App APIs in Pepper: C++ APIs

ppapi/cpp/dev/optional_dev.h

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef PPAPI_CPP_DEV_OPTIONAL_DEV_H_
+#define PPAPI_CPP_DEV_OPTIONAL_DEV_H_
+
+#include "ppapi/c/dev/pp_optional_structs_dev.h"
+#include "ppapi/c/pp_bool.h"
+#include "ppapi/cpp/dev/may_own_ptr_dev.h"
+#include "ppapi/cpp/dev/string_wrapper_dev.h"
+#include "ppapi/cpp/logging.h"
+#include "ppapi/cpp/var.h"
+
+namespace pp {
+
+template <typename T>
+class Optional;
+
+template <>
+class Optional<double> {

[dmichael (off chromium), 2013/12/19 16:34:30]

optional suggestion: I think when you have more optional types, it might be
possible to have 1 template that covers the majority of types (at least
fundamental ones like double). It looks like you could use a similar strategy to
the Callback traits to get the parameter, return, and storage types.

OTOH, if there aren't too many, this style you have now is very readable. So... 
I guess, just take it as a suggestion you can do in the future to reduce code if
it helps.

[yzshen1, 2013/12/19 17:57:58]

I am thinking we could use the generic one for all struct wrapper classes, and
add specialized ones for primitive types. What do you think?

I haven't added the generic version because it is not needed the alarms API. I
think we could add it later.

Thanks!

+ public:
+  typedef const PP_Optional_Double_Dev* CInputType;
+
+  Optional() {}
+
+  Optional(double value) { set(value); }
+
+  // Creates an accessor to |storage| but doesn't take ownership of it.
+  // |storage| must live longer than this object. The contents pointed to by
+  // |storage| must be zero-initialized by the caller.
+  Optional(PP_Optional_Double_Dev* storage, NotOwned)
+      : storage_(storage, NOT_OWNED) {
+  }
+
+  Optional(const Optional<double>& other) { *storage_ = *other.storage_; }
+
+  Optional<double>& operator=(const Optional<double>& other) {
+    return operator=(*other.storage_);
+  }
+
+  Optional<double>& operator=(const PP_Optional_Double_Dev& other) {
+    if (storage_.get() == &other)
+      return *this;
+
+    *storage_ = other;
+    return *this;
+  }
+
+  bool is_set() const { return PP_ToBool(storage_->is_set); }
+  void unset() { storage_->is_set = PP_FALSE; }
+
+  double get() const {
+    PP_DCHECK(is_set());
+    return storage_->value;
+  }
+
+  void set(double value) {
+    storage_->value = value;
+    storage_->is_set = PP_TRUE;
+  }
+
+  const PP_Optional_Double_Dev* ToCInput() const { return storage_.get(); }
+
+  PP_Optional_Double_Dev* StartRawUpdate() { return storage_.get(); }
+  void EndRawUpdate() {}
+
+ private:
+  internal::MayOwnPtr<PP_Optional_Double_Dev> storage_;
+};
+
+template <>
+class Optional<std::string> {
+ public:
+  typedef const PP_Var& CInputType;
+
+  Optional() {}
+
+  Optional(const std::string& value) : wrapper_(value) {}
+
+  // Creates an accessor to |storage| but doesn't take ownership of it.
+  // |storage| must live longer than this object. The contents pointed to by
+  // |storage| must be zero-initialized by the caller.
+  Optional(PP_Var* storage, NotOwned) : wrapper_(storage, NOT_OWNED) {}
+
+  Optional(const Optional<std::string>& other) : wrapper_(other.wrapper_) {}
+
+  Optional<std::string>& operator=(const Optional<std::string>& other) {
+    wrapper_ = other.wrapper_;
+    return *this;
+  }
+
+  Optional<std::string>& operator=(const PP_Var& other) {
+    wrapper_ = other;
+    return *this;
+  }
+
+  bool is_set() const { return wrapper_.is_set(); }
+  void unset() { wrapper_.unset(); }
+  std::string get() const { return wrapper_.get(); }
+  void set(const std::string& value) { wrapper_.set(value); }
+
+  const PP_Var& ToCInput() const { return wrapper_.ToVar(); }
+
+  PP_Var* StartRawUpdate() { return wrapper_.StartRawUpdate(); }
+  void EndRawUpdate() { wrapper_.EndRawUpdate(); }
+
+ private:
+  internal::OptionalStringWrapper wrapper_;
+};
+
+}  // namespace pp
+
+#endif  // PPAPI_CPP_DEV_OPTIONAL_DEV_H_