IABSD.fr/src/usr.bin/less/os.c

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• Author : deraadt
  Date : 2019-09-03 23:08:42
  Hash : d65139b4
  Message : less uses a correct raceless signal method of indicating signal events in a volatile sig_atomic_t variable, and then processing events in the mainloop. But only one variable was used for 3 signals, with |= bit operations which are signal interruptable! Rewrite the code to use 3 independent variables and cleanup how the mainloop observes indications. ok schwarze

• usr.bin/less/os.c

• /*
   * Copyright (C) 1984-2012  Mark Nudelman
   * Modified for use with illumos by Garrett D'Amore.
   * Copyright 2014 Garrett D'Amore <garrett@damore.org>
   *
   * You may distribute under the terms of either the GNU General Public
   * License or the Less License, as specified in the README file.
   *
   * For more information, see the README file.
   */
  
  /*
   * Operating system dependent routines.
   *
   * Most of the stuff in here is based on Unix, but an attempt
   * has been made to make things work on other operating systems.
   * This will sometimes result in a loss of functionality, unless
   * someone rewrites code specifically for the new operating system.
   *
   * The makefile provides defines to decide whether various
   * Unix features are present.
   */
  
  #include <errno.h>
  #include <signal.h>
  #include <time.h>
  
  #include "less.h"
  
  
  /*
   * Like read() system call, but is deliberately interruptible.
   */
  int
  iread(int fd, unsigned char *buf, unsigned int len)
  {
  	int n;
  
  start:
  	flush(0);
  	n = read(fd, buf, len);
  	if (n == -1) {
  		/*
  		 * Certain values of errno indicate we should just retry the
  		 * read.
  		 */
  		if (errno == EINTR)
  			return (READ_INTR);
  		if (errno == EAGAIN)
  			goto start;
  		return (-1);
  	}
  	return (n);
  }
  
  /*
   * errno_message: Return an error message based on the value of "errno".
   */
  char *
  errno_message(char *filename)
  {
  	return (easprintf("%s: %s", filename, strerror(errno)));
  }
  
  static off_t
  muldiv(off_t val, off_t num, off_t den)
  {
  	double v = (((double)val) * num) / den;
  	return ((off_t)(v + 0.5));
  }
  
  /*
   * Return the ratio of two off_t, as a percentage.
   * {{ Assumes a off_t is a long int. }}
   */
  int
  percentage(off_t num, off_t den)
  {
  	return ((int)muldiv(num, (off_t)100, den));
  }
  
  /*
   * Return the specified percentage of a off_t.
   */
  off_t
  percent_pos(off_t pos, int percent, long fraction)
  {
  	/*
  	 * Change percent (parts per 100) to perden
  	 * (parts per NUM_FRAC_DENOM).
  	 */
  	off_t perden = (percent * (NUM_FRAC_DENOM / 100)) + (fraction / 100);
  
  	if (perden == 0)
  		return (0);
  	return (muldiv(pos, perden, (off_t)NUM_FRAC_DENOM));
  }