base/memory/ref_counted_memory.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_MEMORY_REF_COUNTED_MEMORY_H_
   6 #define BASE_MEMORY_REF_COUNTED_MEMORY_H_
   7
   8 #include <string>
   9 #include <vector>
  10
  11 #include "base/base_export.h"
  12 #include "base/compiler_specific.h"
  13 #include "base/memory/ref_counted.h"
  14
  15 namespace base {
  16
  17 // A generic interface to memory. This object is reference counted because one
  18 // of its two subclasses own the data they carry, and we need to have
  19 // heterogeneous containers of these two types of memory.
  20 class BASE_EXPORT RefCountedMemory
  21     : public base::RefCountedThreadSafe<RefCountedMemory> {
  22  public:
  23   // Retrieves a pointer to the beginning of the data we point to. If the data
  24   // is empty, this will return NULL.
  25   virtual const unsigned char* front() const = 0;
  26
  27   // Size of the memory pointed to.
  28   virtual size_t size() const = 0;
  29
  30  protected:
  31   friend class base::RefCountedThreadSafe<RefCountedMemory>;
  32   RefCountedMemory();
  33   virtual ~RefCountedMemory();
  34 };
  35
  36 // An implementation of RefCountedMemory, where the ref counting does not
  37 // matter.
  38 class BASE_EXPORT RefCountedStaticMemory : public RefCountedMemory {
  39  public:
  40   RefCountedStaticMemory()
  41       : data_(NULL), length_(0) {}
  42   RefCountedStaticMemory(const unsigned char* data, size_t length)
  43       : data_(length ? data : NULL), length_(length) {}
  44
  45   // Overridden from RefCountedMemory:
  46   virtual const unsigned char* front() const OVERRIDE;
  47   virtual size_t size() const OVERRIDE;
  48
  49  private:
  50   virtual ~RefCountedStaticMemory();
  51
  52   const unsigned char* data_;
  53   size_t length_;
  54
  55   DISALLOW_COPY_AND_ASSIGN(RefCountedStaticMemory);
  56 };
  57
  58 // An implementation of RefCountedMemory, where we own our the data in a
  59 // vector.
  60 class BASE_EXPORT RefCountedBytes : public RefCountedMemory {
  61  public:
  62   RefCountedBytes();
  63
  64   // Constructs a RefCountedBytes object by _copying_ from |initializer|.
  65   RefCountedBytes(const std::vector<unsigned char>& initializer);
  66
  67   // Constructs a RefCountedBytes object by performing a swap. (To non
  68   // destructively build a RefCountedBytes, use the constructor that takes a
  69   // vector.)
  70   static RefCountedBytes* TakeVector(std::vector<unsigned char>* to_destroy);
  71
  72   // Overridden from RefCountedMemory:
  73   virtual const unsigned char* front() const OVERRIDE;
  74   virtual size_t size() const OVERRIDE;
  75
  76   const std::vector<unsigned char>& data() const { return data_; }
  77   std::vector<unsigned char>& data() { return data_; }
  78
  79  private:
  80   virtual ~RefCountedBytes();
  81
  82   std::vector<unsigned char> data_;
  83
  84   DISALLOW_COPY_AND_ASSIGN(RefCountedBytes);
  85 };
  86
  87 // An implementation of RefCountedMemory, where the bytes are stored in an STL
  88 // string. Use this if your data naturally arrives in that format.
  89 class BASE_EXPORT RefCountedString : public RefCountedMemory {
  90  public:
  91   RefCountedString();
  92
  93   // Constructs a RefCountedString object by performing a swap. (To non
  94   // destructively build a RefCountedString, use the default constructor and
  95   // copy into object->data()).
  96   static RefCountedString* TakeString(std::string* to_destroy);
  97
  98   // Overridden from RefCountedMemory:
  99   virtual const unsigned char* front() const OVERRIDE;
 100   virtual size_t size() const OVERRIDE;
 101
 102   const std::string& data() const { return data_; }
 103   std::string& data() { return data_; }
 104
 105  private:
 106   virtual ~RefCountedString();
 107
 108   std::string data_;
 109
 110   DISALLOW_COPY_AND_ASSIGN(RefCountedString);
 111 };
 112
 113 }  // namespace base
 114
 115 #endif  // BASE_MEMORY_REF_COUNTED_MEMORY_H_