1 /* 2 * SharedBuffer.h 3 * Android 4 * 5 * Copyright 2005 The Android Open Source Project 6 * 7 */ 8 9 #ifndef ANDROID_SHARED_BUFFER_H 10 #define ANDROID_SHARED_BUFFER_H 11 12 #include <stdint.h> 13 #include <sys/types.h> 14 15 // --------------------------------------------------------------------------- 16 17 namespace android { 18 19 class SharedBuffer 20 { 21 public: 22 23 /* flags to use with release() */ 24 enum { 25 eKeepStorage = 0x00000001 26 }; 27 28 /*! allocate a buffer of size 'size' and acquire() it. 29 * call release() to free it. 30 */ 31 static SharedBuffer* alloc(size_t size); 32 33 /*! free the memory associated with the SharedBuffer. 34 * Fails if there are any users associated with this SharedBuffer. 35 * In other words, the buffer must have been release by all its 36 * users. 37 */ 38 static ssize_t dealloc(const SharedBuffer* released); 39 40 //! get the SharedBuffer from the data pointer 41 static inline const SharedBuffer* sharedBuffer(const void* data); 42 43 //! access the data for read 44 inline const void* data() const; 45 46 //! access the data for read/write 47 inline void* data(); 48 49 //! get size of the buffer 50 inline size_t size() const; 51 52 //! get back a SharedBuffer object from its data 53 static inline SharedBuffer* bufferFromData(void* data); 54 55 //! get back a SharedBuffer object from its data 56 static inline const SharedBuffer* bufferFromData(const void* data); 57 58 //! get the size of a SharedBuffer object from its data 59 static inline size_t sizeFromData(const void* data); 60 61 //! edit the buffer (get a writtable, or non-const, version of it) 62 SharedBuffer* edit() const; 63 64 //! edit the buffer, resizing if needed 65 SharedBuffer* editResize(size_t size) const; 66 67 //! like edit() but fails if a copy is required 68 SharedBuffer* attemptEdit() const; 69 70 //! resize and edit the buffer, loose it's content. 71 SharedBuffer* reset(size_t size) const; 72 73 //! acquire/release a reference on this buffer 74 void acquire() const; 75 76 /*! release a reference on this buffer, with the option of not 77 * freeing the memory associated with it if it was the last reference 78 * returns the previous reference count 79 */ 80 int32_t release(uint32_t flags = 0) const; 81 82 //! returns wether or not we're the only owner 83 inline bool onlyOwner() const; 84 85 86 private: 87 inline SharedBuffer() { } 88 inline ~SharedBuffer() { } 89 inline SharedBuffer(const SharedBuffer&); 90 91 // 16 bytes. must be sized to preserve correct alingment. 92 mutable int32_t mRefs; 93 size_t mSize; 94 uint32_t mReserved[2]; 95 }; 96 97 // --------------------------------------------------------------------------- 98 99 const SharedBuffer* SharedBuffer::sharedBuffer(const void* data) { 100 return data ? reinterpret_cast<const SharedBuffer *>(data)-1 : 0; 101 } 102 103 const void* SharedBuffer::data() const { 104 return this + 1; 105 } 106 107 void* SharedBuffer::data() { 108 return this + 1; 109 } 110 111 size_t SharedBuffer::size() const { 112 return mSize; 113 } 114 115 SharedBuffer* SharedBuffer::bufferFromData(void* data) 116 { 117 return ((SharedBuffer*)data)-1; 118 } 119 120 const SharedBuffer* SharedBuffer::bufferFromData(const void* data) 121 { 122 return ((const SharedBuffer*)data)-1; 123 } 124 125 size_t SharedBuffer::sizeFromData(const void* data) 126 { 127 return (((const SharedBuffer*)data)-1)->mSize; 128 } 129 130 bool SharedBuffer::onlyOwner() const { 131 return (mRefs == 1); 132 } 133 134 }; // namespace android 135 136 // --------------------------------------------------------------------------- 137 138 #endif // ANDROID_VECTOR_H 139
