-/* An interface to read() that retries after interrupts.
- Copyright (C) 1993, 1994, 1998, 2002 Free Software Foundation, Inc.
+/* An interface to read and write that retries after interrupts.
+ Copyright (C) 1993, 1994, 1998, 2002-2003 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
#endif
/* Specification. */
-#include "safe-read.h"
+#ifdef SAFE_WRITE
+# include "safe-write.h"
+#else
+# include "safe-read.h"
+#endif
/* Get ssize_t. */
#include <sys/types.h>
extern int errno;
#endif
+#ifdef EINTR
+# define IS_EINTR(x) ((x) == EINTR)
+#else
+# define IS_EINTR(x) 0
+#endif
+
#include <limits.h>
-/* 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
+#ifndef CHAR_BIT
+# define CHAR_BIT 8
+#endif
+
+/* The extra casts work around common compiler bugs. */
+#define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
+/* The outer cast is needed to work around a bug in Cray C 5.0.3.0.
+ It is necessary at least when t == time_t. */
+#define TYPE_MINIMUM(t) ((t) (TYPE_SIGNED (t) \
+ ? ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1) : (t) 0))
+#define TYPE_MAXIMUM(t) ((t) (~ (t) 0 - TYPE_MINIMUM (t)))
-/* Read up to COUNT bytes at BUF from descriptor FD, retrying if interrupted.
- Return the actual number of bytes read, zero for EOF, or (size_t) -1
- for an error. */
+#ifndef INT_MAX
+# define INT_MAX TYPE_MAXIMUM (int)
+#endif
+
+#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_read (int fd, void *buf, size_t count)
+safe_rw (int fd, void const *buf, size_t count)
{
- size_t total_read = 0;
+ ssize_t result;
- if (count > 0)
+ /* POSIX limits COUNT to SSIZE_MAX, but we limit it further, requiring
+ that COUNT <= INT_MAX, to avoid triggering a bug in Tru64 5.1.
+ When decreasing COUNT, keep the file pointer block-aligned.
+ Note that in any case, read(write) may succeed, yet read(write)
+ fewer than COUNT bytes, so the caller must be prepared to handle
+ partial results. */
+ if (count > INT_MAX)
+ count = INT_MAX & ~8191;
+
+ do
{
- char *ptr = (char *) buf;
- do
- {
- 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
- if (errno == EINTR)
- continue;
-#endif
- return result;
- }
- total_read += result;
- ptr += result;
- count -= result;
- }
- while (count > 0);
+ result = rw (fd, buf, count);
}
+ while (result < 0 && IS_EINTR (errno));
- return total_read;
+ return (size_t) result;
}