usr.bin/tail/reverse.c

   1 /*      $NetBSD: reverse.c,v 1.23 2011/09/03 10:59:11 christos 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 1.23 2011/09/03 10:59:11 christos 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))
  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_T_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 }