1 /*- 2 * Copyright (c) 1991 The Regents of the University of California. 3 * 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 static char sccsid[] = "@(#)reverse.c 5.3 (Berkeley) 2/12/92"; 39 #endif /* not lint */ 40 41 #include <sys/param.h> 42 #include <sys/stat.h> 43 #include <sys/mman.h> 44 #include <errno.h> 45 #include <unistd.h> 46 #include <stdio.h> 47 #include <stdlib.h> 48 #include <string.h> 49 #include "extern.h" 50 51 static void r_buf __P((FILE *)); 52 static void r_reg __P((FILE *, enum STYLE, long, struct stat *)); 53 54 /* 55 * reverse -- display input in reverse order by line. 56 * 57 * There are six separate cases for this -- regular and non-regular 58 * files by bytes, lines or the whole file. 59 * 60 * BYTES display N bytes 61 * REG mmap the file and display the lines 62 * NOREG cyclically read characters into a wrap-around buffer 63 * 64 * LINES display N lines 65 * REG mmap the file and display the lines 66 * NOREG cyclically read lines into a wrap-around array of buffers 67 * 68 * FILE display the entire file 69 * REG mmap the file and display the lines 70 * NOREG cyclically read input into a linked list of buffers 71 */ 72 void 73 reverse(fp, style, off, sbp) 74 FILE *fp; 75 enum STYLE style; 76 long off; 77 struct stat *sbp; 78 { 79 if (style != REVERSE && off == 0) 80 return; 81 82 if (S_ISREG(sbp->st_mode)) 83 r_reg(fp, style, off, sbp); 84 else 85 switch(style) { 86 case FBYTES: 87 bytes(fp, off); 88 break; 89 case FLINES: 90 lines(fp, off); 91 break; 92 case REVERSE: 93 r_buf(fp); 94 break; 95 } 96 } 97 98 /* 99 * r_reg -- display a regular file in reverse order by line. 100 */ 101 static void 102 r_reg(fp, style, off, sbp) 103 FILE *fp; 104 register enum STYLE style; 105 long off; 106 struct stat *sbp; 107 { 108 register off_t size; 109 register int llen; 110 register char *p; 111 int fd; 112 113 if (!(size = sbp->st_size)) 114 return; 115 116 fd = fileno(fp); 117 if ((p = 118 mmap(NULL, size, PROT_READ, MAP_FILE, fd, (off_t)0)) == (caddr_t)-1) 119 err("%s", strerror(errno)); 120 p += size - 1; 121 122 if (style == RBYTES && off < size) 123 size = off; 124 125 /* Last char is special, ignore whether newline or not. */ 126 for (llen = 1; --size; ++llen) 127 if (*--p == '\n') { 128 WR(p + 1, llen); 129 llen = 0; 130 if (style == RLINES && !--off) { 131 ++p; 132 break; 133 } 134 } 135 if (llen) 136 WR(p, llen); 137 } 138 139 typedef struct bf { 140 struct bf *next; 141 struct bf *prev; 142 int len; 143 char *l; 144 } BF; 145 146 /* 147 * r_buf -- display a non-regular file in reverse order by line. 148 * 149 * This is the function that saves the entire input, storing the data in a 150 * doubly linked list of buffers and then displays them in reverse order. 151 * It has the usual nastiness of trying to find the newlines, as there's no 152 * guarantee that a newline occurs anywhere in the file, let alone in any 153 * particular buffer. If we run out of memory, input is discarded (and the 154 * user warned). 155 */ 156 static void 157 r_buf(fp) 158 FILE *fp; 159 { 160 register BF *mark, *tl, *tr; 161 register int ch, len, llen; 162 register char *p; 163 off_t enomem; 164 165 #define BSZ (128 * 1024) 166 for (mark = NULL, enomem = 0;;) { 167 /* 168 * Allocate a new block and link it into place in a doubly 169 * linked list. If out of memory, toss the LRU block and 170 * keep going. 171 */ 172 if (enomem || (tl = malloc(sizeof(BF))) == NULL || 173 (tl->l = malloc(BSZ)) == NULL) { 174 if (!mark) 175 err("%s", strerror(errno)); 176 tl = enomem ? tl->next : mark; 177 enomem += tl->len; 178 } else if (mark) { 179 tl->next = mark; 180 tl->prev = mark->prev; 181 mark->prev->next = tl; 182 mark->prev = tl; 183 } else 184 mark->next = mark->prev = (mark = tl); 185 186 /* Fill the block with input data. */ 187 for (p = tl->l, len = 0; 188 len < BSZ && (ch = getc(fp)) != EOF; ++len) 189 *p++ = ch; 190 191 /* 192 * If no input data for this block and we tossed some data, 193 * recover it. 194 */ 195 if (!len) { 196 if (enomem) 197 enomem -= tl->len; 198 tl = tl->prev; 199 break; 200 } 201 202 tl->len = len; 203 if (ch == EOF) 204 break; 205 } 206 207 if (enomem) { 208 (void)fprintf(stderr, 209 "tail: warning: %ld bytes discarded\n", enomem); 210 rval = 1; 211 } 212 213 /* 214 * Step through the blocks in the reverse order read. The last char 215 * is special, ignore whether newline or not. 216 */ 217 for (mark = tl;;) { 218 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--; 219 --p, ++llen) 220 if (*p == '\n') { 221 if (llen) { 222 WR(p + 1, llen); 223 llen = 0; 224 } 225 if (tl == mark) 226 continue; 227 for (tr = tl->next; tr->len; tr = tr->next) { 228 WR(tr->l, tr->len); 229 tr->len = 0; 230 if (tr == mark) 231 break; 232 } 233 } 234 tl->len = llen; 235 if ((tl = tl->prev) == mark) 236 break; 237 } 238 tl = tl->next; 239 if (tl->len) { 240 WR(tl->l, tl->len); 241 tl->len = 0; 242 } 243 while ((tl = tl->next)->len) { 244 WR(tl->l, tl->len); 245 tl->len = 0; 246 } 247 } 248