mirror of https://github.com/YosysHQ/yosys.git
698 lines
22 KiB
C++
698 lines
22 KiB
C++
#include "BigUnsigned.hh"
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// Memory management definitions have moved to the bottom of NumberlikeArray.hh.
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// The templates used by these constructors and converters are at the bottom of
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// BigUnsigned.hh.
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BigUnsigned::BigUnsigned(unsigned long x) { initFromPrimitive (x); }
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BigUnsigned::BigUnsigned(unsigned int x) { initFromPrimitive (x); }
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BigUnsigned::BigUnsigned(unsigned short x) { initFromPrimitive (x); }
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BigUnsigned::BigUnsigned( long x) { initFromSignedPrimitive(x); }
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BigUnsigned::BigUnsigned( int x) { initFromSignedPrimitive(x); }
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BigUnsigned::BigUnsigned( short x) { initFromSignedPrimitive(x); }
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unsigned long BigUnsigned::toUnsignedLong () const { return convertToPrimitive <unsigned long >(); }
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unsigned int BigUnsigned::toUnsignedInt () const { return convertToPrimitive <unsigned int >(); }
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unsigned short BigUnsigned::toUnsignedShort() const { return convertToPrimitive <unsigned short>(); }
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long BigUnsigned::toLong () const { return convertToSignedPrimitive< long >(); }
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int BigUnsigned::toInt () const { return convertToSignedPrimitive< int >(); }
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short BigUnsigned::toShort () const { return convertToSignedPrimitive< short>(); }
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// BIT/BLOCK ACCESSORS
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void BigUnsigned::setBlock(Index i, Blk newBlock) {
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if (newBlock == 0) {
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if (i < len) {
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blk[i] = 0;
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zapLeadingZeros();
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}
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// If i >= len, no effect.
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} else {
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if (i >= len) {
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// The nonzero block extends the number.
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allocateAndCopy(i+1);
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// Zero any added blocks that we aren't setting.
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for (Index j = len; j < i; j++)
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blk[j] = 0;
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len = i+1;
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}
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blk[i] = newBlock;
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}
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}
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/* Evidently the compiler wants BigUnsigned:: on the return type because, at
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* that point, it hasn't yet parsed the BigUnsigned:: on the name to get the
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* proper scope. */
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BigUnsigned::Index BigUnsigned::bitLength() const {
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if (isZero())
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return 0;
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else {
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Blk leftmostBlock = getBlock(len - 1);
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Index leftmostBlockLen = 0;
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while (leftmostBlock != 0) {
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leftmostBlock >>= 1;
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leftmostBlockLen++;
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}
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return leftmostBlockLen + (len - 1) * N;
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}
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}
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void BigUnsigned::setBit(Index bi, bool newBit) {
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Index blockI = bi / N;
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Blk block = getBlock(blockI), mask = Blk(1) << (bi % N);
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block = newBit ? (block | mask) : (block & ~mask);
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setBlock(blockI, block);
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}
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// COMPARISON
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BigUnsigned::CmpRes BigUnsigned::compareTo(const BigUnsigned &x) const {
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// A bigger length implies a bigger number.
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if (len < x.len)
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return less;
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else if (len > x.len)
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return greater;
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else {
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// Compare blocks one by one from left to right.
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Index i = len;
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while (i > 0) {
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i--;
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if (blk[i] == x.blk[i])
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continue;
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else if (blk[i] > x.blk[i])
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return greater;
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else
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return less;
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}
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// If no blocks differed, the numbers are equal.
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return equal;
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}
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}
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// COPY-LESS OPERATIONS
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/*
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* On most calls to copy-less operations, it's safe to read the inputs little by
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* little and write the outputs little by little. However, if one of the
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* inputs is coming from the same variable into which the output is to be
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* stored (an "aliased" call), we risk overwriting the input before we read it.
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* In this case, we first compute the result into a temporary BigUnsigned
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* variable and then copy it into the requested output variable *this.
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* Each put-here operation uses the DTRT_ALIASED macro (Do The Right Thing on
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* aliased calls) to generate code for this check.
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*
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* I adopted this approach on 2007.02.13 (see Assignment Operators in
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* BigUnsigned.hh). Before then, put-here operations rejected aliased calls
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* with an exception. I think doing the right thing is better.
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*
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* Some of the put-here operations can probably handle aliased calls safely
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* without the extra copy because (for example) they process blocks strictly
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* right-to-left. At some point I might determine which ones don't need the
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* copy, but my reasoning would need to be verified very carefully. For now
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* I'll leave in the copy.
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*/
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#define DTRT_ALIASED(cond, op) \
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if (cond) { \
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BigUnsigned tmpThis; \
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tmpThis.op; \
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*this = tmpThis; \
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return; \
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}
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void BigUnsigned::add(const BigUnsigned &a, const BigUnsigned &b) {
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DTRT_ALIASED(this == &a || this == &b, add(a, b));
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// If one argument is zero, copy the other.
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if (a.len == 0) {
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operator =(b);
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return;
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} else if (b.len == 0) {
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operator =(a);
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return;
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}
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// Some variables...
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// Carries in and out of an addition stage
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bool carryIn, carryOut;
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Blk temp;
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Index i;
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// a2 points to the longer input, b2 points to the shorter
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const BigUnsigned *a2, *b2;
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if (a.len >= b.len) {
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a2 = &a;
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b2 = &b;
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} else {
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a2 = &b;
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b2 = &a;
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}
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// Set prelimiary length and make room in this BigUnsigned
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len = a2->len + 1;
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allocate(len);
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// For each block index that is present in both inputs...
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for (i = 0, carryIn = false; i < b2->len; i++) {
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// Add input blocks
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temp = a2->blk[i] + b2->blk[i];
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// If a rollover occurred, the result is less than either input.
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// This test is used many times in the BigUnsigned code.
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carryOut = (temp < a2->blk[i]);
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// If a carry was input, handle it
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if (carryIn) {
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temp++;
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carryOut |= (temp == 0);
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}
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blk[i] = temp; // Save the addition result
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carryIn = carryOut; // Pass the carry along
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}
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// If there is a carry left over, increase blocks until
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// one does not roll over.
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for (; i < a2->len && carryIn; i++) {
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temp = a2->blk[i] + 1;
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carryIn = (temp == 0);
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blk[i] = temp;
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}
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// If the carry was resolved but the larger number
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// still has blocks, copy them over.
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for (; i < a2->len; i++)
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blk[i] = a2->blk[i];
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// Set the extra block if there's still a carry, decrease length otherwise
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if (carryIn)
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blk[i] = 1;
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else
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len--;
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}
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void BigUnsigned::subtract(const BigUnsigned &a, const BigUnsigned &b) {
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DTRT_ALIASED(this == &a || this == &b, subtract(a, b));
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if (b.len == 0) {
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// If b is zero, copy a.
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operator =(a);
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return;
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} else if (a.len < b.len)
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// If a is shorter than b, the result is negative.
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throw "BigUnsigned::subtract: "
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"Negative result in unsigned calculation";
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// Some variables...
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bool borrowIn, borrowOut;
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Blk temp;
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Index i;
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// Set preliminary length and make room
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len = a.len;
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allocate(len);
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// For each block index that is present in both inputs...
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for (i = 0, borrowIn = false; i < b.len; i++) {
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temp = a.blk[i] - b.blk[i];
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// If a reverse rollover occurred,
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// the result is greater than the block from a.
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borrowOut = (temp > a.blk[i]);
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// Handle an incoming borrow
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if (borrowIn) {
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borrowOut |= (temp == 0);
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temp--;
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}
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blk[i] = temp; // Save the subtraction result
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borrowIn = borrowOut; // Pass the borrow along
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}
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// If there is a borrow left over, decrease blocks until
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// one does not reverse rollover.
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for (; i < a.len && borrowIn; i++) {
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borrowIn = (a.blk[i] == 0);
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blk[i] = a.blk[i] - 1;
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}
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/* If there's still a borrow, the result is negative.
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* Throw an exception, but zero out this object so as to leave it in a
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* predictable state. */
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if (borrowIn) {
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len = 0;
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throw "BigUnsigned::subtract: Negative result in unsigned calculation";
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} else
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// Copy over the rest of the blocks
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for (; i < a.len; i++)
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blk[i] = a.blk[i];
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// Zap leading zeros
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zapLeadingZeros();
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}
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/*
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* About the multiplication and division algorithms:
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*
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* I searched unsucessfully for fast C++ built-in operations like the `b_0'
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* and `c_0' Knuth describes in Section 4.3.1 of ``The Art of Computer
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* Programming'' (replace `place' by `Blk'):
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*
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* ``b_0[:] multiplication of a one-place integer by another one-place
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* integer, giving a two-place answer;
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*
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* ``c_0[:] division of a two-place integer by a one-place integer,
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* provided that the quotient is a one-place integer, and yielding
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* also a one-place remainder.''
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*
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* I also missed his note that ``[b]y adjusting the word size, if
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* necessary, nearly all computers will have these three operations
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* available'', so I gave up on trying to use algorithms similar to his.
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* A future version of the library might include such algorithms; I
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* would welcome contributions from others for this.
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*
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* I eventually decided to use bit-shifting algorithms. To multiply `a'
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* and `b', we zero out the result. Then, for each `1' bit in `a', we
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* shift `b' left the appropriate amount and add it to the result.
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* Similarly, to divide `a' by `b', we shift `b' left varying amounts,
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* repeatedly trying to subtract it from `a'. When we succeed, we note
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* the fact by setting a bit in the quotient. While these algorithms
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* have the same O(n^2) time complexity as Knuth's, the ``constant factor''
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* is likely to be larger.
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*
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* Because I used these algorithms, which require single-block addition
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* and subtraction rather than single-block multiplication and division,
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* the innermost loops of all four routines are very similar. Study one
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* of them and all will become clear.
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*/
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/*
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* This is a little inline function used by both the multiplication
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* routine and the division routine.
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*
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* `getShiftedBlock' returns the `x'th block of `num << y'.
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* `y' may be anything from 0 to N - 1, and `x' may be anything from
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* 0 to `num.len'.
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*
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* Two things contribute to this block:
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*
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* (1) The `N - y' low bits of `num.blk[x]', shifted `y' bits left.
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*
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* (2) The `y' high bits of `num.blk[x-1]', shifted `N - y' bits right.
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*
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* But we must be careful if `x == 0' or `x == num.len', in
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* which case we should use 0 instead of (2) or (1), respectively.
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*
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* If `y == 0', then (2) contributes 0, as it should. However,
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* in some computer environments, for a reason I cannot understand,
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* `a >> b' means `a >> (b % N)'. This means `num.blk[x-1] >> (N - y)'
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* will return `num.blk[x-1]' instead of the desired 0 when `y == 0';
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* the test `y == 0' handles this case specially.
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*/
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inline BigUnsigned::Blk getShiftedBlock(const BigUnsigned &num,
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BigUnsigned::Index x, unsigned int y) {
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BigUnsigned::Blk part1 = (x == 0 || y == 0) ? 0 : (num.blk[x - 1] >> (BigUnsigned::N - y));
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BigUnsigned::Blk part2 = (x == num.len) ? 0 : (num.blk[x] << y);
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return part1 | part2;
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}
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void BigUnsigned::multiply(const BigUnsigned &a, const BigUnsigned &b) {
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DTRT_ALIASED(this == &a || this == &b, multiply(a, b));
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// If either a or b is zero, set to zero.
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if (a.len == 0 || b.len == 0) {
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len = 0;
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return;
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}
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/*
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* Overall method:
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*
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* Set this = 0.
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* For each 1-bit of `a' (say the `i2'th bit of block `i'):
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* Add `b << (i blocks and i2 bits)' to *this.
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*/
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// Variables for the calculation
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Index i, j, k;
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unsigned int i2;
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Blk temp;
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bool carryIn, carryOut;
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// Set preliminary length and make room
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len = a.len + b.len;
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allocate(len);
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// Zero out this object
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for (i = 0; i < len; i++)
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blk[i] = 0;
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// For each block of the first number...
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for (i = 0; i < a.len; i++) {
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// For each 1-bit of that block...
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for (i2 = 0; i2 < N; i2++) {
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if ((a.blk[i] & (Blk(1) << i2)) == 0)
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continue;
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/*
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* Add b to this, shifted left i blocks and i2 bits.
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* j is the index in b, and k = i + j is the index in this.
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*
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* `getShiftedBlock', a short inline function defined above,
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* is now used for the bit handling. It replaces the more
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* complex `bHigh' code, in which each run of the loop dealt
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* immediately with the low bits and saved the high bits to
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* be picked up next time. The last run of the loop used to
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* leave leftover high bits, which were handled separately.
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* Instead, this loop runs an additional time with j == b.len.
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* These changes were made on 2005.01.11.
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*/
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for (j = 0, k = i, carryIn = false; j <= b.len; j++, k++) {
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/*
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* The body of this loop is very similar to the body of the first loop
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* in `add', except that this loop does a `+=' instead of a `+'.
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*/
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temp = blk[k] + getShiftedBlock(b, j, i2);
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carryOut = (temp < blk[k]);
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if (carryIn) {
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temp++;
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carryOut |= (temp == 0);
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}
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blk[k] = temp;
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carryIn = carryOut;
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}
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// No more extra iteration to deal with `bHigh'.
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// Roll-over a carry as necessary.
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for (; carryIn; k++) {
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blk[k]++;
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carryIn = (blk[k] == 0);
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}
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}
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}
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// Zap possible leading zero
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if (blk[len - 1] == 0)
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len--;
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}
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/*
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* DIVISION WITH REMAINDER
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* This monstrous function mods *this by the given divisor b while storing the
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* quotient in the given object q; at the end, *this contains the remainder.
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* The seemingly bizarre pattern of inputs and outputs was chosen so that the
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* function copies as little as possible (since it is implemented by repeated
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* subtraction of multiples of b from *this).
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*
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* "modWithQuotient" might be a better name for this function, but I would
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* rather not change the name now.
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*/
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void BigUnsigned::divideWithRemainder(const BigUnsigned &b, BigUnsigned &q) {
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/* Defending against aliased calls is more complex than usual because we
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* are writing to both *this and q.
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*
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* It would be silly to try to write quotient and remainder to the
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* same variable. Rule that out right away. */
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if (this == &q)
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throw "BigUnsigned::divideWithRemainder: Cannot write quotient and remainder into the same variable";
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/* Now *this and q are separate, so the only concern is that b might be
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* aliased to one of them. If so, use a temporary copy of b. */
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if (this == &b || &q == &b) {
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BigUnsigned tmpB(b);
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divideWithRemainder(tmpB, q);
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return;
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}
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/*
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* Knuth's definition of mod (which this function uses) is somewhat
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* different from the C++ definition of % in case of division by 0.
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*
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* We let a / 0 == 0 (it doesn't matter much) and a % 0 == a, no
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* exceptions thrown. This allows us to preserve both Knuth's demand
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* that a mod 0 == a and the useful property that
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* (a / b) * b + (a % b) == a.
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*/
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if (b.len == 0) {
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q.len = 0;
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return;
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}
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/*
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* If *this.len < b.len, then *this < b, and we can be sure that b doesn't go into
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* *this at all. The quotient is 0 and *this is already the remainder (so leave it alone).
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*/
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if (len < b.len) {
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q.len = 0;
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return;
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}
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// At this point we know (*this).len >= b.len > 0. (Whew!)
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/*
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* Overall method:
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*
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* For each appropriate i and i2, decreasing:
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* Subtract (b << (i blocks and i2 bits)) from *this, storing the
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* result in subtractBuf.
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* If the subtraction succeeds with a nonnegative result:
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* Turn on bit i2 of block i of the quotient q.
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* Copy subtractBuf back into *this.
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* Otherwise bit i2 of block i remains off, and *this is unchanged.
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*
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* Eventually q will contain the entire quotient, and *this will
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* be left with the remainder.
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*
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* subtractBuf[x] corresponds to blk[x], not blk[x+i], since 2005.01.11.
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* But on a single iteration, we don't touch the i lowest blocks of blk
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* (and don't use those of subtractBuf) because these blocks are
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* unaffected by the subtraction: we are subtracting
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* (b << (i blocks and i2 bits)), which ends in at least `i' zero
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* blocks. */
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// Variables for the calculation
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Index i, j, k;
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unsigned int i2;
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Blk temp;
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bool borrowIn, borrowOut;
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/*
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* Make sure we have an extra zero block just past the value.
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*
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* When we attempt a subtraction, we might shift `b' so
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* its first block begins a few bits left of the dividend,
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* and then we'll try to compare these extra bits with
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* a nonexistent block to the left of the dividend. The
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* extra zero block ensures sensible behavior; we need
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* an extra block in `subtractBuf' for exactly the same reason.
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*/
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Index origLen = len; // Save real length.
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/* To avoid an out-of-bounds access in case of reallocation, allocate
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* first and then increment the logical length. */
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allocateAndCopy(len + 1);
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len++;
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blk[origLen] = 0; // Zero the added block.
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// subtractBuf holds part of the result of a subtraction; see above.
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Blk *subtractBuf = new Blk[len];
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// Set preliminary length for quotient and make room
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q.len = origLen - b.len + 1;
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q.allocate(q.len);
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|
// Zero out the quotient
|
|
for (i = 0; i < q.len; i++)
|
|
q.blk[i] = 0;
|
|
|
|
// For each possible left-shift of b in blocks...
|
|
i = q.len;
|
|
while (i > 0) {
|
|
i--;
|
|
// For each possible left-shift of b in bits...
|
|
// (Remember, N is the number of bits in a Blk.)
|
|
q.blk[i] = 0;
|
|
i2 = N;
|
|
while (i2 > 0) {
|
|
i2--;
|
|
/*
|
|
* Subtract b, shifted left i blocks and i2 bits, from *this,
|
|
* and store the answer in subtractBuf. In the for loop, `k == i + j'.
|
|
*
|
|
* Compare this to the middle section of `multiply'. They
|
|
* are in many ways analogous. See especially the discussion
|
|
* of `getShiftedBlock'.
|
|
*/
|
|
for (j = 0, k = i, borrowIn = false; j <= b.len; j++, k++) {
|
|
temp = blk[k] - getShiftedBlock(b, j, i2);
|
|
borrowOut = (temp > blk[k]);
|
|
if (borrowIn) {
|
|
borrowOut |= (temp == 0);
|
|
temp--;
|
|
}
|
|
// Since 2005.01.11, indices of `subtractBuf' directly match those of `blk', so use `k'.
|
|
subtractBuf[k] = temp;
|
|
borrowIn = borrowOut;
|
|
}
|
|
// No more extra iteration to deal with `bHigh'.
|
|
// Roll-over a borrow as necessary.
|
|
for (; k < origLen && borrowIn; k++) {
|
|
borrowIn = (blk[k] == 0);
|
|
subtractBuf[k] = blk[k] - 1;
|
|
}
|
|
/*
|
|
* If the subtraction was performed successfully (!borrowIn),
|
|
* set bit i2 in block i of the quotient.
|
|
*
|
|
* Then, copy the portion of subtractBuf filled by the subtraction
|
|
* back to *this. This portion starts with block i and ends--
|
|
* where? Not necessarily at block `i + b.len'! Well, we
|
|
* increased k every time we saved a block into subtractBuf, so
|
|
* the region of subtractBuf we copy is just [i, k).
|
|
*/
|
|
if (!borrowIn) {
|
|
q.blk[i] |= (Blk(1) << i2);
|
|
while (k > i) {
|
|
k--;
|
|
blk[k] = subtractBuf[k];
|
|
}
|
|
}
|
|
}
|
|
}
|
|
// Zap possible leading zero in quotient
|
|
if (q.blk[q.len - 1] == 0)
|
|
q.len--;
|
|
// Zap any/all leading zeros in remainder
|
|
zapLeadingZeros();
|
|
// Deallocate subtractBuf.
|
|
// (Thanks to Brad Spencer for noticing my accidental omission of this!)
|
|
delete [] subtractBuf;
|
|
}
|
|
|
|
/* BITWISE OPERATORS
|
|
* These are straightforward blockwise operations except that they differ in
|
|
* the output length and the necessity of zapLeadingZeros. */
|
|
|
|
void BigUnsigned::bitAnd(const BigUnsigned &a, const BigUnsigned &b) {
|
|
DTRT_ALIASED(this == &a || this == &b, bitAnd(a, b));
|
|
// The bitwise & can't be longer than either operand.
|
|
len = (a.len >= b.len) ? b.len : a.len;
|
|
allocate(len);
|
|
Index i;
|
|
for (i = 0; i < len; i++)
|
|
blk[i] = a.blk[i] & b.blk[i];
|
|
zapLeadingZeros();
|
|
}
|
|
|
|
void BigUnsigned::bitOr(const BigUnsigned &a, const BigUnsigned &b) {
|
|
DTRT_ALIASED(this == &a || this == &b, bitOr(a, b));
|
|
Index i;
|
|
const BigUnsigned *a2, *b2;
|
|
if (a.len >= b.len) {
|
|
a2 = &a;
|
|
b2 = &b;
|
|
} else {
|
|
a2 = &b;
|
|
b2 = &a;
|
|
}
|
|
allocate(a2->len);
|
|
for (i = 0; i < b2->len; i++)
|
|
blk[i] = a2->blk[i] | b2->blk[i];
|
|
for (; i < a2->len; i++)
|
|
blk[i] = a2->blk[i];
|
|
len = a2->len;
|
|
// Doesn't need zapLeadingZeros.
|
|
}
|
|
|
|
void BigUnsigned::bitXor(const BigUnsigned &a, const BigUnsigned &b) {
|
|
DTRT_ALIASED(this == &a || this == &b, bitXor(a, b));
|
|
Index i;
|
|
const BigUnsigned *a2, *b2;
|
|
if (a.len >= b.len) {
|
|
a2 = &a;
|
|
b2 = &b;
|
|
} else {
|
|
a2 = &b;
|
|
b2 = &a;
|
|
}
|
|
allocate(a2->len);
|
|
for (i = 0; i < b2->len; i++)
|
|
blk[i] = a2->blk[i] ^ b2->blk[i];
|
|
for (; i < a2->len; i++)
|
|
blk[i] = a2->blk[i];
|
|
len = a2->len;
|
|
zapLeadingZeros();
|
|
}
|
|
|
|
void BigUnsigned::bitShiftLeft(const BigUnsigned &a, int b) {
|
|
DTRT_ALIASED(this == &a, bitShiftLeft(a, b));
|
|
if (b < 0) {
|
|
if (b << 1 == 0)
|
|
throw "BigUnsigned::bitShiftLeft: "
|
|
"Pathological shift amount not implemented";
|
|
else {
|
|
bitShiftRight(a, -b);
|
|
return;
|
|
}
|
|
}
|
|
Index shiftBlocks = b / N;
|
|
unsigned int shiftBits = b % N;
|
|
// + 1: room for high bits nudged left into another block
|
|
len = a.len + shiftBlocks + 1;
|
|
allocate(len);
|
|
Index i, j;
|
|
for (i = 0; i < shiftBlocks; i++)
|
|
blk[i] = 0;
|
|
for (j = 0, i = shiftBlocks; j <= a.len; j++, i++)
|
|
blk[i] = getShiftedBlock(a, j, shiftBits);
|
|
// Zap possible leading zero
|
|
if (blk[len - 1] == 0)
|
|
len--;
|
|
}
|
|
|
|
void BigUnsigned::bitShiftRight(const BigUnsigned &a, int b) {
|
|
DTRT_ALIASED(this == &a, bitShiftRight(a, b));
|
|
if (b < 0) {
|
|
if (b << 1 == 0)
|
|
throw "BigUnsigned::bitShiftRight: "
|
|
"Pathological shift amount not implemented";
|
|
else {
|
|
bitShiftLeft(a, -b);
|
|
return;
|
|
}
|
|
}
|
|
// This calculation is wacky, but expressing the shift as a left bit shift
|
|
// within each block lets us use getShiftedBlock.
|
|
Index rightShiftBlocks = (b + N - 1) / N;
|
|
unsigned int leftShiftBits = N * rightShiftBlocks - b;
|
|
// Now (N * rightShiftBlocks - leftShiftBits) == b
|
|
// and 0 <= leftShiftBits < N.
|
|
if (rightShiftBlocks >= a.len + 1) {
|
|
// All of a is guaranteed to be shifted off, even considering the left
|
|
// bit shift.
|
|
len = 0;
|
|
return;
|
|
}
|
|
// Now we're allocating a positive amount.
|
|
// + 1: room for high bits nudged left into another block
|
|
len = a.len + 1 - rightShiftBlocks;
|
|
allocate(len);
|
|
Index i, j;
|
|
for (j = rightShiftBlocks, i = 0; j <= a.len; j++, i++)
|
|
blk[i] = getShiftedBlock(a, j, leftShiftBits);
|
|
// Zap possible leading zero
|
|
if (blk[len - 1] == 0)
|
|
len--;
|
|
}
|
|
|
|
// INCREMENT/DECREMENT OPERATORS
|
|
|
|
// Prefix increment
|
|
void BigUnsigned::operator ++() {
|
|
Index i;
|
|
bool carry = true;
|
|
for (i = 0; i < len && carry; i++) {
|
|
blk[i]++;
|
|
carry = (blk[i] == 0);
|
|
}
|
|
if (carry) {
|
|
// Allocate and then increase length, as in divideWithRemainder
|
|
allocateAndCopy(len + 1);
|
|
len++;
|
|
blk[i] = 1;
|
|
}
|
|
}
|
|
|
|
// Postfix increment: same as prefix
|
|
void BigUnsigned::operator ++(int) {
|
|
operator ++();
|
|
}
|
|
|
|
// Prefix decrement
|
|
void BigUnsigned::operator --() {
|
|
if (len == 0)
|
|
throw "BigUnsigned::operator --(): Cannot decrement an unsigned zero";
|
|
Index i;
|
|
bool borrow = true;
|
|
for (i = 0; borrow; i++) {
|
|
borrow = (blk[i] == 0);
|
|
blk[i]--;
|
|
}
|
|
// Zap possible leading zero (there can only be one)
|
|
if (blk[len - 1] == 0)
|
|
len--;
|
|
}
|
|
|
|
// Postfix decrement: same as prefix
|
|
void BigUnsigned::operator --(int) {
|
|
operator --();
|
|
}
|