1 /* $OpenBSD: ringbuf.c,v 1.4 2005/06/06 23:22:04 djm Exp $ */
2
3 /*
4 * Copyright (c) 2004 Damien Miller
5 *
6 * Permission to use, copy, modify, and distribute this software for any
7 * purpose with or without fee is hereby granted, provided that the above
8 * copyright notice and this permission notice appear in all copies.
9 *
10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17 */
18
19 /*
20 * Simple ringbuffer for lines of text.
21 */
22
23 #include <sys/types.h>
24 #include <sys/param.h>
25 #include <sys/uio.h>
26 #include <errno.h>
27 #include <stdio.h>
28 #include <stdlib.h>
29 #include <string.h>
30 #include <unistd.h>
31
32 #include "syslogd.h"
33
34 /* Initialise a ring buffer */
35 struct ringbuf *
ringbuf_init(size_t len)36 ringbuf_init(size_t len)
37 {
38 struct ringbuf *ret;
39
40 if (len == 0 || (ret = malloc(sizeof(*ret))) == NULL)
41 return (NULL);
42
43 if ((ret->buf = malloc(len)) == NULL) {
44 free(ret);
45 return (NULL);
46 }
47
48 ret->len = len;
49 ret->start = ret->end = 0;
50
51 return (ret);
52 }
53
54 /* Free a ring buffer */
55 void
ringbuf_free(struct ringbuf * rb)56 ringbuf_free(struct ringbuf *rb)
57 {
58 free(rb->buf);
59 free(rb);
60 }
61
62 /* Clear a ring buffer */
63 void
ringbuf_clear(struct ringbuf * rb)64 ringbuf_clear(struct ringbuf *rb)
65 {
66 rb->start = rb->end = 0;
67 }
68
69 /* Return the number of bytes used in a ringbuffer */
70 size_t
ringbuf_used(struct ringbuf * rb)71 ringbuf_used(struct ringbuf *rb)
72 {
73 return ((rb->len + rb->end - rb->start) % rb->len);
74 }
75
76 /*
77 * Append a line to a ring buffer, will delete lines from start
78 * of buffer as necessary
79 */
80 int
ringbuf_append_line(struct ringbuf * rb,char * line)81 ringbuf_append_line(struct ringbuf *rb, char *line)
82 {
83 size_t llen, used, copy_len;
84 int overflow = 0;
85
86 if (rb == NULL || line == NULL)
87 return (-1);
88
89 llen = strlen(line);
90 if (line[llen - 1] != '\n')
91 llen++; /* one extra for appended '\n' */
92
93 if (rb == NULL || llen == 0 || llen >= rb->len)
94 return (-1);
95
96 /*
97 * If necessary, advance start pointer to make room for appended
98 * string. Ensure that start pointer is at the beginning of a line
99 * once we are done (i.e move to after '\n').
100 */
101 used = ringbuf_used(rb);
102 if (used + llen >= rb->len) {
103 rb->start = (rb->start + used + llen - rb->len) % rb->len;
104
105 /* Find next '\n' */
106 while (rb->buf[rb->start] != '\n')
107 rb->start = (rb->start + 1) % rb->len;
108 /* Skip it */
109 rb->start = (rb->start + 1) % rb->len;
110
111 overflow = 1;
112 }
113
114 /*
115 * Now append string, starting from last pointer and wrapping if
116 * necessary
117 */
118 if (rb->end + llen > rb->len) {
119 copy_len = rb->len - rb->end;
120 memcpy(rb->buf + rb->end, line, copy_len);
121 memcpy(rb->buf, line + copy_len, llen - copy_len - 1);
122 rb->buf[llen - copy_len - 1] = '\n';
123 } else {
124 memcpy(rb->buf + rb->end, line, llen - 1);
125 rb->buf[rb->end + llen - 1] = '\n';
126 }
127
128 rb->end = (rb->end + llen) % rb->len;
129
130 return (overflow);
131 }
132
133 /*
134 * Copy and nul-terminate a ringbuffer to a string.
135 */
136 ssize_t
ringbuf_to_string(char * buf,size_t len,struct ringbuf * rb)137 ringbuf_to_string(char *buf, size_t len, struct ringbuf *rb)
138 {
139 ssize_t copy_len, n;
140
141 if (buf == NULL || rb == NULL)
142 return (-1);
143
144 copy_len = MIN(len - 1, ringbuf_used(rb));
145
146 if (copy_len <= 0)
147 return (copy_len);
148
149 if (rb->start < rb->end)
150 memcpy(buf, rb->buf + rb->start, copy_len);
151 else {
152 /* If the buffer is wrapped, copy each hunk separately */
153 n = rb->len - rb->start;
154 memcpy(buf, rb->buf + rb->start, MIN(n, copy_len));
155 if (copy_len - n > 0)
156 memcpy(buf + n, rb->buf, MIN(rb->end, copy_len - n));
157 }
158 buf[copy_len] = '\0';
159
160 return (ringbuf_used(rb));
161 }
162