michael@0: /*
michael@0:  * Copyright (C) 2005 The Android Open Source Project
michael@0:  *
michael@0:  * Licensed under the Apache License, Version 2.0 (the "License");
michael@0:  * you may not use this file except in compliance with the License.
michael@0:  * You may obtain a copy of the License at
michael@0:  *
michael@0:  *      http://www.apache.org/licenses/LICENSE-2.0
michael@0:  *
michael@0:  * Unless required by applicable law or agreed to in writing, software
michael@0:  * distributed under the License is distributed on an "AS IS" BASIS,
michael@0:  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
michael@0:  * See the License for the specific language governing permissions and
michael@0:  * limitations under the License.
michael@0:  */
michael@0: 
michael@0: #ifndef ANDROID_SHARED_BUFFER_H
michael@0: #define ANDROID_SHARED_BUFFER_H
michael@0: 
michael@0: #include <stdint.h>
michael@0: #include <sys/types.h>
michael@0: 
michael@0: // ---------------------------------------------------------------------------
michael@0: 
michael@0: namespace android {
michael@0: 
michael@0: class SharedBuffer
michael@0: {
michael@0: public:
michael@0: 
michael@0:     /* flags to use with release() */
michael@0:     enum {
michael@0:         eKeepStorage = 0x00000001
michael@0:     };
michael@0: 
michael@0:     /*! allocate a buffer of size 'size' and acquire() it.
michael@0:      *  call release() to free it.
michael@0:      */
michael@0:     static          SharedBuffer*           alloc(size_t size);
michael@0:     
michael@0:     /*! free the memory associated with the SharedBuffer.
michael@0:      * Fails if there are any users associated with this SharedBuffer.
michael@0:      * In other words, the buffer must have been release by all its
michael@0:      * users.
michael@0:      */
michael@0:     static          ssize_t                 dealloc(const SharedBuffer* released);
michael@0:     
michael@0:     //! get the SharedBuffer from the data pointer
michael@0:     static  inline  const SharedBuffer*     sharedBuffer(const void* data);
michael@0: 
michael@0:     //! access the data for read
michael@0:     inline          const void*             data() const;
michael@0:     
michael@0:     //! access the data for read/write
michael@0:     inline          void*                   data();
michael@0: 
michael@0:     //! get size of the buffer
michael@0:     inline          size_t                  size() const;
michael@0:  
michael@0:     //! get back a SharedBuffer object from its data
michael@0:     static  inline  SharedBuffer*           bufferFromData(void* data);
michael@0:     
michael@0:     //! get back a SharedBuffer object from its data
michael@0:     static  inline  const SharedBuffer*     bufferFromData(const void* data);
michael@0: 
michael@0:     //! get the size of a SharedBuffer object from its data
michael@0:     static  inline  size_t                  sizeFromData(const void* data);
michael@0:     
michael@0:     //! edit the buffer (get a writtable, or non-const, version of it)
michael@0:                     SharedBuffer*           edit() const;
michael@0: 
michael@0:     //! edit the buffer, resizing if needed
michael@0:                     SharedBuffer*           editResize(size_t size) const;
michael@0: 
michael@0:     //! like edit() but fails if a copy is required
michael@0:                     SharedBuffer*           attemptEdit() const;
michael@0:     
michael@0:     //! resize and edit the buffer, loose it's content.
michael@0:                     SharedBuffer*           reset(size_t size) const;
michael@0: 
michael@0:     //! acquire/release a reference on this buffer
michael@0:                     void                    acquire() const;
michael@0:                     
michael@0:     /*! release a reference on this buffer, with the option of not
michael@0:      * freeing the memory associated with it if it was the last reference
michael@0:      * returns the previous reference count
michael@0:      */     
michael@0:                     int32_t                 release(uint32_t flags = 0) const;
michael@0:     
michael@0:     //! returns wether or not we're the only owner
michael@0:     inline          bool                    onlyOwner() const;
michael@0:     
michael@0: 
michael@0: private:
michael@0:         inline SharedBuffer() { }
michael@0:         inline ~SharedBuffer() { }
michael@0:         inline SharedBuffer(const SharedBuffer&);
michael@0:  
michael@0:         // 16 bytes. must be sized to preserve correct alingment.
michael@0:         mutable int32_t        mRefs;
michael@0:                 size_t         mSize;
michael@0:                 uint32_t       mReserved[2];
michael@0: };
michael@0: 
michael@0: // ---------------------------------------------------------------------------
michael@0: 
michael@0: const SharedBuffer* SharedBuffer::sharedBuffer(const void* data) {
michael@0:     return data ? reinterpret_cast<const SharedBuffer *>(data)-1 : 0;
michael@0: }
michael@0: 
michael@0: const void* SharedBuffer::data() const {
michael@0:     return this + 1;
michael@0: }
michael@0: 
michael@0: void* SharedBuffer::data() {
michael@0:     return this + 1;
michael@0: }
michael@0: 
michael@0: size_t SharedBuffer::size() const {
michael@0:     return mSize;
michael@0: }
michael@0: 
michael@0: SharedBuffer* SharedBuffer::bufferFromData(void* data)
michael@0: {
michael@0:     return ((SharedBuffer*)data)-1;
michael@0: }
michael@0:     
michael@0: const SharedBuffer* SharedBuffer::bufferFromData(const void* data)
michael@0: {
michael@0:     return ((const SharedBuffer*)data)-1;
michael@0: }
michael@0: 
michael@0: size_t SharedBuffer::sizeFromData(const void* data)
michael@0: {
michael@0:     return (((const SharedBuffer*)data)-1)->mSize;
michael@0: }
michael@0: 
michael@0: bool SharedBuffer::onlyOwner() const {
michael@0:     return (mRefs == 1);
michael@0: }
michael@0: 
michael@0: }; // namespace android
michael@0: 
michael@0: // ---------------------------------------------------------------------------
michael@0: 
michael@0: #endif // ANDROID_VECTOR_H