SharedBuffer* SharedBuffer::attemptEdit() const
{
if (onlyOwner()) {
return const_cast<SharedBuffer*>(this);
}
return 0;
}
int32_t SharedBuffer::release(uint32_t flags) const
{
int32_t prev = 1;
if (onlyOwner() || ((prev = android_atomic_dec(&mRefs)) == 1)) {
mRefs = 0;
if ((flags & eKeepStorage) == 0) {
free(const_cast<SharedBuffer*>(this));
}
}
return prev;
}
SharedBuffer* SharedBuffer::edit() const
{
if (onlyOwner()) {
return const_cast<SharedBuffer*>(this);
}
SharedBuffer* sb = alloc(mSize);
if (sb) {
memcpy(sb->data(), data(), size());
release();
}
return sb;
}
SharedBuffer* SharedBuffer::editResize(size_t newSize) const
{
if (onlyOwner()) {
SharedBuffer* buf = const_cast<SharedBuffer*>(this);
if (buf->mSize == newSize) return buf;
buf = (SharedBuffer*)realloc(buf, sizeof(SharedBuffer) + newSize);
if (buf != NULL) {
buf->mSize = newSize;
return buf;
}
}
SharedBuffer* sb = alloc(newSize);
if (sb) {
const size_t mySize = mSize;
memcpy(sb->data(), data(), newSize < mySize ? newSize : mySize);
release();
}
return sb;
}
int32_t SharedBuffer::release(uint32_t flags) const
{
const bool useDealloc = ((flags & eKeepStorage) == 0);
if (onlyOwner()) {
// Since we're the only owner, our reference count goes to zero.
mRefs.store(0, std::memory_order_relaxed);
if (useDealloc) {
dealloc(this);
}
// As the only owner, our previous reference count was 1.
return 1;
}
// There's multiple owners, we need to use an atomic decrement.
int32_t prevRefCount = mRefs.fetch_sub(1, std::memory_order_release);
if (prevRefCount == 1) {
// We're the last reference, we need the acquire fence.
atomic_thread_fence(std::memory_order_acquire);
if (useDealloc) {
dealloc(this);
}
}
return prevRefCount;
}
SharedBuffer* SharedBuffer::editResize(size_t newSize) const
{
if (onlyOwner()) {
SharedBuffer* buf = const_cast<SharedBuffer*>(this);
if (buf->mSize == newSize) return buf;
// Don't overflow if the combined size of the new buffer / header is larger than
// size_max.
LOG_ALWAYS_FATAL_IF((newSize >= (SIZE_MAX - sizeof(SharedBuffer))),
"Invalid buffer size %zu", newSize);
buf = (SharedBuffer*)realloc(buf, sizeof(SharedBuffer) + newSize);
if (buf != NULL) {
buf->mSize = newSize;
return buf;
}
}
SharedBuffer* sb = alloc(newSize);
if (sb) {
const size_t mySize = mSize;
memcpy(sb->data(), data(), newSize < mySize ? newSize : mySize);
release();
}
return sb;
}
