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diff --git a/lib/isc/unix/include/isc/offset.h b/lib/isc/unix/include/isc/offset.h
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+/*
+ * Copyright (C) 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC")
+ * Copyright (C) 2000, 2001 Internet Software Consortium.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+ * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/* $Id: offset.h,v 1.15 2007/06/19 23:47:19 tbox Exp $ */
+
+#ifndef ISC_OFFSET_H
+#define ISC_OFFSET_H 1
+
+/*! \file
+ * \brief
+ * File offsets are operating-system dependent.
+ */
+#include <limits.h> /* Required for CHAR_BIT. */
+#include <sys/types.h>
+
+typedef off_t isc_offset_t;
+
+/*%
+ * POSIX says "Additionally, blkcnt_t and off_t are extended signed integral
+ * types", so the maximum value is all 1s except for the high bit.
+ * This definition is more complex than it really needs to be because it was
+ * crafted to keep both the SunOS 5.6 and the HP/UX 11 compilers quiet about
+ * integer overflow. For example, though this is equivalent to just left
+ * shifting 1 to the high bit and then inverting the bits, the SunOS compiler
+ * is unhappy about shifting a positive "1" to negative in a signed integer.
+ */
+#define ISC_OFFSET_MAXIMUM \
+ (~(((off_t)-1 >> (sizeof(off_t) * CHAR_BIT - 1)) \
+ << (sizeof(off_t) * CHAR_BIT - 1)))
+
+#endif /* ISC_OFFSET_H */