1 /* $OpenBSD: reverse.c,v 1.14 2003/07/01 11:12:59 henning 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. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36 #ifndef lint 37 #if 0 38 static char sccsid[] = "@(#)reverse.c 8.1 (Berkeley) 6/6/93"; 39 #endif 40 static char rcsid[] = "$OpenBSD: reverse.c,v 1.14 2003/07/01 11:12:59 henning Exp $"; 41 #endif /* not lint */ 42 43 #include <sys/param.h> 44 #include <sys/stat.h> 45 #include <sys/mman.h> 46 47 #include <err.h> 48 #include <errno.h> 49 #include <limits.h> 50 #include <stdio.h> 51 #include <stdlib.h> 52 #include <string.h> 53 #include <unistd.h> 54 55 #include "extern.h" 56 57 static void r_buf(FILE *); 58 static int r_reg(FILE *, enum STYLE, long, struct stat *); 59 60 #define COPYCHAR(fp, ch) \ 61 do { \ 62 if ((ch = getc(fp)) == EOF) { \ 63 ierr(); \ 64 return (0); \ 65 } \ 66 if (putchar(ch) == EOF) { \ 67 oerr(); \ 68 return (0); \ 69 } \ 70 } while (0) 71 72 /* 73 * reverse -- display input in reverse order by line. 74 * 75 * There are six separate cases for this -- regular and non-regular 76 * files by bytes, lines or the whole file. 77 * 78 * BYTES display N bytes 79 * REG reverse scan and display the lines 80 * NOREG cyclically read characters into a wrap-around buffer 81 * 82 * LINES display N lines 83 * REG reverse scan and display the lines 84 * NOREG cyclically read lines into a wrap-around array of buffers 85 * 86 * FILE display the entire file 87 * REG reverse scan and display the lines 88 * NOREG cyclically read input into a linked list of buffers 89 */ 90 void 91 reverse(fp, style, off, sbp) 92 FILE *fp; 93 enum STYLE style; 94 long off; 95 struct stat *sbp; 96 { 97 if (style != REVERSE && off == 0) 98 return; 99 100 if (!S_ISREG(sbp->st_mode) || r_reg(fp, style, off, sbp) != 0) 101 switch(style) { 102 case FBYTES: 103 case RBYTES: 104 (void)bytes(fp, off); 105 break; 106 case FLINES: 107 case RLINES: 108 (void)lines(fp, off); 109 break; 110 case REVERSE: 111 r_buf(fp); 112 break; 113 } 114 } 115 116 /* 117 * r_reg -- display a regular file in reverse order by line. 118 */ 119 static int 120 r_reg(FILE *fp, enum STYLE style, long off, struct stat *sbp) 121 { 122 off_t start, pos, end; 123 int ch; 124 125 end = sbp->st_size; 126 if (end == 0) 127 return (0); 128 129 /* Position before char, ignore last char whether newline or not */ 130 pos = end-2; 131 ch = EOF; 132 start = 0; 133 134 if (style == RBYTES && off < end) 135 start = end - off; 136 137 for (; pos >= start; pos--) { 138 /* A seek per char isn't a problem with a smart stdio */ 139 if (fseeko(fp, pos, SEEK_SET) != 0) { 140 ierr(); 141 return (0); 142 } 143 if ((ch = getc(fp)) == '\n') { 144 while (--end > pos) 145 COPYCHAR(fp, ch); 146 end++; 147 if (style == RLINES && --off == 0) 148 break; 149 } 150 else if (ch == EOF) { 151 ierr(); 152 return (0); 153 } 154 } 155 if (pos < start) { 156 if (ch != EOF && ungetc(ch, fp) == EOF) { 157 ierr(); 158 return (0); 159 } 160 while (--end >= start) 161 COPYCHAR(fp, ch); 162 } 163 return (0); 164 } 165 166 typedef struct bf { 167 struct bf *next; 168 struct bf *prev; 169 int len; 170 char *l; 171 } BF; 172 173 /* 174 * r_buf -- display a non-regular file in reverse order by line. 175 * 176 * This is the function that saves the entire input, storing the data in a 177 * doubly linked list of buffers and then displays them in reverse order. 178 * It has the usual nastiness of trying to find the newlines, as there's no 179 * guarantee that a newline occurs anywhere in the file, let alone in any 180 * particular buffer. If we run out of memory, input is discarded (and the 181 * user warned). 182 */ 183 static void 184 r_buf(fp) 185 FILE *fp; 186 { 187 BF *mark, *tr, *tl = NULL; 188 int ch, len, llen; 189 char *p; 190 off_t enomem; 191 192 #define BSZ (128 * 1024) 193 for (mark = NULL, enomem = 0;;) { 194 /* 195 * Allocate a new block and link it into place in a doubly 196 * linked list. If out of memory, toss the LRU block and 197 * keep going. 198 */ 199 if (enomem || (tl = malloc(sizeof(BF))) == NULL || 200 (tl->l = malloc(BSZ)) == NULL) { 201 if (!mark) 202 err(1, NULL); 203 tl = enomem ? tl->next : mark; 204 enomem += tl->len; 205 } else if (mark) { 206 tl->next = mark; 207 tl->prev = mark->prev; 208 mark->prev->next = tl; 209 mark->prev = tl; 210 } else { 211 mark = tl; 212 mark->next = mark->prev = mark; 213 } 214 215 if (!enomem) 216 tl->len = 0; 217 218 /* Fill the block with input data. */ 219 for (p = tl->l, len = 0; 220 len < BSZ && (ch = getc(fp)) != EOF; ++len) 221 *p++ = ch; 222 223 /* 224 * If no input data for this block and we tossed some data, 225 * recover it. 226 */ 227 if (!len) { 228 if (enomem) 229 enomem -= tl->len; 230 tl = tl->prev; 231 break; 232 } 233 234 tl->len = len; 235 if (ch == EOF) 236 break; 237 } 238 239 if (enomem) { 240 (void)fprintf(stderr, 241 "tail: warning: %lld bytes discarded\n", (long long)enomem); 242 rval = 1; 243 } 244 245 /* 246 * Step through the blocks in the reverse order read. The last char 247 * is special, ignore whether newline or not. 248 */ 249 for (mark = tl;;) { 250 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--; 251 --p, ++llen) 252 if (*p == '\n') { 253 if (llen) { 254 WR(p + 1, llen); 255 llen = 0; 256 } 257 if (tl == mark) 258 continue; 259 for (tr = tl->next; tr->len; tr = tr->next) { 260 WR(tr->l, tr->len); 261 tr->len = 0; 262 if (tr == mark) 263 break; 264 } 265 } 266 tl->len = llen; 267 if ((tl = tl->prev) == mark) 268 break; 269 } 270 tl = tl->next; 271 if (tl->len) { 272 WR(tl->l, tl->len); 273 tl->len = 0; 274 } 275 while ((tl = tl->next)->len) { 276 WR(tl->l, tl->len); 277 tl->len = 0; 278 } 279 } 280