[vm] Revise Dart_IntegerToHexCString to avoid dependency on Bigint

runtime/vm/object.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef RUNTIME_VM_OBJECT_H_
 #define RUNTIME_VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 6440 matching lines @@
   virtual double AsDoubleValue() const;
   virtual int64_t AsInt64Value() const;
   virtual int64_t AsTruncatedInt64Value() const { return AsInt64Value(); }
   virtual uint32_t AsTruncatedUint32Value() const;
 
   virtual bool FitsIntoSmi() const;
 
   // Returns 0, -1 or 1.
   virtual int CompareWith(const Integer& other) const;
 
+  // Converts integer to hex string.
+  // TODO(alexmarkov): this method can become non-virtual once Bigint class is
+  // decoupled from Integer hierarchy.
+  virtual const char* ToHexCString(Zone* zone) const;
+
   // Return the most compact presentation of an integer.
   RawInteger* AsValidInteger() const;
 
   // Returns null to indicate that a bigint operation is required.
   RawInteger* ArithmeticOp(Token::Kind operation,
                            const Integer& other,
                            Heap::Space space = Heap::kNew) const;
   RawInteger* BitOp(Token::Kind operation,
                     const Integer& other,
                     Heap::Space space = Heap::kNew) const;
@@ skipping 137 matching lines @@
   virtual bool IsNegative() const { return Neg(); }
   virtual bool Equals(const Instance& other) const;
 
   virtual double AsDoubleValue() const;
   virtual int64_t AsInt64Value() const;
   virtual int64_t AsTruncatedInt64Value() const;
   virtual uint32_t AsTruncatedUint32Value() const;
 
   virtual int CompareWith(const Integer& other) const;
 
+  virtual const char* ToHexCString(Zone* zone) const;
+
   virtual bool CheckAndCanonicalizeFields(Thread* thread,
                                           const char** error_str) const;
 
   virtual bool FitsIntoSmi() const;
   bool FitsIntoInt64() const;
   bool FitsIntoUint64() const;
   uint64_t AsUint64Value() const;
 
   static intptr_t InstanceSize() {
     return RoundedAllocationSize(sizeof(RawBigint));
   }
 
   // Offsets of fields accessed directly by optimized code.
   static intptr_t neg_offset() { return OFFSET_OF(RawBigint, neg_); }
   static intptr_t used_offset() { return OFFSET_OF(RawBigint, used_); }
   static intptr_t digits_offset() { return OFFSET_OF(RawBigint, digits_); }
 
   // Accessors used by native calls from Dart.
   RawBool* neg() const { return raw_ptr()->neg_; }
   RawSmi* used() const { return raw_ptr()->used_; }
   RawTypedData* digits() const { return raw_ptr()->digits_; }
 
   // Accessors used by runtime calls from C++.
   bool Neg() const;
   intptr_t Used() const;
   uint32_t DigitAt(intptr_t index) const;
 
   const char* ToDecCString(Zone* zone) const;
-  const char* ToHexCString(Zone* zone) const;
 
   static const intptr_t kBitsPerDigit = 32;  // Same as _Bigint._DIGIT_BITS
   static const intptr_t kBytesPerDigit = 4;
   static const int64_t kDigitBase = 1LL << kBitsPerDigit;
   static const int64_t kDigitMask = kDigitBase - 1;
 
   static RawBigint* New(Heap::Space space = Heap::kNew);  // For snapshots.
 
   static RawBigint* New(bool neg,
                         intptr_t used,
@@ skipping 2328 matching lines @@
 
 inline void TypeArguments::SetHash(intptr_t value) const {
   // This is only safe because we create a new Smi, which does not cause
   // heap allocation.
   StoreSmi(&raw_ptr()->hash_, Smi::New(value));
 }
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_OBJECT_H_