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Diffstat (limited to 'TAO/tao/Align.h')
| -rw-r--r-- | TAO/tao/Align.h | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/TAO/tao/Align.h b/TAO/tao/Align.h new file mode 100644 index 00000000000..f1b75a7c0b5 --- /dev/null +++ b/TAO/tao/Align.h @@ -0,0 +1,84 @@ +// 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. +// +// ============================================================================ + +#ifndef 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 */ |