usr.bin/tail/reverse.c

   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. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * @(#)reverse.c        8.1 (Berkeley) 6/6/93
  33  * $FreeBSD: src/usr.bin/tail/reverse.c,v 1.9.2.3 2001/12/19 20:29:31 iedowse Exp $
  34  * $DragonFly: src/usr.bin/tail/reverse.c,v 1.5 2006/08/13 02:12:18 swildner Exp $
  35  */
  36
  37 #include <sys/param.h>
  38 #include <sys/stat.h>
  39 #include <sys/mman.h>
  40
  41 #include <limits.h>
  42 #include <errno.h>
  43 #include <unistd.h>
  44 #include <stdio.h>
  45 #include <stdlib.h>
  46 #include <string.h>
  47 #include <err.h>
  48 #include "extern.h"
  49
  50 static void r_buf(FILE *);
  51 static void r_reg(FILE *, enum STYLE, off_t, struct stat *);
  52
  53 /*
  54  * reverse -- display input in reverse order by line.
  55  *
  56  * There are six separate cases for this -- regular and non-regular
  57  * files by bytes, lines or the whole file.
  58  *
  59  * BYTES        display N bytes
  60  *      REG     mmap the file and display the lines
  61  *      NOREG   cyclically read characters into a wrap-around buffer
  62  *
  63  * LINES        display N lines
  64  *      REG     mmap the file and display the lines
  65  *      NOREG   cyclically read lines into a wrap-around array of buffers
  66  *
  67  * FILE         display the entire file
  68  *      REG     mmap the file and display the lines
  69  *      NOREG   cyclically read input into a linked list of buffers
  70  */
  71 void
  72 reverse(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
  73 {
  74         if (style != REVERSE && off == 0)
  75                 return;
  76
  77         if (S_ISREG(sbp->st_mode))
  78                 r_reg(fp, style, off, sbp);
  79         else
  80                 switch(style) {
  81                 case FBYTES:
  82                 case RBYTES:
  83                         display_bytes(fp, off);
  84                         break;
  85                 case FLINES:
  86                 case RLINES:
  87                         display_lines(fp, off);
  88                         break;
  89                 case REVERSE:
  90                         r_buf(fp);
  91                         break;
  92                 }
  93 }
  94
  95 /*
  96  * r_reg -- display a regular file in reverse order by line.
  97  */
  98 static void
  99 r_reg(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
 100 {
 101         struct mapinfo map;
 102         off_t curoff, size, lineend;
 103         int i;
 104
 105         if (!(size = sbp->st_size))
 106                 return;
 107
 108         map.start = NULL;
 109         map.mapoff = map.maxoff = size;
 110         map.fd = fileno(fp);
 111
 112         /*
 113          * Last char is special, ignore whether newline or not. Note that
 114          * size == 0 is dealt with above, and size == 1 sets curoff to -1.
 115          */
 116         curoff = size - 2;
 117         lineend = size;
 118         while (curoff >= 0) {
 119                 if (curoff < map.mapoff ||
 120                     curoff >= (intmax_t)(map.mapoff + map.maplen)) {
 121                         if (maparound(&map, curoff) != 0) {
 122                                 ierr();
 123                                 return;
 124                         }
 125                 }
 126                 for (i = curoff - map.mapoff; i >= 0; i--) {
 127                         if (style == RBYTES && --off == 0)
 128                                 break;
 129                         if (map.start[i] == '\n')
 130                                 break;
 131                 }
 132                 /* `i' is either the map offset of a '\n', or -1. */
 133                 curoff = map.mapoff + i;
 134                 if (i < 0)
 135                         continue;
 136
 137                 /* Print the line and update offsets. */
 138                 if (mapprint(&map, curoff + 1, lineend - curoff - 1) != 0) {
 139                         ierr();
 140                         return;
 141                 }
 142                 lineend = curoff + 1;
 143                 curoff--;
 144
 145                 if (style == RLINES)
 146                         off--;
 147
 148                 if (off == 0 && style != REVERSE) {
 149                         /* Avoid printing anything below. */
 150                         curoff = 0;
 151                         break;
 152                 }
 153         }
 154         if (curoff < 0 && mapprint(&map, 0, lineend) != 0) {
 155                 ierr();
 156                 return;
 157         }
 158         if (map.start != NULL && munmap(map.start, map.maplen))
 159                 ierr();
 160 }
 161
 162 typedef struct bf {
 163         struct bf *next;
 164         struct bf *prev;
 165         int len;
 166         char *l;
 167 } BF;
 168
 169 /*
 170  * r_buf -- display a non-regular file in reverse order by line.
 171  *
 172  * This is the function that saves the entire input, storing the data in a
 173  * doubly linked list of buffers and then displays them in reverse order.
 174  * It has the usual nastiness of trying to find the newlines, as there's no
 175  * guarantee that a newline occurs anywhere in the file, let alone in any
 176  * particular buffer.  If we run out of memory, input is discarded (and the
 177  * user warned).
 178  */
 179 static void
 180 r_buf(FILE *fp)
 181 {
 182         BF *mark, *tl = NULL, *tr = NULL;
 183         int ch = 0, len, llen;
 184         char *p;
 185         off_t enomem;
 186
 187 #define BSZ     (128 * 1024)
 188         for (mark = NULL, enomem = 0;;) {
 189                 /*
 190                  * Allocate a new block and link it into place in a doubly
 191                  * linked list.  If out of memory, toss the LRU block and
 192                  * keep going.
 193                  */
 194                 if (enomem || (tl = malloc(sizeof(BF))) == NULL ||
 195                     (tl->l = malloc(BSZ)) == NULL) {
 196                         if (!mark)
 197                                 err(1, "malloc");
 198                         tl = enomem ? tl->next : mark;
 199                         enomem += tl->len;
 200                 } else if (mark) {
 201                         tl->next = mark;
 202                         tl->prev = mark->prev;
 203                         mark->prev->next = tl;
 204                         mark->prev = tl;
 205                 } else {
 206                         mark = tl;
 207                         mark->next = mark->prev = mark;
 208                 }
 209
 210                 /* Fill the block with input data. */
 211                 for (p = tl->l, len = 0;
 212                     len < BSZ && (ch = getc(fp)) != EOF; ++len)
 213                         *p++ = ch;
 214
 215                 if (ferror(fp)) {
 216                         ierr();
 217                         return;
 218                 }
 219
 220                 /*
 221                  * If no input data for this block and we tossed some data,
 222                  * recover it.
 223                  */
 224                 if (!len) {
 225                         if (enomem)
 226                                 enomem -= tl->len;
 227                         tl = tl->prev;
 228                         break;
 229                 }
 230
 231                 tl->len = len;
 232                 if (ch == EOF)
 233                         break;
 234         }
 235
 236         if (enomem) {
 237                 warnx("warning: %jd bytes discarded", (intmax_t)enomem);
 238                 rval = 1;
 239         }
 240
 241         /*
 242          * Step through the blocks in the reverse order read.  The last char
 243          * is special, ignore whether newline or not.
 244          */
 245         for (mark = tl;;) {
 246                 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--;
 247                     --p, ++llen)
 248                         if (*p == '\n') {
 249                                 if (llen) {
 250                                         WR(p + 1, llen);
 251                                         llen = 0;
 252                                 }
 253                                 if (tl == mark)
 254                                         continue;
 255                                 for (tr = tl->next; tr->len; tr = tr->next) {
 256                                         WR(tr->l, tr->len);
 257                                         tr->len = 0;
 258                                         if (tr == mark)
 259                                                 break;
 260                                 }
 261                         }
 262                 tl->len = llen;
 263                 if ((tl = tl->prev) == mark)
 264                         break;
 265         }
 266         tl = tl->next;
 267         if (tl->len) {
 268                 WR(tl->l, tl->len);
 269                 tl->len = 0;
 270         }
 271         while ((tl = tl->next)->len) {
 272                 WR(tl->l, tl->len);
 273                 tl->len = 0;
 274         }
 275 }