Re-land r93365 - add RefCountedString

base/memory/ref_counted_memory.h

 // Copyright (c) 2011 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_MEMORY_REF_COUNTED_MEMORY_H_
 #define BASE_MEMORY_REF_COUNTED_MEMORY_H_
 #pragma once
 
+#include <string>
 #include <vector>
 
 #include "base/base_api.h"
 #include "base/memory/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
@@ skipping 14 matching lines @@
   virtual ~RefCountedMemory();
 };
 
 // An implementation of RefCountedMemory, where the ref counting does not
 // matter.
 class BASE_API RefCountedStaticMemory : public RefCountedMemory {
  public:
   RefCountedStaticMemory()
       : data_(NULL), length_(0) {}
   RefCountedStaticMemory(const unsigned char* data, size_t length)
-      : data_(data), length_(length) {}
+      : data_(length ? data : NULL), length_(length) {}
 
-  // Overriden from RefCountedMemory:
+  // Overridden from RefCountedMemory:
   virtual const unsigned char* front() const;
   virtual size_t size() const;
 
  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 BASE_API RefCountedBytes : public RefCountedMemory {
  public:
   RefCountedBytes();
 
   // Constructs a RefCountedBytes object by _copying_ from |initializer|.
   RefCountedBytes(const std::vector<unsigned char>& initializer);
 
   // 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);
 
-  // Overriden from RefCountedMemory:
+  // Overridden from RefCountedMemory:
   virtual const unsigned char* front() const;
   virtual size_t size() const;
 
-  std::vector<unsigned char> data;
+  std::vector<unsigned char>* data() { return &data_; }
 
- protected:
+ private:
   friend class base::RefCountedThreadSafe<RefCountedBytes>;
   virtual ~RefCountedBytes();
 
- private:
+  std::vector<unsigned char> data_;
+
   DISALLOW_COPY_AND_ASSIGN(RefCountedBytes);
 };
 
+namespace base {
+
+// An implementation of RefCountedMemory, where the bytes are stored in an STL
+// string. Use this if your data naturally arrives in that format.
+class BASE_API RefCountedString : public RefCountedMemory {
+ public:
+  RefCountedString();
+
+  // Constructs a RefCountedString object by performing a swap. (To non
+  // destructively build a RefCountedString, use the default constructor and
+  // copy into object->data()).
+  static RefCountedString* TakeString(std::string* to_destroy);
+
+  // Overridden from RefCountedMemory:
+  virtual const unsigned char* front() const;
+  virtual size_t size() const;
+
+  std::string* data() { return &data_; }

[brettw, 2011/07/19 19:58:45]

Is there any reason not to return this as a ref? I guess I would have done:
  const std::string& data() const { return data_; }
  std::string& data() { return data_; }
Maybe the same for RefCountedBytes, which would clean up some of the callers?
What do you think?

[joth, 2011/07/20 12:53:03]

I was overpowered by the "references must be const" rule.
Done. This does mean I'm now sometimes taking the address of the returned ref
which is a little odd in my eye, but technically fine.

+
+ private:
+  friend class base::RefCountedThreadSafe<RefCountedString>;
+  virtual ~RefCountedString();
+
+  std::string data_;
+
+  DISALLOW_COPY_AND_ASSIGN(RefCountedString);
+};
+
+}  // namespace
+
 #endif  // BASE_MEMORY_REF_COUNTED_MEMORY_H_