Bignum implementation of Strtod.

src/double.h

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 64 matching lines @@
     f <<= DiyFp::kSignificandSize - kSignificandSize;
     e -= DiyFp::kSignificandSize - kSignificandSize;
     return DiyFp(f, e);
   }
 
   // Returns the double's bit as uint64.
   uint64_t AsUint64() const {
     return d64_;
   }
 
+  double NextDouble() const {
+    if (d64_ == kInfinity) return kInfinity;
+    return Double(d64_ + 1).value();
+  }
+
   int Exponent() const {
     if (IsDenormal()) return kDenormalExponent;
 
     uint64_t d64 = AsUint64();
     int biased_e =
         static_cast<int>((d64 & kExponentMask) >> kPhysicalSignificandSize);
     return biased_e - kExponentBias;
   }
 
   uint64_t Significand() const {
@@ skipping 18 matching lines @@
     uint64_t d64 = AsUint64();
     return (d64 & kExponentMask) == kExponentMask;
   }
 
   bool IsNan() const {
     uint64_t d64 = AsUint64();
     return ((d64 & kExponentMask) == kExponentMask) &&
         ((d64 & kSignificandMask) != 0);
   }
 
-
   bool IsInfinite() const {
     uint64_t d64 = AsUint64();
     return ((d64 & kExponentMask) == kExponentMask) &&
         ((d64 & kSignificandMask) == 0);
   }
 
-
   int Sign() const {
     uint64_t d64 = AsUint64();
     return (d64 & kSignMask) == 0? 1: -1;
   }
 
+  DiyFp UpperBoundary() const {
+    return DiyFp(Significand() * 2 + 1, Exponent() - 1);
+  }
 
   // Returns the two boundaries of this.
   // The bigger boundary (m_plus) is normalized. The lower boundary has the same
   // exponent as m_plus.
   void NormalizedBoundaries(DiyFp* out_m_minus, DiyFp* out_m_plus) const {
     DiyFp v = this->AsDiyFp();
     bool significand_is_zero = (v.f() == kHiddenBit);
     DiyFp m_plus = DiyFp::Normalize(DiyFp((v.f() << 1) + 1, v.e() - 1));
     DiyFp m_minus;
     if (significand_is_zero && v.e() != kDenormalExponent) {
@@ skipping 61 matching lines @@
       biased_exponent = static_cast<uint64_t>(exponent + kExponentBias);
     }
     return (significand & kSignificandMask) |
         (biased_exponent << kPhysicalSignificandSize);
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_DOUBLE_H_