Add utility functions for creating and accessing Dart_CObject structures

runtime/bin/dartutils.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 BIN_DARTUTILS_H_
 #define BIN_DARTUTILS_H_
 
 #include "bin/builtin.h"
 #include "include/dart_api.h"
 #include "platform/globals.h"
@@ skipping 86 matching lines @@
   static const char* kIdFieldName;
 
  private:
   static const char* GetCanonicalPath(const char* reference_dir,
                                       const char* filename);
 
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(DartUtils);
 };
 
+
+class CObject {
+ public:
+  explicit CObject(Dart_CObject *cobject) : cobject_(cobject) {}
+  Dart_CObject::Type type() { return cobject_->type; }
+
+  bool IsNull() { return type() == Dart_CObject::kNull; }
+  bool IsBool() { return type() == Dart_CObject::kBool; }
+  bool IsInt32() { return type() == Dart_CObject::kInt32; }
+  bool IsInt64() { return type() == Dart_CObject::kInt64; }
+  bool IsBigint() { return type() == Dart_CObject::kBigint; }
+  bool IsDouble() { return type() == Dart_CObject::kDouble; }
+  bool IsString() { return type() == Dart_CObject::kString; }
+  bool IsArray() { return type() == Dart_CObject::kArray; }
+  bool IsByteArray() { return type() == Dart_CObject::kByteArray; }
+
+  bool IsTrue() {
+    return type() == Dart_CObject::kBool && cobject_->value.as_bool;
+  }
+  bool IsFalse() {

[Mads Ager (google), 2012/02/20 12:38:38]

Blank line to separate these two?

[Søren Gjesse, 2012/02/21 08:24:25]

Done.

+    return type() == Dart_CObject::kBool && !cobject_->value.as_bool;
+  }
+
+  void* operator new(size_t size) {

[Mads Ager (google), 2012/02/20 12:38:38]

Could we make the new operator private? It seems to me that users should be
using the methods below to create CObjects?

[Søren Gjesse, 2012/02/21 08:24:25]

So I know it looks a bit confusing, but an instance of "class CObject" here is a
wrapper for a Dart_CObject pointer. The instance of "class CObject" only
provides easy access to Dart_CObject structures. So the NewXXX methods below all
returns Dart_CObject pointers, whereas a "new CObject" only creates a new
wrapper. The "class CObject" instance is like a handle to the raw object
Dart_CObject.

So the usage pattern is like this: 

Dart_CObject* raw_array = CObject:NewArray(10);
CObject array = new CObject(raw_array);
CObject answer = new CObject(CObject:NewInt32(42););

array->SetAt(2, answer);
ASSERT(array[2]->IsInt32());

// Then return array caller...

One can also just have wrappers stack allocated:

Dart_CObject* raw_array = CObject:NewArray(10);
CObject array(raw_array);
CObject answer(CObject:NewInt32(42););

array.SetAt(2, &answer);
ASSERT(array[2]->IsInt32());

// Then return array.AsApiObject() to caller...

I did start out with "class CObject" embedding a Dart_CObject member, but then
one would have to have both "class CObjectEmbedded" and "class CObjectRef" to
handle newly created Dart_CObject structures and Dart_CObject structures
received in callback. Also a "class CObjectEmbedded" embedding a Dart_CObject
member whould still have to dynamically allocate additional storage for e.g.
strings and arrays.

This might not be the most elegant approach - I would like to hide some of the
wrapping details, but I could not come up with anything better. Also without the
zone allocation of both the "class CObject" wrappers and the Dart_CObject "raw
objects" this would have been much more complicated. 

Also one should be aware that each call to the operator[] on a COBjectArray
creates a new CObject wrapper in the zone.

+    return Dart_ScopeAllocate(size);
+  }
+
+  static CObject* Null();
+  static CObject* True();
+  static CObject* False();
+  static CObject* Bool(bool value);
+  static Dart_CObject* New(Dart_CObject::Type type, int additional_bytes = 0);

[Mads Ager (google), 2012/02/20 12:38:38]

Can we make this one private as well? This doesn't seem like something a user
should use either?

[Søren Gjesse, 2012/02/21 08:24:25]

Done.

+  static Dart_CObject* NewInt32(int32_t value);
+  static Dart_CObject* NewInt64(int64_t value);
+  // kBigint,

[Mads Ager (google), 2012/02/20 12:38:38]

Add a TODO style comment instead?

[Søren Gjesse, 2012/02/21 08:24:25]

Done.

+  static Dart_CObject* NewDouble(double value);
+  static Dart_CObject* NewString(int length);
+  static Dart_CObject* NewString(const char* str);
+  static Dart_CObject* NewArray(int length);
+  // kByteArray,

[Mads Ager (google), 2012/02/20 12:38:38]

Ditto.

[Søren Gjesse, 2012/02/21 08:24:25]

Done.

+
+  Dart_CObject* AsApiCObject() { return cobject_; }
+
+ protected:
+  CObject() : cobject_(NULL) {}
+  Dart_CObject* cobject_;
+
+ private:
+  static Dart_CObject api_null_;
+  static Dart_CObject api_true_;
+  static Dart_CObject api_false_;
+  static CObject null_;
+  static CObject true_;
+  static CObject false_;
+};
+
+
+#define DECLARE_COBJECT_CONSTRUCTORS(t)                                        \
+  explicit CObject##t(Dart_CObject *cobject) : CObject(cobject) {              \
+    ASSERT(type() == Dart_CObject::k##t);                                      \
+    cobject_ = cobject;                                                        \
+  }                                                                            \
+  explicit CObject##t(CObject* cobject) : CObject() {                          \
+    ASSERT(cobject != NULL);                                                   \
+    ASSERT(cobject->type() == Dart_CObject::k##t);                             \
+    cobject_ = cobject->AsApiCObject();                                        \
+  }
+
+
+class CObjectBool : public CObject {
+ public:
+  DECLARE_COBJECT_CONSTRUCTORS(Bool)
+
+  bool Value() const { return cobject_->value.as_bool; }
+};
+
+
+class CObjectInt32 : public CObject {
+ public:
+  DECLARE_COBJECT_CONSTRUCTORS(Int32)
+
+  int32_t Value() const { return cobject_->value.as_int32; }
+};
+
+
+class CObjectInt64 : public CObject {
+ public:
+  DECLARE_COBJECT_CONSTRUCTORS(Int64)
+
+  int64_t Value() const { return cobject_->value.as_int64; }
+};
+
+
+class CObjectBigint : public CObject {
+ public:
+  DECLARE_COBJECT_CONSTRUCTORS(Bigint)
+
+  char* Value() const { return cobject_->value.as_bigint; }
+};
+
+
+class CObjectDouble : public CObject {
+ public:
+  DECLARE_COBJECT_CONSTRUCTORS(Double)
+
+  double Value() const { return cobject_->value.as_double; }
+};
+
+
+class CObjectString : public CObject {
+ public:
+  DECLARE_COBJECT_CONSTRUCTORS(String)
+
+  int Length() const { return strlen(cobject_->value.as_string); }
+  char* CString() const { return cobject_->value.as_string; }
+};
+
+
+class CObjectArray : public CObject {
+ public:
+  DECLARE_COBJECT_CONSTRUCTORS(Array)
+
+  int Length() const { return cobject_->value.as_array.length; }
+  CObject* operator[](int index) const {
+    return new CObject(cobject_->value.as_array.values[index]);
+  }
+  void SetAt(int index, CObject* value) {
+    cobject_->value.as_array.values[index] = value->AsApiCObject();
+  }
+};
+
 #endif  // BIN_DARTUTILS_H_