X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Fsafe-read.c;h=6f8bd780ed01a25da8452bb0b77a95eb302fbbc6;hb=12797e006016ec69a5c0760999d5cd7c2a372b54;hp=79d85417d867c2a6cdcb92ee17f94869fa337676;hpb=849efe7683e163ede9240b27d675977c71c76ce8;p=gnulib.git

diff --git a/lib/safe-read.c b/lib/safe-read.c
index 79d85417d..6f8bd780e 100644
--- a/lib/safe-read.c
+++ b/lib/safe-read.c
@@ -1,5 +1,7 @@
-/* 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, 2004 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
@@ -20,7 +22,11 @@
 #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>
@@ -29,55 +35,48 @@
 #endif
 
 #include <errno.h>
-#ifndef errno
-extern int errno;
+
+#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
+#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 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.  */
+/* 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;
+  /* 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 };
 
-  if (count > 0)
+  for (;;)
     {
-      char *ptr = (char *) buf;
-      do
-	{
-	  size_t nbytes_to_read = count;
-	  ssize_t result;
+      ssize_t result = rw (fd, buf, count);
 
-	  /* 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);
+      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;
     }
-
-  return total_read;
 }