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>
37 # define IS_EINTR(x) ((x) == EINTR)
39 # define IS_EINTR(x) 0
48 /* The extra casts work around common compiler bugs. */
49 #define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
50 /* The outer cast is needed to work around a bug in Cray C 5.0.3.0.
51 It is necessary at least when t == time_t. */
52 #define TYPE_MINIMUM(t) ((t) (TYPE_SIGNED (t) \
53 ? ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1) : (t) 0))
54 #define TYPE_MAXIMUM(t) ((t) (~ (t) 0 - TYPE_MINIMUM (t)))
57 # define INT_MAX TYPE_MAXIMUM (int)
60 /* We don't pass an nbytes count > SSIZE_MAX to read() - POSIX says the
61 effect would be implementation-defined. Also we don't pass an nbytes
62 count > INT_MAX but <= SSIZE_MAX to read() - this triggers a bug in
64 #define MAX_BYTES_TO_READ INT_MAX
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 into unspecified
76 behaviour. But keep the file pointer block aligned when doing so.
77 Note that in this case we don't need to call read() multiple times here,
78 because the caller is prepared to partial results. */
79 if (nbytes_to_read > MAX_BYTES_TO_READ)
80 nbytes_to_read = MAX_BYTES_TO_READ & ~8191;
84 result = read (fd, buf, nbytes_to_read);
86 while (result < 0 && IS_EINTR (errno));
88 return (size_t) result;