rippled/src/Amount.cpp

#include <cmath>
#include <iomanip>

#include <boost/lexical_cast.hpp>

#include "SerializedTypes.h"

// amount = value * [10 ^ offset]
// representation range is 10^80 - 10^(-80)
// on the wire, high 8 bits are (offset+142), low 56 bits are value
// value is zero if amount is zero, otherwise value is 10^15 - (10^16 - 1) inclusive

void STAmount::canonicalize()
{
	if(value==0)
	{
		offset=0;
		value=0;
		return;
	}
	while(value<cMinValue)
	{
		if(offset<=cMinOffset) throw std::runtime_error("value overflow");
		value*=10;
		--offset;
	}
	while(value>cMaxValue)
	{
		if(offset>=cMaxOffset) throw std::runtime_error("value underflow");
		value/=10;
		++offset;
	}
	assert( (value==0) || ( (value>=cMinValue) && (value<=cMaxValue) ) );
	assert( (offset>=cMinOffset) && (offset<=cMaxOffset) );
}

STAmount* STAmount::construct(SerializerIterator& sit, const char *name)
{
	uint64 value = sit.get64();

	int offset = static_cast<int>(value >> (64-8));
	value &= ~(255ull << (64-8));

	if(value==0)
	{
		if(offset!=0)
			throw std::runtime_error("invalid currency value");
	}
	else
	{
		offset -= 142; // center the range
		if( (value<cMinValue) || (value>cMaxValue) || (offset<cMinOffset) || (offset>cMaxOffset) )
			throw std::runtime_error("invalid currency value");
	}
	return new STAmount(name, value, offset);
}

std::string STAmount::getText() const
{
	if(value==0) return "0";
	if( (offset<-25) || (offset>-5) )
		return boost::lexical_cast<std::string>(value) + "e" + boost::lexical_cast<std::string>(offset);

	std::string val="000000000000000000000000000";
	val+=boost::lexical_cast<std::string>(value);
	val+="00000000000000000000000";

	std::string pre=val.substr(0, offset+43);
	std::string post=val.substr(offset+43);

	size_t s_pre=pre.find_first_not_of('0');
	if(s_pre==std::string::npos) pre="0";
	else pre=pre.substr(s_pre);

	size_t s_post=post.find_last_not_of('0');
	if(s_post==std::string::npos)
		return pre;
	else
		return pre + "." + post.substr(0, s_post+1);
}

void STAmount::add(Serializer& s) const
{
	if (value==0)
		s.add64(0);
	else
		s.add64(value + (static_cast<uint64>(offset+142) << (64-8)));
}

bool STAmount::isEquivalent(const SerializedType& t) const
{
	const STAmount* v = dynamic_cast<const STAmount*>(&t);
	if(!v) return false;
	return (value == v->value) && (offset == v->offset);
}

bool STAmount::operator==(const STAmount& a) const
{
	return (offset == a.offset) && (value == a.value);
}

bool STAmount::operator!=(const STAmount& a) const
{
	return (offset != a.offset) || (value != a.value);
}

bool STAmount::operator<(const STAmount& a) const
{
	if(value == 0) return false;
	if(offset < a.offset) return true;
	if(a.offset < offset) return false;
	return value < a.value;
}

bool STAmount::operator>(const STAmount& a) const
{
	if(value == 0) return a.value != 0;
	if(offset > a.offset) return true;
	if(a.offset > offset) return false;
	return value > a.value;
}

bool STAmount::operator<=(const STAmount& a) const
{
	if(value == 0) return a.value== 0;
	if(offset<a.offset) return true;
	if(a.offset<offset) return false;
	return value <= a.value;
}

bool STAmount::operator>=(const STAmount& a) const
{
	if(value == 0) return true;
	if(offset>a.offset) return true;
	if(a.offset>offset) return false;
	return value >= a.value;
}

STAmount& STAmount::operator+=(const STAmount& a)
{
	*this = *this + a;
	return *this;
}

STAmount& STAmount::operator-=(const STAmount& a)
{
	*this = *this - a;
	return *this;
}

STAmount& STAmount::operator=(const STAmount& a)
{
	value=a.value;
	offset=a.offset;
	return *this;
}

STAmount& STAmount::operator=(uint64 v)
{
	return *this=STAmount(v, 0);
}

STAmount& STAmount::operator+=(uint64 v)
{
	return *this+=STAmount(v);
}

STAmount& STAmount::operator-=(uint64 v)
{
	return *this-=STAmount(v);
}

STAmount::operator double() const
{
	if(!value) return 0.0;
	return (static_cast<double>(value)) * pow(10.0, offset);
}

STAmount operator+(STAmount v1, STAmount v2)
{ // We can check for precision loss here (value%10)!=0
	while(v1.offset < v2.offset)
	{
		v1.value/=10;
		v1.offset+=1;
	}
	while(v2.offset < v1.offset)
	{
		v2.value/=10;
		v2.offset+=1;
	}
	// this addition cannot overflow
	return STAmount(v1.name, v1.value + v2.value, v1.offset);
}

STAmount operator-(STAmount v1, STAmount v2)
{ // We can check for precision loss here (value%10)!=0
	if(v2.offset > v1.offset) throw std::runtime_error("value underflow");
	while(v1.offset > v2.offset)
	{
		v2.value/=10;
		++v2.offset;
	}
	if(v1.value < v2.value) throw std::runtime_error("value underflow");
	return STAmount(v1.name, v1.value - v2.value, v1.offset);
}

STAmount operator/(const STAmount& num, const STAmount& den)
{
	CBigNum numerator, denominator, quotient;

	if(den.value == 0) throw std::runtime_error("illegal offer");
	if(num.value == 0) return STAmount();

	// Compute (numerator * 10^16) / denominator
	if( (BN_add_word(&numerator, num.value) != 1) ||
		(BN_add_word(&denominator, den.value) != 1) ||
		(BN_mul_word(&numerator, 10000000000000000ull) != 1) ||
		(BN_div(&quotient, NULL, &numerator, &denominator, CAutoBN_CTX()) != 1) )
	{
		throw std::runtime_error("internal bn error");
	}

	// 10^15 <= quotient <= 10^17
	assert(BN_num_bytes(&quotient)<=60);

	return STAmount(quotient.getulong(), num.offset - den.offset - 16);
}

STAmount operator*(const STAmount &v1, const STAmount &v2)
{
	if( (v1.value == 0) || (v2.value == 0) ) return STAmount();

	// Compute (numerator*10 * denominator*10) / 10^18
	CBigNum v;
	if( (BN_add_word(&v, (v1.value*10) + 3) != 1) ||
	    (BN_mul_word(&v, (v2.value*10) + 3) != 1) ||
		(BN_div_word(&v, 1000000000000000000ull) == ((BN_ULONG)-1)) )
	{
		throw std::runtime_error("internal bn error");
	}

	// 10^16 <= product <= 10^18
	assert(BN_num_bytes(&v)<=60);
	return STAmount(v.getulong(), v1.offset + v2.offset + 16);
}

STAmount getRate(const STAmount& offerOut, const STAmount& offerIn)
{
	// offerOut = how much comes out of the offer, from the offeror to the taker
	// offerIn = how much goes into the offer, from the taker to the offeror
	return offerOut / offerIn;
}

STAmount getClaimed(STAmount& offerOut, STAmount& offerIn, STAmount& paid)
{ // if someone is offering (offerOut) for (offerIn), and I pay (paid), how much do I get?

	// If you pay nothing, you get nothing. Offer is untouched
	if (paid.value == 0) return STAmount();

	if( (offerIn.value == 0) || (offerOut.value == 0) )
	{ // If the other is invalid or empty, you pay nothing and get nothing and the offer is dead
		offerIn.zero();
		offerOut.zero();
		paid.zero();
		return STAmount();
	}

	if(paid >= offerIn)
	{ // If you pay equal to or more than the offer amount, you get the whole offer and pay its input
		STAmount ret(offerOut);
		paid = offerIn;
		offerOut.zero();
		offerIn.zero();
		return ret;
	}

	// partial satisfaction of a normal offer
	STAmount ret = (paid * offerOut) / offerIn;
	offerOut -= ret;
	offerIn -= paid;
	if( (offerOut.value == 0) || (offerIn.value == 0) )
	{
		offerIn.zero();
		offerOut.zero();
	}
	return ret;
}

STAmount getNeeded(const STAmount& offerOut, const STAmount& offerIn, const STAmount& needed)
{ // Someone wants to get (needed) out of the offer, how much should they pay in?
	if(offerOut.isZero()) return STAmount();
	if(needed >= offerOut) return needed;
	STAmount ret = (needed * offerIn) / offerOut;
	return (ret > offerIn) ? offerIn : ret;
}