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