| 1 | /* An interface to read and write that retries after interrupts. |
| 2 | |
| 3 | Copyright (C) 1993-1994, 1998, 2002-2006, 2009-2014 Free Software |
| 4 | Foundation, Inc. |
| 5 | |
| 6 | This program is free software: you can redistribute it and/or modify |
| 7 | it under the terms of the GNU Lesser General Public License as published by |
| 8 | the Free Software Foundation; either version 3 of the License, or |
| 9 | (at your option) any later version. |
| 10 | |
| 11 | This program is distributed in the hope that it will be useful, |
| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | GNU Lesser General Public License for more details. |
| 15 | |
| 16 | You should have received a copy of the GNU Lesser General Public License |
| 17 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
| 18 | |
| 19 | #include <config.h> |
| 20 | |
| 21 | /* Specification. */ |
| 22 | #ifdef SAFE_WRITE |
| 23 | # include "safe-write.h" |
| 24 | #else |
| 25 | # include "safe-read.h" |
| 26 | #endif |
| 27 | |
| 28 | /* Get ssize_t. */ |
| 29 | #include <sys/types.h> |
| 30 | #include <unistd.h> |
| 31 | |
| 32 | #include <errno.h> |
| 33 | |
| 34 | #ifdef EINTR |
| 35 | # define IS_EINTR(x) ((x) == EINTR) |
| 36 | #else |
| 37 | # define IS_EINTR(x) 0 |
| 38 | #endif |
| 39 | |
| 40 | #include <limits.h> |
| 41 | |
| 42 | #ifdef SAFE_WRITE |
| 43 | # define safe_rw safe_write |
| 44 | # define rw write |
| 45 | #else |
| 46 | # define safe_rw safe_read |
| 47 | # define rw read |
| 48 | # undef const |
| 49 | # define const /* empty */ |
| 50 | #endif |
| 51 | |
| 52 | /* Read(write) up to COUNT bytes at BUF from(to) descriptor FD, retrying if |
| 53 | interrupted. Return the actual number of bytes read(written), zero for EOF, |
| 54 | or SAFE_READ_ERROR(SAFE_WRITE_ERROR) upon error. */ |
| 55 | size_t |
| 56 | safe_rw (int fd, void const *buf, size_t count) |
| 57 | { |
| 58 | /* Work around a bug in Tru64 5.1. Attempting to read more than |
| 59 | INT_MAX bytes fails with errno == EINVAL. See |
| 60 | <http://lists.gnu.org/archive/html/bug-gnu-utils/2002-04/msg00010.html>. |
| 61 | When decreasing COUNT, keep it block-aligned. */ |
| 62 | enum { BUGGY_READ_MAXIMUM = INT_MAX & ~8191 }; |
| 63 | |
| 64 | for (;;) |
| 65 | { |
| 66 | ssize_t result = rw (fd, buf, count); |
| 67 | |
| 68 | if (0 <= result) |
| 69 | return result; |
| 70 | else if (IS_EINTR (errno)) |
| 71 | continue; |
| 72 | else if (errno == EINVAL && BUGGY_READ_MAXIMUM < count) |
| 73 | count = BUGGY_READ_MAXIMUM; |
| 74 | else |
| 75 | return result; |
| 76 | } |
| 77 | } |