Merge frem coreutils.

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

diff --git a/lib/safe-read.c b/lib/safe-read.c
index 79d8541..c21d1cf 100644 (file)
--- a/lib/safe-read.c
+++ b/lib/safe-read.c
@@ -1,5 +1,5 @@
-/* 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
@@ -20,7 +20,11 @@
 #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>
@@ -33,51 +37,46 @@
 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
+#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;
+  ssize_t result;
 
-  if (count > 0)
-    {
-      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;
+  /* 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;
 
-         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);
+  do
+    {
+      result = rw (fd, buf, count);
     }
+  while (result < 0 && IS_EINTR (errno));
 
-  return total_read;
+  return (size_t) result;
 }