src/systemc/ext/dt/int/sc_nbutils.hh

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  Licensed to Accellera Systems Initiative Inc. (Accellera) under one or
  more contributor license agreements.  See the NOTICE file distributed
  with this work for additional information regarding copyright ownership.
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  License.  You may obtain a copy of the License at

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  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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/*****************************************************************************

  sc_nbutils.h -- External and friend functions for both sc_signed and
                  sc_unsigned classes.

  Original Author: Ali Dasdan, Synopsys, Inc.

 *****************************************************************************/

/*****************************************************************************

  MODIFICATION LOG - modifiers, enter your name, affiliation, date and
  changes you are making here.

      Name, Affiliation, Date:
  Description of Modification:

 *****************************************************************************/

// $Log: sc_nbutils.h,v $
// Revision 1.6  2011/09/08 16:12:15  acg
//  Philipp A. Hartmann: fix issue with Sun machines wrt real math libraries.
//
// Revision 1.5  2011/08/26 23:00:01  acg
//  Torsten Maehne: remove use of ieeefp.h.
//
// Revision 1.4  2011/08/15 16:43:24  acg
//  Torsten Maehne: changes to remove unused argument warnings.
//
// Revision 1.3  2011/02/18 20:19:15  acg
//  Andy Goodrich: updating Copyright notice.
//
// Revision 1.2  2010/09/06 16:35:48  acg
//  Andy Goodrich: changed i386 to __i386__ in ifdef's.
//
// Revision 1.1.1.1  2006/12/15 20:20:05  acg
// SystemC 2.3
//
// Revision 1.3  2006/01/13 18:49:32  acg
// Added $Log command so that CVS check in comments are reproduced in the
// source.
//

#ifndef __SYSTEMC_EXT_DT_INT_SC_NBUTILS_HH__
#define __SYSTEMC_EXT_DT_INT_SC_NBUTILS_HH__

#include <cmath>
#include <ios>
#include <limits>
#include <ostream>

#include "../../utils/sc_report_handler.hh"
#include "../bit/messages.hh"
#include "messages.hh"
#include "sc_nbdefs.hh"

namespace sc_dt
{

//-----------------------------------------------------------------------------
//"sc_io_base"
//
// This inline function returns the type of an i/o stream's base as a SystemC
// base designator.
//   stream_object = reference to the i/o stream whose base is to be returned.
//
//"sc_io_show_base"
//
// This inline function returns true if the base should be shown when a SystemC
// value is displayed via the supplied stream operator.
//   stream_object = reference to the i/o stream to return showbase value for.
//-----------------------------------------------------------------------------
inline sc_numrep
sc_io_base(::std::ostream &os, sc_numrep def_base)
{
    std::ios::fmtflags flags = os.flags() & std::ios::basefield;
    if (flags & ::std::ios::dec) return SC_DEC;
    if (flags & ::std::ios::hex) return SC_HEX;
    if (flags & ::std::ios::oct) return SC_OCT;
    return def_base;
}

inline bool
sc_io_show_base(::std::ostream &os)
{
    return (os.flags() & ::std::ios::showbase) != 0;
}

const std::string to_string(sc_numrep);

inline ::std::ostream &
operator << (::std::ostream &os, sc_numrep numrep)
{
    os << to_string(numrep);
    return os;
}

// ----------------------------------------------------------------------------

// One transition of the FSM to find base and sign of a number.
extern small_type fsm_move(
        char c, small_type &b, small_type &s, small_type &state);

// Parse a character string into its equivalent binary bits.
extern void parse_binary_bits(
        const char *src_p, int dst_n, sc_digit *data_p, sc_digit *ctrl_p=0);

// Parse a character string into its equivalent hexadecimal bits.
extern void parse_hex_bits(
        const char *src_p, int dst_n, sc_digit *data_p, sc_digit *ctrl_p=0);

// Find the base and sign of a number in v.
extern const char *get_base_and_sign(
        const char *v, small_type &base, small_type &sign);

// Create a number out of v in base.
extern small_type
vec_from_str(int unb, int und, sc_digit *u,
             const char *v, sc_numrep base=SC_NOBASE);


// ----------------------------------------------------------------------------
//  Naming convention for the vec_ functions below:
//    vec_OP(u, v, w)  : computes w = u OP v.
//    vec_OP_on(u, v)  : computes u = u OP v if u has more digits than v.
//    vec_OP_on2(u, v) : computes u = u OP v if u has fewer digits than v.
//    _large           : parameters are vectors.
//    _small           : one of the parameters is a single digit.
//    Xlen             : the number of digits in X.
// ----------------------------------------------------------------------------

// ----------------------------------------------------------------------------
//  Functions for vector addition: w = u + v or u += v.
// ----------------------------------------------------------------------------

extern void vec_add(int ulen, const sc_digit *u,
                    int vlen, const sc_digit *v, sc_digit *w);
extern void vec_add_on(int ulen, sc_digit *u, int vlen, const sc_digit *v);
extern void vec_add_on2(int ulen, sc_digit *u, int vlen, const sc_digit *v);
extern void vec_add_small(int ulen, const sc_digit *u,
                          sc_digit v, sc_digit *w);
extern void vec_add_small_on(int ulen, sc_digit *u, sc_digit v);

// ----------------------------------------------------------------------------
//  Functions for vector subtraction: w = u - v, u -= v, or u = v - u.
// ----------------------------------------------------------------------------

extern void vec_sub(int ulen, const sc_digit *u,
                    int vlen, const sc_digit *v, sc_digit *w);
extern void vec_sub_on(int ulen, sc_digit *u, int vlen, const sc_digit *v);
extern void vec_sub_on2(int ulen, sc_digit *u, int vlen, const sc_digit *v);
extern void vec_sub_small(int ulen, const sc_digit *u,
                          sc_digit v, sc_digit *w);
extern void vec_sub_small_on(int ulen, sc_digit *u, sc_digit v);


// ----------------------------------------------------------------------------
//  Functions for vector multiplication: w = u * v or u *= v.
// ----------------------------------------------------------------------------

extern void vec_mul(int ulen, const sc_digit *u,
                    int vlen, const sc_digit *v, sc_digit *w);
extern void vec_mul_small(int ulen, const sc_digit *u,
                          sc_digit v, sc_digit *w);
extern void vec_mul_small_on(int ulen, sc_digit *u, sc_digit v);


// ----------------------------------------------------------------------------
//  Functions for vector division: w = u / v.
// ----------------------------------------------------------------------------

extern void vec_div_large(int ulen, const sc_digit *u,
                          int vlen, const sc_digit *v, sc_digit *w);
extern void vec_div_small(int ulen, const sc_digit *u,
                          sc_digit v, sc_digit *w);


// ----------------------------------------------------------------------------
//  Functions for vector remainder: w = u % v or u %= v.
// ----------------------------------------------------------------------------

extern void vec_rem_large(int ulen, const sc_digit *u,
                          int vlen, const sc_digit *v, sc_digit *w);
extern sc_digit vec_rem_small(int ulen, const sc_digit *u, sc_digit v);
extern sc_digit vec_rem_on_small(int ulen, sc_digit *u, sc_digit v);


// ----------------------------------------------------------------------------
//  Functions to convert between vectors of char and sc_digit.
// ----------------------------------------------------------------------------

extern int vec_to_char(int ulen, const sc_digit *u, int vlen, uchar *v);
extern void vec_from_char(int ulen, const uchar *u, int vlen, sc_digit *v);


// ----------------------------------------------------------------------------
//  Functions to shift left or right, or to create a mirror image of vectors.
// ----------------------------------------------------------------------------

extern void vec_shift_left(int ulen, sc_digit *u, int nsl);
extern void vec_shift_right(int vlen, sc_digit *u, int nsr, sc_digit fill=0);
extern void vec_reverse(int unb, int und, sc_digit *ud, int l, int r=0);


// ----------------------------------------------------------------------------
//  Various utility functions.
// ----------------------------------------------------------------------------

// Return the low half part of d.
inline sc_digit low_half(sc_digit d) { return (d & HALF_DIGIT_MASK); }

// Return the high half part of d. The high part of the digit may have
// more bits than BITS_PER_HALF_DIGIT due to, e.g., overflow in the
// multiplication. Hence, in other functions that use high_half(),
// make sure that the result contains BITS_PER_HALF_DIGIT if
// necessary. This is done by high_half_masked().
inline sc_digit high_half(sc_digit d) { return (d >> BITS_PER_HALF_DIGIT); }
inline sc_digit
high_half_masked(sc_digit d)
{
    return (high_half(d) & HALF_DIGIT_MASK);
}

// Concatenate the high part h and low part l. Assumes that h and l
// are less than or equal to HALF_DIGIT_MASK;
inline sc_digit
concat(sc_digit h, sc_digit l)
{
    return ((h << BITS_PER_HALF_DIGIT) | l);
}

// Create a number with n 1's.
inline sc_digit
one_and_ones(int n)
{
    return (((sc_digit) 1 << n) - 1);
}

// Create a number with one 1 and n 0's.
inline sc_digit one_and_zeros(int n) { return ((sc_digit) 1 << n); }


// ----------------------------------------------------------------------------

// Find the digit that bit i is in.
inline int digit_ord(int i) { return (i / BITS_PER_DIGIT); }

// Find the bit in digit_ord(i) that bit i corressponds to.
inline int bit_ord(int i) { return (i % BITS_PER_DIGIT); }


// ----------------------------------------------------------------------------
//  Functions to compare, zero, complement vector(s).
// ----------------------------------------------------------------------------

// Compare u and v and return r
//  r = 0 if u == v
//  r < 0 if u < v
//  r > 0 if u > v
// - Assume that all the leading zero digits are already skipped.
// - ulen and/or vlen can be zero.
// - Every digit is less than or equal to DIGIT_MASK;
inline int
vec_cmp(int ulen, const sc_digit *u,
        int vlen, const sc_digit *v)
{

#ifdef DEBUG_SYSTEMC
    // sc_assert((ulen <= 0) || (u != NULL));
    // sc_assert((vlen <= 0) || (v != NULL));

    // ulen and vlen can be equal to 0 because vec_cmp can be called
    // after vec_skip_leading_zeros.
    sc_assert((ulen >= 0) && (u != NULL));
    sc_assert((vlen >= 0) && (v != NULL));
    // If ulen > 0, then the leading digit of u must be non-zero.
    sc_assert((ulen <= 0) || (u[ulen - 1] != 0));
    sc_assert((vlen <= 0) || (v[vlen - 1] != 0));
#endif

    if (ulen != vlen)
        return (ulen - vlen);

    // ulen == vlen >= 1
    while ((--ulen >= 0) && (u[ulen] == v[ulen]))
    {}

    if (ulen < 0)
        return 0;

#ifdef DEBUG_SYSTEMC
    // Test to see if the result is wrong due to the presence of
    // overflow bits.
    sc_assert((u[ulen] & DIGIT_MASK) != (v[ulen] & DIGIT_MASK));
#endif

    return (int)(u[ulen] - v[ulen]);
}

// Find the index of the first non-zero digit.
// - ulen (before) = the number of digits in u.
// - the returned value = the index of the first non-zero digit.
// A negative value of -1 indicates that every digit in u is zero.
inline int
vec_find_first_nonzero(int ulen, const sc_digit *u)
{

#ifdef DEBUG_SYSTEMC
    // sc_assert((ulen <= 0) || (u != NULL));
    sc_assert((ulen > 0) && (u != NULL));
#endif

    while ((--ulen >= 0) && (! u[ulen]))
    {}

    return ulen;
}

// Skip all the leading zero digits.
// - ulen (before) = the number of digits in u.
// - the returned value = the number of non-zero digits in u.
// - the returned value is non-negative.
inline int
vec_skip_leading_zeros(int ulen, const sc_digit *u)
{
#ifdef DEBUG_SYSTEMC
    // sc_assert((ulen <= 0) || (u != NULL));
    sc_assert((ulen > 0) && (u != NULL));
#endif

    return (1 + vec_find_first_nonzero(ulen, u));
}

// Compare u and v and return r
//  r = 0 if u == v
//  r < 0 if u < v
//  r > 0 if u > v
inline int
vec_skip_and_cmp(int ulen, const sc_digit *u, int vlen, const sc_digit *v)
{
#ifdef DEBUG_SYSTEMC
    sc_assert((ulen > 0) && (u != NULL));
    sc_assert((vlen > 0) && (v != NULL));
#endif

    ulen = vec_skip_leading_zeros(ulen, u);
    vlen = vec_skip_leading_zeros(vlen, v);
    // ulen and/or vlen can be equal to zero here.
    return vec_cmp(ulen, u, vlen, v);
}

// Set u[i] = 0 where i = from ... (ulen - 1).
inline void
vec_zero(int from, int ulen, sc_digit *u)
{
#ifdef DEBUG_SYSTEMC
    sc_assert((ulen > 0) && (u != NULL));
#endif
    for (int i = from; i < ulen; i++)
        u[i] = 0;
}

// Set u[i] = 0 where i = 0 .. (ulen - 1).
inline void vec_zero(int ulen, sc_digit *u) { vec_zero(0, ulen, u); }

// Copy n digits from v to u.
inline void
vec_copy(int n, sc_digit *u, const sc_digit *v)
{
#ifdef DEBUG_SYSTEMC
    sc_assert((n > 0) && (u != NULL) && (v != NULL));
#endif
    for (int i = 0; i < n; ++i)
        u[i] = v[i];
}

// Copy v to u, where ulen >= vlen, and zero the rest of the digits in u.
inline void
vec_copy_and_zero(int ulen, sc_digit *u, int vlen, const sc_digit *v)
{

#ifdef DEBUG_SYSTEMC
    sc_assert((ulen > 0) && (u != NULL));
    sc_assert((vlen > 0) && (v != NULL));
    sc_assert(ulen >= vlen);
#endif
    vec_copy(vlen, u, v);
    vec_zero(vlen, ulen, u);

}

// 2's-complement the digits in u.
inline void
vec_complement(int ulen, sc_digit *u)
{

#ifdef DEBUG_SYSTEMC
    sc_assert((ulen > 0) && (u != NULL));
#endif

    sc_digit carry = 1;

    for (int i = 0; i < ulen; ++i) {
        carry += (~u[i] & DIGIT_MASK);
        u[i] = carry & DIGIT_MASK;
        carry >>= BITS_PER_DIGIT;
    }
}


// ----------------------------------------------------------------------------
//  Functions to handle built-in types or signs.
// ----------------------------------------------------------------------------

// u = v
// - v is an unsigned long or uint64, and positive integer.
template<class Type>
inline void
from_uint(int ulen, sc_digit *u, Type v)
{
#ifdef DEBUG_SYSTEMC
    // sc_assert((ulen <= 0) || (u != NULL));
    sc_assert((ulen > 0) && (u != NULL));
    sc_assert(v >= 0);
#endif

    int i = 0;

    while (v && (i < ulen)) {
        u[i++] = static_cast<sc_digit>(v & DIGIT_MASK);
        v >>= BITS_PER_DIGIT;
    }
    vec_zero(i, ulen, u);
}

#ifndef __GNUC__
#  define SC_LIKELY_(x) !!(x)
#else
#  define SC_LIKELY_(x) __builtin_expect(!!(x), 1)
#endif

// Get u's sign and return its absolute value.
// u can be long, unsigned long, int64, or uint64.
template<class Type>
inline small_type
get_sign(Type &u)
{
    if (u > 0)
        return SC_POS;

    if (u == 0)
        return SC_ZERO;

    // no positive number representable for minimum value,
    // leave as is to avoid Undefined Behaviour
    if (SC_LIKELY_(u > (std::numeric_limits<Type>::min)()))
        u = -u;

    return SC_NEG;
}

#undef SC_LIKELY_


// Return us * vs:
// - Return SC_ZERO if either sign is SC_ZERO.
// - Return SC_POS if us == vs
// - Return SC_NEG if us != vs.
inline small_type
mul_signs(small_type us, small_type vs)
{
    if ((us == SC_ZERO) || (vs == SC_ZERO))
        return SC_ZERO;

    if (us == vs)
        return SC_POS;

    return SC_NEG;
}


// ----------------------------------------------------------------------------
//  Functions to test for errors and print out error messages.
// ----------------------------------------------------------------------------

#ifdef SC_MAX_NBITS

void test_bound_failed(int nb);

inline void
test_bound(int nb)
{
    if (nb > SC_MAX_NBITS) {
        test_bound_failed(nb);
        sc_core::sc_abort(); // can't recover from here
    }
}

#endif

template<class Type>
inline void
div_by_zero(Type s)
{
    if (s == 0) {
        SC_REPORT_ERROR(sc_core::SC_ID_OPERATION_FAILED_,
                        "div_by_zero<Type>(Type) : division by zero");
        sc_core::sc_abort(); // can't recover from here
    }
}


// ----------------------------------------------------------------------------
//  Functions to check if a given vector is zero or make one.
// ----------------------------------------------------------------------------

// If u[i] is zero for every i = 0,..., ulen - 1, return SC_ZERO,
// else return s.
inline small_type
check_for_zero(small_type s, int ulen, const sc_digit *u)
{

#ifdef DEBUG_SYSTEMC
    // sc_assert(ulen >= 0);
    sc_assert((ulen > 0) && (u != NULL));
#endif

    if (vec_find_first_nonzero(ulen, u) < 0)
        return SC_ZERO;

    return s;
}

// If u[i] is zero for every i = 0,..., ulen - 1, return true,
// else return false.
inline bool
check_for_zero(int ulen, const sc_digit *u)
{

#ifdef DEBUG_SYSTEMC
    // sc_assert(ulen >= 0);
    sc_assert((ulen > 0) && (u != NULL));
#endif

    if (vec_find_first_nonzero(ulen, u) < 0)
        return true;

    return false;
}

inline small_type
make_zero(int nd, sc_digit *d)
{
    vec_zero(nd, d);
    return SC_ZERO;
}


// ----------------------------------------------------------------------------
//  Functions for both signed and unsigned numbers to convert sign-magnitude
//  (SM) and 2's complement (2C) representations.
//  added = 1 => for signed.
//  added = 0 => for unsigned.
//  IF_SC_SIGNED can be used as 'added'.
// ----------------------------------------------------------------------------

// Trim the extra leading bits of a signed or unsigned number.
inline void
trim(small_type added, int nb, int nd, sc_digit *d)
{
#ifdef DEBUG_SYSTEMC
    sc_assert((nb > 0) && (nd > 0) && (d != NULL));
#endif
    d[nd - 1] &= one_and_ones(bit_ord(nb - 1) + added);
}

// Convert an (un)signed number from sign-magnitude representation to
// 2's complement representation and trim the extra bits.
inline void
convert_SM_to_2C_trimmed(small_type added,
                         small_type s, int nb, int nd, sc_digit *d)
{
    if (s == SC_NEG) {
        vec_complement(nd, d);
        trim(added, nb, nd, d);
    }
}

// Convert an (un)signed number from sign-magnitude representation to
// 2's complement representation but do not trim the extra bits.
inline void
convert_SM_to_2C(small_type s, int nd, sc_digit *d)
{
    if (s == SC_NEG)
        vec_complement(nd, d);
}


// ----------------------------------------------------------------------------
//  Functions to convert between sign-magnitude (SM) and 2's complement
//  (2C) representations of signed numbers.
// ----------------------------------------------------------------------------

// Trim the extra leading bits off a signed number.
inline void
trim_signed(int nb, int nd, sc_digit *d)
{
#ifdef DEBUG_SYSTEMC
    sc_assert((nb > 0) && (nd > 0) && (d != NULL));
#endif
    d[nd - 1] &= one_and_ones(bit_ord(nb - 1) + 1);
}

// Convert a signed number from 2's complement representation to
// sign-magnitude representation, and return its sign. nd is d's
// actual size, without zeros eliminated.
inline small_type
convert_signed_2C_to_SM(int nb, int nd, sc_digit *d)
{
#ifdef DEBUG_SYSTEMC
    sc_assert((nb > 0) && (nd > 0) && (d != NULL));
#endif

    small_type s;

    int xnb = bit_ord(nb - 1) + 1;

    // Test the sign bit.
    if (d[nd - 1] & one_and_zeros(xnb - 1)) {
        s = SC_NEG;
        vec_complement(nd, d);
    } else {
        s = SC_POS;
    }

    // Trim the last digit.
    d[nd - 1] &= one_and_ones(xnb);

    // Check if the new number is zero.
    if (s == SC_POS)
        return check_for_zero(s, nd, d);

    return s;
}

// Convert a signed number from sign-magnitude representation to 2's
// complement representation, get its sign, convert back to
// sign-magnitude representation, and return its sign. nd is d's
// actual size, without zeros eliminated.
inline small_type
convert_signed_SM_to_2C_to_SM(small_type s, int nb, int nd, sc_digit *d)
{
    convert_SM_to_2C(s, nd, d);
    return convert_signed_2C_to_SM(nb, nd, d);
}

// Convert a signed number from sign-magnitude representation to 2's
// complement representation and trim the extra bits.
inline void
convert_signed_SM_to_2C_trimmed(small_type s, int nb, int nd, sc_digit *d)
{
    convert_SM_to_2C_trimmed(1, s, nb, nd, d);
}

// Convert a signed number from sign-magnitude representation to 2's
// complement representation but do not trim the extra bits.
inline void
convert_signed_SM_to_2C(small_type s, int nd, sc_digit *d)
{
    convert_SM_to_2C(s, nd, d);
}


// ----------------------------------------------------------------------------
//  Functions to convert between sign-magnitude (SM) and 2's complement
//  (2C) representations of unsigned numbers.
// ----------------------------------------------------------------------------

// Trim the extra leading bits off an unsigned number.
inline void
trim_unsigned(int nb, int nd, sc_digit *d)
{
#ifdef DEBUG_SYSTEMC
    sc_assert((nb > 0) && (nd > 0) && (d != NULL));
#endif

    d[nd - 1] &= one_and_ones(bit_ord(nb - 1));
}

// Convert an unsigned number from 2's complement representation to
// sign-magnitude representation, and return its sign. nd is d's
// actual size, without zeros eliminated.
inline small_type
convert_unsigned_2C_to_SM(int nb, int nd, sc_digit *d)
{
    trim_unsigned(nb, nd, d);
    return check_for_zero(SC_POS, nd, d);
}

// Convert an unsigned number from sign-magnitude representation to
// 2's complement representation, get its sign, convert back to
// sign-magnitude representation, and return its sign. nd is d's
// actual size, without zeros eliminated.
inline small_type
convert_unsigned_SM_to_2C_to_SM(small_type s, int nb, int nd, sc_digit *d)
{
    convert_SM_to_2C(s, nd, d);
    return convert_unsigned_2C_to_SM(nb, nd, d);
}

// Convert an unsigned number from sign-magnitude representation to
// 2's complement representation and trim the extra bits.
inline void
convert_unsigned_SM_to_2C_trimmed(small_type s, int nb, int nd, sc_digit *d)
{
    convert_SM_to_2C_trimmed(0, s, nb, nd, d);
}

// Convert an unsigned number from sign-magnitude representation to
// 2's complement representation but do not trim the extra bits.
inline void
convert_unsigned_SM_to_2C(small_type s, int nd, sc_digit *d)
{
    convert_SM_to_2C(s, nd, d);
}


// ----------------------------------------------------------------------------
//  Functions to copy one (un)signed number to another.
// ----------------------------------------------------------------------------

// Copy v to u.
inline void
copy_digits_signed(small_type &us,
                   int unb, int und, sc_digit *ud,
                   int vnb, int vnd, const sc_digit *vd)
{
    if (und <= vnd) {
        vec_copy(und, ud, vd);

        if (unb <= vnb)
            us = convert_signed_SM_to_2C_to_SM(us, unb, und, ud);
    } else { // und > vnd
        vec_copy_and_zero(und, ud, vnd, vd);
    }
}

// Copy v to u.
inline void
copy_digits_unsigned(small_type &us,
                     int unb, int und, sc_digit *ud,
                     int /* vnb */, int vnd, const sc_digit *vd)
{
    if (und <= vnd)
        vec_copy(und, ud, vd);
    else // und > vnd
        vec_copy_and_zero(und, ud, vnd, vd);

    us = convert_unsigned_SM_to_2C_to_SM(us, unb, und, ud);
}


// ----------------------------------------------------------------------------
//  Faster set(i, v), without bound checking.
// ----------------------------------------------------------------------------

// A version of set(i, v) without bound checking.
inline void
safe_set(int i, bool v, sc_digit *d)
{

#ifdef DEBUG_SYSTEMC
    sc_assert((i >= 0) && (d != NULL));
#endif

    int bit_num = bit_ord(i);
    int digit_num = digit_ord(i);

    if (v)
        d[digit_num] |= one_and_zeros(bit_num);
    else
        d[digit_num] &= ~(one_and_zeros(bit_num));
}


// ----------------------------------------------------------------------------
//  Function to check if a double number is bad (NaN or infinite).
// ----------------------------------------------------------------------------

inline bool
is_nan(double v)
{
    return std::numeric_limits<double>::has_quiet_NaN && (v != v);
}

inline bool
is_inf(double v)
{
    return v ==  std::numeric_limits<double>::infinity() ||
           v == -std::numeric_limits<double>::infinity();
}

inline void
is_bad_double(double v)
{
    // Windows throws exception.
    if (is_nan(v) || is_inf(v))
        SC_REPORT_ERROR(sc_core::SC_ID_VALUE_NOT_VALID_,
                        "is_bad_double(double v) : "
                        "v is not finite - NaN or Inf");
}

} // namespace sc_dt

#endif // __SYSTEMC_EXT_DT_INT_SC_NBUTILS_HH__