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