usr.bin/tail/read.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  * @(#)read.c   8.1 (Berkeley) 6/6/93
  33  * $FreeBSD: src/usr.bin/tail/read.c,v 1.6.8.1 2001/01/24 08:41:14 ru Exp $
  34  * $DragonFly: src/usr.bin/tail/read.c,v 1.6 2008/02/05 14:35:43 matthias Exp $
  35  */
  36
  37 #include <sys/types.h>
  38 #include <sys/stat.h>
  39 #include <fcntl.h>
  40 #include <errno.h>
  41 #include <unistd.h>
  42 #include <stdio.h>
  43 #include <stdlib.h>
  44 #include <string.h>
  45 #include <err.h>
  46 #include "extern.h"
  47
  48 /*
  49  * display_bytes -- read bytes to an offset from the end and display.
  50  *
  51  * This is the function that reads to a byte offset from the end of the input,
  52  * storing the data in a wrap-around buffer which is then displayed.  If the
  53  * rflag is set, the data is displayed in lines in reverse order, and this
  54  * routine has the usual nastiness of trying to find the newlines.  Otherwise,
  55  * it is displayed from the character closest to the beginning of the input to
  56  * the end.
  57  */
  58 int
  59 display_bytes(FILE *fp, off_t off)
  60 {
  61         int ch, len, tlen;
  62         char *ep, *p, *t;
  63         int wrap;
  64         char *sp;
  65
  66         if ((sp = p = malloc(off)) == NULL)
  67                 err(1, "malloc");
  68
  69         for (wrap = 0, ep = p + off; (ch = getc(fp)) != EOF;) {
  70                 *p = ch;
  71                 if (++p == ep) {
  72                         wrap = 1;
  73                         p = sp;
  74                 }
  75         }
  76         if (ferror(fp)) {
  77                 ierr();
  78                 free(sp);
  79                 return 1;
  80         }
  81
  82         if (rflag) {
  83                 for (t = p - 1, len = 0; t >= sp; --t, ++len)
  84                         if (*t == '\n' && len) {
  85                                 WR(t + 1, len);
  86                                 len = 0;
  87                 }
  88                 if (wrap) {
  89                         tlen = len;
  90                         for (t = ep - 1, len = 0; t >= p; --t, ++len)
  91                                 if (*t == '\n') {
  92                                         if (len) {
  93                                                 WR(t + 1, len);
  94                                                 len = 0;
  95                                         }
  96                                         if (tlen) {
  97                                                 WR(sp, tlen);
  98                                                 tlen = 0;
  99                                         }
 100                                 }
 101                         if (len)
 102                                 WR(t + 1, len);
 103                         if (tlen)
 104                                 WR(sp, tlen);
 105                 }
 106         } else {
 107                 if (wrap && (len = ep - p))
 108                         WR(p, len);
 109                 if ((len = p - sp) != 0)
 110                         WR(sp, len);
 111         }
 112         free(sp);
 113         return 0;
 114 }
 115
 116 /*
 117  * display_lines -- read lines to an offset from the end and display.
 118  *
 119  * This is the function that reads to a line offset from the end of the input,
 120  * storing the data in an array of buffers which is then displayed.  If the
 121  * rflag is set, the data is displayed in lines in reverse order, and this
 122  * routine has the usual nastiness of trying to find the newlines.  Otherwise,
 123  * it is displayed from the line closest to the beginning of the input to
 124  * the end.
 125  */
 126 int
 127 display_lines(FILE *fp, off_t off)
 128 {
 129         struct {
 130                 ssize_t blen;
 131                 ssize_t len;
 132                 char *l;
 133         } *lines;
 134         int ch, rc = 0;
 135         char *p = NULL;
 136         int blen, cnt, recno, wrap;
 137         char *sp;
 138
 139         if ((lines = malloc(off * sizeof(*lines))) == NULL)
 140                 err(1, "malloc");
 141         bzero(lines, off * sizeof(*lines));
 142         sp = NULL;
 143         blen = cnt = recno = wrap = 0;
 144
 145         while ((ch = getc(fp)) != EOF) {
 146                 if (++cnt > blen) {
 147                         if ((sp = realloc(sp, blen += 1024)) == NULL)
 148                                 err(1, "realloc");
 149                         p = sp + cnt - 1;
 150                 }
 151                 *p++ = ch;
 152                 if (ch == '\n') {
 153                         if (lines[recno].blen < cnt) {
 154                                 lines[recno].blen = cnt + 256;
 155                                 if ((lines[recno].l = realloc(lines[recno].l,
 156                                     lines[recno].blen)) == NULL)
 157                                         err(1, "realloc");
 158                         }
 159                         bcopy(sp, lines[recno].l, lines[recno].len = cnt);
 160                         cnt = 0;
 161                         p = sp;
 162                         if (++recno == off) {
 163                                 wrap = 1;
 164                                 recno = 0;
 165                         }
 166                 }
 167         }
 168         if (ferror(fp)) {
 169                 ierr();
 170                 rc = 1;
 171                 goto out;
 172         }
 173         if (cnt) {
 174                 lines[recno].l = sp;
 175                 sp = NULL;
 176                 lines[recno].len = cnt;
 177                 if (++recno == off) {
 178                         wrap = 1;
 179                         recno = 0;
 180                 }
 181         }
 182
 183         if (rflag) {
 184                 for (cnt = recno - 1; cnt >= 0; --cnt)
 185                         WR(lines[cnt].l, lines[cnt].len);
 186                 if (wrap)
 187                         for (cnt = off - 1; cnt >= recno; --cnt)
 188                                 WR(lines[cnt].l, lines[cnt].len);
 189         } else {
 190                 if (wrap)
 191                         for (cnt = recno; cnt < off; ++cnt)
 192                                 WR(lines[cnt].l, lines[cnt].len);
 193                 for (cnt = 0; cnt < recno; ++cnt)
 194                         WR(lines[cnt].l, lines[cnt].len);
 195         }
 196 out:
 197         for (cnt = 0; cnt < off; cnt++)
 198                 free(lines[cnt].l);
 199         free(sp);
 200         free(lines);
 201         return (rc);
 202 }