usr/src/cmd/tail/misc.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  * 4. 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
  33 #include <sys/types.h>
  34 #include <sys/stat.h>
  35 #include <sys/mman.h>
  36
  37 #include <err.h>
  38 #include <errno.h>
  39 #include <stdio.h>
  40 #include <stdlib.h>
  41 #include <string.h>
  42 #include <unistd.h>
  43
  44 #include "extern.h"
  45
  46 void
  47 ierr(const char *fname)
  48 {
  49         warn("%s", fname);
  50         rval = 1;
  51 }
  52
  53 void
  54 oerr(void)
  55 {
  56         err(1, "stdout");
  57 }
  58
  59 /*
  60  * Print `len' bytes from the file associated with `mip', starting at
  61  * absolute file offset `startoff'. May move map window.
  62  */
  63 int
  64 mapprint(struct mapinfo *mip, off_t startoff, off_t len)
  65 {
  66         int n;
  67
  68         while (len > 0) {
  69                 if (startoff < mip->mapoff || startoff >= mip->mapoff +
  70                     (off_t)mip->maplen) {
  71                         if (maparound(mip, startoff) != 0)
  72                                 return (1);
  73                 }
  74                 n = (mip->mapoff + mip->maplen) - startoff;
  75                 if (n > len)
  76                         n = len;
  77                 WR(mip->start + (startoff - mip->mapoff), n);
  78                 startoff += n;
  79                 len -= n;
  80         }
  81         return (0);
  82 }
  83
  84 /*
  85  * Move the map window so that it contains the byte at absolute file
  86  * offset `offset'. The start of the map window will be TAILMAPLEN
  87  * aligned.
  88  */
  89 int
  90 maparound(struct mapinfo *mip, off_t offset)
  91 {
  92
  93         if (mip->start != NULL && munmap(mip->start, mip->maplen) != 0)
  94                 return (1);
  95
  96         mip->mapoff = offset & ~((off_t)TAILMAPLEN - 1);
  97         mip->maplen = TAILMAPLEN;
  98         if ((off_t)mip->maplen > mip->maxoff - mip->mapoff)
  99                 mip->maplen = mip->maxoff - mip->mapoff;
 100         if (mip->maplen == 0)
 101                 abort();
 102         if ((mip->start = mmap(NULL, mip->maplen, PROT_READ, MAP_SHARED,
 103             mip->fd, mip->mapoff)) == MAP_FAILED)
 104                 return (1);
 105
 106         return (0);
 107 }