Tweaks to PPB_VarArrayBuffer in preperation for taking out of Dev.

ppapi/cpp/dev/var_array_buffer_dev.h

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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_VAR_ARRAY_BUFFER_DEV_H_
 #define PPAPI_CPP_DEV_VAR_ARRAY_BUFFER_DEV_H_
 
 #include "ppapi/cpp/var.h"
 
 /// @file
 /// This file defines the API for interacting with an ArrayBuffer.
 
 namespace pp {
 
 /// VarArrayBuffer_Dev provides a way to interact with JavaScript ArrayBuffers,
 /// which represent a contiguous sequence of bytes. Note that
 /// VarArrayBuffer_Devs are not part of the embedding page's DOM, and can only
 /// be shared with JavaScript via pp::Instance's PostMessage and HandleMessage
 /// functions.
 class VarArrayBuffer_Dev : public Var {
  public:
   /// Contruct a VarArrayBuffer_Dev given a var for which is_array_buffer() is
-  /// true. This will refer to the same buffer as var, but allows you to access
-  /// methods specific to VarArrayBuffer_Dev.
+  /// true. This will refer to the same ArrayBuffer as var, but allows you to
+  /// access methods specific to VarArrayBuffer_Dev.
   ///
-  /// @param[in] var An array buffer Var.
+  /// @param[in] var An ArrayBuffer Var.
   explicit VarArrayBuffer_Dev(const Var& var);
 
+  /// Copy constructor.
   VarArrayBuffer_Dev(const VarArrayBuffer_Dev& buffer) : Var(buffer) {}
 
+  virtual ~VarArrayBuffer_Dev() {}
+
+  /// This function assigns one VarArrayBuffer to another VarArrayBuffer.
+  ///
+  /// @param[in] other The VarArrayBuffer to be assigned.
+  ///
+  /// @return The resulting VarArrayBuffer.
+  VarArrayBuffer_Dev& operator=(const VarArrayBuffer_Dev& other);
+
+  /// This function assigns one VarArrayBuffer to another VarArrayBuffer. Var's
+  /// assignment operator is overloaded here so that we can check for assigning
+  /// a non-ArrayBuffer var to a VarArrayBuffer_Dev.
+  ///
+  /// @param[in] other The VarArrayBuffer to be assigned.
+  ///
+  /// @return The resulting VarArrayBuffer (as a Var&).
+  virtual Var& operator=(const Var& other);
+
   /// Construct a new VarArrayBuffer_Dev which is size_in_bytes bytes long and
   /// initialized to zero.
   ///
-  /// @param[in] size_in_bytes The size of the constructed array in bytes.
+  /// @param[in] size_in_bytes The size of the constructed ArrayBuffer in bytes.
   VarArrayBuffer_Dev(uint32_t size_in_bytes);
 
   /// Return the length of the VarArrayBuffer_Dev in bytes.
   ///
   /// @return The length of the VarArrayBuffer_Dev in bytes.
   uint32_t ByteLength() const;
 
-  /// Return a pointer to the buffer associated with this VarArrayBuffer_Dev.
+  /// Maps the ArrayBuffer in to the module's address space and returns a
+  /// pointer to the internal buffer for this ArrayBuffer.
   ///
-  /// @return A pointer to the buffer associated with this VarArrayBuffer_Dev.
+  /// Note that calling Map() can be a relatively expensive operation. Use care
+  /// when calling it in performance-critical code. For example, you should call
+  /// it only once when looping over an ArrayBuffer:
+  ///
+  /// <code>
+  ///   char* data = static_cast<char*>(array_buffer_var.Map());
+  ///   uint32_t byte_length = array_buffer_var.ByteLength();
+  ///   for (uint32_t i = 0; i < byte_length; ++i)
+  ///     data[i] = 'A';
+  /// </code>
+  ///
+  /// @return A pointer to the internal buffer for this ArrayBuffer.
   void* Map();
-  const void* Map() const;
 
-  virtual ~VarArrayBuffer_Dev() {}
-
- private:
-  // We cache the buffer so that repeated calls to Map() are quick.
-  void* buffer_;
+  /// Unmaps this ArrayBuffer var from the module address space. Use this if
+  /// you want to save memory but might want to Map the buffer again later.
+  void Unmap();
 };
 
 }  // namespace pp
 
 #endif  // PPAPI_CPP_DEV_VAR_ARRAY_BUFFER_DEV_H_