First fix to minimize copying of image data.

base/ref_counted_memory.h

+// Copyright (c) 2009 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 BASE_REF_COUNTED_MEMORY_H_
+#define BASE_REF_COUNTED_MEMORY_H_
+
+#include <vector>
+
+#include "base/ref_counted.h"
+
+// TODO(erg): The contents of this file should be in a namespace. This would
+// require touching >100 files in chrome/ though.
+
+// A generic interface to memory. This object is reference counted because one
+// of its two subclasses own the data they carry, and we need to have
+// heterogeneous containers of these two types of memory.
+class RefCountedMemory : public base::RefCountedThreadSafe< RefCountedMemory > {
+ public:
+  virtual ~RefCountedMemory() {}
+
+  // Retrieves a pointer to the beginning of the data we point to.
+  virtual const unsigned char* front() const = 0;
+
+  // Size of the memory pointed to.
+  virtual size_t size() const = 0;
+};
+
+// An implementation of RefCountedMemory, where the ref counting does not
+// matter.
+class RefCountedStaticMemory : public RefCountedMemory {
+ public:
+  RefCountedStaticMemory()
+      : data_(NULL), length_(0) {}
+  RefCountedStaticMemory(const unsigned char* data, size_t length)
+      : data_(data), length_(length) {}
+
+  virtual const unsigned char* front() const { return data_; }
+  virtual size_t size() const { return length_; }
+
+ private:
+  const unsigned char* data_;
+  size_t length_;
+
+  DISALLOW_COPY_AND_ASSIGN(RefCountedStaticMemory);
+};
+
+// An implementation of RefCountedMemory, where we own our the data in a
+// vector.
+class RefCountedBytes : public RefCountedMemory {
+ public:
+  // Constructs a RefCountedBytes object by performing a swap. (To non
+  // destructively build a RefCountedBytes, use the constructor that takes a
+  // vector.)
+  static RefCountedBytes* TakeVector(std::vector<unsigned char>* to_destroy) {
+    RefCountedBytes* bytes = new RefCountedBytes;
+    bytes->data.swap(*to_destroy);
+    return bytes;
+  }
+
+  RefCountedBytes() {}
+
+  // Constructs a RefCountedBytes object by _copying_ from |initializer|.
+  RefCountedBytes(const std::vector<unsigned char>& initializer)
+      : data(initializer) {}
+
+  virtual const unsigned char* front() const { return &data.front(); }
+  virtual size_t size() const { return data.size(); }
+
+  std::vector<unsigned char> data;
+
+  DISALLOW_COPY_AND_ASSIGN(RefCountedBytes);

[brettw, 2009/10/16 23:03:12]

It's not your fault, but can you fix this? Without "private"
DISALLOW_COPY_AND_ASSIGN does nothing. The similar code left in ref_counted_util
should have a private added as well.

+};
+
+#endif  // BASE_REF_COUNTED_MEMORY_H_