1 /* $NetBSD: reverse.c,v 1.25 2026/08/15 14:17:23 riastradh 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. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #include <sys/cdefs.h> 36 #ifndef lint 37 #if 0 38 static char sccsid[] = "@(#)reverse.c 8.1 (Berkeley) 6/6/93"; 39 #endif 40 __RCSID("$NetBSD: reverse.c,v 1.25 2026/08/15 14:17:23 riastradh Exp $"); 41 #endif /* not lint */ 42 43 #include <sys/param.h> 44 #include <sys/stat.h> 45 #include <sys/mman.h> 46 47 #include <limits.h> 48 #include <errno.h> 49 #include <unistd.h> 50 #include <stdio.h> 51 #include <stdlib.h> 52 #include <string.h> 53 #include "extern.h" 54 55 static void r_buf(FILE *); 56 static void r_reg(FILE *, enum STYLE, off_t, struct stat *); 57 58 /* 59 * reverse -- display input in reverse order by line. 60 * 61 * There are six separate cases for this -- regular and non-regular 62 * files by bytes, lines or the whole file. 63 * 64 * BYTES display N bytes 65 * REG mmap the file and display the lines 66 * NOREG cyclically read characters into a wrap-around buffer 67 * 68 * LINES display N lines 69 * REG mmap the file and display the lines 70 * NOREG cyclically read lines into a wrap-around array of buffers 71 * 72 * FILE display the entire file 73 * REG mmap the file and display the lines 74 * NOREG cyclically read input into a linked list of buffers 75 */ 76 void 77 reverse(FILE *fp, enum STYLE style, off_t off, struct stat *sbp) 78 { 79 if (style != REVERSE && off == 0) 80 return; 81 82 if (S_ISREG(sbp->st_mode) && sbp->st_size > 0) 83 r_reg(fp, style, off, sbp); 84 else 85 switch(style) { 86 case FBYTES: 87 case RBYTES: 88 (void)displaybytes(fp, off); 89 break; 90 case FLINES: 91 case RLINES: 92 (void)displaylines(fp, off); 93 break; 94 case REVERSE: 95 r_buf(fp); 96 break; 97 default: 98 break; 99 } 100 } 101 102 /* 103 * r_reg -- display a regular file in reverse order by line. 104 */ 105 static void 106 r_reg(FILE *fp, enum STYLE style, off_t off, struct stat *sbp) 107 { 108 off_t size; 109 int llen; 110 char *p; 111 char *start; 112 113 if (!(size = sbp->st_size)) 114 return; 115 116 if ((uint64_t)size > SIZE_MAX) { 117 /* XXX: need a cleaner way to check this on amd64 */ 118 errno = EFBIG; 119 xerr(0, "%s", fname); 120 return; 121 } 122 123 if ((start = mmap(NULL, (size_t)size, PROT_READ, 124 MAP_FILE|MAP_SHARED, fileno(fp), (off_t)0)) == MAP_FAILED) { 125 xerr(0, "%s", fname); 126 return; 127 } 128 p = start + size - 1; 129 130 if (style == RBYTES && off < size) 131 size = off; 132 133 /* Last char is special, ignore whether newline or not. */ 134 for (llen = 1; --size; ++llen) 135 if (*--p == '\n') { 136 WR(p + 1, llen); 137 llen = 0; 138 if (style == RLINES && !--off) { 139 ++p; 140 break; 141 } 142 } 143 if (llen) 144 WR(p, llen); 145 if (munmap(start, (size_t)sbp->st_size)) 146 xerr(0, "%s", fname); 147 } 148 149 typedef struct bf { 150 struct bf *next; 151 struct bf *prev; 152 int len; 153 char *l; 154 } BF; 155 156 /* 157 * r_buf -- display a non-regular file in reverse order by line. 158 * 159 * This is the function that saves the entire input, storing the data in a 160 * doubly linked list of buffers and then displays them in reverse order. 161 * It has the usual nastiness of trying to find the newlines, as there's no 162 * guarantee that a newline occurs anywhere in the file, let alone in any 163 * particular buffer. If we run out of memory, input is discarded (and the 164 * user warned). 165 */ 166 static void 167 r_buf(FILE *fp) 168 { 169 BF *mark, *tl, *tr; 170 int ch, len, llen; 171 char *p; 172 off_t enomem; 173 174 #define BSZ (128 * 1024) 175 tl = NULL; 176 for (mark = NULL, enomem = 0;;) { 177 /* 178 * Allocate a new block and link it into place in a doubly 179 * linked list. If out of memory, toss the LRU block and 180 * keep going. 181 */ 182 if (enomem) { 183 if (!mark) { 184 errno = ENOMEM; 185 xerr(1, NULL); 186 } 187 tl = tl->next; 188 enomem += tl->len; 189 } else if ((tl = malloc(sizeof(*tl))) == NULL || 190 (tl->l = malloc(BSZ)) == NULL) { 191 if (tl) 192 free(tl); 193 if (!mark) { 194 errno = ENOMEM; 195 xerr(1, NULL); 196 } 197 tl = 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 ch = 0; 211 for (p = tl->l, len = 0; 212 len < BSZ && (ch = getc(fp)) != EOF; ++len) 213 *p++ = ch; 214 215 /* 216 * If no input data for this block and we tossed some data, 217 * recover it. 218 */ 219 if (!len) { 220 if (enomem) 221 enomem -= tl->len; 222 tl = tl->prev; 223 break; 224 } 225 226 tl->len = len; 227 if (ch == EOF) 228 break; 229 } 230 231 if (enomem) { 232 xerrx(0, "Warning: %lld bytes discarded", (long long)enomem); 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
Indexes created Sun Oct 25 00:26:45 UTC 2026