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[] = "from: @(#)reverse.c 5.3 (Berkeley) 2/12/92";*/ 39 static char rcsid[] = "$Id: reverse.c,v 1.2 1993/08/01 18:08:02 mycroft Exp $"; 40 #endif /* not lint */ 41 42 #include <sys/param.h> 43 #include <sys/stat.h> 44 #include <sys/mman.h> 45 #include <errno.h> 46 #include <unistd.h> 47 #include <stdio.h> 48 #include <stdlib.h> 49 #include <string.h> 50 #include "extern.h" 51 52 static void r_buf __P((FILE *)); 53 static void r_reg __P((FILE *, enum STYLE, long, struct stat *)); 54 55 /* 56 * reverse -- display input in reverse order by line. 57 * 58 * There are six separate cases for this -- regular and non-regular 59 * files by bytes, lines or the whole file. 60 * 61 * BYTES display N bytes 62 * REG mmap the file and display the lines 63 * NOREG cyclically read characters into a wrap-around buffer 64 * 65 * LINES display N lines 66 * REG mmap the file and display the lines 67 * NOREG cyclically read lines into a wrap-around array of buffers 68 * 69 * FILE display the entire file 70 * REG mmap the file and display the lines 71 * NOREG cyclically read input into a linked list of buffers 72 */ 73 void 74 reverse(fp, style, off, sbp) 75 FILE *fp; 76 enum STYLE style; 77 long off; 78 struct stat *sbp; 79 { 80 if (style != REVERSE && off == 0) 81 return; 82 83 if (S_ISREG(sbp->st_mode)) 84 r_reg(fp, style, off, sbp); 85 else 86 switch(style) { 87 case FBYTES: 88 bytes(fp, off); 89 break; 90 case FLINES: 91 lines(fp, off); 92 break; 93 case REVERSE: 94 r_buf(fp); 95 break; 96 } 97 } 98 99 /* 100 * r_reg -- display a regular file in reverse order by line. 101 */ 102 static void 103 r_reg(fp, style, off, sbp) 104 FILE *fp; 105 register enum STYLE style; 106 long off; 107 struct stat *sbp; 108 { 109 register off_t size; 110 register int llen; 111 register char *p; 112 int fd; 113 114 if (!(size = sbp->st_size)) 115 return; 116 117 fd = fileno(fp); 118 if ((p = 119 mmap(NULL, size, PROT_READ, MAP_FILE, fd, (off_t)0)) == (caddr_t)-1) 120 err("%s", strerror(errno)); 121 p += size - 1; 122 123 if (style == RBYTES && off < size) 124 size = off; 125 126 /* Last char is special, ignore whether newline or not. */ 127 for (llen = 1; --size; ++llen) 128 if (*--p == '\n') { 129 WR(p + 1, llen); 130 llen = 0; 131 if (style == RLINES && !--off) { 132 ++p; 133 break; 134 } 135 } 136 if (llen) 137 WR(p, llen); 138 } 139 140 typedef struct bf { 141 struct bf *next; 142 struct bf *prev; 143 int len; 144 char *l; 145 } BF; 146 147 /* 148 * r_buf -- display a non-regular file in reverse order by line. 149 * 150 * This is the function that saves the entire input, storing the data in a 151 * doubly linked list of buffers and then displays them in reverse order. 152 * It has the usual nastiness of trying to find the newlines, as there's no 153 * guarantee that a newline occurs anywhere in the file, let alone in any 154 * particular buffer. If we run out of memory, input is discarded (and the 155 * user warned). 156 */ 157 static void 158 r_buf(fp) 159 FILE *fp; 160 { 161 register BF *mark, *tl, *tr; 162 register int ch, len, llen; 163 register char *p; 164 off_t enomem; 165 166 #define BSZ (128 * 1024) 167 for (mark = NULL, enomem = 0;;) { 168 /* 169 * Allocate a new block and link it into place in a doubly 170 * linked list. If out of memory, toss the LRU block and 171 * keep going. 172 */ 173 if (enomem || (tl = malloc(sizeof(BF))) == NULL || 174 (tl->l = malloc(BSZ)) == NULL) { 175 if (!mark) 176 err("%s", strerror(errno)); 177 tl = enomem ? tl->next : mark; 178 enomem += tl->len; 179 } else if (mark) { 180 tl->next = mark; 181 tl->prev = mark->prev; 182 mark->prev->next = tl; 183 mark->prev = tl; 184 } else 185 mark->next = mark->prev = (mark = tl); 186 187 /* Fill the block with input data. */ 188 for (p = tl->l, len = 0; 189 len < BSZ && (ch = getc(fp)) != EOF; ++len) 190 *p++ = ch; 191 192 /* 193 * If no input data for this block and we tossed some data, 194 * recover it. 195 */ 196 if (!len) { 197 if (enomem) 198 enomem -= tl->len; 199 tl = tl->prev; 200 break; 201 } 202 203 tl->len = len; 204 if (ch == EOF) 205 break; 206 } 207 208 if (enomem) { 209 (void)fprintf(stderr, 210 "tail: warning: %ld bytes discarded\n", enomem); 211 rval = 1; 212 } 213 214 /* 215 * Step through the blocks in the reverse order read. The last char 216 * is special, ignore whether newline or not. 217 */ 218 for (mark = tl;;) { 219 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--; 220 --p, ++llen) 221 if (*p == '\n') { 222 if (llen) { 223 WR(p + 1, llen); 224 llen = 0; 225 } 226 if (tl == mark) 227 continue; 228 for (tr = tl->next; tr->len; tr = tr->next) { 229 WR(tr->l, tr->len); 230 tr->len = 0; 231 if (tr == mark) 232 break; 233 } 234 } 235 tl->len = llen; 236 if ((tl = tl->prev) == mark) 237 break; 238 } 239 tl = tl->next; 240 if (tl->len) { 241 WR(tl->l, tl->len); 242 tl->len = 0; 243 } 244 while ((tl = tl->next)->len) { 245 WR(tl->l, tl->len); 246 tl->len = 0; 247 } 248 } 249