Include "xalloc.h".

[gnulib.git] / lib / safe-read.c

diff --git a/lib/safe-read.c b/lib/safe-read.c
index 7fd4415..c21d1cf 100644 (file)
--- a/lib/safe-read.c
+++ b/lib/safe-read.c
@@ -1,5 +1,5 @@
-/* safe-read.c -- an interface to read that retries after interrupts
-   Copyright (C) 1993, 1994 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
@@ -12,54 +12,71 @@
    GNU General Public License for more details.
 
    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., 675 Mass Ave, Cambridge, MA 02139, USA.
-   */
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
 
-#ifdef HAVE_CONFIG_H
-#include <config.h>
+#if HAVE_CONFIG_H
+# include <config.h>
 #endif
 
-#include <sys/types.h>
+/* Specification.  */
+#ifdef SAFE_WRITE
+# include "safe-write.h"
+#else
+# include "safe-read.h"
+#endif
 
-#ifdef HAVE_UNISTD_H
-#include <unistd.h>
+/* Get ssize_t.  */
+#include <sys/types.h>
+#if HAVE_UNISTD_H
+# include <unistd.h>
 #endif
 
 #include <errno.h>
-#ifndef STDC_HEADERS
+#ifndef errno
 extern int errno;
 #endif
 
-/* Read LEN bytes at PTR from descriptor DESC, for file FILENAME,
-   retrying if necessary.  Return a negative value if an error occurs,
-   otherwise return the actual number of bytes read,
-   which must be LEN unless end-of-file was reached.  */
+#ifdef EINTR
+# define IS_EINTR(x) ((x) == EINTR)
+#else
+# define IS_EINTR(x) 0
+#endif
 
-   The canonical source for this function is in the gcc distribution
-   in file cccp.c.  So don't make any changes here.  */
+#include <limits.h>
 
-static int
-safe_read (desc, ptr, len)
-     int desc;
-     char *ptr;
-     int len;
-{
-  int left = len;
-  while (left > 0) {
-    int nchars = read (desc, ptr, left);
-    if (nchars < 0)
-      {
-#ifdef EINTR
-       if (errno == EINTR)
-         continue;
+#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
-       return nchars;
-      }
-    if (nchars == 0)
-      break;
-    ptr += nchars;
-    left -= nchars;
-  }
-  return len - left;
+
+/* 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)
+{
+  ssize_t result;
+
+  /* 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
+    {
+      result = rw (fd, buf, count);
+    }
+  while (result < 0 && IS_EINTR (errno));
+
+  return (size_t) result;
 }