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verinum.cc
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verinum.cc
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/*
* Copyright (c) 1998-2021 Stephen Williams (steve@icarus.com)
*
* This source code is free software; you can redistribute it
* and/or modify it in source code form under the terms of the GNU
* General Public License as published by the Free Software
* Foundation; either version 2 of the License, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
# include "config.h"
# include "verinum.h"
# include <iostream>
# include <cassert>
# include <climits>
# include <cmath> // Needed to get pow for as_double().
# include <cstdio> // Needed to get snprintf for as_string().
# include <algorithm>
using namespace std;
#if !defined(HAVE_LROUND)
/*
* If the system doesn't provide the lround function, then we provide
* it ourselves here. It is simply the nearest integer, rounded away
* from zero.
*/
extern "C" long int lround(double x)
{
if (x >= 0.0)
return (long)floor(x+0.5);
else
return (long)ceil(x-0.5);
}
#endif
static verinum::V add_with_carry(verinum::V l, verinum::V r, verinum::V&c);
verinum::verinum()
: bits_(0), nbits_(0), has_len_(false), has_sign_(false), is_single_(false), string_flag_(false)
{
}
verinum::verinum(const V*bits, unsigned nbits, bool has_len__)
: has_len_(has_len__), has_sign_(false), is_single_(false), string_flag_(false)
{
nbits_ = nbits;
bits_ = new V [nbits];
for (unsigned idx = 0 ; idx < nbits ; idx += 1) {
bits_[idx] = bits[idx];
}
}
static string process_verilog_string_quotes(const string&str)
{
string res;
int idx = 0;
int str_len = str.length();
while (idx < str_len) {
if (str[idx] == '\\') {
idx += 1;
assert(idx < str_len);
switch (str[idx]) {
case 'n':
res = res + '\n';
idx += 1;
break;
case 't':
res = res + '\t';
idx += 1;
break;
case 'v':
res = res + '\v';
idx += 1;
break;
case 'f':
res = res + '\f';
idx += 1;
break;
case 'a':
res = res + '\a';
idx += 1;
break;
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7': {
char byte_val = 0;
int odx = 0;
while (odx < 3 && idx+odx < str_len
&& str[idx+odx] >= '0'
&& str[idx+odx] <= '7') {
byte_val = 8*byte_val + str[idx+odx]-'0';
odx += 1;
}
idx += odx;
res = res + byte_val;
break;
}
case 'x': {
char byte_val = 0;
int odx = 1;
while (odx < 3 && idx+odx < str_len) {
if (str[idx+odx] >= '0' && str[idx+odx] <= '9') {
byte_val = 16*byte_val + str[idx+odx]-'0';
odx += 1;
} else if (str[idx+odx] >= 'a' && str[idx+odx] <= 'f') {
byte_val = 16*byte_val + str[idx+odx]-'a'+10;
odx += 1;
} else if (str[idx+odx] >= 'A' && str[idx+odx] <= 'F') {
byte_val = 16*byte_val + str[idx+odx]-'A'+10;
odx += 1;
} else {
break;
}
}
idx += odx;
res = res + byte_val;
break;
}
default:
res = res + str[idx];
idx += 1;
break;
}
} else {
res = res + str[idx];
idx += 1;
}
}
return res;
}
verinum::verinum(const string&s)
: has_len_(true), has_sign_(false), is_single_(false), string_flag_(true)
{
string str = process_verilog_string_quotes(s);
nbits_ = str.length() * 8;
// Special case: The string "" is 8 bits of 0.
if (nbits_ == 0) {
nbits_ = 8;
bits_ = new V [nbits_];
bits_[0] = V0;
bits_[1] = V0;
bits_[2] = V0;
bits_[3] = V0;
bits_[4] = V0;
bits_[5] = V0;
bits_[6] = V0;
bits_[7] = V0;
return;
}
bits_ = new V [nbits_];
unsigned idx, cp;
V*bp = bits_+nbits_;
for (idx = nbits_, cp = 0 ; idx > 0 ; idx -= 8, cp += 1) {
char ch = str[cp];
*(--bp) = (ch&0x80) ? V1 : V0;
*(--bp) = (ch&0x40) ? V1 : V0;
*(--bp) = (ch&0x20) ? V1 : V0;
*(--bp) = (ch&0x10) ? V1 : V0;
*(--bp) = (ch&0x08) ? V1 : V0;
*(--bp) = (ch&0x04) ? V1 : V0;
*(--bp) = (ch&0x02) ? V1 : V0;
*(--bp) = (ch&0x01) ? V1 : V0;
}
}
verinum::verinum(verinum::V val, unsigned n, bool h)
: has_len_(h), has_sign_(false), is_single_(false), string_flag_(false)
{
nbits_ = n;
bits_ = new V[nbits_];
for (unsigned idx = 0 ; idx < nbits_ ; idx += 1)
bits_[idx] = val;
}
verinum::verinum(uint64_t val, unsigned n)
: has_len_(true), has_sign_(false), is_single_(false), string_flag_(false)
{
nbits_ = n;
bits_ = new V[nbits_];
for (unsigned idx = 0 ; idx < nbits_ ; idx += 1) {
bits_[idx] = (val&1) ? V1 : V0;
val >>= (uint64_t)1;
}
}
/* The second argument is not used! It is there to make this
* constructor unique. */
verinum::verinum(double val, bool)
: has_len_(false), has_sign_(true), is_single_(false), string_flag_(false)
{
bool is_neg = false;
double fraction;
int exponent;
const unsigned BITS_IN_LONG = 8*sizeof(long);
/* We return `bx for a NaN or +/- infinity. */
if (val != val || (val && (val == 0.5*val))) {
nbits_ = 1;
bits_ = new V[nbits_];
bits_[0] = Vx;
return;
}
/* Convert to a positive result. */
if (val < 0.0) {
is_neg = true;
val = -val;
}
/* Round to the nearest integer now, as this may increase the
number of bits we need to allocate. */
val = round(val);
/* Get the exponent and fractional part of the number. */
fraction = frexp(val, &exponent);
nbits_ = exponent+1;
bits_ = new V[nbits_];
/* If the value is small enough just use lround(). */
if (nbits_ <= BITS_IN_LONG) {
long sval = lround(val);
if (is_neg) sval = -sval;
for (unsigned idx = 0; idx < nbits_; idx += 1) {
bits_[idx] = (sval&1) ? V1 : V0;
sval >>= 1;
}
/* Trim the result. */
signed_trim();
return;
}
unsigned nwords = (exponent-1)/BITS_IN_LONG;
fraction = ldexp(fraction, (exponent-1) % BITS_IN_LONG + 1);
if (nwords == 0) {
unsigned long bits = (unsigned long) fraction;
fraction = fraction - (double) bits;
for (unsigned idx = 0; idx < nbits_; idx += 1) {
bits_[idx] = (bits&1) ? V1 : V0;
bits >>= 1;
}
} else {
for (int wd = nwords; wd >= 0; wd -= 1) {
unsigned long bits = (unsigned long) fraction;
fraction = fraction - (double) bits;
unsigned max_idx = (wd+1)*BITS_IN_LONG;
if (max_idx > nbits_) max_idx = nbits_;
for (unsigned idx = wd*BITS_IN_LONG; idx < max_idx; idx += 1) {
bits_[idx] = (bits&1) ? V1 : V0;
bits >>= 1;
}
fraction = ldexp(fraction, BITS_IN_LONG);
}
}
/* Convert a negative number if needed. */
if (is_neg) {
*this = -(*this);
}
/* Trim the result. */
signed_trim();
}
/* This is used by the double constructor above. It is needed to remove
* extra sign bits that can occur when calculating a negative value. */
void verinum::signed_trim()
{
/* Do we have any extra digits? */
unsigned tlen = nbits_-1;
verinum::V sign = bits_[tlen];
while ((tlen > 0) && (bits_[tlen] == sign)) tlen -= 1;
/* tlen now points to the first digit that is not the sign.
* or bit 0. Set the length to include this bit and one proper
* sign bit if needed. */
if (bits_[tlen] != sign) tlen += 1;
tlen += 1;
/* Trim the bits if needed. */
if (tlen < nbits_) {
V* tbits = new V[tlen];
for (unsigned idx = 0; idx < tlen; idx += 1)
tbits[idx] = bits_[idx];
delete[] bits_;
bits_ = tbits;
nbits_ = tlen;
}
}
verinum::verinum(const verinum&that)
{
string_flag_ = that.string_flag_;
nbits_ = that.nbits_;
bits_ = new V[nbits_];
has_len_ = that.has_len_;
has_sign_ = that.has_sign_;
is_single_ = that.is_single_;
for (unsigned idx = 0 ; idx < nbits_ ; idx += 1)
bits_[idx] = that.bits_[idx];
}
verinum::verinum(const verinum&that, unsigned nbits)
{
string_flag_ = that.string_flag_ && (that.nbits_ == nbits);
nbits_ = nbits;
bits_ = new V[nbits_];
has_len_ = true;
has_sign_ = that.has_sign_;
is_single_ = false;
unsigned copy = nbits;
if (copy > that.nbits_)
copy = that.nbits_;
for (unsigned idx = 0 ; idx < copy ; idx += 1)
bits_[idx] = that.bits_[idx];
if (copy < nbits_) {
if (has_sign_ || that.is_single_) {
for (unsigned idx = copy ; idx < nbits_ ; idx += 1)
bits_[idx] = bits_[idx-1];
} else {
for (unsigned idx = copy ; idx < nbits_ ; idx += 1)
bits_[idx] = verinum::V0;
}
}
}
verinum::verinum(int64_t that)
: has_len_(false), has_sign_(true), is_single_(false), string_flag_(false)
{
int64_t tmp;
if (that < 0) tmp = (that+1)/2;
else tmp = that/2;
nbits_ = 1;
while (tmp != 0) {
nbits_ += 1;
tmp /= 2;
}
nbits_ += 1;
bits_ = new V[nbits_];
for (unsigned idx = 0 ; idx < nbits_ ; idx += 1) {
bits_[idx] = (that & 1)? V1 : V0;
that >>= 1;
}
}
verinum::~verinum()
{
delete[]bits_;
}
verinum& verinum::operator= (const verinum&that)
{
if (this == &that) return *this;
if (nbits_ != that.nbits_) {
delete[]bits_;
nbits_ = that.nbits_;
bits_ = new V[that.nbits_];
}
for (unsigned idx = 0 ; idx < nbits_ ; idx += 1)
bits_[idx] = that.bits_[idx];
has_len_ = that.has_len_;
has_sign_ = that.has_sign_;
is_single_ = that.is_single_;
string_flag_ = that.string_flag_;
return *this;
}
verinum::V verinum::get(unsigned idx) const
{
assert(idx < nbits_);
return bits_[idx];
}
verinum::V verinum::set(unsigned idx, verinum::V val)
{
assert(idx < nbits_);
return bits_[idx] = val;
}
void verinum::set(unsigned off, const verinum&val)
{
assert(off + val.len() <= nbits_);
for (unsigned idx = 0 ; idx < val.len() ; idx += 1)
bits_[off+idx] = val[idx];
}
unsigned verinum::as_unsigned() const
{
if (nbits_ == 0)
return 0;
if (!is_defined())
return 0;
unsigned val = 0;
unsigned mask = 1;
for (unsigned idx = 0 ; idx < nbits_ ; idx += 1, mask <<= 1)
if (bits_[idx] == V1) {
if (mask == 0) return ~mask;
val |= mask;
}
return val;
}
unsigned long verinum::as_ulong() const
{
if (nbits_ == 0)
return 0;
if (!is_defined())
return 0;
unsigned long val = 0;
unsigned long mask = 1;
for (unsigned idx = 0 ; idx < nbits_ ; idx += 1, mask <<= 1)
if (bits_[idx] == V1) {
if (mask == 0) return ~mask;
val |= mask;
}
return val;
}
uint64_t verinum::as_ulong64() const
{
if (nbits_ == 0)
return 0;
if (!is_defined())
return 0;
uint64_t val = 0;
uint64_t mask = 1;
for (unsigned idx = 0 ; idx < nbits_ ; idx += 1, mask <<= 1)
if (bits_[idx] == V1) {
if (mask == 0) return ~mask;
val |= mask;
}
return val;
}
/*
* This function returns the native long integer that represents the
* value of this object. It accounts for sign extension if the value
* is signed.
*
* If the value is undefined, return 0.
*
* This function presumes that the native format is 2s complement
* (pretty safe these days) and masks/sets bits accordingly. If the
* value is too large for the native form, it truncates the high bits.
*/
signed long verinum::as_long() const
{
#define IVLLBITS (8 * sizeof(long) - 1)
if (nbits_ == 0)
return 0;
if (!is_defined())
return 0;
signed long val = 0;
unsigned diag_top = 0;
unsigned top = nbits_;
if (top > IVLLBITS) {
diag_top = top;
top = IVLLBITS;
}
int lost_bits=0;
if (has_sign_ && (bits_[nbits_-1] == V1)) {
val = -1;
signed long mask = ~1L;
for (unsigned idx = 0 ; idx < top ; idx += 1) {
if (bits_[idx] == V0) val &= mask;
mask = (mask << 1) | 1L;
}
if (diag_top) {
for (unsigned idx = top; idx < diag_top; idx += 1) {
if (bits_[idx] == V0) lost_bits=1;
}
}
} else {
signed long mask = 1;
for (unsigned idx = 0 ; idx < top ; idx += 1, mask <<= 1) {
if (bits_[idx] == V1) val |= mask;
}
if (diag_top) {
for (unsigned idx = top; idx < diag_top; idx += 1) {
if (bits_[idx] == V1) lost_bits=1;
}
}
}
if (lost_bits) cerr << "warning: verinum::as_long() truncated " <<
diag_top << " bits to " << IVLLBITS << ", returns " << val << endl;
return val;
#undef IVLLBITS
}
double verinum::as_double() const
{
if (nbits_ == 0) return 0.0;
double val = 0.0;
/* Do we have/want a signed value? */
if (has_sign_ && bits_[nbits_-1] == V1) {
V carry = V1;
for (unsigned idx = 0; idx < nbits_; idx += 1) {
V sum = add_with_carry(~bits_[idx], V0, carry);
if (sum == V1)
val += pow(2.0, (double)idx);
}
val *= -1.0;
} else {
for (unsigned idx = 0; idx < nbits_; idx += 1) {
if (bits_[idx] == V1)
val += pow(2.0, (double)idx);
}
}
return val;
}
string verinum::as_string() const
{
assert( nbits_%8 == 0 );
if (nbits_ == 0)
return "";
string res;
for (unsigned idx = nbits_ ; idx > 0 ; idx -= 8) {
char char_val = 0;
V*bp = bits_+idx;
if (*(--bp) == V1) char_val |= 0x80;
if (*(--bp) == V1) char_val |= 0x40;
if (*(--bp) == V1) char_val |= 0x20;
if (*(--bp) == V1) char_val |= 0x10;
if (*(--bp) == V1) char_val |= 0x08;
if (*(--bp) == V1) char_val |= 0x04;
if (*(--bp) == V1) char_val |= 0x02;
if (*(--bp) == V1) char_val |= 0x01;
if (char_val == '"' || char_val == '\\') {
char tmp[5];
snprintf(tmp, sizeof tmp, "\\%03o", char_val);
res = res + tmp;
} else if (isprint(char_val)) {
res = res + char_val;
} else {
char tmp[5];
snprintf(tmp, sizeof tmp, "\\%03o", (unsigned char)char_val);
res = res + tmp;
}
}
return res;
}
bool verinum::is_before(const verinum&that) const
{
if (that.nbits_ > nbits_) return true;
if (that.nbits_ < nbits_) return false;
for (unsigned idx = nbits_ ; idx > 0 ; idx -= 1) {
if (bits_[idx-1] < that.bits_[idx-1]) return true;
if (bits_[idx-1] > that.bits_[idx-1]) return false;
}
return false;
}
bool verinum::is_defined() const
{
for (unsigned idx = 0 ; idx < nbits_ ; idx += 1) {
if (bits_[idx] == Vx) return false;
if (bits_[idx] == Vz) return false;
}
return true;
}
bool verinum::is_zero() const
{
for (unsigned idx = 0 ; idx < nbits_ ; idx += 1)
if (bits_[idx] != V0) return false;
return true;
}
bool verinum::is_negative() const
{
return (bits_[nbits_-1] == V1) && has_sign();
}
unsigned verinum::significant_bits() const
{
unsigned sbits = nbits_;
if (has_sign_) {
V sgn_bit = bits_[sbits-1];
while ((sbits > 1) && (bits_[sbits-2] == sgn_bit))
sbits -= 1;
} else {
while ((sbits > 1) && (bits_[sbits-1] == verinum::V0))
sbits -= 1;
}
return sbits;
}
void verinum::cast_to_int2()
{
for (unsigned idx = 0 ; idx < nbits_ ; idx += 1) {
if (bits_[idx] == Vx || bits_[idx] == Vz)
bits_[idx] = V0;
}
}
verinum pad_to_width(const verinum&that, unsigned width)
{
if (that.len() >= width)
return that;
if (that.len() == 0) {
verinum val (verinum::V0, width, that.has_len());
val.has_sign(that.has_sign());
return val;
}
verinum::V pad = that[that.len()-1];
if (pad==verinum::V1 && !that.has_sign() && !that.is_single())
pad = verinum::V0;
if (that.has_len() && !that.has_sign() && !that.is_single()) {
if (pad==verinum::Vx)
pad = verinum::V0;
if (pad==verinum::Vz)
pad = verinum::V0;
}
verinum val(pad, width, that.has_len());
for (unsigned idx = 0 ; idx < that.len() ; idx += 1)
val.set(idx, that[idx]);
val.has_sign(that.has_sign());
if (that.is_string() && (width % 8) == 0) {
val = verinum(val.as_string());
}
return val;
}
verinum cast_to_width(const verinum&that, unsigned width)
{
if (that.has_len() && (that.len() == width))
return that;
if (that.len() >= width)
return verinum(that, width);
if (that.len() == 0) {
verinum val (verinum::V0, width, true);
val.has_sign(that.has_sign());
return val;
}
verinum::V pad = that[that.len()-1];
if (pad==verinum::V1 && !that.has_sign() && !that.is_single())
pad = verinum::V0;
if (that.has_len() && !that.has_sign() && !that.is_single()) {
if (pad==verinum::Vx)
pad = verinum::V0;
if (pad==verinum::Vz)
pad = verinum::V0;
}
verinum val(pad, width, true);
for (unsigned idx = 0 ; idx < that.len() ; idx += 1)
val.set(idx, that[idx]);
val.has_sign(that.has_sign());
return val;
}
/*
* This function returns a version of the verinum that has only as
* many bits as are needed to accurately represent the value. It takes
* into account the signedness of the value.
*
* If the input value has a definite length, then that value is just
* returned as is.
*/
verinum trim_vnum(const verinum&that)
{
unsigned tlen;
if (that.has_len())
return that;
if (that.len() < 2)
return that;
if (that.has_sign()) {
unsigned top = that.len()-1;
verinum::V sign = that.get(top);
while ((top > 0) && (that.get(top) == sign))
top -= 1;
/* top points to the first digit that is not the
sign. Set the length to include this and one proper
sign bit. */
if (that.get(top) != sign)
top += 1;
tlen = top+1;
} else {
/* If the result is unsigned and has an indefinite
length, then trim off all but one leading zero. */
unsigned top = that.len()-1;
while ((top > 0) && (that.get(top) == verinum::V0))
top -= 1;
/* Now top is the index of the highest non-zero bit. If
that turns out to the highest bit in the vector, then
there is no trimming possible. */
if (top+1 == that.len())
return that;
/* Make tlen wide enough to include the highest non-zero
bit, plus one extra 0 bit. */
tlen = top+2;
/* This can only happen when the verinum is all zeros,
so make it a single bit wide. */
if (that.get(top) == verinum::V0) tlen -= 1;
}
verinum tmp (verinum::V0, tlen, false);
tmp.has_sign(that.has_sign());
for (unsigned idx = 0 ; idx < tmp.len() ; idx += 1)
tmp.set(idx, that.get(idx));
return tmp;
}
ostream& operator<< (ostream&o, verinum::V v)
{
switch (v) {
case verinum::V0:
o << "0";
break;
case verinum::V1:
o << "1";
break;
case verinum::Vx:
o << "x";
break;
case verinum::Vz:
o << "z";
break;
}
return o;
}
/*
* This operator is used by various dumpers to write the Verilog
* number in a Verilog format.
*/
ostream& operator<< (ostream&o, const verinum&v)
{
if (v.is_string()) {
o << "\"" << v.as_string() << "\"";
return o;
}
/* If the verinum number has a fixed length, dump all the bits
literally. This is how we express the fixed length in the
output. */
if (v.has_len()) {
o << v.len();
}
/* If the number is fully defined (no x or z) then print it
out as a decimal number. */
unsigned dec_len = 8*sizeof(int); /* avoid 32/64 bit differences. */
if (! v.has_sign()) dec_len -= 1; /* an unsigned number. */
if (v.is_defined() && v.len() <= dec_len) {
if (v.has_sign())
o << "'sd" << v.as_long();
else
o << "'d" << v.as_ulong();
return o;
}
/* Oh, well. Print the minimum to get the value properly
displayed. */
if (v.has_sign())
o << "'sb";
else
o << "'b";
if (v.len() == 0) {
o << "0";
return o;
}
verinum::V trim_left = v.get(v.len()-1);
unsigned idx;
if (v.has_sign()) {
for (idx = v.len()-1; idx > 0; idx -= 1)
if (trim_left != v.get(idx-1))
break;
o << trim_left;
} else {
idx = v.len();
}
while (idx > 0) {
o << v.get(idx-1);
idx -= 1;
}
return o;
}
verinum::V operator == (const verinum&left, const verinum&right)
{
verinum::V left_pad = verinum::V0;
verinum::V right_pad = verinum::V0;
if (left.has_sign() && right.has_sign()) {
left_pad = left.get(left.len()-1);
right_pad = right.get(right.len()-1);
if (left_pad == verinum::V1 && right_pad == verinum::V0)
return verinum::V0;
if (left_pad == verinum::V0 && right_pad == verinum::V1)
return verinum::V0;
}
unsigned max_len = left.len();
if (right.len() > max_len)
max_len = right.len();
for (unsigned idx = 0 ; idx < max_len ; idx += 1) {
verinum::V left_bit = idx < left.len() ? left[idx] : left_pad;
verinum::V right_bit = idx < right.len()? right[idx] : right_pad;
if (left_bit != right_bit)
return verinum::V0;
}
return verinum::V1;
}
verinum::V operator <= (const verinum&left, const verinum&right)
{
verinum::V left_pad = verinum::V0;
verinum::V right_pad = verinum::V0;
bool signed_calc = left.has_sign() && right.has_sign();
if (signed_calc) {
left_pad = left.get(left.len()-1);
right_pad = right.get(right.len()-1);
if (left_pad == verinum::V1 && right_pad == verinum::V0)
return verinum::V1;
if (left_pad == verinum::V0 && right_pad == verinum::V1)
return verinum::V0;
}
unsigned idx;
for (idx = left.len() ; idx > right.len() ; idx -= 1) {
if (left[idx-1] != right_pad) {
// A change of padding for a negative left argument
// denotes the left value is less than the right.
return (signed_calc &&
(left_pad == verinum::V1)) ? verinum::V1 :
verinum::V0;
}
}
for (idx = right.len() ; idx > left.len() ; idx -= 1) {
if (right[idx-1] != left_pad) {
// A change of padding for a negative right argument
// denotes the left value is not less than the right.
return (signed_calc &&
(right_pad == verinum::V1)) ? verinum::V0 :
verinum::V1;
}
}
idx = right.len();
if (left.len() < idx) idx = left.len();
while (idx > 0) {
if (left[idx-1] == verinum::Vx) return verinum::Vx;
if (left[idx-1] == verinum::Vz) return verinum::Vx;
if (right[idx-1] == verinum::Vx) return verinum::Vx;
if (right[idx-1] == verinum::Vz) return verinum::Vx;
if (left[idx-1] > right[idx-1]) return verinum::V0;
if (left[idx-1] < right[idx-1]) return verinum::V1;
idx -= 1;
}
return verinum::V1;
}
verinum::V operator < (const verinum&left, const verinum&right)
{
verinum::V left_pad = verinum::V0;
verinum::V right_pad = verinum::V0;
bool signed_calc = left.has_sign() && right.has_sign();
if (signed_calc) {
left_pad = left.get(left.len()-1);
right_pad = right.get(right.len()-1);
if (left_pad == verinum::V1 && right_pad == verinum::V0)
return verinum::V1;
if (left_pad == verinum::V0 && right_pad == verinum::V1)
return verinum::V0;
}
unsigned idx;
for (idx = left.len() ; idx > right.len() ; idx -= 1) {
if (left[idx-1] != right_pad) {
// A change of padding for a negative left argument
// denotes the left value is less than the right.
return (signed_calc &&
(left_pad == verinum::V1)) ? verinum::V1 :
verinum::V0;
}
}
for (idx = right.len() ; idx > left.len() ; idx -= 1) {
if (right[idx-1] != left_pad) {
// A change of padding for a negative right argument
// denotes the left value is not less than the right.
return (signed_calc &&
(right_pad == verinum::V1)) ? verinum::V0 :
verinum::V1;
}
}
while (idx > 0) {
if (left[idx-1] == verinum::Vx) return verinum::Vx;
if (left[idx-1] == verinum::Vz) return verinum::Vx;
if (right[idx-1] == verinum::Vx) return verinum::Vx;
if (right[idx-1] == verinum::Vz) return verinum::Vx;
if (left[idx-1] > right[idx-1]) return verinum::V0;
if (left[idx-1] < right[idx-1]) return verinum::V1;
idx -= 1;
}
return verinum::V0;
}
static verinum::V add_with_carry(verinum::V l, verinum::V r, verinum::V&c)
{
unsigned sum = 0;
switch (c) {
case verinum::Vx:
case verinum::Vz:
c = verinum::Vx;
return verinum::Vx;
case verinum::V0:
break;