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// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// This file provides a C++ wrapping around the Mojo C API for shared buffers,
// replacing the prefix of "Mojo" with a "mojo" namespace, and using more
// strongly-typed representations of |MojoHandle|s.
//
// Please see "mojo/public/c/system/buffer.h" for complete documentation of the
// API.
#ifndef MOJO_PUBLIC_CPP_SYSTEM_BUFFER_H_
#define MOJO_PUBLIC_CPP_SYSTEM_BUFFER_H_
#include <stdint.h>
#include <memory>
#include "base/check_op.h"
#include "base/compiler_specific.h"
#include "mojo/public/c/system/buffer.h"
#include "mojo/public/cpp/system/handle.h"
#include "mojo/public/cpp/system/system_export.h"
namespace mojo {
namespace internal {
struct Unmapper {
void operator()(void* buffer) {
MojoResult result = MojoUnmapBuffer(buffer);
DCHECK_EQ(MOJO_RESULT_OK, result);
}
};
} // namespace internal
using ScopedSharedBufferMapping = std::unique_ptr<void, internal::Unmapper>;
class SharedBufferHandle;
typedef ScopedHandleBase<SharedBufferHandle> ScopedSharedBufferHandle;
// A strongly-typed representation of a |MojoHandle| referring to a shared
// buffer.
class MOJO_CPP_SYSTEM_EXPORT SharedBufferHandle : public Handle {
public:
enum class AccessMode {
READ_WRITE,
READ_ONLY,
};
SharedBufferHandle() {}
explicit SharedBufferHandle(MojoHandle value) : Handle(value) {}
// Copying and assignment allowed.
// Creates a new SharedBufferHandle. Returns an invalid handle on failure.
//
// Note for those converting legacy shared memory to the
// base::*SharedMemoryRegion API: if SharedBufferHandle::Create is used for
// your shared memory regions, the mojo::Create*SharedMemoryRegion methods in
// mojo/public/cpp/base/shared_memory_utils.h should be used. These know how
// to use a broker to create regions in unprivileged contexts in the same way
// as this SharedBufferHandle::Create method.
static ScopedSharedBufferHandle Create(uint64_t num_bytes);
// Clones this shared buffer handle. If |access_mode| is READ_ONLY or this is
// a read-only handle, the new handle will be read-only. On failure, this will
// return an empty result.
ScopedSharedBufferHandle Clone(AccessMode access_mode) const;
// Maps |size| bytes of this shared buffer. On failure, this will return a
// null mapping.
ScopedSharedBufferMapping Map(uint64_t size) const;
// Maps |size| bytes of this shared buffer, starting |offset| bytes into the
// buffer. On failure, this will return a null mapping.
ScopedSharedBufferMapping MapAtOffset(uint64_t size, uint64_t offset) const;
// Get the size of this shared buffer.
uint64_t GetSize() const;
};
static_assert(sizeof(SharedBufferHandle) == sizeof(Handle),
"Bad size for C++ SharedBufferHandle");
static_assert(sizeof(ScopedSharedBufferHandle) == sizeof(SharedBufferHandle),
"Bad size for C++ ScopedSharedBufferHandle");
} // namespace mojo
#endif // MOJO_PUBLIC_CPP_SYSTEM_BUFFER_H_
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