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// This may look like C, but it's really -*- C++ -*-
// @(#) $Id$
// ============================================================================
//
// = LIBRARY
// TAO
//
// = FILENAME
// Align.h
//
// = DESCRIPTION
// Pointer alignment utilities
//
// A "ptr_arith_t" type is defined for doing numerical operations
// on pointers, such as aligning them. Pointer sizes vary from 2
// to 8 bytes in today's environments; a portable data type is much
// needed.
//
// = AUTHOR
// Copyright 1994-1995 by Sun Microsystems, Inc.
//
// ============================================================================
#if !defined (TAO_ALIGN_H)
#define TAO_ALIGN_H
// Type for doing arithmetic on pointers ... as elsewhere, we assume
// that "unsigned" versions of a type are the same size as the
// "signed" version of the same type.
#if ACE_SIZEOF_VOID_P == ACE_SIZEOF_INT
typedef u_int ptr_arith_t;
#elif ACE_SIZEOF_VOID_P == ACE_SIZEOF_LONG
typedef u_long ptr_arith_t;
#elif ACE_SIZEOF_VOID_P == ACE_SIZEOF_LONG_LONG
typedef u_long long ptr_arith_t;
#else
# error "Can't find a suitable type for doing pointer arithmetic."
#endif /* error */
// Efficiently align "value" up to "alignment", knowing that all such
// boundaries are binary powers and that we're using two's complement
// arithmetic.
// Since the alignment is a power of two its binary representation is:
// alignment = 0...010...0
//
// hence
//
// alignment - 1 = 0...001...1 = T1
//
// so the complement is:
//
// ~(alignment - 1) = 1...110...0 = T2
//
// Notice that there is a multiple of <alignment> in the range
// [<value>,<value> + T1], also notice that if
//
// X = ( <value> + T1 ) & T2
//
// then
//
// <value> <= X <= <value> + T1
//
// because the & operator only changes the last bits, and since X is a
// multiple of <alignment> (its last bits are zero) we have found the
// multiple we wanted.
//
#define align_binary(ptr, alignment) \
((ptr + ((ptr_arith_t)((alignment)-1))) & (~((ptr_arith_t)((alignment)-1))))
// Efficiently round "ptr" up to an "alignment" boundary, knowing that
// all such boundaries are binary powers and that we're using two's
// complement arithmetic.
//
#define ptr_align_binary(ptr, alignment) \
((char *) align_binary (((ptr_arith_t) (ptr)), (alignment)))
#endif /* TAO_ALIGN_H */
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