[vm] Revise Dart_IntegerToHexCString to avoid dependency on Bigint

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index ed2c2c13ce9c63bf2b246838ef52332f122e69b2..c26c7881cde5a0631840ed96cbfff57b14eb049b 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -6461,6 +6461,9 @@ class Integer : public Number {
   // Return the most compact presentation of an integer.
   RawInteger* AsValidInteger() const;
 
+  // Converts integer to hex string.
+  virtual const char* ToHexCString(Zone* zone) const;

[siva, 2017/07/31 22:03:51]

Club this with virtual methods listed above.

Also please add a Note that when the Bigint class this decoupled from Integer
this method can become a regular method (de-virtualized).

[alexmarkov, 2017/08/01 15:42:28]

Done.

+
   // Returns null to indicate that a bigint operation is required.
   RawInteger* ArithmeticOp(Token::Kind operation,
                            const Integer& other,
@@ -6643,7 +6646,7 @@ class Bigint : public Integer {
   uint32_t DigitAt(intptr_t index) const;
 
   const char* ToDecCString(Zone* zone) const;
-  const char* ToHexCString(Zone* zone) const;
+  virtual const char* ToHexCString(Zone* zone) const;

[siva, 2017/07/31 22:03:51]

Club this with all virtual methods declared above.

[alexmarkov, 2017/08/01 15:42:28]

Done.

 
   static const intptr_t kBitsPerDigit = 32;  // Same as _Bigint._DIGIT_BITS
   static const intptr_t kBytesPerDigit = 4;