rb, size_t count)
{
size_t bytes_used = ringbuf_bytes_used(rb);
if (count > bytes_used)
return 0;
const uint8_t *bufend = ringbuf_end(rb);
assert(bufend > rb->head);
count = MIN(bufend - rb->tail, count);
ssize_t n = write(fd, rb->tail, count);
if (n > 0) {
assert(rb->tail + n <= bufend);
rb->tail += n;
/* wrap? */
if (rb->tail == bufend)
rb->tail = rb->buf;
assert(n + ringbuf_bytes_used(rb) == bytes_used);
}
return n;
}
void *
ringbuf_copy(ringbuf_t dst, ringbuf_t src, size_t count)
{
size_t src_bytes_used = ringbuf_bytes_used(src);
if (count > src_bytes_used)
return 0;
int overflow = count > ringbuf_bytes_free(dst);
const uint8_t *src_bufend = ringbuf_end(src);
const uint8_t *dst_bufend = ringbuf_end(dst);
size_t ncopied = 0;
while (ncopied != count) {
assert(src_bufend > src->tail);
size_t nsrc = MIN(src_bufend - src->tail, count - ncopied);
assert(dst_bufend > dst->head);
size_t n = MIN(dst_bufend - dst->head, nsrc);
memcpy(dst->head, src->tail, n);
src->tail += n;
dst->head += n;
ncopied += n;
/* wrap ? */
if (src->tail == src_bufend)
src->tail = src->buf;
if (dst->head == dst_bufend)
dst->head = dst->buf;
}
assert(count + ringbuf_bytes_used(src) == src_bytes_used);
if (overflow) {
dst->tail = ringbuf_nextp(dst, dst->head);
assert(ringbuf_is_full(dst));
}
return dst->head;
}