1 /* An interface to read that retries after interrupts.
2 Copyright (C) 1993, 1994, 1998, 2002 Free Software Foundation, Inc.
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2, or (at your option)
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software Foundation,
16 Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
23 #include "safe-read.h"
26 #include <sys/types.h>
42 /* The extra casts work around common compiler bugs. */
43 #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
44 /* The outer cast is needed to work around a bug in Cray C 5.0.3.0.
45 It is necessary at least when t == time_t. */
46 #define TYPE_MINIMUM(t) ((t) (TYPE_SIGNED (t) \
47 ? ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1) : (t) 0))
48 #define TYPE_MAXIMUM(t) ((t) (~ (t) 0 - TYPE_MINIMUM (t)))
51 # define INT_MAX TYPE_MAXIMUM (int)
54 /* We don't pass an nbytes count > SSIZE_MAX to read() - POSIX says the
55 effect would be implementation-defined. Also we don't pass an nbytes
56 count > INT_MAX but <= SSIZE_MAX to read() - this triggers a bug in
58 #define MAX_BYTES_TO_READ INT_MAX
61 /* If a system doesn't have support for EINTR, define it
62 to be a value to which errno will never be set. */
63 # define EINTR (INT_MAX - 10)
66 /* Read up to COUNT bytes at BUF from descriptor FD, retrying if interrupted.
67 Return the actual number of bytes read, zero for EOF, or SAFE_READ_ERROR
70 safe_read (int fd, void *buf, size_t count)
72 size_t nbytes_to_read = count;
75 /* Limit the number of bytes to read, to avoid running
76 into unspecified behaviour. But keep the file pointer block
77 aligned when doing so. */
78 if (nbytes_to_read > MAX_BYTES_TO_READ)
79 nbytes_to_read = MAX_BYTES_TO_READ & ~8191;
83 result = read (fd, buf, nbytes_to_read);
85 while (result < 0 && errno == EINTR);
87 return (size_t) result;