gecko-dev/content/media/SharedBuffer.h

48 lines
1.5 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef MOZILLA_SHAREDBUFFER_H_
#define MOZILLA_SHAREDBUFFER_H_
#include "mozilla/mozalloc.h"
#include "nsCOMPtr.h"
#include "nsAutoPtr.h"
namespace mozilla {
/**
* Heap-allocated chunk of arbitrary data with threadsafe refcounting.
* Typically you would allocate one of these, fill it in, and then treat it as
* immutable while it's shared.
* This only guarantees 4-byte alignment of the data. For alignment we
* simply assume that the refcount is at least 4-byte aligned and its size
* is divisible by 4.
*/
class SharedBuffer {
public:
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(SharedBuffer)
~SharedBuffer() {}
void* Data() { return this + 1; }
// Takes ownership of aData (which will be freed via moz_free()).
// aData consists of aChannels consecutive buffers, each of aLength samples.
static already_AddRefed<SharedBuffer> Create(size_t aSize)
{
void* m = moz_xmalloc(sizeof(SharedBuffer) + aSize);
nsRefPtr<SharedBuffer> p = new (m) SharedBuffer();
NS_ASSERTION((reinterpret_cast<char*>(p.get() + 1) - reinterpret_cast<char*>(p.get())) % 4 == 0,
"SharedBuffers should be at least 4-byte aligned");
return p.forget();
}
private:
SharedBuffer() {}
};
}
#endif /* MOZILLA_SHAREDBUFFER_H_ */