1 /* $NetBSD: reverse.c,v 1.13 2001/01/16 02:41:18 cgd Exp $ */ 2 3 /*- 4 * Copyright (c) 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Edward Sze-Tyan Wang. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 #include <sys/cdefs.h> 40 #ifndef lint 41 #if 0 42 static char sccsid[] = "@(#)reverse.c 8.1 (Berkeley) 6/6/93"; 43 #endif 44 __RCSID("$NetBSD: reverse.c,v 1.13 2001/01/16 02:41:18 cgd Exp $"); 45 #endif /* not lint */ 46 47 #include <sys/param.h> 48 #include <sys/stat.h> 49 #include <sys/mman.h> 50 51 #include <limits.h> 52 #include <errno.h> 53 #include <unistd.h> 54 #include <stdio.h> 55 #include <stdlib.h> 56 #include <string.h> 57 #include "extern.h" 58 59 static void r_buf __P((FILE *)); 60 static void r_reg __P((FILE *, enum STYLE, long, struct stat *)); 61 62 /* 63 * reverse -- display input in reverse order by line. 64 * 65 * There are six separate cases for this -- regular and non-regular 66 * files by bytes, lines or the whole file. 67 * 68 * BYTES display N bytes 69 * REG mmap the file and display the lines 70 * NOREG cyclically read characters into a wrap-around buffer 71 * 72 * LINES display N lines 73 * REG mmap the file and display the lines 74 * NOREG cyclically read lines into a wrap-around array of buffers 75 * 76 * FILE display the entire file 77 * REG mmap the file and display the lines 78 * NOREG cyclically read input into a linked list of buffers 79 */ 80 void 81 reverse(fp, style, off, sbp) 82 FILE *fp; 83 enum STYLE style; 84 long off; 85 struct stat *sbp; 86 { 87 if (style != REVERSE && off == 0) 88 return; 89 90 if (S_ISREG(sbp->st_mode)) 91 r_reg(fp, style, off, sbp); 92 else 93 switch(style) { 94 case FBYTES: 95 case RBYTES: 96 (void)bytes(fp, off); 97 break; 98 case FLINES: 99 case RLINES: 100 (void)lines(fp, off); 101 break; 102 case REVERSE: 103 r_buf(fp); 104 break; 105 default: 106 break; 107 } 108 } 109 110 /* 111 * r_reg -- display a regular file in reverse order by line. 112 */ 113 static void 114 r_reg(fp, style, off, sbp) 115 FILE *fp; 116 enum STYLE style; 117 long off; 118 struct stat *sbp; 119 { 120 off_t size; 121 int llen; 122 char *p; 123 char *start; 124 125 if (!(size = sbp->st_size)) 126 return; 127 128 if (size > SIZE_T_MAX) { 129 err(0, "%s: %s", fname, strerror(EFBIG)); 130 return; 131 } 132 133 if ((start = mmap(NULL, (size_t)size, PROT_READ, 134 MAP_FILE|MAP_SHARED, fileno(fp), (off_t)0)) == (caddr_t)-1) { 135 err(0, "%s: %s", fname, strerror(EFBIG)); 136 return; 137 } 138 p = start + size - 1; 139 140 if (style == RBYTES && off < size) 141 size = off; 142 143 /* Last char is special, ignore whether newline or not. */ 144 for (llen = 1; --size; ++llen) 145 if (*--p == '\n') { 146 WR(p + 1, llen); 147 llen = 0; 148 if (style == RLINES && !--off) { 149 ++p; 150 break; 151 } 152 } 153 if (llen) 154 WR(p, llen); 155 if (munmap(start, (size_t)sbp->st_size)) 156 err(0, "%s: %s", fname, strerror(errno)); 157 } 158 159 typedef struct bf { 160 struct bf *next; 161 struct bf *prev; 162 int len; 163 char *l; 164 } BF; 165 166 /* 167 * r_buf -- display a non-regular file in reverse order by line. 168 * 169 * This is the function that saves the entire input, storing the data in a 170 * doubly linked list of buffers and then displays them in reverse order. 171 * It has the usual nastiness of trying to find the newlines, as there's no 172 * guarantee that a newline occurs anywhere in the file, let alone in any 173 * particular buffer. If we run out of memory, input is discarded (and the 174 * user warned). 175 */ 176 static void 177 r_buf(fp) 178 FILE *fp; 179 { 180 BF *mark, *tl, *tr; 181 int ch, len, llen; 182 char *p; 183 off_t enomem; 184 185 #define BSZ (128 * 1024) 186 tl = NULL; 187 for (mark = NULL, enomem = 0;;) { 188 /* 189 * Allocate a new block and link it into place in a doubly 190 * linked list. If out of memory, toss the LRU block and 191 * keep going. 192 */ 193 if (enomem || (tl = malloc(sizeof(BF))) == NULL || 194 (tl->l = malloc(BSZ)) == NULL) { 195 if (!mark) 196 err(1, "%s", strerror(errno)); 197 tl = enomem ? tl->next : mark; 198 enomem += tl->len; 199 } else if (mark) { 200 tl->next = mark; 201 tl->prev = mark->prev; 202 mark->prev->next = tl; 203 mark->prev = tl; 204 } else { 205 mark = tl; 206 mark->next = mark->prev = mark; 207 } 208 209 /* Fill the block with input data. */ 210 for (p = tl->l, len = 0; 211 len < BSZ && (ch = getc(fp)) != EOF; ++len) 212 *p++ = ch; 213 214 /* 215 * If no input data for this block and we tossed some data, 216 * recover it. 217 */ 218 if (!len) { 219 if (enomem) 220 enomem -= tl->len; 221 tl = tl->prev; 222 break; 223 } 224 225 tl->len = len; 226 if (ch == EOF) 227 break; 228 } 229 230 if (enomem) { 231 (void)fprintf(stderr, 232 "tail: warning: %lld bytes discarded\n", (long long)enomem); 233 rval = 1; 234 } 235 236 /* 237 * Step through the blocks in the reverse order read. The last char 238 * is special, ignore whether newline or not. 239 */ 240 for (mark = tl;;) { 241 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--; 242 --p, ++llen) 243 if (*p == '\n') { 244 if (llen) { 245 WR(p + 1, llen); 246 llen = 0; 247 } 248 if (tl == mark) 249 continue; 250 for (tr = tl->next; tr->len; tr = tr->next) { 251 WR(tr->l, tr->len); 252 tr->len = 0; 253 if (tr == mark) 254 break; 255 } 256 } 257 tl->len = llen; 258 if ((tl = tl->prev) == mark) 259 break; 260 } 261 tl = tl->next; 262 if (tl->len) { 263 WR(tl->l, tl->len); 264 tl->len = 0; 265 } 266 while ((tl = tl->next)->len) { 267 WR(tl->l, tl->len); 268 tl->len = 0; 269 } 270 } 271