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// Copyright 2013 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.
#ifndef MOJO_PUBLIC_BINDINGS_LIB_BINDINGS_SERIALIZATION_H_
#define MOJO_PUBLIC_BINDINGS_LIB_BINDINGS_SERIALIZATION_H_
#include <string.h>
#include <vector>
#include "mojo/public/bindings/lib/bindings.h"
#include "mojo/public/bindings/lib/message.h"
namespace mojo {
namespace internal {
size_t Align(size_t size);
// Pointers are encoded as relative offsets. The offsets are relative to the
// address of where the offset value is stored, such that the pointer may be
// recovered with the expression:
//
// ptr = reinterpret_cast<char*>(offset) + *offset
//
// A null pointer is encoded as an offset value of 0.
//
void EncodePointer(const void* ptr, uint64_t* offset);
const void* DecodePointerRaw(const uint64_t* offset);
template <typename T>
inline void DecodePointer(const uint64_t* offset, T** ptr) {
*ptr = reinterpret_cast<T*>(const_cast<void*>(DecodePointerRaw(offset)));
}
// Check that the given pointer references memory contained within the message.
bool ValidatePointer(const void* ptr, const Message& message);
// Handles are encoded as indices into a vector of handles. These functions
// manipulate the value of |handle|, mapping it to and from an index.
void EncodeHandle(Handle* handle, std::vector<Handle>* handles);
bool DecodeHandle(Handle* handle, const std::vector<Handle>& handles);
// All objects (structs and arrays) support the following operations:
// - computing size
// - cloning
// - encoding pointers and handles
// - decoding pointers and handles
//
// The following functions are used to select the proper ObjectTraits<>
// specialization.
template <typename T>
inline size_t ComputeAlignedSizeOf(const T* obj) {
return obj ? ObjectTraits<T>::ComputeAlignedSizeOf(obj) : 0;
}
template <typename T>
inline T* Clone(const T* obj, Buffer* buf) {
return obj ? ObjectTraits<T>::Clone(obj, buf) : NULL;
}
template <typename T>
inline void EncodePointersAndHandles(T* obj,
std::vector<Handle>* handles) {
ObjectTraits<T>::EncodePointersAndHandles(obj, handles);
}
template <typename T>
inline bool DecodePointersAndHandles(T* obj, const Message& message) {
return ObjectTraits<T>::DecodePointersAndHandles(obj, message);
}
// The following 2 functions are used to encode/decode all objects (structs and
// arrays) in a consistent manner.
template <typename T>
inline void Encode(T* obj, std::vector<Handle>* handles) {
if (obj->ptr)
EncodePointersAndHandles(obj->ptr, handles);
EncodePointer(obj->ptr, &obj->offset);
}
template <typename T>
inline bool Decode(T* obj, const Message& message) {
DecodePointer(&obj->offset, &obj->ptr);
if (obj->ptr) {
if (!ValidatePointer(obj->ptr, message))
return false;
if (!DecodePointersAndHandles(obj->ptr, message))
return false;
}
return true;
}
// What follows is code to support the ObjectTraits<> specialization of
// Array<T>. There are two interesting cases: arrays of primitives and arrays
// of objects. Arrays of objects are represented as arrays of pointers to
// objects.
template <typename T>
struct ArrayHelper {
typedef T ElementType;
static size_t ComputeAlignedSizeOfElements(const ArrayHeader* header,
const ElementType* elements) {
return 0;
}
static void CloneElements(const ArrayHeader* header,
ElementType* elements,
Buffer* buf) {
}
static void EncodePointersAndHandles(const ArrayHeader* header,
ElementType* elements,
std::vector<Handle>* handles) {
}
static bool DecodePointersAndHandles(const ArrayHeader* header,
ElementType* elements,
const Message& message) {
return true;
}
};
template <>
struct ArrayHelper<Handle> {
typedef Handle ElementType;
static size_t ComputeAlignedSizeOfElements(const ArrayHeader* header,
const ElementType* elements) {
return 0;
}
static void CloneElements(const ArrayHeader* header,
ElementType* elements,
Buffer* buf) {
}
static void EncodePointersAndHandles(const ArrayHeader* header,
ElementType* elements,
std::vector<Handle>* handles);
static bool DecodePointersAndHandles(const ArrayHeader* header,
ElementType* elements,
const Message& message);
};
template <typename P>
struct ArrayHelper<P*> {
typedef StructPointer<P> ElementType;
static size_t ComputeAlignedSizeOfElements(const ArrayHeader* header,
const ElementType* elements) {
size_t result = 0;
for (uint32_t i = 0; i < header->num_elements; ++i)
result += ComputeAlignedSizeOf(elements[i].ptr);
return result;
}
static void CloneElements(const ArrayHeader* header,
ElementType* elements,
Buffer* buf) {
for (uint32_t i = 0; i < header->num_elements; ++i)
elements[i].ptr = Clone(elements[i].ptr, buf);
}
static void EncodePointersAndHandles(const ArrayHeader* header,
ElementType* elements,
std::vector<Handle>* handles) {
for (uint32_t i = 0; i < header->num_elements; ++i)
Encode(&elements[i], handles);
}
static bool DecodePointersAndHandles(const ArrayHeader* header,
ElementType* elements,
const Message& message) {
for (uint32_t i = 0; i < header->num_elements; ++i) {
if (!Decode(&elements[i], message))
return false;
}
return true;
}
};
template <typename T>
class ObjectTraits<Array<T> > {
public:
static size_t ComputeAlignedSizeOf(const Array<T>* array) {
return Align(array->header_.num_bytes) +
ArrayHelper<T>::ComputeAlignedSizeOfElements(&array->header_,
array->storage());
}
static Array<T>* Clone(const Array<T>* array, Buffer* buf) {
Array<T>* clone = Array<T>::New(buf, array->header_.num_elements);
memcpy(clone->storage(),
array->storage(),
array->header_.num_bytes - sizeof(Array<T>));
ArrayHelper<T>::CloneElements(&clone->header_, clone->storage(), buf);
return clone;
}
static void EncodePointersAndHandles(Array<T>* array,
std::vector<Handle>* handles) {
ArrayHelper<T>::EncodePointersAndHandles(&array->header_, array->storage(),
handles);
}
static bool DecodePointersAndHandles(Array<T>* array,
const Message& message) {
return ArrayHelper<T>::DecodePointersAndHandles(&array->header_,
array->storage(),
message);
}
};
} // namespace internal
} // namespace mojo
#endif // MOJO_PUBLIC_BINDINGS_LIB_BINDINGS_SERIALIZATION_H_
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