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* Copyright (C) 2005 The Android Open Source Project
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <stdint.h>
#include <sys/types.h>
// ---------------------------------------------------------------------------
namespace android {
class SharedBuffer
/* flags to use with release() */
enum {
eKeepStorage = 0x00000001
/*! allocate a buffer of size 'size' and acquire() it.
* call release() to free it.
static SharedBuffer* alloc(size_t size);
/*! free the memory associated with the SharedBuffer.
* Fails if there are any users associated with this SharedBuffer.
* In other words, the buffer must have been release by all its
* users.
static ssize_t dealloc(const SharedBuffer* released);
//! access the data for read
inline const void* data() const;
//! access the data for read/write
inline void* data();
//! get size of the buffer
inline size_t size() const;
//! get back a SharedBuffer object from its data
static inline SharedBuffer* bufferFromData(void* data);
//! get back a SharedBuffer object from its data
static inline const SharedBuffer* bufferFromData(const void* data);
//! get the size of a SharedBuffer object from its data
static inline size_t sizeFromData(const void* data);
//! edit the buffer (get a writtable, or non-const, version of it)
SharedBuffer* edit() const;
//! edit the buffer, resizing if needed
SharedBuffer* editResize(size_t size) const;
//! like edit() but fails if a copy is required
SharedBuffer* attemptEdit() const;
//! resize and edit the buffer, loose it's content.
SharedBuffer* reset(size_t size) const;
//! acquire/release a reference on this buffer
void acquire() const;
/*! release a reference on this buffer, with the option of not
* freeing the memory associated with it if it was the last reference
* returns the previous reference count
int32_t release(uint32_t flags = 0) const;
//! returns wether or not we're the only owner
inline bool onlyOwner() const;
inline SharedBuffer() { }
inline ~SharedBuffer() { }
SharedBuffer(const SharedBuffer&);
SharedBuffer& operator = (const SharedBuffer&);
// 16 bytes. must be sized to preserve correct alignment.
mutable int32_t mRefs;
size_t mSize;
uint32_t mReserved[2];
// ---------------------------------------------------------------------------
const void* SharedBuffer::data() const {
return this + 1;
void* SharedBuffer::data() {
return this + 1;
size_t SharedBuffer::size() const {
return mSize;
SharedBuffer* SharedBuffer::bufferFromData(void* data) {
return data ? static_cast<SharedBuffer *>(data)-1 : 0;
const SharedBuffer* SharedBuffer::bufferFromData(const void* data) {
return data ? static_cast<const SharedBuffer *>(data)-1 : 0;
size_t SharedBuffer::sizeFromData(const void* data) {
return data ? bufferFromData(data)->mSize : 0;
bool SharedBuffer::onlyOwner() const {
return (mRefs == 1);
}; // namespace android
// ---------------------------------------------------------------------------