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  * version 2 for more details (a copy is included in the LICENSE file that

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 #ifndef SHARE_VM_UTILITIES_SIZES_HPP

 #define SHARE_VM_UTILITIES_SIZES_HPP

 #include "memory/allocation.hpp"

 #include "utilities/globalDefinitions.hpp"

 // The following two classes are used to represent 'sizes' and 'offsets' in the VM;

 // they serve as 'unit' types. ByteSize is used for sizes measured in bytes, while

 // WordSize is used for sizes measured in machine words (i.e., 32bit or 64bit words

 // depending on platform).

 //

 // The classes are defined with friend functions operating on them instead of member

 // functions so that they (the classes) can be re-#define'd to int types in optimized

 // mode. This allows full type checking and maximum safety in debug mode, and full

 // optimizations (constant folding) and zero overhead (time and space wise) in the

 // optimized build (some compilers do not optimize one-element value classes but

 // instead create an object in memory - thus the overhead may be significant).

 //

 // Note: 1) DO NOT add new overloaded friend functions that do not have a unique function

 //          function name but require signature types for resolution. This will not work

 //          in optimized mode as both, ByteSize and WordSize are mapped to the same type

 //          and thus the distinction would not be possible anymore (=> compiler errors).

 //

 //       2) DO NOT add non-static member functions as they cannot be mapped so something

 //          compilable in the optimized build. Static member functions could be added

 //          but require a corresponding class definition in the optimized build.

 //

 // These classes should help doing a transition from (currently) word-size based offsets

 // to byte-size based offsets in the VM (this will be important if we desire to pack

 // objects more densely in the VM for 64bit machines). Such a transition should proceed

 // in two steps to minimize the risk of introducing hard-to-find bugs:

 //

 // a) first transition the whole VM into a form where all sizes are strongly typed

 // b) change all WordSize's to ByteSize's where desired and fix the compilation errors

 #ifdef ASSERT

 class ByteSize VALUE_OBJ_CLASS_SPEC {

  private:

   int _size;

   // Note: This constructor must be private to avoid implicit conversions!

   ByteSize(int size)                                  { _size = size; }

  public:

   // constructors

   inline friend ByteSize in_ByteSize(int size);

   // accessors

   inline friend int in_bytes(ByteSize x);

   // operators

   friend ByteSize operator + (ByteSize x, ByteSize y) { return ByteSize(in_bytes(x) + in_bytes(y)); }

   friend ByteSize operator - (ByteSize x, ByteSize y) { return ByteSize(in_bytes(x) - in_bytes(y)); }

   friend ByteSize operator * (ByteSize x, int      y) { return ByteSize(in_bytes(x) * y          ); }

   // comparison

   friend bool operator == (ByteSize x, ByteSize y)    { return in_bytes(x) == in_bytes(y); }

   friend bool operator != (ByteSize x, ByteSize y)    { return in_bytes(x) != in_bytes(y); }

   friend bool operator <  (ByteSize x, ByteSize y)    { return in_bytes(x) <  in_bytes(y); }

   friend bool operator <= (ByteSize x, ByteSize y)    { return in_bytes(x) <= in_bytes(y); }

   friend bool operator >  (ByteSize x, ByteSize y)    { return in_bytes(x) >  in_bytes(y); }

   friend bool operator >= (ByteSize x, ByteSize y)    { return in_bytes(x) >= in_bytes(y); }

 };

 inline ByteSize in_ByteSize(int size) { return ByteSize(size); }

 inline int      in_bytes(ByteSize x)  { return x._size; }

 class WordSize VALUE_OBJ_CLASS_SPEC {

  private:

   int _size;

   // Note: This constructor must be private to avoid implicit conversions!

   WordSize(int size)                                  { _size = size; }

  public:

   // constructors

   inline friend WordSize in_WordSize(int size);

   // accessors

   inline friend int in_words(WordSize x);

   // operators

   friend WordSize operator + (WordSize x, WordSize y) { return WordSize(in_words(x) + in_words(y)); }

   friend WordSize operator - (WordSize x, WordSize y) { return WordSize(in_words(x) - in_words(y)); }

   friend WordSize operator * (WordSize x, int      y) { return WordSize(in_words(x) * y          ); }

   // comparison

   friend bool operator == (WordSize x, WordSize y)    { return in_words(x) == in_words(y); }

   friend bool operator != (WordSize x, WordSize y)    { return in_words(x) != in_words(y); }

   friend bool operator <  (WordSize x, WordSize y)    { return in_words(x) <  in_words(y); }

   friend bool operator <= (WordSize x, WordSize y)    { return in_words(x) <= in_words(y); }

   friend bool operator >  (WordSize x, WordSize y)    { return in_words(x) >  in_words(y); }

   friend bool operator >= (WordSize x, WordSize y)    { return in_words(x) >= in_words(y); }

 };

 inline WordSize in_WordSize(int size) { return WordSize(size); }

 inline int      in_words(WordSize x)  { return x._size; }

 #else // ASSERT

 // The following definitions must match the corresponding friend declarations

 // in the Byte/WordSize classes if they are typedef'ed to be int. This will

 // be the case in optimized mode to ensure zero overhead for these types.

 //

 // Note: If a compiler does not inline these function calls away, one may

 //       want to use #define's to make sure full optimization (constant

 //       folding in particular) is possible.

 typedef int ByteSize;

 inline ByteSize in_ByteSize(int size)                 { return size; }

 inline int      in_bytes   (ByteSize x)               { return x; }

 typedef int WordSize;

 inline WordSize in_WordSize(int size)                 { return size; }

 inline int      in_words   (WordSize x)               { return x; }

 #endif // ASSERT

 // Use the following #define to get C++ field member offsets

 #define byte_offset_of(klass,field)   in_ByteSize((int)offset_of(klass, field))

 #endif // SHARE_VM_UTILITIES_SIZES_HPP