diff options
Diffstat (limited to 'lib/safe-read.c')
-rw-r--r-- | lib/safe-read.c | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/lib/safe-read.c b/lib/safe-read.c new file mode 100644 index 000000000..2e43070da --- /dev/null +++ b/lib/safe-read.c @@ -0,0 +1,77 @@ +/* An interface to read and write that retries after interrupts. + + Copyright (C) 1993, 1994, 1998, 2002, 2003, 2004, 2005, 2006 Free + Software Foundation, Inc. + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU Lesser General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with this program. If not, see <http://www.gnu.org/licenses/>. */ + +#include <config.h> + +/* Specification. */ +#ifdef SAFE_WRITE +# include "safe-write.h" +#else +# include "safe-read.h" +#endif + +/* Get ssize_t. */ +#include <sys/types.h> +#include <unistd.h> + +#include <errno.h> + +#ifdef EINTR +# define IS_EINTR(x) ((x) == EINTR) +#else +# define IS_EINTR(x) 0 +#endif + +#include <limits.h> + +#ifdef SAFE_WRITE +# define safe_rw safe_write +# define rw write +#else +# define safe_rw safe_read +# define rw read +# undef const +# define const /* empty */ +#endif + +/* Read(write) up to COUNT bytes at BUF from(to) descriptor FD, retrying if + interrupted. Return the actual number of bytes read(written), zero for EOF, + or SAFE_READ_ERROR(SAFE_WRITE_ERROR) upon error. */ +size_t +safe_rw (int fd, void const *buf, size_t count) +{ + /* Work around a bug in Tru64 5.1. Attempting to read more than + INT_MAX bytes fails with errno == EINVAL. See + <http://lists.gnu.org/archive/html/bug-gnu-utils/2002-04/msg00010.html>. + When decreasing COUNT, keep it block-aligned. */ + enum { BUGGY_READ_MAXIMUM = INT_MAX & ~8191 }; + + for (;;) + { + ssize_t result = rw (fd, buf, count); + + if (0 <= result) + return result; + else if (IS_EINTR (errno)) + continue; + else if (errno == EINVAL && BUGGY_READ_MAXIMUM < count) + count = BUGGY_READ_MAXIMUM; + else + return result; + } +} |