From e76d578bad013b6ac4942b09f28f3e64b97b3e15 Mon Sep 17 00:00:00 2001
From: Jim Meyering <jim@meyering.net>
Date: Tue, 7 Jan 2003 14:03:15 +0000
Subject: Rework so that it may serve to define full_read, too.

---
 lib/full-write.c | 61 +++++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 40 insertions(+), 21 deletions(-)

(limited to 'lib')

diff --git a/lib/full-write.c b/lib/full-write.c
index a952f8c81..5bb90b44d 100644
--- a/lib/full-write.c
+++ b/lib/full-write.c
@@ -1,7 +1,6 @@
-/* An interface to write() that writes all it is asked to write.
+/* An interface to read and write that retries (if necessary) until complete.
 
-   Copyright (C) 1993, 1994, 1997, 1998, 1999, 2000, 2001, 2002 Free Software
-   Foundation, Inc.
+   Copyright (C) 1993, 1994, 1997-2003 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
@@ -21,41 +20,61 @@
 # include <config.h>
 #endif
 
-/* Specification.  */
-#include "full-write.h"
+#ifdef FULL_READ
+# include "full-read.h"
+# include "safe-read.h"
+# define safe_rw safe_read
+# define full_rw full_read
+# undef const
+# define const /* empty */
+#else
+# include "full-write.h"
+# include "safe-write.h"
+# define safe_rw safe_write
+# define full_rw full_write
+#endif
 
 #include <errno.h>
 #ifndef errno
 extern int errno;
 #endif
 
-#include "safe-write.h"
+#ifdef FULL_READ
+/* Set errno to zero upon EOF.  */
+# define ZERO_BYTE_TRANSFER_ERRNO 0
+#else
+/* Some buggy drivers return 0 when one tries to write beyond
+   a device's end.  (Example: Linux 1.2.13 on /dev/fd0.)
+   Set errno to ENOSPC so they get a sensible diagnostic.  */
+# define ZERO_BYTE_TRANSFER_ERRNO ENOSPC
+#endif
 
-/* Write COUNT bytes at BUF to descriptor FD, retrying if interrupted
-   or if partial writes occur.  Return the number of bytes successfully
-   written, setting errno if that is less than COUNT.  */
+/* Write(read) COUNT bytes at BUF to(from) descriptor FD, retrying if
+   interrupted or if a partial write(read) occurs.  Return the number
+   of bytes transferred.
+   When writing, set errno if fewer than COUNT bytes are written.
+   When reading, if fewer than COUNT bytes are read, you must examine
+   errno to distinguish failure from EOF (errno == 0).  */
 size_t
-full_write (int fd, const void *buf, size_t count)
+full_rw (int fd, const void *buf, size_t count)
 {
-  size_t total_written = 0;
+  size_t total = 0;
   const char *ptr = buf;
 
   while (count > 0)
     {
-      size_t written = safe_write (fd, ptr, count);
-      if (written == (size_t)-1)
+      size_t n_rw = safe_rw (fd, ptr, count);
+      if (n_rw == (size_t) -1)
 	break;
-      if (written == 0)
+      if (n_rw == 0)
 	{
-	  /* Some buggy drivers return 0 when you fall off a device's
-	     end.  (Example: Linux 1.2.13 on /dev/fd0.)  */
-	  errno = ENOSPC;
+	  errno = ZERO_BYTE_TRANSFER_ERRNO;
 	  break;
 	}
-      total_written += written;
-      ptr += written;
-      count -= written;
+      total += n_rw;
+      ptr += n_rw;
+      count -= n_rw;
     }
 
-  return total_written;
+  return total;
 }
-- 
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