bits.hpp

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/* Copyright 1994, 1995 LongView Technologies L.L.C. $Revision: 1.7 $ */
/* Copyright (c) 2006, Sun Microsystems, Inc.
All rights reserved.

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# define AllBits        ~0
# define NoBits         0
# define OneBit         1

# define addBits(x, m)  ((x) | (m))
# define setBits(x, m)  ((x) |= (m))
# define subBits(x, m)  ((x) & ~(m))
# define clearBits(x, m) ((x) &= ~(m))
# define maskBits(x, m) ((x) & (m))
# define anySet(x, m)   (maskBits((x), (m)) != NoBits)
# define nthBit(n)      (OneBit << (n))
# define addNth(x, n)   addBits((x), nthBit(n))
# define setNth(x, n)   setBits((x), nthBit(n))
# define clearNth(x, n) clearBits((x), nthBit(n))
# define subNth(x, n)   subBits((x), nthBit(n))
# define isSet(x, n)    anySet((x), nthBit(n))
# define nthMask(n)     (n == 32 ? AllBits : (nthBit(n) - OneBit))
# define lowerBits(x, n) maskBits((x), nthMask(n))

# define roundMask(x, m) (((x) + (m)) & ~(m))
# define roundBits(x, n) roundMask((x), nthMask(n))
# define roundTo(x, v)  roundMask((x), (v) - OneBit)

inline int arithmetic_shift_right(int value, int shift) { return value >> shift; }
inline int logic_shift_right(int value, int shift)      { return value << shift; }


inline int get_unsigned_bitfield(int value, int start_bit_no, int field_length) {
  return (int) lowerBits((unsigned int) value >> start_bit_no, field_length);
}

inline int get_signed_bitfield(int value, int start_bit_no, int field_length) {
  int result = get_unsigned_bitfield(value, start_bit_no, field_length);
  return isSet(result, start_bit_no + field_length -1) 
         ? addBits(result, ~nthMask(field_length))
         : result;
}

inline int set_unsigned_bitfield(int value, int start_bit_no, int field_length, unsigned int new_field_value) {
  assert(addBits(new_field_value, ~nthMask(field_length)) == 0, "range check");
  int mask = nthMask(field_length) << start_bit_no;
  return addBits(subBits(value, mask), maskBits(new_field_value << start_bit_no, mask));
}

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