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   // Returns true if |other| is byte for byte equal.
  31   bool Equals(const scoped_refptr<RefCountedMemory>& other) const;
  32
  33   // Handy method to simplify calling front() with a reinterpret_cast.
  34   template<typename T> const T* front_as() const {
  35     return reinterpret_cast<const T*>(front());
  36   }
  37
  38  protected:
  39   friend class base::RefCountedThreadSafe<RefCountedMemory>;
  40   RefCountedMemory();
  41   virtual ~RefCountedMemory();
  42 };
  43
  44 // An implementation of RefCountedMemory, where the ref counting does not
  45 // matter.
  46 class BASE_EXPORT RefCountedStaticMemory : public RefCountedMemory {
  47  public:
  48   RefCountedStaticMemory()
  49       : data_(NULL), length_(0) {}
  50   RefCountedStaticMemory(const void* data, size_t length)
  51       : data_(static_cast<const unsigned char*>(length ? data : NULL)),
  52         length_(length) {}
  53
  54   // Overridden from RefCountedMemory:
  55   const unsigned char* front() const override;
  56   size_t size() const override;
  57
  58  private:
  59   ~RefCountedStaticMemory() override;
  60
  61   const unsigned char* data_;
  62   size_t length_;
  63
  64   DISALLOW_COPY_AND_ASSIGN(RefCountedStaticMemory);
  65 };
  66
  67 // An implementation of RefCountedMemory, where we own the data in a vector.
  68 class BASE_EXPORT RefCountedBytes : public RefCountedMemory {
  69  public:
  70   RefCountedBytes();
  71
  72   // Constructs a RefCountedBytes object by _copying_ from |initializer|.
  73   explicit RefCountedBytes(const std::vector<unsigned char>& initializer);
  74
  75   // Constructs a RefCountedBytes object by copying |size| bytes from |p|.
  76   RefCountedBytes(const unsigned char* p, size_t size);
  77
  78   // Constructs a RefCountedBytes object by performing a swap. (To non
  79   // destructively build a RefCountedBytes, use the constructor that takes a
  80   // vector.)
  81   static RefCountedBytes* TakeVector(std::vector<unsigned char>* to_destroy);
  82
  83   // Overridden from RefCountedMemory:
  84   const unsigned char* front() const override;
  85   size_t size() const override;
  86
  87   const std::vector<unsigned char>& data() const { return data_; }
  88   std::vector<unsigned char>& data() { return data_; }
  89
  90  private:
  91   ~RefCountedBytes() override;
  92
  93   std::vector<unsigned char> data_;
  94
  95   DISALLOW_COPY_AND_ASSIGN(RefCountedBytes);
  96 };
  97
  98 // An implementation of RefCountedMemory, where the bytes are stored in an STL
  99 // string. Use this if your data naturally arrives in that format.
 100 class BASE_EXPORT RefCountedString : public RefCountedMemory {
 101  public:
 102   RefCountedString();
 103
 104   // Constructs a RefCountedString object by performing a swap. (To non
 105   // destructively build a RefCountedString, use the default constructor and
 106   // copy into object->data()).
 107   static RefCountedString* TakeString(std::string* to_destroy);
 108
 109   // Overridden from RefCountedMemory:
 110   const unsigned char* front() const override;
 111   size_t size() const override;
 112
 113   const std::string& data() const { return data_; }
 114   std::string& data() { return data_; }
 115
 116  private:
 117   ~RefCountedString() override;
 118
 119   std::string data_;
 120
 121   DISALLOW_COPY_AND_ASSIGN(RefCountedString);
 122 };
 123
 124 // An implementation of RefCountedMemory that holds a chunk of memory
 125 // previously allocated with malloc or calloc, and that therefore must be freed
 126 // using free().
 127 class BASE_EXPORT RefCountedMallocedMemory : public base::RefCountedMemory {
 128  public:
 129   RefCountedMallocedMemory(void* data, size_t length);
 130
 131   // Overridden from RefCountedMemory:
 132   const unsigned char* front() const override;
 133   size_t size() const override;
 134
 135  private:
 136   ~RefCountedMallocedMemory() override;
 137
 138   unsigned char* data_;
 139   size_t length_;
 140
 141   DISALLOW_COPY_AND_ASSIGN(RefCountedMallocedMemory);
 142 };
 143
 144 }  // namespace base
 145
 146 #endif  // BASE_MEMORY_REF_COUNTED_MEMORY_H_