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. 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  * @(#)read.c   8.1 (Berkeley) 6/6/93
  37  * $FreeBSD: src/usr.bin/tail/read.c,v 1.6.8.1 2001/01/24 08:41:14 ru Exp $
  38  * $DragonFly: src/usr.bin/tail/read.c,v 1.6 2008/02/05 14:35:43 matthias Exp $
  39  */
  40
  41 #include <sys/types.h>
  42 #include <sys/stat.h>
  43 #include <fcntl.h>
  44 #include <errno.h>
  45 #include <unistd.h>
  46 #include <stdio.h>
  47 #include <stdlib.h>
  48 #include <string.h>
  49 #include <err.h>
  50 #include "extern.h"
  51
  52 /*
  53  * display_bytes -- read bytes to an offset from the end and display.
  54  *
  55  * This is the function that reads to a byte offset from the end of the input,
  56  * storing the data in a wrap-around buffer which is then displayed.  If the
  57  * rflag is set, the data is displayed in lines in reverse order, and this
  58  * routine has the usual nastiness of trying to find the newlines.  Otherwise,
  59  * it is displayed from the character closest to the beginning of the input to
  60  * the end.
  61  */
  62 int
  63 display_bytes(FILE *fp, off_t off)
  64 {
  65         int ch, len, tlen;
  66         char *ep, *p, *t;
  67         int wrap;
  68         char *sp;
  69
  70         if ((sp = p = malloc(off)) == NULL)
  71                 err(1, "malloc");
  72
  73         for (wrap = 0, ep = p + off; (ch = getc(fp)) != EOF;) {
  74                 *p = ch;
  75                 if (++p == ep) {
  76                         wrap = 1;
  77                         p = sp;
  78                 }
  79         }
  80         if (ferror(fp)) {
  81                 ierr();
  82                 free(sp);
  83                 return 1;
  84         }
  85
  86         if (rflag) {
  87                 for (t = p - 1, len = 0; t >= sp; --t, ++len)
  88                         if (*t == '\n' && len) {
  89                                 WR(t + 1, len);
  90                                 len = 0;
  91                 }
  92                 if (wrap) {
  93                         tlen = len;
  94                         for (t = ep - 1, len = 0; t >= p; --t, ++len)
  95                                 if (*t == '\n') {
  96                                         if (len) {
  97                                                 WR(t + 1, len);
  98                                                 len = 0;
  99                                         }
 100                                         if (tlen) {
 101                                                 WR(sp, tlen);
 102                                                 tlen = 0;
 103                                         }
 104                                 }
 105                         if (len)
 106                                 WR(t + 1, len);
 107                         if (tlen)
 108                                 WR(sp, tlen);
 109                 }
 110         } else {
 111                 if (wrap && (len = ep - p))
 112                         WR(p, len);
 113                 if ((len = p - sp) != 0)
 114                         WR(sp, len);
 115         }
 116         free(sp);
 117         return 0;
 118 }
 119
 120 /*
 121  * display_lines -- read lines to an offset from the end and display.
 122  *
 123  * This is the function that reads to a line offset from the end of the input,
 124  * storing the data in an array of buffers which is then displayed.  If the
 125  * rflag is set, the data is displayed in lines in reverse order, and this
 126  * routine has the usual nastiness of trying to find the newlines.  Otherwise,
 127  * it is displayed from the line closest to the beginning of the input to
 128  * the end.
 129  */
 130 int
 131 display_lines(FILE *fp, off_t off)
 132 {
 133         struct {
 134                 ssize_t blen;
 135                 ssize_t len;
 136                 char *l;
 137         } *lines;
 138         int ch, rc = 0;
 139         char *p = NULL;
 140         int blen, cnt, recno, wrap;
 141         char *sp;
 142
 143         if ((lines = malloc(off * sizeof(*lines))) == NULL)
 144                 err(1, "malloc");
 145         bzero(lines, off * sizeof(*lines));
 146         sp = NULL;
 147         blen = cnt = recno = wrap = 0;
 148
 149         while ((ch = getc(fp)) != EOF) {
 150                 if (++cnt > blen) {
 151                         if ((sp = realloc(sp, blen += 1024)) == NULL)
 152                                 err(1, "realloc");
 153                         p = sp + cnt - 1;
 154                 }
 155                 *p++ = ch;
 156                 if (ch == '\n') {
 157                         if (lines[recno].blen < cnt) {
 158                                 lines[recno].blen = cnt + 256;
 159                                 if ((lines[recno].l = realloc(lines[recno].l,
 160                                     lines[recno].blen)) == NULL)
 161                                         err(1, "realloc");
 162                         }
 163                         bcopy(sp, lines[recno].l, lines[recno].len = cnt);
 164                         cnt = 0;
 165                         p = sp;
 166                         if (++recno == off) {
 167                                 wrap = 1;
 168                                 recno = 0;
 169                         }
 170                 }
 171         }
 172         if (ferror(fp)) {
 173                 ierr();
 174                 rc = 1;
 175                 goto out;
 176         }
 177         if (cnt) {
 178                 lines[recno].l = sp;
 179                 sp = NULL;
 180                 lines[recno].len = cnt;
 181                 if (++recno == off) {
 182                         wrap = 1;
 183                         recno = 0;
 184                 }
 185         }
 186
 187         if (rflag) {
 188                 for (cnt = recno - 1; cnt >= 0; --cnt)
 189                         WR(lines[cnt].l, lines[cnt].len);
 190                 if (wrap)
 191                         for (cnt = off - 1; cnt >= recno; --cnt)
 192                                 WR(lines[cnt].l, lines[cnt].len);
 193         } else {
 194                 if (wrap)
 195                         for (cnt = recno; cnt < off; ++cnt)
 196                                 WR(lines[cnt].l, lines[cnt].len);
 197                 for (cnt = 0; cnt < recno; ++cnt)
 198                         WR(lines[cnt].l, lines[cnt].len);
 199         }
 200 out:
 201         for (cnt = 0; cnt < off; cnt++)
 202                 free(lines[cnt].l);
 203         free(sp);
 204         free(lines);
 205         return (rc);
 206 }