1 /* $OpenBSD: ringbuf.c,v 1.10 2016/10/16 22:12:50 bluhm 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 <stdio.h> 24 #include <stdlib.h> 25 #include <string.h> 26 27 #include "syslogd.h" 28 29 #define MINIMUM(a, b) (((a) < (b)) ? (a) : (b)) 30 31 /* Initialise a ring buffer */ 32 struct ringbuf * 33 ringbuf_init(size_t len) 34 { 35 struct ringbuf *ret; 36 37 if (len == 0 || (ret = malloc(sizeof(*ret))) == NULL) 38 return (NULL); 39 40 if ((ret->buf = malloc(len)) == NULL) { 41 free(ret); 42 return (NULL); 43 } 44 45 ret->len = len; 46 ret->start = ret->end = 0; 47 48 return (ret); 49 } 50 51 /* Free a ring buffer */ 52 void 53 ringbuf_free(struct ringbuf *rb) 54 { 55 free(rb->buf); 56 free(rb); 57 } 58 59 /* Clear a ring buffer */ 60 void 61 ringbuf_clear(struct ringbuf *rb) 62 { 63 rb->start = rb->end = 0; 64 } 65 66 /* Return the number of bytes used in a ringbuffer */ 67 size_t 68 ringbuf_used(struct ringbuf *rb) 69 { 70 return ((rb->len + rb->end - rb->start) % rb->len); 71 } 72 73 /* 74 * Append a line to a ring buffer, will delete lines from start 75 * of buffer as necessary 76 */ 77 int 78 ringbuf_append_line(struct ringbuf *rb, char *line) 79 { 80 size_t llen, used, copy_len; 81 int overflow = 0; 82 83 if (rb == NULL || line == NULL) 84 return (-1); 85 86 llen = strlen(line); 87 if (llen == 0) 88 return (-1); 89 90 if (line[llen - 1] != '\n') 91 llen++; /* one extra for appended '\n' */ 92 93 if (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 137 ringbuf_to_string(char *buf, size_t len, struct ringbuf *rb) 138 { 139 size_t copy_len, n; 140 141 if (buf == NULL || rb == NULL || len == 0) 142 return (-1); 143 144 copy_len = MINIMUM(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, MINIMUM(n, copy_len)); 155 if (copy_len > n) 156 memcpy(buf + n, rb->buf, 157 MINIMUM(rb->end, copy_len - n)); 158 } 159 buf[copy_len] = '\0'; 160 161 return (ringbuf_used(rb)); 162 } 163