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 || curoff >= map.mapoff + map.maplen) {
 124                         if (maparound(&map, curoff) != 0) {
 125                                 ierr();
 126                                 return;
 127                         }
 128                 }
 129                 for (i = curoff - map.mapoff; i >= 0; i--) {
 130                         if (style == RBYTES && --off == 0)
 131                                 break;
 132                         if (map.start[i] == '\n')
 133                                 break;
 134                 }
 135                 /* `i' is either the map offset of a '\n', or -1. */
 136                 curoff = map.mapoff + i;
 137                 if (i < 0)
 138                         continue;
 139
 140                 /* Print the line and update offsets. */
 141                 if (mapprint(&map, curoff + 1, lineend - curoff - 1) != 0) {
 142                         ierr();
 143                         return;
 144                 }
 145                 lineend = curoff + 1;
 146                 curoff--;
 147
 148                 if (style == RLINES)
 149                         off--;
 150
 151                 if (off == 0 && style != REVERSE) {
 152                         /* Avoid printing anything below. */
 153                         curoff = 0;
 154                         break;
 155                 }
 156         }
 157         if (curoff < 0 && mapprint(&map, 0, lineend) != 0) {
 158                 ierr();
 159                 return;
 160         }
 161         if (map.start != NULL && munmap(map.start, map.maplen))
 162                 ierr();
 163 }
 164
 165 typedef struct bf {
 166         struct bf *next;
 167         struct bf *prev;
 168         int len;
 169         char *l;
 170 } BF;
 171
 172 /*
 173  * r_buf -- display a non-regular file in reverse order by line.
 174  *
 175  * This is the function that saves the entire input, storing the data in a
 176  * doubly linked list of buffers and then displays them in reverse order.
 177  * It has the usual nastiness of trying to find the newlines, as there's no
 178  * guarantee that a newline occurs anywhere in the file, let alone in any
 179  * particular buffer.  If we run out of memory, input is discarded (and the
 180  * user warned).
 181  */
 182 static void
 183 r_buf(FILE *fp)
 184 {
 185         BF *mark, *tl = NULL, *tr = NULL;
 186         int ch = 0, len, llen;
 187         char *p;
 188         off_t enomem;
 189
 190 #define BSZ     (128 * 1024)
 191         for (mark = NULL, enomem = 0;;) {
 192                 /*
 193                  * Allocate a new block and link it into place in a doubly
 194                  * linked list.  If out of memory, toss the LRU block and
 195                  * keep going.
 196                  */
 197                 if (enomem || (tl = malloc(sizeof(BF))) == NULL ||
 198                     (tl->l = malloc(BSZ)) == NULL) {
 199                         if (!mark)
 200                                 err(1, "malloc");
 201                         tl = enomem ? tl->next : mark;
 202                         enomem += tl->len;
 203                 } else if (mark) {
 204                         tl->next = mark;
 205                         tl->prev = mark->prev;
 206                         mark->prev->next = tl;
 207                         mark->prev = tl;
 208                 } else {
 209                         mark = tl;
 210                         mark->next = mark->prev = mark;
 211                 }
 212
 213                 /* Fill the block with input data. */
 214                 for (p = tl->l, len = 0;
 215                     len < BSZ && (ch = getc(fp)) != EOF; ++len)
 216                         *p++ = ch;
 217
 218                 if (ferror(fp)) {
 219                         ierr();
 220                         return;
 221                 }
 222
 223                 /*
 224                  * If no input data for this block and we tossed some data,
 225                  * recover it.
 226                  */
 227                 if (!len) {
 228                         if (enomem)
 229                                 enomem -= tl->len;
 230                         tl = tl->prev;
 231                         break;
 232                 }
 233
 234                 tl->len = len;
 235                 if (ch == EOF)
 236                         break;
 237         }
 238
 239         if (enomem) {
 240                 warnx("warning: %qd bytes discarded", enomem);
 241                 rval = 1;
 242         }
 243
 244         /*
 245          * Step through the blocks in the reverse order read.  The last char
 246          * is special, ignore whether newline or not.
 247          */
 248         for (mark = tl;;) {
 249                 for (p = tl->l + (len = tl->len) - 1, llen = 0; len--;
 250                     --p, ++llen)
 251                         if (*p == '\n') {
 252                                 if (llen) {
 253                                         WR(p + 1, llen);
 254                                         llen = 0;
 255                                 }
 256                                 if (tl == mark)
 257                                         continue;
 258                                 for (tr = tl->next; tr->len; tr = tr->next) {
 259                                         WR(tr->l, tr->len);
 260                                         tr->len = 0;
 261                                         if (tr == mark)
 262                                                 break;
 263                                 }
 264                         }
 265                 tl->len = llen;
 266                 if ((tl = tl->prev) == mark)
 267                         break;
 268         }
 269         tl = tl->next;
 270         if (tl->len) {
 271                 WR(tl->l, tl->len);
 272                 tl->len = 0;
 273         }
 274         while ((tl = tl->next)->len) {
 275                 WR(tl->l, tl->len);
 276                 tl->len = 0;
 277         }
 278 }