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. 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  * @(#)reverse.c        8.1 (Berkeley) 6/6/93
  37  * $FreeBSD: src/usr.bin/tail/reverse.c,v 1.9.2.3 2001/12/19 20:29:31 iedowse Exp $
  38  * $DragonFly: src/usr.bin/tail/reverse.c,v 1.5 2006/08/13 02:12:18 swildner Exp $
  39  */
  40
  41 #include <sys/param.h>
  42 #include <sys/stat.h>
  43 #include <sys/mman.h>
  44
  45 #include <limits.h>
  46 #include <errno.h>
  47 #include <unistd.h>
  48 #include <stdio.h>
  49 #include <stdlib.h>
  50 #include <string.h>
  51 #include <err.h>
  52 #include "extern.h"
  53
  54 static void r_buf(FILE *);
  55 static void r_reg(FILE *, enum STYLE, off_t, struct stat *);
  56
  57 /*
  58  * reverse -- display input in reverse order by line.
  59  *
  60  * There are six separate cases for this -- regular and non-regular
  61  * files by bytes, lines or the whole file.
  62  *
  63  * BYTES        display N bytes
  64  *      REG     mmap the file and display the lines
  65  *      NOREG   cyclically read characters into a wrap-around buffer
  66  *
  67  * LINES        display N lines
  68  *      REG     mmap the file and display the lines
  69  *      NOREG   cyclically read lines into a wrap-around array of buffers
  70  *
  71  * FILE         display the entire file
  72  *      REG     mmap the file and display the lines
  73  *      NOREG   cyclically read input into a linked list of buffers
  74  */
  75 void
  76 reverse(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
  77 {
  78         if (style != REVERSE && off == 0)
  79                 return;
  80
  81         if (S_ISREG(sbp->st_mode))
  82                 r_reg(fp, style, off, sbp);
  83         else
  84                 switch(style) {
  85                 case FBYTES:
  86                 case RBYTES:
  87                         display_bytes(fp, off);
  88                         break;
  89                 case FLINES:
  90                 case RLINES:
  91                         display_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(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
 104 {
 105         struct mapinfo map;
 106         off_t curoff, size, lineend;
 107         int i;
 108
 109         if (!(size = sbp->st_size))
 110                 return;
 111
 112         map.start = NULL;
 113         map.mapoff = map.maxoff = size;
 114         map.fd = fileno(fp);
 115
 116         /*
 117          * Last char is special, ignore whether newline or not. Note that
 118          * size == 0 is dealt with above, and size == 1 sets curoff to -1.
 119          */
 120         curoff = size - 2;
 121         lineend = size;
 122         while (curoff >= 0) {
 123                 if (curoff < map.mapoff ||
 124                     curoff >= (intmax_t)(map.mapoff + map.maplen)) {
 125                         if (maparound(&map, curoff) != 0) {
 126                                 ierr();
 127                                 return;
 128                         }
 129                 }
 130                 for (i = curoff - map.mapoff; i >= 0; i--) {
 131                         if (style == RBYTES && --off == 0)
 132                                 break;
 133                         if (map.start[i] == '\n')
 134                                 break;
 135                 }
 136                 /* `i' is either the map offset of a '\n', or -1. */
 137                 curoff = map.mapoff + i;
 138                 if (i < 0)
 139                         continue;
 140
 141                 /* Print the line and update offsets. */
 142                 if (mapprint(&map, curoff + 1, lineend - curoff - 1) != 0) {
 143                         ierr();
 144                         return;
 145                 }
 146                 lineend = curoff + 1;
 147                 curoff--;
 148
 149                 if (style == RLINES)
 150                         off--;
 151
 152                 if (off == 0 && style != REVERSE) {
 153                         /* Avoid printing anything below. */
 154                         curoff = 0;
 155                         break;
 156                 }
 157         }
 158         if (curoff < 0 && mapprint(&map, 0, lineend) != 0) {
 159                 ierr();
 160                 return;
 161         }
 162         if (map.start != NULL && munmap(map.start, map.maplen))
 163                 ierr();
 164 }
 165
 166 typedef struct bf {
 167         struct bf *next;
 168         struct bf *prev;
 169         int len;
 170         char *l;
 171 } BF;
 172
 173 /*
 174  * r_buf -- display a non-regular file in reverse order by line.
 175  *
 176  * This is the function that saves the entire input, storing the data in a
 177  * doubly linked list of buffers and then displays them in reverse order.
 178  * It has the usual nastiness of trying to find the newlines, as there's no
 179  * guarantee that a newline occurs anywhere in the file, let alone in any
 180  * particular buffer.  If we run out of memory, input is discarded (and the
 181  * user warned).
 182  */
 183 static void
 184 r_buf(FILE *fp)
 185 {
 186         BF *mark, *tl = NULL, *tr = NULL;
 187         int ch = 0, len, llen;
 188         char *p;
 189         off_t enomem;
 190
 191 #define BSZ     (128 * 1024)
 192         for (mark = NULL, enomem = 0;;) {
 193                 /*
 194                  * Allocate a new block and link it into place in a doubly
 195                  * linked list.  If out of memory, toss the LRU block and
 196                  * keep going.
 197                  */
 198                 if (enomem || (tl = malloc(sizeof(BF))) == NULL ||
 199                     (tl->l = malloc(BSZ)) == NULL) {
 200                         if (!mark)
 201                                 err(1, "malloc");
 202                         tl = enomem ? tl->next : mark;
 203                         enomem += tl->len;
 204                 } else if (mark) {
 205                         tl->next = mark;
 206                         tl->prev = mark->prev;
 207                         mark->prev->next = tl;
 208                         mark->prev = tl;
 209                 } else {
 210                         mark = tl;
 211                         mark->next = mark->prev = mark;
 212                 }
 213
 214                 /* Fill the block with input data. */
 215                 for (p = tl->l, len = 0;
 216                     len < BSZ && (ch = getc(fp)) != EOF; ++len)
 217                         *p++ = ch;
 218
 219                 if (ferror(fp)) {
 220                         ierr();
 221                         return;
 222                 }
 223
 224                 /*
 225                  * If no input data for this block and we tossed some data,
 226                  * recover it.
 227                  */
 228                 if (!len) {
 229                         if (enomem)
 230                                 enomem -= tl->len;
 231                         tl = tl->prev;
 232                         break;
 233                 }
 234
 235                 tl->len = len;
 236                 if (ch == EOF)
 237                         break;
 238         }
 239
 240         if (enomem) {
 241                 warnx("warning: %jd bytes discarded", (intmax_t)enomem);
 242                 rval = 1;
 243         }
 244
 245         /*
 246          * Step through the blocks in the reverse order read.  The last char
 247          * is special, ignore whether newline or not.
 248          */
 249         for (mark = tl;;) {
 250                 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--;
 251                     --p, ++llen)
 252                         if (*p == '\n') {
 253                                 if (llen) {
 254                                         WR(p + 1, llen);
 255                                         llen = 0;
 256                                 }
 257                                 if (tl == mark)
 258                                         continue;
 259                                 for (tr = tl->next; tr->len; tr = tr->next) {
 260                                         WR(tr->l, tr->len);
 261                                         tr->len = 0;
 262                                         if (tr == mark)
 263                                                 break;
 264                                 }
 265                         }
 266                 tl->len = llen;
 267                 if ((tl = tl->prev) == mark)
 268                         break;
 269         }
 270         tl = tl->next;
 271         if (tl->len) {
 272                 WR(tl->l, tl->len);
 273                 tl->len = 0;
 274         }
 275         while ((tl = tl->next)->len) {
 276                 WR(tl->l, tl->len);
 277                 tl->len = 0;
 278         }
 279 }