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https://github.com/Xahau/xahaud.git
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Add, subtract, multiply, and divide with specified rounding direction.
CAUTION: This is still untested and undebugged code. Only divRound has been even slightly tested.
This commit is contained in:
JoelKatz
266
src/cpp/ripple/AmountRound.cpp
Normal file
266
src/cpp/ripple/AmountRound.cpp
Normal file
@@ -0,0 +1,266 @@
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#include <boost/test/unit_test.hpp>
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#include "SerializedTypes.h"
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#include "Log.h"
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SETUP_LOG();
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#if (ULONG_MAX > UINT_MAX)
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#define BN_add_word64(bn, word) BN_add_word(bn, word)
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#define BN_sub_word64(bn, word) BN_sub_word(bn, word)
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#define BN_mul_word64(bn, word) BN_mul_word(bn, word)
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#define BN_div_word64(bn, word) BN_div_word(bn, word)
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#else
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#include "BigNum64.h"
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#endif
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static const uint64 tenTo14 = 100000000000000ull;
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static const uint64 tenTo14m1 = tenTo14 - 1;
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static const uint64 tenTo17 = tenTo14 * 1000;
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static const uint64 tenTo17m1 = tenTo17 - 1;
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// CAUTION: This is still very early code and is *NOT* ready for real use yet.
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// Only divRound is tested, and that's only slightly tested.
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static void canonicalizeRound(bool isNative, uint64& value, int& offset, bool roundUp)
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{
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cLog(lsINFO) << "canonicalize< " << value << ":" << offset << (roundUp ? " up" : " down");
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if (isNative && (offset < 0))
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{
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if (roundUp)
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value += 9;
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else
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value -= 9;
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value /= 10;
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++offset;
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}
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else if (!isNative && (value > STAmount::cMinValue))
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{
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if (roundUp)
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value += 9;
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else
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value -= 9;
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value /= 10;
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++offset;
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}
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cLog(lsINFO) << "canonicalize> " << value << ":" << offset << (roundUp ? " up" : " down");
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}
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STAmount STAmount::addRound(const STAmount& v1, const STAmount& v2, bool roundUp)
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{
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v1.throwComparable(v2);
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if (v2.mValue == 0)
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return v1;
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if (v1.mValue == 0)
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return STAmount(v1.getFName(), v1.mCurrency, v1.mIssuer, v2.mValue, v2.mOffset, v2.mIsNegative);
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if (v1.mIsNative)
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return STAmount(v1.getFName(), v1.getSNValue() + v2.getSNValue());
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int ov1 = v1.mOffset, ov2 = v2.mOffset;
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int64 vv1 = static_cast<int64>(v1.mValue), vv2=static_cast<uint64>(v2.mValue);
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if (v1.mIsNegative) vv1 = -vv1;
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if (v2.mIsNegative) vv2 = -vv2;
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while (ov1 < ov2)
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{
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if (roundUp)
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vv1 += 9;
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else
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vv1 -= 9;
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vv1 /= 10;
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++ov1;
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}
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while (ov2 < ov1)
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{
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if (roundUp)
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vv1 += 9;
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else
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vv1 -= 9;
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vv1 /= 10;
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++ov2;
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}
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int64 fv = vv1 + vv2;
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if (fv >= 0)
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{
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uint64 v = static_cast<uint64>(fv);
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canonicalizeRound(false, v, ov1, roundUp);
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return STAmount(v1.getFName(), v1.mCurrency, v1.mIssuer, v, ov1, false);
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}
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else
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{
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uint64 v = static_cast<uint64>(-fv);
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canonicalizeRound(false, v, ov1, !roundUp);
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return STAmount(v1.getFName(), v1.mCurrency, v1.mIssuer, v, ov1, true);
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}
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}
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STAmount STAmount::subRound(const STAmount& v1, const STAmount& v2, bool roundUp)
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{
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v1.throwComparable(v2);
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if (v2.mValue == 0)
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return v1;
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if (v1.mValue == 0)
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return STAmount(v1.getFName(), v1.mCurrency, v1.mIssuer, v2.mValue, v2.mOffset, !v2.mIsNegative);
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if (v1.mIsNative)
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return STAmount(v1.getFName(), v1.getSNValue() - v2.getSNValue());
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int ov1 = v1.mOffset, ov2 = v2.mOffset;
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int64 vv1 = static_cast<int64>(v1.mValue), vv2=static_cast<uint64>(v2.mValue);
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if (v1.mIsNegative) vv1 = -vv1;
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if (v2.mIsNegative) vv2 = -vv2;
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while (ov1 < ov2)
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{
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if (roundUp)
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vv1 += 9;
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else
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vv1 -= 9;
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vv1 /= 10;
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++ov1;
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}
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while (ov2 < ov1)
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{
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if (roundUp)
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vv1 -= 9;
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else
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vv1 += 9;
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vv1 /= 10;
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++ov2;
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}
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int64 fv = vv1 + vv2;
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if (fv >= 0)
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return STAmount(v1.getFName(), v1.mCurrency, v1.mIssuer, fv, ov1, false);
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else
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return STAmount(v1.getFName(), v1.mCurrency, v1.mIssuer, -fv, ov1, true);
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}
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STAmount STAmount::mulRound(const STAmount& v1, const STAmount& v2,
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const uint160& uCurrencyID, const uint160& uIssuerID, bool roundUp)
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{
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if (v1.isZero() || v2.isZero())
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return STAmount(uCurrencyID, uIssuerID);
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if (v1.mIsNative && v2.mIsNative && uCurrencyID.isZero())
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{
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uint64 minV = (v1.getSNValue() < v2.getSNValue()) ? v1.getSNValue() : v2.getSNValue();
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uint64 maxV = (v1.getSNValue() < v2.getSNValue()) ? v2.getSNValue() : v1.getSNValue();
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if (minV > 3000000000ull) // sqrt(cMaxNative)
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throw std::runtime_error("Native value overflow");
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if (((maxV >> 32) * minV) > 2095475792ull) // cMaxNative / 2^32
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throw std::runtime_error("Native value overflow");
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return STAmount(v1.getFName(), minV * maxV);
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}
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uint64 value1 = v1.mValue, value2 = v2.mValue;
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int offset1 = v1.mOffset, offset2 = v2.mOffset;
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if (v1.mIsNative)
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{
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while (value1 < STAmount::cMinValue)
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{
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value1 *= 10;
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--offset1;
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}
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}
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if (v2.mIsNative)
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{
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while (value2 < STAmount::cMinValue)
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{
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value2 *= 10;
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--offset2;
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}
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}
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bool resultNegative = v1.mIsNegative != v2.mIsNegative;
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// Compute (numerator * denominator) / 10^14 with rounding
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// 10^16 <= result <= 10^18
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CBigNum v;
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if ((BN_add_word64(&v, value1) != 1) || (BN_mul_word64(&v, value2) != 1) ||
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(BN_add_word64(&v, (resultNegative == roundUp) ? (-tenTo14m1) : tenTo14m1) != 1) ||
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(BN_div_word64(&v, tenTo14) == ((uint64) -1)))
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throw std::runtime_error("internal bn error");
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// 10^16 <= product <= 10^18
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assert(BN_num_bytes(&v) <= 64);
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uint64 amount = v.getuint64();
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int offset = offset1 + offset2 + 14;
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canonicalizeRound(uCurrencyID.isZero(), amount, offset, resultNegative != roundUp);
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return STAmount(uCurrencyID, uIssuerID, amount, offset, resultNegative);
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}
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STAmount STAmount::divRound(const STAmount& num, const STAmount& den,
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const uint160& uCurrencyID, const uint160& uIssuerID, bool roundUp)
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{
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if (den.isZero()) throw std::runtime_error("division by zero");
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if (num.isZero()) return STAmount(uCurrencyID, uIssuerID);
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uint64 numVal = num.mValue, denVal = den.mValue;
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int numOffset = num.mOffset, denOffset = den.mOffset;
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if (num.mIsNative)
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while (numVal < STAmount::cMinValue)
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{ // Need to bring into range
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numVal *= 10;
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--numOffset;
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}
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if (den.mIsNative)
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while (denVal < STAmount::cMinValue)
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{
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denVal *= 10;
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--denOffset;
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}
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bool resultNegative = num.mIsNegative != num.mIsNegative;
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// Compute (numerator * 10^17) / denominator
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CBigNum v;
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if ((BN_add_word64(&v, numVal) != 1) || (BN_mul_word64(&v, tenTo17) != 1))
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throw std::runtime_error("internal bn error");
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if (resultNegative != roundUp)
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BN_add_word64(&v, denVal - 1);
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else
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BN_sub_word64(&v, denVal - 1);
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if (BN_div_word64(&v, denVal) == ((uint64) -1))
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throw std::runtime_error("internal bn error");
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// 10^16 <= quotient <= 10^18
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assert(BN_num_bytes(&v) <= 64);
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uint64 amount = v.getuint64();
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int offset = numOffset - denOffset - 17;
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canonicalizeRound(uCurrencyID.isZero(), amount, offset, resultNegative != roundUp);
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return STAmount(uCurrencyID, uIssuerID, amount, offset, resultNegative);
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}
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BOOST_AUTO_TEST_SUITE(amountRound)
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BOOST_AUTO_TEST_CASE( amountRound_test )
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{
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STAmount one(CURRENCY_ONE, ACCOUNT_ONE, 1);
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STAmount two(CURRENCY_ONE, ACCOUNT_ONE, 2);
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STAmount three(CURRENCY_ONE, ACCOUNT_ONE, 3);
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STAmount oneThird1 = STAmount::divRound(one, three, CURRENCY_ONE, ACCOUNT_ONE, false);
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STAmount oneThird2 = STAmount::divide(one, three, CURRENCY_ONE, ACCOUNT_ONE);
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STAmount oneThird3 = STAmount::divRound(one, three, CURRENCY_ONE, ACCOUNT_ONE, true);
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cLog(lsINFO) << oneThird1;
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cLog(lsINFO) << oneThird2;
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cLog(lsINFO) << oneThird3;
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}
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BOOST_AUTO_TEST_SUITE_END()
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// vim:ts=4
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@@ -7,6 +7,12 @@ static int BN_add_word64(BIGNUM *a, uint64 w)
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return BN_add(a, &bn, a);
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}
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static int BN_sub_word64(BIGNUM *a, uint64 w)
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{
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CBigNum bn(w);
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return BN_sub(a, &bn, a);
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}
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static int BN_mul_word64(BIGNUM *a, uint64 w)
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{
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CBigNum bn(w);
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@@ -427,6 +427,14 @@ public:
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static STAmount multiply(const STAmount& v1, const STAmount& v2)
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{ return multiply(v1, v2, v1); }
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// Add, subtract, multiply, or divide rounding result in specified direction
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static STAmount addRound(const STAmount& v1, const STAmount& v2, bool roundUp);
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static STAmount subRound(const STAmount& v1, const STAmount& v2, bool roundUp);
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static STAmount mulRound(const STAmount& v1, const STAmount& v2,
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const uint160& currency, const uint160& issuer, bool roundUp);
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static STAmount divRound(const STAmount& v1, const STAmount& v2,
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const uint160& currency, const uint160& issuer, bool roundUp);
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// Someone is offering X for Y, what is the rate?
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// Rate: smaller is better, the taker wants the most out: in/out
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static uint64 getRate(const STAmount& offerOut, const STAmount& offerIn);
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