1 /* $OpenBSD: reverse.c,v 1.4 1999/02/03 02:09:30 millert Exp $ */ 2 /* $NetBSD: reverse.c,v 1.6 1994/11/23 07:42:10 jtc Exp $ */ 3 4 /*- 5 * Copyright (c) 1991, 1993 6 * The Regents of the University of California. All rights reserved. 7 * 8 * This code is derived from software contributed to Berkeley by 9 * Edward Sze-Tyan Wang. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by the University of 22 * California, Berkeley and its contributors. 23 * 4. Neither the name of the University nor the names of its contributors 24 * may be used to endorse or promote products derived from this software 25 * without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 28 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 29 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 30 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 31 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 32 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 33 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 34 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 35 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 36 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 37 * SUCH DAMAGE. 38 */ 39 40 #ifndef lint 41 #if 0 42 static char sccsid[] = "@(#)reverse.c 8.1 (Berkeley) 6/6/93"; 43 #endif 44 static char rcsid[] = "$OpenBSD: reverse.c,v 1.4 1999/02/03 02:09:30 millert Exp $"; 45 #endif /* not lint */ 46 47 #include <sys/param.h> 48 #include <sys/stat.h> 49 #include <sys/mman.h> 50 51 #include <err.h> 52 #include <errno.h> 53 #include <limits.h> 54 #include <stdio.h> 55 #include <stdlib.h> 56 #include <string.h> 57 #include <unistd.h> 58 59 #include "extern.h" 60 61 static void r_buf __P((FILE *)); 62 static int r_reg __P((FILE *, enum STYLE, long, struct stat *)); 63 64 /* 65 * reverse -- display input in reverse order by line. 66 * 67 * There are six separate cases for this -- regular and non-regular 68 * files by bytes, lines or the whole file. 69 * 70 * BYTES display N bytes 71 * REG mmap the file and display the lines 72 * NOREG cyclically read characters into a wrap-around buffer 73 * 74 * LINES display N lines 75 * REG mmap the file and display the lines 76 * NOREG cyclically read lines into a wrap-around array of buffers 77 * 78 * FILE display the entire file 79 * REG mmap the file and display the lines 80 * NOREG cyclically read input into a linked list of buffers 81 */ 82 void 83 reverse(fp, style, off, sbp) 84 FILE *fp; 85 enum STYLE style; 86 long off; 87 struct stat *sbp; 88 { 89 if (style != REVERSE && off == 0) 90 return; 91 92 if (!S_ISREG(sbp->st_mode) || r_reg(fp, style, off, sbp) != 0) 93 switch(style) { 94 case FBYTES: 95 case RBYTES: 96 bytes(fp, off); 97 break; 98 case FLINES: 99 case RLINES: 100 lines(fp, off); 101 break; 102 case REVERSE: 103 r_buf(fp); 104 break; 105 } 106 } 107 108 /* 109 * r_reg -- display a regular file in reverse order by line. 110 */ 111 static int 112 r_reg(fp, style, off, sbp) 113 FILE *fp; 114 register enum STYLE style; 115 long off; 116 struct stat *sbp; 117 { 118 register off_t size; 119 register int llen; 120 register char *p; 121 char *start; 122 123 if (!(size = sbp->st_size)) 124 return (0); 125 126 if (size > SIZE_T_MAX) 127 return (1); 128 129 if ((start = mmap(NULL, (size_t)size, PROT_READ, 0, fileno(fp), 130 (off_t)0)) == (caddr_t)-1) 131 return (1); 132 p = start + size - 1; 133 134 if (style == RBYTES && off < size) 135 size = off; 136 137 /* Last char is special, ignore whether newline or not. */ 138 for (llen = 1; --size; ++llen) 139 if (*--p == '\n') { 140 WR(p + 1, llen); 141 llen = 0; 142 if (style == RLINES && !--off) { 143 ++p; 144 break; 145 } 146 } 147 if (llen) 148 WR(p, llen); 149 if (munmap(start, (size_t)sbp->st_size)) 150 ierr(); 151 152 return (0); 153 } 154 155 typedef struct bf { 156 struct bf *next; 157 struct bf *prev; 158 int len; 159 char *l; 160 } BF; 161 162 /* 163 * r_buf -- display a non-regular file in reverse order by line. 164 * 165 * This is the function that saves the entire input, storing the data in a 166 * doubly linked list of buffers and then displays them in reverse order. 167 * It has the usual nastiness of trying to find the newlines, as there's no 168 * guarantee that a newline occurs anywhere in the file, let alone in any 169 * particular buffer. If we run out of memory, input is discarded (and the 170 * user warned). 171 */ 172 static void 173 r_buf(fp) 174 FILE *fp; 175 { 176 register BF *mark, *tr, *tl = NULL; 177 register int ch, len, llen; 178 register char *p; 179 off_t enomem; 180 181 #define BSZ (128 * 1024) 182 for (mark = NULL, enomem = 0;;) { 183 /* 184 * Allocate a new block and link it into place in a doubly 185 * linked list. If out of memory, toss the LRU block and 186 * keep going. 187 */ 188 if (enomem || (tl = malloc(sizeof(BF))) == NULL || 189 (tl->l = malloc(BSZ)) == NULL) { 190 if (!mark) 191 err(1, NULL); 192 tl = enomem ? tl->next : mark; 193 enomem += tl->len; 194 } else if (mark) { 195 tl->next = mark; 196 tl->prev = mark->prev; 197 mark->prev->next = tl; 198 mark->prev = tl; 199 } else 200 mark->next = mark->prev = (mark = tl); 201 202 /* Fill the block with input data. */ 203 for (p = tl->l, len = 0; 204 len < BSZ && (ch = getc(fp)) != EOF; ++len) 205 *p++ = ch; 206 207 /* 208 * If no input data for this block and we tossed some data, 209 * recover it. 210 */ 211 if (!len) { 212 if (enomem) 213 enomem -= tl->len; 214 tl = tl->prev; 215 break; 216 } 217 218 tl->len = len; 219 if (ch == EOF) 220 break; 221 } 222 223 if (enomem) { 224 (void)fprintf(stderr, 225 "tail: warning: %qd bytes discarded\n", enomem); 226 rval = 1; 227 } 228 229 /* 230 * Step through the blocks in the reverse order read. The last char 231 * is special, ignore whether newline or not. 232 */ 233 for (mark = tl;;) { 234 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--; 235 --p, ++llen) 236 if (*p == '\n') { 237 if (llen) { 238 WR(p + 1, llen); 239 llen = 0; 240 } 241 if (tl == mark) 242 continue; 243 for (tr = tl->next; tr->len; tr = tr->next) { 244 WR(tr->l, tr->len); 245 tr->len = 0; 246 if (tr == mark) 247 break; 248 } 249 } 250 tl->len = llen; 251 if ((tl = tl->prev) == mark) 252 break; 253 } 254 tl = tl->next; 255 if (tl->len) { 256 WR(tl->l, tl->len); 257 tl->len = 0; 258 } 259 while ((tl = tl->next)->len) { 260 WR(tl->l, tl->len); 261 tl->len = 0; 262 } 263 } 264