usr.bin/tail/read.c

   1 /*      $NetBSD: read.c,v 1.14 2008/09/30 04:03:37 dholland 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[] = "@(#)read.c      8.1 (Berkeley) 6/6/93";
  39 #endif
  40 __RCSID("$NetBSD: read.c,v 1.14 2008/09/30 04:03:37 dholland Exp $");
  41 #endif /* not lint */
  42
  43 #include <sys/types.h>
  44 #include <sys/stat.h>
  45 #include <fcntl.h>
  46 #include <errno.h>
  47 #include <unistd.h>
  48 #include <stdio.h>
  49 #include <stdlib.h>
  50 #include <string.h>
  51 #include "extern.h"
  52
  53 /*
  54  * displaybytes -- read bytes to an offset from the end and display.
  55  *
  56  * This is the function that reads to a byte offset from the end of the input,
  57  * storing the data in a wrap-around buffer which is then displayed.  If the
  58  * rflag is set, the data is displayed in lines in reverse order, and this
  59  * routine has the usual nastiness of trying to find the newlines.  Otherwise,
  60  * it is displayed from the character closest to the beginning of the input to
  61  * the end.
  62  *
  63  * Non-zero return means than a (non-fatal) error occurred.
  64  */
  65 int
  66 displaybytes(FILE *fp, off_t off)
  67 {
  68         int ch, len, tlen;
  69         char *ep, *p, *t;
  70         int wrap;
  71         char *sp;
  72
  73         if ((sp = p = malloc(off)) == NULL)
  74                 err(1, "%s", strerror(errno));
  75
  76         for (wrap = 0, ep = p + off; (ch = getc(fp)) != EOF;) {
  77                 *p = ch;
  78                 if (++p == ep) {
  79                         wrap = 1;
  80                         p = sp;
  81                 }
  82         }
  83         if (ferror(fp)) {
  84                 ierr();
  85                 return (1);
  86         }
  87
  88         if (rflag) {
  89                 for (t = p - 1, len = 0; t >= sp; --t, ++len)
  90                         if (*t == '\n' && len) {
  91                                 WR(t + 1, len);
  92                                 len = 0;
  93                 }
  94                 if (wrap) {
  95                         tlen = len;
  96                         for (t = ep - 1, len = 0; t >= p; --t, ++len)
  97                                 if (*t == '\n') {
  98                                         if (len) {
  99                                                 WR(t + 1, len);
 100                                                 len = 0;
 101                                         }
 102                                         if (tlen) {
 103                                                 WR(sp, tlen);
 104                                                 tlen = 0;
 105                                         }
 106                                 }
 107                         if (len)
 108                                 WR(t + 1, len);
 109                         if (tlen)
 110                                 WR(sp, tlen);
 111                 }
 112         } else {
 113                 if (wrap && (len = ep - p))
 114                         WR(p, len);
 115                 if ((len = p - sp) != 0)
 116                         WR(sp, len);
 117         }
 118         return (0);
 119 }
 120
 121 /*
 122  * displaylines -- read lines to an offset from the end and display.
 123  *
 124  * This is the function that reads to a line offset from the end of the input,
 125  * storing the data in an array of buffers which is then displayed.  If the
 126  * rflag is set, the data is displayed in lines in reverse order, and this
 127  * routine has the usual nastiness of trying to find the newlines.  Otherwise,
 128  * it is displayed from the line closest to the beginning of the input to
 129  * the end.
 130  *
 131  * Non-zero return means than a (non-fatal) error occurred.
 132  */
 133 int
 134 displaylines(FILE *fp, off_t off)
 135 {
 136         struct {
 137                 int blen;
 138                 int len;
 139                 char *l;
 140         } *lines;
 141         int ch;
 142         char *p;
 143         int blen, cnt, recno, wrap;
 144         char *sp, *n;
 145
 146         p = NULL;
 147         if ((lines = malloc(off * sizeof(*lines))) == NULL)
 148                 err(1, "%s", strerror(errno));
 149
 150         memset(lines, 0, sizeof(*lines) * off);
 151
 152         sp = NULL;
 153         blen = cnt = recno = wrap = 0;
 154
 155         while ((ch = getc(fp)) != EOF) {
 156                 if (++cnt > blen) {
 157                         if ((n = realloc(sp, blen + 1024)) == NULL)
 158                                 err(1, "%s", strerror(errno));
 159                         sp = n;
 160                         blen += 1024;
 161                         p = sp + cnt - 1;
 162                 }
 163                 *p++ = ch;
 164                 if (ch == '\n') {
 165                         if (lines[recno].blen < cnt) {
 166                                 if ((n = realloc(lines[recno].l,
 167                                     cnt + 256)) == NULL)
 168                                         err(1, "%s", strerror(errno));
 169                                 lines[recno].l = n;
 170                                 lines[recno].blen = cnt + 256;
 171                         }
 172                         memmove(lines[recno].l, sp, lines[recno].len = cnt);
 173                         cnt = 0;
 174                         p = sp;
 175                         if (++recno == off) {
 176                                 wrap = 1;
 177                                 recno = 0;
 178                         }
 179                 }
 180         }
 181         if (ferror(fp)) {
 182                 free(lines);
 183                 ierr();
 184                 return (1);
 185         }
 186         if (cnt) {
 187                 lines[recno].l = sp;
 188                 lines[recno].len = cnt;
 189                 if (++recno == off) {
 190                         wrap = 1;
 191                         recno = 0;
 192                 }
 193         }
 194
 195         if (rflag) {
 196                 for (cnt = recno - 1; cnt >= 0; --cnt)
 197                         WR(lines[cnt].l, lines[cnt].len);
 198                 if (wrap)
 199                         for (cnt = off - 1; cnt >= recno; --cnt)
 200                                 WR(lines[cnt].l, lines[cnt].len);
 201         } else {
 202                 if (wrap)
 203                         for (cnt = recno; cnt < off; ++cnt)
 204                                 WR(lines[cnt].l, lines[cnt].len);
 205                 for (cnt = 0; cnt < recno; ++cnt)
 206                         WR(lines[cnt].l, lines[cnt].len);
 207         }
 208         free(lines);
 209         return (0);
 210 }