1 /* $NetBSD: reverse.c,v 1.14 2002/06/14 00:47:41 wiz 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 1.14 2002/06/14 00:47:41 wiz 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(FILE *); 60 static void r_reg(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(FILE *fp, enum STYLE style, long int off, struct stat *sbp) 82 { 83 if (style != REVERSE && off == 0) 84 return; 85 86 if (S_ISREG(sbp->st_mode)) 87 r_reg(fp, style, off, sbp); 88 else 89 switch(style) { 90 case FBYTES: 91 case RBYTES: 92 (void)bytes(fp, off); 93 break; 94 case FLINES: 95 case RLINES: 96 (void)lines(fp, off); 97 break; 98 case REVERSE: 99 r_buf(fp); 100 break; 101 default: 102 break; 103 } 104 } 105 106 /* 107 * r_reg -- display a regular file in reverse order by line. 108 */ 109 static void 110 r_reg(FILE *fp, enum STYLE style, long int off, struct stat *sbp) 111 { 112 off_t size; 113 int llen; 114 char *p; 115 char *start; 116 117 if (!(size = sbp->st_size)) 118 return; 119 120 if (size > SIZE_T_MAX) { 121 err(0, "%s: %s", fname, strerror(EFBIG)); 122 return; 123 } 124 125 if ((start = mmap(NULL, (size_t)size, PROT_READ, 126 MAP_FILE|MAP_SHARED, fileno(fp), (off_t)0)) == (caddr_t)-1) { 127 err(0, "%s: %s", fname, strerror(EFBIG)); 128 return; 129 } 130 p = start + size - 1; 131 132 if (style == RBYTES && off < size) 133 size = off; 134 135 /* Last char is special, ignore whether newline or not. */ 136 for (llen = 1; --size; ++llen) 137 if (*--p == '\n') { 138 WR(p + 1, llen); 139 llen = 0; 140 if (style == RLINES && !--off) { 141 ++p; 142 break; 143 } 144 } 145 if (llen) 146 WR(p, llen); 147 if (munmap(start, (size_t)sbp->st_size)) 148 err(0, "%s: %s", fname, strerror(errno)); 149 } 150 151 typedef struct bf { 152 struct bf *next; 153 struct bf *prev; 154 int len; 155 char *l; 156 } BF; 157 158 /* 159 * r_buf -- display a non-regular file in reverse order by line. 160 * 161 * This is the function that saves the entire input, storing the data in a 162 * doubly linked list of buffers and then displays them in reverse order. 163 * It has the usual nastiness of trying to find the newlines, as there's no 164 * guarantee that a newline occurs anywhere in the file, let alone in any 165 * particular buffer. If we run out of memory, input is discarded (and the 166 * user warned). 167 */ 168 static void 169 r_buf(FILE *fp) 170 { 171 BF *mark, *tl, *tr; 172 int ch, len, llen; 173 char *p; 174 off_t enomem; 175 176 #define BSZ (128 * 1024) 177 tl = NULL; 178 for (mark = NULL, enomem = 0;;) { 179 /* 180 * Allocate a new block and link it into place in a doubly 181 * linked list. If out of memory, toss the LRU block and 182 * keep going. 183 */ 184 if (enomem || (tl = malloc(sizeof(BF))) == NULL || 185 (tl->l = malloc(BSZ)) == NULL) { 186 if (!mark) 187 err(1, "%s", strerror(errno)); 188 tl = enomem ? tl->next : mark; 189 enomem += tl->len; 190 } else if (mark) { 191 tl->next = mark; 192 tl->prev = mark->prev; 193 mark->prev->next = tl; 194 mark->prev = tl; 195 } else { 196 mark = tl; 197 mark->next = mark->prev = mark; 198 } 199 200 /* Fill the block with input data. */ 201 for (p = tl->l, len = 0; 202 len < BSZ && (ch = getc(fp)) != EOF; ++len) 203 *p++ = ch; 204 205 /* 206 * If no input data for this block and we tossed some data, 207 * recover it. 208 */ 209 if (!len) { 210 if (enomem) 211 enomem -= tl->len; 212 tl = tl->prev; 213 break; 214 } 215 216 tl->len = len; 217 if (ch == EOF) 218 break; 219 } 220 221 if (enomem) { 222 (void)fprintf(stderr, 223 "tail: warning: %lld bytes discarded\n", (long long)enomem); 224 rval = 1; 225 } 226 227 /* 228 * Step through the blocks in the reverse order read. The last char 229 * is special, ignore whether newline or not. 230 */ 231 for (mark = tl;;) { 232 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--; 233 --p, ++llen) 234 if (*p == '\n') { 235 if (llen) { 236 WR(p + 1, llen); 237 llen = 0; 238 } 239 if (tl == mark) 240 continue; 241 for (tr = tl->next; tr->len; tr = tr->next) { 242 WR(tr->l, tr->len); 243 tr->len = 0; 244 if (tr == mark) 245 break; 246 } 247 } 248 tl->len = llen; 249 if ((tl = tl->prev) == mark) 250 break; 251 } 252 tl = tl->next; 253 if (tl->len) { 254 WR(tl->l, tl->len); 255 tl->len = 0; 256 } 257 while ((tl = tl->next)->len) { 258 WR(tl->l, tl->len); 259 tl->len = 0; 260 } 261 } 262