2 * Empire - A multi-player, client/server Internet based war game.
3 * Copyright (C) 1986-2007, Dave Pare, Jeff Bailey, Thomas Ruschak,
4 * Ken Stevens, Steve McClure
6 * This program 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 2 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, write to the Free Software
18 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
22 * See files README, COPYING and CREDITS in the root of the source
23 * tree for related information and legal notices. It is expected
24 * that future projects/authors will amend these files as needed.
28 * ringbuf.c: Simple ring buffer
30 * Known contributors to this file:
31 * Markus Armbruster, 2007
44 * Initialize empty ring buffer.
45 * Not necessary if *R is already zeroed.
48 ring_init(struct ring *r)
50 r->cons = r->prod = 0;
54 * Return number of bytes held in ring buffer.
57 ring_len(struct ring *r)
59 assert(r->prod - r->cons <= RING_SIZE);
60 return r->prod - r->cons;
64 * Return how much space is left in ring buffer.
67 ring_space(struct ring *r)
69 return RING_SIZE - (r->prod - r->cons);
73 * Peek at ring buffer contents.
74 * N must be between -RING_SIZE-1 and RING_SIZE.
75 * If N>=0, peek at the (N+1)-th byte to be gotten.
76 * If N<0, peek at the -N-th byte that has been put in.
77 * Return the byte as unsigned char coverted to int, or EOF if there
78 * aren't that many bytes in the ring buffer.
81 ring_peek(struct ring *r, int n)
85 assert(-RING_SIZE - 1 <= n && n <= RING_SIZE);
87 idx = n >= 0 ? r->cons + n : r->prod - -n;
88 if (idx < r->cons && idx >= r->prod)
90 return r->buf[idx % RING_SIZE];
94 * Get and remove the oldest byte from the ring buffer.
95 * Return it as unsigned char coverted to int, or EOF if the buffer was
99 ring_getc(struct ring *r)
101 if (r->cons == r->prod)
103 return r->buf[r->cons++ % RING_SIZE];
107 * Attempt to put byte C into the ring buffer.
108 * Return EOF when the buffer is full, else C.
111 ring_putc(struct ring *r, unsigned char c)
113 if (r->prod - r->cons == RING_SIZE)
115 return r->buf[r->prod++ % RING_SIZE] = c;
119 * Attempt to put SZ bytes from BUF into the ring buffer.
120 * Return space left in ring buffer when it fits, else don't change
121 * the ring buffer and return how much space is missing.
124 ring_putm(struct ring *r, void *buf, size_t sz)
127 int left = ring_space(r) - sz;
133 for (i = 0; i < sz; i++)
134 res = ring_putc(r, p[i]);
142 * Discard the N oldest bytes from the ring buffer.
143 * It must hold at least that many.
146 ring_discard(struct ring *r, int n)
148 assert(n <= ring_len(r));
153 * Search the ring buffer for zero-terminated string S.
154 * If found, return a non-negative value referring to the beginning of
155 * S in the buffer when passed to ring_peek(). Else return -1.
158 ring_search(struct ring *r, char *s)
160 size_t len = strlen(s);
163 for (i = r->cons; i + len <= r->prod; i++) {
164 for (j = 0; j < len && s[j] == r->buf[(i + j) % RING_SIZE]; j++) ;
172 * Fill ring buffer from file referred by file descriptor FD.
173 * If ring buffer is already full, do nothing and return 0.
174 * Else attempt to read as many bytes as space permits, with readv(),
175 * and return its value.
178 ring_from_file(struct ring *r, int fd)
180 unsigned cons = r->cons % RING_SIZE;
181 unsigned prod = r->prod % RING_SIZE;
186 if (r->prod == r->cons + RING_SIZE)
189 iov[0].iov_base = r->buf + prod;
192 iov[0].iov_len = RING_SIZE - prod;
193 /* r->buf[..cons-1] */
194 iov[1].iov_base = r->buf;
195 iov[1].iov_len = cons;
198 /* r->buf[prod..cons-1] */
199 iov[0].iov_len = cons - prod;
202 res = readv(fd, iov, cnt);
210 * Drain ring buffer to file referred by file descriptor FD.
211 * If ring buffer is already empty, do nothing and return 0.
212 * Else attempt to write complete contents with writev(), and return
216 ring_to_file(struct ring *r, int fd)
218 unsigned cons = r->cons % RING_SIZE;
219 unsigned prod = r->prod % RING_SIZE;
224 if (r->cons == r->prod)
227 iov[0].iov_base = r->buf + cons;
230 iov[0].iov_len = RING_SIZE - cons;
231 /* r->buf[..prod-1] */
232 iov[1].iov_base = r->buf;
233 iov[1].iov_len = prod;
236 /* r->buf[cons..prod-1] */
237 iov[0].iov_len = prod - cons;
240 res = writev(fd, iov, cnt);