base: Add AsBinary() function to Value API.

This function should simplify some constructions.

Instead of:

if (!value->IsType(Value::TYPE_BINARY))
  return false;
  BinaryValue* binary_value = static_cast<BinaryValue*>(value);

You can do:

BinaryValue* binary_value = value->AsBinary();
if (!binary_value)
  return false;

BUG=None
TEST=base_unittests --gtest_filter=Values*

R=evan@chromium.org

Review URL: http://codereview.chromium.org/7748017

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@98266 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 22 insertions, 13 deletions

diff --git a/base/values.cc b/base/values.cc
index 1798695..ad53469 100644
--- a/base/values.cc
+++ b/base/values.cc
@@ -18,7 +18,7 @@ Value* CopyWithoutEmptyChildren(Value* node) {
   DCHECK(node);
   switch (node->GetType()) {
     case Value::TYPE_LIST: {
-      ListValue* list = static_cast<ListValue*>(node);
+      ListValue* list = node->AsList();
       ListValue* copy = new ListValue;
       for (ListValue::const_iterator it = list->begin(); it != list->end();
            ++it) {
@@ -97,6 +97,10 @@ StringValue* Value::CreateStringValue(const string16& in_value) {
   return new StringValue(in_value);
 }
 
+BinaryValue* Value::AsBinary() {
+  return NULL;
+}
+
 ListValue* Value::AsList() {
   return NULL;
 }
@@ -301,6 +305,10 @@ BinaryValue* BinaryValue::CreateWithCopiedBuffer(const char* buffer,
   return new BinaryValue(buffer_copy, size);
 }
 
+BinaryValue* BinaryValue::AsBinary() {
+  return this;
+}
+
 BinaryValue* BinaryValue::DeepCopy() const {
   return CreateWithCopiedBuffer(buffer_, size_);
 }
@@ -489,11 +497,11 @@ bool DictionaryValue::GetBinary(const std::string& path,
                                 BinaryValue** out_value) const {
   Value* value;
   bool result = Get(path, &value);
-  if (!result || !value->IsType(TYPE_BINARY))
+  if (!result || !value->AsBinary())
     return false;
 
   if (out_value)
-    *out_value = static_cast<BinaryValue*>(value);
+    *out_value = value->AsBinary();
 
   return true;
 }
@@ -519,7 +527,7 @@ bool DictionaryValue::GetList(const std::string& path,
     return false;
 
   if (out_value)
-    *out_value = static_cast<ListValue*>(value);
+    *out_value = value->AsList();
 
   return true;
 }
@@ -597,7 +605,7 @@ bool DictionaryValue::GetListWithoutPathExpansion(const std::string& key,
     return false;
 
   if (out_value)
-    *out_value = static_cast<ListValue*>(value);
+    *out_value = value->AsList();
 
   return true;
 }
@@ -810,7 +818,7 @@ bool ListValue::GetList(size_t index, ListValue** out_value) const {
     return false;
 
   if (out_value)
-    *out_value = static_cast<ListValue*>(value);
+    *out_value = value->AsList();
 
   return true;
 }
diff --git a/base/values.h b/base/values.h
index 2f41215..185729d 100644
--- a/base/values.h
+++ b/base/values.h
@@ -87,6 +87,7 @@ class BASE_EXPORT Value {
   // Returns true if the current object represents a given type.
   bool IsType(Type type) const { return type == type_; }
 
+  virtual BinaryValue* AsBinary();
   virtual ListValue* AsList();
 
   // These methods allow the convenient retrieval of settings.
@@ -195,6 +196,7 @@ class BASE_EXPORT BinaryValue: public Value {
   const char* GetBuffer() const { return buffer_; }
 
   // Overridden from Value:
+  virtual BinaryValue* AsBinary() OVERRIDE;
   virtual BinaryValue* DeepCopy() const OVERRIDE;
   virtual bool Equals(const Value* other) const OVERRIDE;
 
diff --git a/base/values_unittest.cc b/base/values_unittest.cc
index c8d3e3c..0ca19d9 100644
--- a/base/values_unittest.cc
+++ b/base/values_unittest.cc
@@ -416,14 +416,13 @@ TEST(ValuesTest, DeepCopy) {
   ASSERT_TRUE(copy_dict->Get("binary", &copy_binary));
   ASSERT_TRUE(copy_binary);
   ASSERT_NE(copy_binary, original_binary);
-  ASSERT_TRUE(copy_binary->IsType(Value::TYPE_BINARY));
-  ASSERT_NE(original_binary->GetBuffer(),
-    static_cast<BinaryValue*>(copy_binary)->GetBuffer());
-  ASSERT_EQ(original_binary->GetSize(),
-    static_cast<BinaryValue*>(copy_binary)->GetSize());
+  BinaryValue* binary_value = copy_binary->AsBinary();
+  ASSERT_TRUE(binary_value);
+  ASSERT_NE(original_binary->GetBuffer(), binary_value->GetBuffer());
+  ASSERT_EQ(original_binary->GetSize(), binary_value->GetSize());
   ASSERT_EQ(0, memcmp(original_binary->GetBuffer(),
-               static_cast<BinaryValue*>(copy_binary)->GetBuffer(),
-               original_binary->GetSize()));
+                      binary_value->GetBuffer(),
+                      original_binary->GetSize()));
 
   Value* copy_value = NULL;
   ASSERT_TRUE(copy_dict->Get("list", &copy_value));