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// This file is available under and governed by the GNU General Public
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// However, the following notice accompanied the original version of this
// file:
//
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package jdk.nashorn.internal.runtime.doubleconv;
// This "Do It Yourself Floating Point" class implements a floating-point number
// with a uint64 significand and an int exponent. Normalized DiyFp numbers will
// have the most significant bit of the significand set.
// Multiplication and Subtraction do not normalize their results.
// DiyFp are not designed to contain special doubles (NaN and Infinity).
class DiyFp {
private long f_;
private int e_;
static final int kSignificandSize = 64;
static final long kUint64MSB = 0x8000000000000000L;
DiyFp() {
this.f_ = 0;
this.e_ = 0;
}
DiyFp(final long f, final int e) {
this.f_ = f;
this.e_ = e;
}
// this = this - other.
// The exponents of both numbers must be the same and the significand of this
// must be bigger than the significand of other.
// The result will not be normalized.
void subtract(final DiyFp other) {
assert (e_ == other.e_);
assert Long.compareUnsigned(f_, other.f_) >= 0;
f_ -= other.f_;
}
// Returns a - b.
// The exponents of both numbers must be the same and this must be bigger
// than other. The result will not be normalized.
static DiyFp minus(final DiyFp a, final DiyFp b) {
final DiyFp result = new DiyFp(a.f_, a.e_);
result.subtract(b);
return result;
}
// this = this * other.
final void multiply(final DiyFp other) {
// Simply "emulates" a 128 bit multiplication.
// However: the resulting number only contains 64 bits. The least
// significant 64 bits are only used for rounding the most significant 64
// bits.
final long kM32 = 0xFFFFFFFFL;
final long a = f_ >>> 32;
final long b = f_ & kM32;
final long c = other.f_ >>> 32;
final long d = other.f_ & kM32;
final long ac = a * c;
final long bc = b * c;
final long ad = a * d;
final long bd = b * d;
long tmp = (bd >>> 32) + (ad & kM32) + (bc & kM32);
// By adding 1U << 31 to tmp we round the final result.
// Halfway cases will be round up.
tmp += 1L << 31;
final long result_f = ac + (ad >>> 32) + (bc >>> 32) + (tmp >>> 32);
e_ += other.e_ + 64;
f_ = result_f;
}
// returns a * b;
static DiyFp times(final DiyFp a, final DiyFp b) {
final DiyFp result = new DiyFp(a.f_, a.e_);
result.multiply(b);
return result;
}
void normalize() {
assert(f_ != 0);
long significand = this.f_;
int exponent = this.e_;
// This method is mainly called for normalizing boundaries. In general
// boundaries need to be shifted by 10 bits. We thus optimize for this case.
final long k10MSBits = 0xFFC00000L << 32;
while ((significand & k10MSBits) == 0) {
significand <<= 10;
exponent -= 10;
}
while ((significand & kUint64MSB) == 0) {
significand <<= 1;
exponent--;
}
this.f_ = significand;
this.e_ = exponent;
}
static DiyFp normalize(final DiyFp a) {
final DiyFp result = new DiyFp(a.f_, a.e_);
result.normalize();
return result;
}
long f() { return f_; }
int e() { return e_; }
void setF(final long new_value) { f_ = new_value; }
void setE(final int new_value) { e_ = new_value; }
@Override
public String toString() {
return "DiyFp[f=" + f_ + ", e=" + e_ + "]";
}
}