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authorJim Meyering <jim@meyering.net>2002-12-01 11:53:02 +0000
committerJim Meyering <jim@meyering.net>2002-12-01 11:53:02 +0000
commit4c6c221ee2b48595f812e58780097f79ca18506f (patch)
tree93887db390117c8d56a4f126b7098a10bc62d3c7
parentef266f5a81f6f1ce28747cd5431bebf0cd720545 (diff)
downloadcoreutils-4c6c221ee2b48595f812e58780097f79ca18506f.tar.xz
Merge from gnulib.
-rw-r--r--lib/safe-read.c71
1 files changed, 40 insertions, 31 deletions
diff --git a/lib/safe-read.c b/lib/safe-read.c
index 134b80454..e4cb1d3a2 100644
--- a/lib/safe-read.c
+++ b/lib/safe-read.c
@@ -1,4 +1,4 @@
-/* safe-read.c -- an interface to read that retries after interrupts
+/* An interface to read that retries after interrupts.
Copyright (C) 1993, 1994, 1998, 2002 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
@@ -13,16 +13,17 @@
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software Foundation,
- Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
- */
+ Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
#if HAVE_CONFIG_H
# include <config.h>
#endif
-#include <sys/types.h>
-#include <stdlib.h>
+/* Specification. */
+#include "safe-read.h"
+/* Get ssize_t. */
+#include <sys/types.h>
#if HAVE_UNISTD_H
# include <unistd.h>
#endif
@@ -32,39 +33,47 @@
extern int errno;
#endif
-#include "safe-read.h"
-
-/* Read LEN bytes at PTR from descriptor DESC, retrying if interrupted.
- Return the actual number of bytes read, zero upon EOF,
- or SAFE_READ_ERROR upon error.
- Abort if LEN is SAFE_READ_ERROR (aka `(size_t) -1').
+#include <limits.h>
- WARNING: although both LEN and the return value are of type size_t,
- the range of the return value is restricted -- by virtue of being
- returned from read(2) -- and will never be larger than SSIZE_MAX,
- with the exception of SAFE_READ_ERROR, of course.
- So don't test `safe_read (..., N) == N' unless you're sure that
- N <= SSIZE_MAX. */
+/* We don't pass an nbytes count > SSIZE_MAX to read() - POSIX says the
+ effect would be implementation-defined. Also we don't pass an nbytes
+ count > INT_MAX but <= SSIZE_MAX to read() - this triggers a bug in
+ Tru64 5.1. */
+#define MAX_BYTES_TO_READ INT_MAX
+/* Read up to COUNT bytes at BUF from descriptor FD, retrying if interrupted.
+ Return the actual number of bytes read, zero for EOF, or SAFE_READ_ERROR
+ upon error. */
size_t
-safe_read (int desc, void *ptr, size_t len)
+safe_read (int fd, void *buf, size_t count)
{
- ssize_t n_chars;
+ size_t total_read = 0;
+ char *ptr = buf;
- if (len == SAFE_READ_ERROR)
- abort ();
- if (len == 0)
- return len;
+ while (count > 0)
+ {
+ size_t nbytes_to_read = count;
+ ssize_t result;
+
+ /* Limit the number of bytes to read in one round, to avoid running
+ into unspecified behaviour. But keep the file pointer block
+ aligned when doing so. */
+ if (nbytes_to_read > MAX_BYTES_TO_READ)
+ nbytes_to_read = MAX_BYTES_TO_READ & ~8191;
+ result = read (fd, ptr, nbytes_to_read);
+ if (result < 0)
+ {
#ifdef EINTR
- do
- {
- n_chars = read (desc, ptr, len);
- }
- while (n_chars < 0 && errno == EINTR);
-#else
- n_chars = read (desc, ptr, len);
+ if (errno == EINTR)
+ continue;
#endif
+ return SAFE_READ_ERROR;
+ }
+ total_read += result;
+ ptr += result;
+ count -= result;
+ }
- return n_chars;
+ return total_read;
}