1/*	$NetBSD$	*/
2
3/* Buffer primitives for comparison operations.
4
5   Copyright (C) 1993, 1995, 1998, 2001, 2002 Free Software Foundation, Inc.
6
7   This program is free software; you can redistribute it and/or modify
8   it under the terms of the GNU General Public License as published by
9   the Free Software Foundation; either version 2, or (at your option)
10   any later version.
11
12   This program is distributed in the hope that it will be useful,
13   but WITHOUT ANY WARRANTY; without even the implied warranty of
14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15   GNU General Public License for more details.
16
17   You should have received a copy of the GNU General Public License
18   along with this program; see the file COPYING.
19   If not, write to the Free Software Foundation,
20   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
21
22#if HAVE_CONFIG_H
23# include <config.h>
24#endif
25
26#include <errno.h>
27#include <limits.h>
28
29#include <signal.h>
30#ifndef SA_RESTART
31# ifdef SA_INTERRUPT /* e.g. SunOS 4.1.x */
32#  define SA_RESTART SA_INTERRUPT
33# else
34#  define SA_RESTART 0
35# endif
36#endif
37
38#if HAVE_UNISTD_H
39# include <unistd.h>
40#endif
41
42#if HAVE_INTTYPES_H
43# include <inttypes.h>
44#endif
45
46#include <sys/types.h>
47#include "cmpbuf.h"
48
49/* Determine whether an integer type is signed, and its bounds.
50   This code assumes two's (or one's!) complement with no holes.  */
51
52/* The extra casts work around common compiler bugs,
53   e.g. Cray C 5.0.3.0 when t == time_t.  */
54#ifndef TYPE_SIGNED
55# define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
56#endif
57#ifndef TYPE_MINIMUM
58# define TYPE_MINIMUM(t) ((t) (TYPE_SIGNED (t) \
59			       ? ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1) \
60			       : (t) 0))
61#endif
62#ifndef TYPE_MAXIMUM
63# define TYPE_MAXIMUM(t) ((t) (~ (t) 0 - TYPE_MINIMUM (t)))
64#endif
65
66#ifndef PTRDIFF_MAX
67# define PTRDIFF_MAX TYPE_MAXIMUM (ptrdiff_t)
68#endif
69#ifndef SIZE_MAX
70# define SIZE_MAX TYPE_MAXIMUM (size_t)
71#endif
72#ifndef SSIZE_MAX
73# define SSIZE_MAX TYPE_MAXIMUM (ssize_t)
74#endif
75
76#undef MIN
77#define MIN(a, b) ((a) <= (b) ? (a) : (b))
78
79/* Read NBYTES bytes from descriptor FD into BUF.
80   NBYTES must not be SIZE_MAX.
81   Return the number of characters successfully read.
82   On error, return SIZE_MAX, setting errno.
83   The number returned is always NBYTES unless end-of-file or error.  */
84
85size_t
86block_read (int fd, char *buf, size_t nbytes)
87{
88  char *bp = buf;
89  char const *buflim = buf + nbytes;
90  size_t readlim = SSIZE_MAX;
91
92  do
93    {
94      size_t bytes_to_read = MIN (buflim - bp, readlim);
95      ssize_t nread = read (fd, bp, bytes_to_read);
96      if (nread <= 0)
97	{
98	  if (nread == 0)
99	    break;
100
101	  /* Accommodate Tru64 5.1, which can't read more than INT_MAX
102	     bytes at a time.  They call that a 64-bit OS?  */
103	  if (errno == EINVAL && INT_MAX < bytes_to_read)
104	    {
105	      readlim = INT_MAX;
106	      continue;
107	    }
108
109	  /* This is needed for programs that have signal handlers on
110	     older hosts without SA_RESTART.  It also accommodates
111	     ancient AIX hosts that set errno to EINTR after uncaught
112	     SIGCONT.  See <news:1r77ojINN85n@ftp.UU.NET>
113	     (1993-04-22).  */
114	  if (! SA_RESTART && errno == EINTR)
115	    continue;
116
117	  return SIZE_MAX;
118	}
119      bp += nread;
120    }
121  while (bp < buflim);
122
123  return bp - buf;
124}
125
126/* Least common multiple of two buffer sizes A and B.  However, if
127   either A or B is zero, or if the multiple is greater than LCM_MAX,
128   return a reasonable buffer size.  */
129
130size_t
131buffer_lcm (size_t a, size_t b, size_t lcm_max)
132{
133  size_t lcm, m, n, q, r;
134
135  /* Yield reasonable values if buffer sizes are zero.  */
136  if (!a)
137    return b ? b : 8 * 1024;
138  if (!b)
139    return a;
140
141  /* n = gcd (a, b) */
142  for (m = a, n = b;  (r = m % n) != 0;  m = n, n = r)
143    continue;
144
145  /* Yield a if there is an overflow.  */
146  q = a / n;
147  lcm = q * b;
148  return lcm <= lcm_max && lcm / b == q ? lcm : a;
149}
150