Offer logic seems to be working now.

src/Amount.cpp

@@ -59,7 +59,7 @@ STAmount* STAmount::construct(SerializerIterator& sit, const char *name)
 std::string STAmount::getText() const
 { // This should be re-implemented to put a '.' in the string form of the integer value
 	std::ostringstream str;
-	str << std::setprecision(16) << static_cast<double>(*this);
+	str << std::setprecision(14) << static_cast<double>(*this);
 	return str.str();
 }
 
@@ -192,17 +192,16 @@ STAmount operator-(STAmount v1, STAmount v2)
 	return STAmount(v1.name, v1.value - v2.value, v1.offset);
 }
 
-STAmount getRate(const STAmount& offerIn, const STAmount& offerOut)
+STAmount operator/(const STAmount& num, const STAmount& den)
 {
 	CBigNum numerator, denominator, quotient;
 
-	if(offerOut.value == 0) throw std::runtime_error("illegal offer");
-	if(offerIn.value == 0) return STAmount();
+	if(den.value == 0) throw std::runtime_error("illegal offer");
+	if(num.value == 0) return STAmount();
 
 	// Compute (numerator * 10^16) / denominator
-	if(	(BN_zero(&numerator) != 1) || (BN_zero(&denominator) != 1) ||
-		(BN_add_word(&numerator, offerIn.value) != 1) ||
-		(BN_add_word(&denominator, offerOut.value) != 1) ||
+	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) )
 	{
@@ -212,5 +211,63 @@ STAmount getRate(const STAmount& offerIn, const STAmount& offerOut)
 	// 10^15 <= quotient <= 10^17
 	assert(BN_num_bytes(&quotient)<=60);
 
-	return STAmount(quotient.getulong(), offerIn.offset - offerOut.offset - 16);
+	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 * denominator) / 10^15
+	CBigNum v;
+	if( (BN_add_word(&v, v1.value) != 1) ||
+	    (BN_mul_word(&v, v2.value) != 1) ||
+		(BN_div_word(&v, 1000000000000000ull) == ((BN_ULONG)-1)) )
+	{
+		throw std::runtime_error("internal bn error");
+	}
+
+	// 10^15 <= product <= 10^17
+	assert(BN_num_bytes(&v)<=60);
+	return STAmount(v.getulong(), v1.offset + v2.offset + 15);
+}
+
+STAmount getRate(const STAmount& offerOut, const STAmount& offerIn)
+{
+	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;
 }

src/SerializedTypes.h

@@ -195,6 +195,8 @@ public:
 
 	int getOffset() const { return offset; }
 	uint64 getValue() const { return value; }
+	void zero() { offset=0; value=0; }
+	bool isZero() const { return value==0; }
 
 	virtual bool isEquivalent(const SerializedType& t) const;
 
@@ -216,15 +218,18 @@ public:
 
 	friend STAmount operator+(STAmount v1, STAmount v2);
 	friend STAmount operator-(STAmount v1, STAmount v2);
+	friend STAmount operator/(const STAmount& v1, const STAmount& v2);
+	friend STAmount operator*(const STAmount& v1, const STAmount& v2);
 
 	// Someone is offering X for Y, what is the rate?
-	friend STAmount getRate(const STAmount& offerIn, const STAmount& offerOut);
+	friend STAmount getRate(const STAmount& offerOut, const STAmount& offerIn);
 
-	// Someone is offering X for Y, I pay Z, how much do I get?
-	friend STAmount getClaimed(const STAmount& offerIn, const STAmount& offerOut, const STAmount& paid);
+	// Someone is offering X for Y, I try to pay Z, how much do I get?
+	// And what's left of the offer? And how much do I actually pay?
+	friend STAmount getClaimed(STAmount& offerOut, STAmount& offerIn, STAmount& paid);
 
 	// Someone is offering X for Y, I need Z, how much do I pay
-	friend STAmount getNeeded(const STAmount& offerIn, const STAmount& offerOut, const STAmount& needed);
+	friend STAmount getNeeded(const STAmount& offerOut, const STAmount& offerIn, const STAmount& needed);
 };
 
 class STHash128 : public SerializedType