2 * Empire - A multi-player, client/server Internet based war game.
3 * Copyright (C) 1986-2015, Dave Pare, Jeff Bailey, Thomas Ruschak,
4 * Ken Stevens, Steve McClure, Markus Armbruster
6 * Empire is free software: you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation, either version 3 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program. If not, see <http://www.gnu.org/licenses/>.
21 * See files README, COPYING and CREDITS in the root of the source
22 * tree for related information and legal notices. It is expected
23 * that future projects/authors will amend these files as needed.
27 * ringbuf.c: Simple ring buffer
29 * Known contributors to this file:
30 * Markus Armbruster, 2007-2017
42 * Initialize empty ring buffer.
43 * Not necessary if *R is already zeroed.
46 ring_init(struct ring *r)
48 r->cons = r->prod = 0;
52 * Return number of bytes held in ring buffer.
55 ring_len(struct ring *r)
57 assert(r->prod - r->cons <= RING_SIZE);
58 return r->prod - r->cons;
62 * Return how much space is left in ring buffer.
65 ring_space(struct ring *r)
67 return RING_SIZE - (r->prod - r->cons);
71 * Peek at ring buffer contents.
72 * @n must be between -RING_SIZE-1 and RING_SIZE.
73 * If @n>=0, peek at the (@n+1)-th byte to be gotten.
74 * If @n<0, peek at the -@n-th byte that has been put in.
75 * Return the byte as unsigned char coverted to int, or EOF if there
76 * aren't that many bytes in the ring buffer.
79 ring_peek(struct ring *r, int n)
83 assert(-RING_SIZE - 1 <= n && n <= RING_SIZE);
90 /* Beware, r->prod - -n can wrap around, avoid that */
91 if (r->prod < r->cons + -n)
96 return r->buf[idx % RING_SIZE];
100 * Get and remove the oldest byte from the ring buffer.
101 * Return it as unsigned char converted to int, or EOF if the buffer was
105 ring_getc(struct ring *r)
107 if (r->cons == r->prod)
109 return r->buf[r->cons++ % RING_SIZE];
113 * Attempt to put byte @c into the ring buffer.
114 * Return EOF when the buffer is full, else @c.
117 ring_putc(struct ring *r, unsigned char c)
119 if (r->prod - r->cons == RING_SIZE)
121 return r->buf[r->prod++ % RING_SIZE] = c;
125 * Attempt to put @sz bytes from @buf into the ring buffer.
126 * Return space left in ring buffer when it fits, else don't change
127 * the ring buffer and return how much space is missing times -1.
130 ring_putm(struct ring *r, void *buf, size_t sz)
133 int left = ring_space(r) - sz;
139 for (i = 0; i < sz; i++)
140 res = ring_putc(r, p[i]);
148 * Discard the N oldest bytes from the ring buffer.
149 * It must hold at least that many.
152 ring_discard(struct ring *r, int n)
154 assert(0 <= n && n <= ring_len(r));
159 * Search the ring buffer for zero-terminated string S.
160 * Start at the @(n+1)-th byte to be gotten.
161 * If found, return the number of bytes in the buffer before S.
165 ring_search(struct ring *r, char *s, int n)
167 size_t len = strlen(s);
170 for (i = r->cons + n; i + len <= r->prod; i++) {
171 for (j = 0; s[j] && s[j] == (char)r->buf[(i + j) % RING_SIZE]; j++)
180 * Fill ring buffer from file referred by file descriptor @fd.
181 * If ring buffer is already full, do nothing and return 0.
182 * Else attempt to read as many bytes as space permits, with readv(),
183 * and return its value.
186 ring_from_file(struct ring *r, int fd)
188 unsigned cons = r->cons % RING_SIZE;
189 unsigned prod = r->prod % RING_SIZE;
194 if (r->prod == r->cons + RING_SIZE)
197 iov[0].iov_base = r->buf + prod;
200 iov[0].iov_len = RING_SIZE - prod;
201 /* r->buf[..cons-1] */
202 iov[1].iov_base = r->buf;
203 iov[1].iov_len = cons;
206 /* r->buf[prod..cons-1] */
207 iov[0].iov_len = cons - prod;
210 res = readv(fd, iov, cnt);
218 * Set up @iov[] to describe complete contents of ring buffer.
219 * @iov[] must have at least two elements.
220 * Return number of elements used (zero for an empty ring buffer).
223 ring_to_iovec(struct ring *r, struct iovec iov[])
225 unsigned cons = r->cons % RING_SIZE;
226 unsigned prod = r->prod % RING_SIZE;
228 if (r->cons == r->prod)
231 iov[0].iov_base = r->buf + cons;
233 /* r->buf[cons..prod-1] */
234 iov[0].iov_len = prod - cons;
238 iov[0].iov_len = RING_SIZE - cons;
239 /* r->buf[..prod-1] */
240 iov[1].iov_base = r->buf;
241 iov[1].iov_len = prod;
246 * Drain ring buffer to file referred by file descriptor @fd.
247 * If ring buffer is already empty, do nothing and return 0.
248 * Else attempt to write complete contents with writev(), and return
252 ring_to_file(struct ring *r, int fd)
258 cnt = ring_to_iovec(r, iov);
259 res = writev(fd, iov, cnt);
262 ring_discard(r, res);