Big-Data-HPC-Platform/rtl/nbcd/nbcd.cpp

/*##############################################################################

    Copyright (C) 2011 HPCC Systems.

    All rights reserved. This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as
    published by the Free Software Foundation, either version 3 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 Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
############################################################################## */

#include "platform.h"
#include "nbcd.hpp"
#include "jlib.hpp"

#ifdef _WIN32
 #define NOMEMCPY volatile          // stop VC++ doing a stupid optimization
#else
 #define NOMEMCPY
#endif

static double Pow10[] = { 1, 10, 100, 1000, 10000, 1e5, 1e6, 1e7, 1e8, 1e9, 1e10,1e11,1e12,1e13,1e14,1e15,1e16 };
int signMap[16] = { 0,0,0,0,0,0,0,0,0,0,+1,-1,+1,-1,+1,+1 };




TempDecimal::TempDecimal(const TempDecimal & other)
{
    memcpy(this, &other, sizeof(*this));
}

TempDecimal & TempDecimal::abs()
{
    negative = false;
    return *this;
}


TempDecimal & TempDecimal::add(const TempDecimal & other)
{
    if (negative == other.negative)
        return addDigits(other);
    else
        return subtractDigits(other);
}



TempDecimal & TempDecimal::addDigits(const TempDecimal & other)
{
    extendRange(other);
    byte oLo = other.lsb;
    byte oHi = other.msb;
    byte hi = msb;

    unsigned idx;
    byte carry = 0;
    for (idx = oLo; (idx <= oHi); idx++)
    {
        digits[idx] += other.digits[idx] + carry;
        carry = 0;
        if (digits[idx] > 9)
        {
            carry++;
            digits[idx] -= 10;
        }
    }

    for (;carry && idx <= hi; idx++)
    {
        digits[idx]++;
        carry = 0;
        if (digits[idx] > 9)
        {
            carry = 1;
            digits[idx] -= 10;
        }
    }

    if (carry && hi != lastDigit)
    {
        digits[++hi] = carry;
        msb = hi;
    }
    return *this;
}

int TempDecimal::compareNull() const
{
    byte idx;
    for (idx = lsb; idx <= msb; idx++)
    {
        if (digits[idx]) return negative ? -1 : +1;
    }
    return 0;
}


int TempDecimal::compare(const TempDecimal & other) const
{
    int lo1, hi1, lo2, hi2;
    clip(lo1, hi1);
    other.clip(lo2, hi2);

    //First check for zero comparison..
    if (lo1 > hi1)
    {
        if (lo2 > hi2)
            return 0;
        return other.negative ? +1 : -1;
    }
    if (lo2 > hi2)
        return negative ? -1 : +1;

    if (negative ^ other.negative)
        return negative ? -1 : +1;

    if (hi1 != hi2)
        return (hi1 > hi2) ^ negative ? +1 : -1;

    int limit = lo1 < lo2 ? lo2 : lo1;
    for (;hi1 >= limit; hi1--)
    {
        int diff = digits[hi1] - other.digits[hi1];
        if (diff != 0)
            return (diff > 0) ^ negative ? +1 : -1;
    }

    if (lo1 == lo2)
        return 0;
    if (lo1 < lo2)
        return negative ? -1 : +1;
    return negative ? +1 : -1;
}


TempDecimal & TempDecimal::divide(const TempDecimal & other)
{
    //NB: Round towards zero
    int lo1, hi1, lo2, hi2;
    clip(lo1, hi1);
    other.clip(lo2, hi2);

    int nd1 = hi1+1-lo1;
    int nd2 = hi2+1-lo2;
    int hi = (hi1-hi2)+zeroDigit;
    int iters = hi+1;
    if (hi < 0)
    {
        setZero();
        return *this;
    }
    if (hi2 < lo2)
    {
        //divide by zero
        setZero();
        return *this;
    }

    lsb = 0;
    msb = hi >= maxDigits ? maxDigits-1 : hi;

    const byte spare = 2;
    byte temp[maxDigits*2 + 3];
    unsigned numeratorDigits = hi + 1 + nd2;
    memset(temp, 0, numeratorDigits+spare);             // ensure two zero in msb, and below lsb.  Also 2 zeros for looking 2 bytes ahead..

    byte * numerator = temp+spare;
    if (numeratorDigits > nd1)
        memcpy(numerator + numeratorDigits - 1 - nd1, digits+lo1, nd1);
    else
        memcpy(numerator, digits + hi1 + 1 - (numeratorDigits-1), numeratorDigits-1);

    unsigned divisor01 = other.digits[hi2] * 10;
    if (hi2 != lo2)
        divisor01 += other.digits[hi2-1];

    //MORE: Terminate early for exact divide..
    const byte * divisor = other.digits + lo2;
    for (int iter = iters; iter--; )
    {
        //The following guess for q is never too small, may be 1 too large
        byte * curNumerator = numerator + iter;
        unsigned numerator012 = curNumerator[nd2] * 100 + curNumerator[nd2-1] * 10 + curNumerator[nd2-2];
        unsigned q = numerator012 / divisor01;
        if (q == 10) q--;

        if (q)
        {
            unsigned carry = 0;
            for (int i = 0; i < nd2; i++)
            {
                int next = 90 + curNumerator[i] - divisor[i] * q - carry;
                div_t values = div(next, 10);
                carry = 9 - values.quot;
                curNumerator[i] = values.rem;
            }
            carry -= curNumerator[nd2];
            if (carry)
            {
                q--;
                assertex(carry==1);
                carry = 0;
                for (int i = 0; i < nd2; i++)
                {
                    byte next = curNumerator[i] + divisor[i] + carry;
                    carry = 0;
                    if (next >= 10)
                    {
                        next -= 10;
                        carry = 1;
                    }
                    curNumerator[i] = next;
                }
                assertex(carry);
            }
        }
        if (iter < maxDigits)
            digits[iter] = q;
    }
    //MORE: This should really calculate the next digit, and conditionally round the least significant digit.

    negative ^= other.negative;
    return *this;
}


void TempDecimal::extendRange(byte oLsb, byte oMsb)
{
    byte index;
    if (lsb > oLsb)
    {
        for (index = oLsb; index != lsb; index++)
            digits[index] =0;
        lsb = oLsb;
    }
    if (msb < oMsb)
    {
        for (index = msb+1; index <= oMsb; index++)
            digits[index] = 0;
        msb = oMsb;
    }
}


TempDecimal & TempDecimal::modulus(const TempDecimal & other)
{
    TempDecimal left(*this);
    left.divide(other).truncate(0).multiply(other);
    return subtract(left);
}


TempDecimal & TempDecimal::multiply(const TempDecimal & other)
{
    int low1, high1, low2, high2, lowt, hight;

    clip(low1, high1);
    other.clip(low2, high2);
    lowt = low1+low2-zeroDigit;
    if (lowt < 0) lowt = 0;
    hight = high1 + high2 - zeroDigit;
    if (hight >= maxDigits) hight = maxDigits-1;
    else if (hight < 0)
    {
        if (hight < -1)
        {
            setZero();
            return *this;
        }
        hight = 0;
    }


    unsigned temp[maxDigits*2];
    _clear(temp);
//  memset(temp+low1+low2, 0, (high1+high2-low1-low2+2)*sizeof(unsigned));  // only need to clear part of the target we're adding to.

    //More: could copy across 1st time round - might be worth it.
    const byte * digits1 = digits;
    const byte * digits2 = other.digits;
    for (int i = low1; i <= high1; i++)
    {
        byte next = digits1[i];
        if (next)
        {
            for (int j=low2; j <= high2; j++)
                temp[i+j] += next * digits2[j];
        }
    }

    //Now copy the results, taking cary of the carries 
    unsigned carry = 0;
    int j;
    for (j = low1+low2 - zeroDigit; j < lowt; j++)
        carry = (temp[j+zeroDigit]+carry)/10;
    for (j = lowt; j <= hight; j++)
    {
        div_t next = div(temp[j+zeroDigit]+carry, 10);
        digits[j] = next.rem;
        carry = next.quot;
    }
    if ((hight < maxDigits-1) && (carry != 0))
        digits[++hight] = carry % 10;

    lsb = lowt;
    msb = hight;
    negative ^= other.negative;
    return *this;
}


TempDecimal & TempDecimal::negate()
{
    negative = !negative;
    return *this;
}

TempDecimal & TempDecimal::power(unsigned value)
{
    if (value == 0)
        setInt(1);
    else
        doPower(value);
    return *this;
}


TempDecimal & TempDecimal::power(int value)
{
    if ( value >= 0)
        return power((unsigned)value);

#if 1
    //This probably gives slightly more expected results, but both suffer from rounding errors.
    TempDecimal reciprocal;
    reciprocal.setInt(1);
    reciprocal.divide(*this);
    set(reciprocal);
    doPower((unsigned)-value);
    return *this;
#else
    doPower((unsigned)-value);
    TempDecimal reciprocal;
    reciprocal.setInt(1);
    reciprocal.divide(*this);
    set(reciprocal);
    return *this;
#endif
}


TempDecimal & TempDecimal::incLSD()
{
    unsigned index = lsb;
    while (index <= msb)
    {
        if (++digits[index] != 10)
        {
            lsb = index;
            return *this;
        }
        digits[index] = 0;
        index++;
    }
    digits[++msb] = 1;
    return *this;
}


TempDecimal & TempDecimal::round(int places)
{
    //out of range - either 0 or overflow
    if (places < -maxPrecision)
    {
        setZero();
        return *this;
    }
    if (zeroDigit - places <= lsb)
        return *this;

    lsb = zeroDigit - places;
    if (lsb > msb)
    {
        digits[lsb] = 0;
        if ((lsb == msb+1) && digits[msb] >= 5)
            digits[lsb]++;
        msb = lsb;
        return *this;
    }
    if (digits[lsb-1] < 5)
        return *this;

    return incLSD();
}


TempDecimal & TempDecimal::roundup(int places)
{
    if ((places >= maxPrecision) || (zeroDigit - places <= lsb))
        return *this;

    unsigned lower = lsb;
    lsb = zeroDigit - places;
    for (unsigned i=lower; i < lsb; i++)
    {
        if (digits[i])
            return incLSD();
    }
    return *this;
}


void TempDecimal::getPrecision(unsigned & digits, unsigned & precision)
{
    //Ensures digits>=precision && precision >= 0
    unsigned top = msb >= zeroDigit ? msb+1 : zeroDigit;
    unsigned low = lsb >= zeroDigit ? zeroDigit : lsb;
    digits = (top == low) ? 1 : top - low;
    precision = zeroDigit-low;
}

void TempDecimal::getClipPrecision(unsigned & digits, unsigned & precision)
{
    int lo, hi;
    clip(lo, hi);

    if (lo > hi)
    {
        digits = 1;
        precision = 0;
    }
    else
    {
        //Ensures digits>=precision && precision >= 0
        unsigned top = hi >= zeroDigit ? hi+1 : zeroDigit;
        unsigned low = lo >= zeroDigit ? zeroDigit : lo;
        digits = (top == low) ? 1 : top - low;
        precision = zeroDigit-low;
    }
}

TempDecimal & TempDecimal::setPrecision(byte numDigits, byte precision)
{
    unsigned char newhigh = zeroDigit + numDigits - precision - 1;
    unsigned char newlow = zeroDigit - precision;
    if (msb > newhigh)
        msb = newhigh;
    if (lsb < newlow)
        lsb = newlow;
    if (lsb > msb)
    {
        lsb = msb;
        digits[lsb] = 0;
    }
    return *this;
}


TempDecimal & TempDecimal::subtract(const TempDecimal & other)
{
    if (negative != other.negative)
        return addDigits(other);
    else
        return subtractDigits(other);
}


TempDecimal & TempDecimal::subtractDigits(const TempDecimal & other)
{
    extendRange(other);
    byte oLo = other.lsb;
    byte oHi = other.msb;
    byte hi = msb;

    unsigned idx;
    byte carry = 0;
    for (idx = oLo; (idx <= oHi); idx++)
    {
        int next = digits[idx] - (other.digits[idx] + carry);
        carry = 0;
        if (next < 0)
        {
            carry++;
            next += 10;
        }
        digits[idx] = next;
    }

    for (;carry && idx <= hi; idx++)
    {
        digits[idx]--;
        carry = 0;
        if (digits[idx] == 255)
        {
            carry = 1;
            digits[idx] += 10;
        }
    }

    if (carry)
    {
        //underflow => complement the result and add 1
        negative = !negative;
        carry = 1;
        for (idx = lsb; idx <= hi; idx++)
        {
            byte next = 9 - digits[idx] + carry;
            carry = 0;
            if (next == 10)
            {
                carry = 1;
                next -= 10;
            }
            digits[idx] = next;
        }
        assertex(!carry);
    }
    return *this;
}

TempDecimal & TempDecimal::truncate(int places)
{
    //out of range - either 0 or overflow
    if (places <= -maxIntegerDigits)
    {
        setZero();
        return *this;
    }

    if (zeroDigit - places > lsb)
    {
        lsb = zeroDigit - places;
        if (lsb > msb)
        {
            digits[lsb] = 0;
            msb = lsb;
        }
    }
    return *this;
}


size32_t TempDecimal::getStringLength() const
{
    int lo, hi;
    clip(lo, hi);

    if (lo > hi) // (lo == hi) && (digits[lo] == 0))        
        return 1;
    byte top = (hi < zeroDigit) ? zeroDigit-1 : hi;
    byte bottom = (lo > zeroDigit) ? zeroDigit : lo;

    unsigned outLen = (top + 1 - bottom);
    if (negative)           outLen++;       // '-'
    if (lo < zeroDigit) outLen++;       // '.'
    if (hi < zeroDigit) outLen++;       // '0'
    return outLen;
}


void TempDecimal::getCString(size32_t length, char * buffer) const
{
    unsigned len = getStringLength();
    if (len >= length)
    {
        memset(buffer, '*', length-1);
        buffer[length-1] = 0;
        return;
    }

    unsigned written = doGetString(buffer);
    assertex(len == written);
    buffer[len] = 0;
}

char * TempDecimal::getCString() const
{
    unsigned len = getStringLength();
    char * buffer = (char *)malloc(len+1);
    unsigned written = doGetString(buffer);
    assertex(len == written);
    buffer[len] = 0;
    return buffer;
}


void TempDecimal::getDecimal(byte length, byte precision, void * buffer, byte signs) const
{
    doGetDecimal(length, 2*length-1, precision, buffer);
    byte sign = negative ? (signs & 0x0f) : (signs >> 4);
    ((byte *)buffer)[length-1] |= sign;
}


__int64 TempDecimal::getInt64() const
{
    unsigned __int64 value = getUInt64();
    if (negative)
        return -(__int64)value;
    return (__int64)value;
}


int TempDecimal::getInt() const
{
    unsigned int value = getUInt();
    if (negative)
        return -(int) value;
    return (int) value;
}


double TempDecimal::getReal() const
{
    int lo, hi;
    clip(lo, hi);

    double total = 0;
    byte sigDigits = 16; // Only worth taking 16 places over
    int i;
    for (i = hi; sigDigits && i >= lo; i--, sigDigits-- )
        total = total * 10 + digits[i];
    i++;

    if ( i > zeroDigit )
    {
        unsigned amount = i - zeroDigit;
        while ( amount > 15 )
        {
            total *= 1e16;
            amount -= 16;
        }
        total *= Pow10[ amount ];
    }
    else if ( i < zeroDigit )
    {
        unsigned amount = zeroDigit - i;
        while ( amount > 15 )
        {
            total /= 1e16;
            amount -= 16;
        }
        total /= Pow10[ amount ];
    }

    if (negative )
        return -total;
    else
        return total;
}


void TempDecimal::getString(size32_t length, char * buffer) const
{
    unsigned len = getStringLength();
    if (len > length)
    {
        memset(buffer, '*', length);
        return;
    }

    unsigned written = doGetString(buffer);
    assertex(len == written);
    memset(buffer+len, ' ', length-len);
}


void TempDecimal::getStringX(size32_t & length, char * & buffer) const
{
    unsigned len = getStringLength();
    buffer = (char *)malloc(len);
    unsigned written = doGetString(buffer);
    assertex(len == written);
    length = len;
}


void TempDecimal::getUDecimal(byte length, byte precision, void * buffer) const
{
    doGetDecimal(length, 2*length, precision, buffer);
}


unsigned int TempDecimal::getUInt() const
{
    const unsigned hi = msb;
    unsigned int value = 0;
    if (hi >= zeroDigit)
    {
        value = digits[hi];
        unsigned lo = lsb;
        if (lo < zeroDigit)
        {
            for (unsigned idx = hi-1; idx >= zeroDigit; idx--)
                value = value * 10 + digits[idx];
        }
        else
        {
            unsigned idx;
            for (idx = hi-1; idx >= lo; idx--)
                value = value * 10 + digits[idx];
            for (;idx >= zeroDigit;idx--)
                value *= 10;
        }
    }
    return value;
}


unsigned __int64 TempDecimal::getUInt64() const
{
    //MORE: This isn't the most efficient way of doing it - see num2str in jutil for some hints.
    const unsigned hi = msb;
    unsigned __int64 value = 0;
    if (hi >= zeroDigit)
    {
        value = digits[hi];
        unsigned lo = lsb;
        if (lo < zeroDigit)
        {
            for (unsigned idx = hi-1; idx >= zeroDigit; idx--)
                value = value * 10 + digits[idx];
        }
        else
        {
            unsigned idx;
            for (idx = hi-1; idx >= lo; idx--)
                value = value * 10 + digits[idx];
            for (;idx >= zeroDigit;idx--)
                value *= 10;
        }
    }
    return value;
}


void TempDecimal::overflow()
{
}


void TempDecimal::set(const TempDecimal & value)
{
    memcpy(this, &value, sizeof(*this));
}

void TempDecimal::setCString(const char * buffer)
{
    const char * cur = buffer;
    while (*cur == ' ')
        cur++;

    negative = false;
    if (*cur == '-')
    {
        negative = true;
        cur++;
    }

    const char * start = cur;
    while (isdigit(*cur))
        cur++;

    unsigned numDigits = (cur-start);
    if (numDigits > maxIntegerDigits)
    {
        overflow();
        numDigits = maxIntegerDigits;
    }

    int idx;
    for (idx = 0; (unsigned)idx < numDigits; idx++)
        digits[zeroDigit+idx] = cur[-(idx+1)] - '0'; // careful - if idx is unsigned, -(idx+1) is not sign-extended and fails if int size is not pointer size
    msb = zeroDigit+(numDigits-1);

    if (*cur == '.')
    {
        cur++;

        const char * start = cur;
        const char * limit = cur + maxPrecision;
        byte * digit = digits + zeroDigit;
        while ((cur < limit) && (isdigit(*cur)))
            *--digit = *cur++ - '0';
        lsb = zeroDigit - (cur-start);
    }
    else
        lsb = zeroDigit;
}


void TempDecimal::setDecimal(byte length, byte precision, const void * _buffer)
{
    const byte * buffer = (const byte *)_buffer;
    lsb = zeroDigit - precision;
    msb = lsb + length*2 - 2;
    unsigned idx = 0;
    while (msb > maxDigits)
    {
        msb -= 2;
        idx++;
    }
    unsigned cur = msb;
    if (msb == maxDigits)
    {
        msb--;
        cur = msb;
        digits[cur--] = buffer[idx] & 0x0f;
        idx++;
    }
    for (; (int)idx < length-1; idx++)
    {
        byte next = buffer[idx];
        digits[cur--] = next >> 4;
        digits[cur--] = next & 0x0f;
    }
    byte next = buffer[idx];
    digits[cur--] = next >> 4;
    negative = (signMap[next & 0x0f] == -1);
}


void TempDecimal::setInt64(__int64 value)
{
    if (value >= 0)
        setUInt64((unsigned __int64)value);
    else
    {
        setUInt64((unsigned __int64)-value);
        negative = true;
    }
}


void TempDecimal::setInt(int value)
{
    if (value >= 0)
        setUInt((unsigned int)value);
    else
    {
        setUInt((unsigned int)-value);
        negative = true;
    }
}

void TempDecimal::setReal(double value)
{
    setZero();

    int    dec;
    int    sign;
    char digitText[DOUBLE_SIG_DIGITS+2];
    if (!safe_ecvt(sizeof(digitText), digitText, value, DOUBLE_SIG_DIGITS, &dec, &sign))
        return;

    int len = DOUBLE_SIG_DIGITS;
    int hi = zeroDigit - 1 + dec;
    int lo  = hi - (len -1);

    const char * finger = digitText;
    //Number too big - should it create a maximum value? or truncate as it currently does.
    if (hi >= maxDigits)  // Most of this work is dealing with out of range cases
    {
        if (lo >= maxDigits)
            return;
        
        finger += (hi - (maxDigits-1));
        hi = maxDigits-1;
    }
    
    if (lo < 0)
    {
        if (hi < 0)
            return;
        
        lo = 0;
    }
    
    msb = hi;
    lsb  = lo;
    
    for ( int i = hi; i >= lo; i-- )
    {
        byte next = *finger++ - '0';
        if (next < 10)
            digits[i] = next;
        else
        {
            //infinity????
            setZero();
            return;
        }
    }

    if (sign)
        negative = true;
}


void TempDecimal::setString(size32_t length, const char * buffer)
{
    const char * limit = buffer+length;
    const char * cur = buffer;
    while ((cur < limit) && (*cur == ' '))
        cur++;

    negative = false;
    if ((cur < limit) && (*cur == '-'))
    {
        negative = true;
        cur++;
    }

    const char * start = cur;
    while ((cur < limit) && (isdigit(*cur)))
        cur++;

    unsigned numDigits = (cur-start);
    if (numDigits > maxIntegerDigits)
    {
        overflow();
        numDigits = maxIntegerDigits;
    }

    int idx;
    for (idx = 0; idx < (int)numDigits; idx++)
        digits[zeroDigit+idx] = cur[-(idx+1)] - '0'; // careful - if idx is unsigned, -(idx+1) is not sign-extended and fails if int size is not pointer size
    msb = zeroDigit+(numDigits-1);

    if ((cur < limit) && (*cur == '.'))
    {
        cur++;

        const char * start = cur;
        if (limit-cur > maxPrecision)
            limit = cur + maxPrecision;
        byte * digit = digits + zeroDigit;
        while ((cur < limit) && (isdigit(*cur)))
            *--digit = *cur++ - '0';
        lsb = zeroDigit - (cur-start);
    }
    else
        lsb = zeroDigit;
}


void TempDecimal::setUInt(unsigned int value)
{
    negative = false;
    lsb = zeroDigit;
    unsigned idx = zeroDigit;
    while (value > 9)
    {
        unsigned int next = value / 10;
        digits[idx++] = value - next*10;
        value = next;
    }
    digits[idx] = value;
    msb = idx;
}


void TempDecimal::setUInt64(unsigned __int64 value)
{
    negative = false;
    //MORE: This isn't the most efficient way of doing it - see num2str in jutil for some hints.
    lsb = zeroDigit;
    unsigned idx = zeroDigit;
    while (value > 9)
    {
        unsigned __int64 next = value / 10;
        digits[idx++] = (byte)(value - next*10);
        value = next;
    }
    digits[idx] = (byte)value;
    msb = idx;
}


void TempDecimal::setUDecimal(byte length, byte precision, const void * _buffer)
{
    const byte * buffer = (const byte *)_buffer;
    lsb = zeroDigit - precision;
    msb = lsb + length*2 - 1;
    unsigned cur = msb;
    for (unsigned idx=0; idx < length; idx++)
    {
        byte next = buffer[idx];
        digits[cur--] = next >> 4;
        digits[cur--] = next & 0x0f;
    }
    negative = false;
}

//-- helper functions:

void TempDecimal::clip(int & newLsb, int & newMsb) const
{
    int lo = lsb;
    int hi = msb;
    while (digits[lo] == 0 && lo < hi)
        lo++;
    while (digits[hi] == 0 && hi >= lo)
        hi--;
    newLsb = lo;
    newMsb = hi;
}

void TempDecimal::clip(int & newLsb, int & newMsb, unsigned minLsb, unsigned maxMsb) const
{
    clip(newLsb, newMsb);
    if (newLsb < (int)minLsb)
        newLsb = minLsb;
    if (newMsb > (int)maxMsb)
        newMsb = maxMsb;
    if (newMsb < newLsb)
        newMsb = newLsb-1;
}

unsigned TempDecimal::doGetString(char * buffer) const
{
    char * cur = buffer;
    int lo, hi;
    clip(lo, hi);

    if (lo > hi) // || (lo == hi) && (digits[hi] == 0))
    {
        *cur = '0';
        return 1;
    }

    if (negative)
        *cur++ = '-';

    int idx;
    if (hi < zeroDigit)
    {
        *cur++ = '0';
        *cur++ = '.';
        for (idx = zeroDigit-1; idx > hi; idx--)
            *cur++ = '0';

        for (;idx >= lo; idx--)
            *cur++ = '0' + digits[idx];
    }
    else
    {
        if (lo < zeroDigit)
        {
            for (idx = hi; idx >= zeroDigit; idx--)
                *cur++ = '0' + digits[idx];

            *cur++ = '.';
            for (; idx >= lo; idx--)
                *cur++ = '0' + digits[idx];
        }
        else
        {
            for (idx = hi; idx >= lo; idx--)
                *cur++ = '0' + digits[idx];

            for (; idx >= zeroDigit; idx--)
                *cur++ = '0';
        }
    }
    return cur-buffer;
}


void TempDecimal::doGetDecimal(byte length, byte maxDigits, byte precision, void * buffer) const
{
    int tgtHighPos = zeroDigit+maxDigits-precision-1;
    int tgtLowPos = tgtHighPos - length*2 + 1;
    int lowPos, highPos;
    clip(lowPos, highPos, zeroDigit-precision, zeroDigit+maxDigits-precision-1);
    if ((lowPos > highPos) || (highPos > tgtHighPos))
    {
        //zero or overflow...
        memset(buffer, 0, length);
        return;
    }

    int copyHighPos = highPos;
    if (tgtLowPos > copyHighPos)
        copyHighPos = tgtLowPos;
    else if (tgtHighPos < copyHighPos)
        copyHighPos = tgtHighPos;       // overflow....
    int copyLowPos = lowPos;
    if (tgtLowPos > copyLowPos)
        copyLowPos = tgtLowPos;

    NOMEMCPY byte * tgt = (byte *)buffer;
    //First pad with zeros.
    if (tgtHighPos > copyHighPos)
    {
        unsigned zeros = tgtHighPos-copyHighPos;
        while (zeros >= 2)
        {
            *tgt++ = 0;
            zeros -= 2;
        }
        if (zeros != 0)
            *tgt++ = digits[copyHighPos--];
    }

    //Now will with characters
    while (copyLowPos < copyHighPos)
    {
        byte next = digits[copyHighPos];
        byte next2 = digits[copyHighPos-1];
        *tgt++ = (byte)(next << 4) | next2;
        copyHighPos -= 2;
    }
    if (copyLowPos == copyHighPos)
    {
        *tgt++ = digits[copyLowPos] << 4;
        copyLowPos -= 2;
    }
    while (copyLowPos > tgtLowPos)
    {
        *tgt++ = 0;
        copyLowPos -= 2;
    }
}

void TempDecimal::doPower(unsigned value)
{
    if (value == 1)
        return;

    if (value & 1)
    {
        TempDecimal saved(*this);
        doPower(value >> 1);
        multiply(*this);
        multiply(saved);
    }
    else
    {
        doPower(value >> 1);
        multiply(*this);
    }
}

void TempDecimal::setZero()
{
    negative = false;
    lsb = msb = zeroDigit;
    digits[zeroDigit] = 0;
}

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


bool dec2Bool(size32_t bytes, const void * _data)
{
    const byte * data = (const byte *)_data;
    //ignore the sign
    if (data[--bytes] & 0xf0)
        return true;
    while (bytes--)
        if (*data++)
            return true;
    return false;
}


bool udec2Bool(size32_t bytes, const void * _data)
{
    const byte * data = (const byte *)_data;
    while (bytes--)
        if (*data++)
            return true;
    return false;
}


int decCompareDecimal(size32_t bytes, const void * _left, const void * _right)
{
    const byte * left = (const byte *)_left;
    const byte * right = (const byte *)_right;

    bytes--;
    byte signLeft = left[bytes] & 0x0f;
    byte signRight = right[bytes] & 0x0f;
    if (signMap[signLeft] != signMap[signRight])
    {
        int res = signMap[signLeft] - signMap[signRight];
        // could be +0 and -0......
        if ((left[bytes] & 0xf0) || (right[bytes] & 0xf0))
            return res;
        while (bytes--)
            if (left[bytes] || right[bytes])
                return res;
        return 0;
    }

    bool numbersAreNegative = (signMap[signLeft] == -1);
    while (bytes--)
    {
        byte l = *left++;
        byte r = *right++;
        int res = l - r;
        if (res)
            return numbersAreNegative ? -res : res;
    }

    int res = (*left & 0xf0) - (*right & 0xf0);
    if (res)
        return numbersAreNegative ? -res : res;
    return 0;
}


int decCompareUDecimal(size32_t bytes, const void * _left, const void * _right)
{
    const byte * left = (const byte *)_left;
    const byte * right = (const byte *)_right;

    while (bytes--)
    {
        byte l = *left++;
        byte r = *right++;
        int res = l - r;
        if (res)
            return res;
    }
    return 0;
}


bool decValid(bool isSigned, unsigned digits, const void * data)
{
    if (data && digits)
    {
        if ((isSigned && digits % 2 == 0) || (!isSigned && digits % 2 != 0))
        {
            if (*((byte*)data)&0xf0)
                return false;
            digits++;
        }
        unsigned bytes = isSigned ? digits/2+1 : (digits+1)/2;
        byte *dp = (byte * )data;
        if (isSigned)
        {
            byte sign = dp[--bytes] & 0x0f;
            // allow 0x0F and 0x0C for positive and 0x0D for negative signs
            if (!(sign == 0x0f || sign == 0x0d || sign == 0x0c))
                return false;
            if ((byte)(dp[bytes] & 0xf0u) > 0x90u)
                return false;
        }
        // This code assumes 32bit registers.
        unsigned dwords = bytes / 4;
        bytes %= 4;
        while(bytes--)
        {
            byte b = dp[dwords*4 + bytes];
            if (((b&0xF0u) > 0x90u) || ((b&0x0Fu) > 0x09u))
                return false;
        }
        // see http://www.cs.uiowa.edu/~jones/bcd/bcd.html for an explanation of this code
        unsigned __int32  *wp = (unsigned __int32 *)data;
        while (dwords--)
        {
            unsigned __int32 l = wp[dwords];
            if ((unsigned __int32 )(l&0xF0000000) > 0x90000000u)
                return false;
            __int32 l1 = l  + 0x66666666;
            __int32 l2 = l1 ^ l;
            __int32 l3 = l2 & 0x11111110;
            if (l3)
                return false;
        }
    }
    return true;
}