1 /* $OpenBSD: ringbuf.c,v 1.8 2015/01/16 06:40:21 deraadt 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 <stdio.h> 25 #include <stdlib.h> 26 #include <string.h> 27 28 #include "syslogd.h" 29 30 #define MINIMUM(a, b) (((a) < (b)) ? (a) : (b)) 31 32 /* Initialise a ring buffer */ 33 struct ringbuf * 34 ringbuf_init(size_t len) 35 { 36 struct ringbuf *ret; 37 38 if (len == 0 || (ret = malloc(sizeof(*ret))) == NULL) 39 return (NULL); 40 41 if ((ret->buf = malloc(len)) == NULL) { 42 free(ret); 43 return (NULL); 44 } 45 46 ret->len = len; 47 ret->start = ret->end = 0; 48 49 return (ret); 50 } 51 52 /* Free a ring buffer */ 53 void 54 ringbuf_free(struct ringbuf *rb) 55 { 56 free(rb->buf); 57 free(rb); 58 } 59 60 /* Clear a ring buffer */ 61 void 62 ringbuf_clear(struct ringbuf *rb) 63 { 64 rb->start = rb->end = 0; 65 } 66 67 /* Return the number of bytes used in a ringbuffer */ 68 size_t 69 ringbuf_used(struct ringbuf *rb) 70 { 71 return ((rb->len + rb->end - rb->start) % rb->len); 72 } 73 74 /* 75 * Append a line to a ring buffer, will delete lines from start 76 * of buffer as necessary 77 */ 78 int 79 ringbuf_append_line(struct ringbuf *rb, char *line) 80 { 81 size_t llen, used, copy_len; 82 int overflow = 0; 83 84 if (rb == NULL || line == NULL) 85 return (-1); 86 87 llen = strlen(line); 88 if (llen == 0) 89 return (-1); 90 91 if (line[llen - 1] != '\n') 92 llen++; /* one extra for appended '\n' */ 93 94 if (llen >= rb->len) 95 return (-1); 96 97 /* 98 * If necessary, advance start pointer to make room for appended 99 * string. Ensure that start pointer is at the beginning of a line 100 * once we are done (i.e move to after '\n'). 101 */ 102 used = ringbuf_used(rb); 103 if (used + llen >= rb->len) { 104 rb->start = (rb->start + used + llen - rb->len) % rb->len; 105 106 /* Find next '\n' */ 107 while (rb->buf[rb->start] != '\n') 108 rb->start = (rb->start + 1) % rb->len; 109 /* Skip it */ 110 rb->start = (rb->start + 1) % rb->len; 111 112 overflow = 1; 113 } 114 115 /* 116 * Now append string, starting from last pointer and wrapping if 117 * necessary 118 */ 119 if (rb->end + llen > rb->len) { 120 copy_len = rb->len - rb->end; 121 memcpy(rb->buf + rb->end, line, copy_len); 122 memcpy(rb->buf, line + copy_len, llen - copy_len - 1); 123 rb->buf[llen - copy_len - 1] = '\n'; 124 } else { 125 memcpy(rb->buf + rb->end, line, llen - 1); 126 rb->buf[rb->end + llen - 1] = '\n'; 127 } 128 129 rb->end = (rb->end + llen) % rb->len; 130 131 return (overflow); 132 } 133 134 /* 135 * Copy and nul-terminate a ringbuffer to a string. 136 */ 137 ssize_t 138 ringbuf_to_string(char *buf, size_t len, struct ringbuf *rb) 139 { 140 size_t copy_len, n; 141 142 if (buf == NULL || rb == NULL || len == 0) 143 return (-1); 144 145 copy_len = MINIMUM(len - 1, ringbuf_used(rb)); 146 147 if (copy_len == 0) 148 return (copy_len); 149 150 if (rb->start < rb->end) 151 memcpy(buf, rb->buf + rb->start, copy_len); 152 else { 153 /* If the buffer is wrapped, copy each hunk separately */ 154 n = rb->len - rb->start; 155 memcpy(buf, rb->buf + rb->start, MINIMUM(n, copy_len)); 156 if (copy_len > n) 157 memcpy(buf + n, rb->buf, MINIMUM(rb->end, copy_len - n)); 158 } 159 buf[copy_len] = '\0'; 160 161 return (ringbuf_used(rb)); 162 } 163