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Mypal/js/public/StructuredClone.h

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* 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 js_StructuredClone_h
#define js_StructuredClone_h
#include "mozilla/Attributes.h"
#include "mozilla/BufferList.h"
#include "mozilla/Move.h"
#include <stdint.h>
#include "jstypes.h"
#include "js/RootingAPI.h"
#include "js/TypeDecls.h"
#include "js/Value.h"
struct JSRuntime;
struct JSStructuredCloneReader;
struct JSStructuredCloneWriter;
// API for the HTML5 internal structured cloning algorithm.
namespace JS {
enum class StructuredCloneScope : uint32_t {
SameProcessSameThread,
SameProcessDifferentThread,
/**
* When writing, this means we're writing for an audience in a different
* process. Produce serialized data that can be sent to other processes,
* bitwise copied, or even stored as bytes in a database and read by later
* versions of Firefox years from now. The HTML5 spec refers to this as
* "ForStorage" as in StructuredSerializeForStorage, though we use
* DifferentProcess for IPC as well as storage.
*
* Transferable objects are limited to ArrayBuffers, whose contents are
* copied into the serialized data (rather than just writing a pointer).
*/
DifferentProcess,
/**
* Handle a backwards-compatibility case with IndexedDB (bug 1434308): when
* reading, this means to treat legacy SameProcessSameThread data as if it
* were DifferentProcess.
*
* Do not use this for writing; use DifferentProcess instead.
*/
DifferentProcessForIndexedDB,
/**
* Existing code wants to be able to create an uninitialized
* JSStructuredCloneData without knowing the scope, then populate it with
* data (at which point the scope *is* known.)
*/
Unassigned
};
enum TransferableOwnership {
/** Transferable data has not been filled in yet */
SCTAG_TMO_UNFILLED = 0,
/** Structured clone buffer does not yet own the data */
SCTAG_TMO_UNOWNED = 1,
/** All values at least this large are owned by the clone buffer */
SCTAG_TMO_FIRST_OWNED = 2,
/** Data is a pointer that can be freed */
SCTAG_TMO_ALLOC_DATA = 2,
/** Data is a memory mapped pointer */
SCTAG_TMO_MAPPED_DATA = 3,
/**
* Data is embedding-specific. The engine can free it by calling the
* freeTransfer op. The embedding can also use SCTAG_TMO_USER_MIN and
* greater, up to 32 bits, to distinguish specific ownership variants.
*/
SCTAG_TMO_CUSTOM = 4,
SCTAG_TMO_USER_MIN
};
class CloneDataPolicy
{
bool sharedArrayBuffer_;
public:
// The default is to allow all policy-controlled aspects.
CloneDataPolicy() :
sharedArrayBuffer_(true)
{}
// In the JS engine, SharedArrayBuffers can only be cloned intra-process
// because the shared memory areas are allocated in process-private memory.
// Clients should therefore deny SharedArrayBuffers when cloning data that
// are to be transmitted inter-process.
//
// Clients should also deny SharedArrayBuffers when cloning data that are to
// be transmitted intra-process if policy needs dictate such denial.
CloneDataPolicy& denySharedArrayBuffer() {
sharedArrayBuffer_ = false;
return *this;
}
bool isSharedArrayBufferAllowed() const {
return sharedArrayBuffer_;
}
};
} /* namespace JS */
namespace js {
template <typename T, typename AllocPolicy> struct BufferIterator;
}
/**
* Read structured data from the reader r. This hook is used to read a value
* previously serialized by a call to the WriteStructuredCloneOp hook.
*
* tag and data are the pair of uint32_t values from the header. The callback
* may use the JS_Read* APIs to read any other relevant parts of the object
* from the reader r. closure is any value passed to the JS_ReadStructuredClone
* function. Return the new object on success, nullptr on error/exception.
*/
typedef JSObject* (*ReadStructuredCloneOp)(JSContext* cx, JSStructuredCloneReader* r,
uint32_t tag, uint32_t data, void* closure);
/**
* Structured data serialization hook. The engine can write primitive values,
* Objects, Arrays, Dates, RegExps, TypedArrays, ArrayBuffers, Sets, Maps,
* and SharedTypedArrays. Any other type of object requires application support.
* This callback must first use the JS_WriteUint32Pair API to write an object
* header, passing a value greater than JS_SCTAG_USER to the tag parameter.
* Then it can use the JS_Write* APIs to write any other relevant parts of
* the value v to the writer w. closure is any value passed to the
* JS_WriteStructuredClone function.
*
* Return true on success, false on error/exception.
*/
typedef bool (*WriteStructuredCloneOp)(JSContext* cx, JSStructuredCloneWriter* w,
JS::HandleObject obj, void* closure);
/**
* This is called when JS_WriteStructuredClone is given an invalid transferable.
* To follow HTML5, the application must throw a DATA_CLONE_ERR DOMException
* with error set to one of the JS_SCERR_* values.
*/
typedef void (*StructuredCloneErrorOp)(JSContext* cx, uint32_t errorid);
/**
* This is called when JS_ReadStructuredClone receives a transferable object
* not known to the engine. If this hook does not exist or returns false, the
* JS engine calls the reportError op if set, otherwise it throws a
* DATA_CLONE_ERR DOM Exception. This method is called before any other
* callback and must return a non-null object in returnObject on success.
*/
typedef bool (*ReadTransferStructuredCloneOp)(JSContext* cx, JSStructuredCloneReader* r,
uint32_t tag, void* content, uint64_t extraData,
void* closure,
JS::MutableHandleObject returnObject);
/**
* Called when JS_WriteStructuredClone receives a transferable object not
* handled by the engine. If this hook does not exist or returns false, the JS
* engine will call the reportError hook or fall back to throwing a
* DATA_CLONE_ERR DOM Exception. This method is called before any other
* callback.
*
* tag: indicates what type of transferable this is. Must be greater than
* 0xFFFF0201 (value of the internal SCTAG_TRANSFER_MAP_PENDING_ENTRY)
*
* ownership: see TransferableOwnership, above. Used to communicate any needed
* ownership info to the FreeTransferStructuredCloneOp.
*
* content, extraData: what the ReadTransferStructuredCloneOp will receive
*/
typedef bool (*TransferStructuredCloneOp)(JSContext* cx,
JS::Handle<JSObject*> obj,
void* closure,
// Output:
uint32_t* tag,
JS::TransferableOwnership* ownership,
void** content,
uint64_t* extraData);
/**
* Called when freeing an unknown transferable object. Note that it
* should never trigger a garbage collection (and will assert in a
* debug build if it does.)
*/
typedef void (*FreeTransferStructuredCloneOp)(uint32_t tag, JS::TransferableOwnership ownership,
void* content, uint64_t extraData, void* closure);
// The maximum supported structured-clone serialization format version.
// Increment this when anything at all changes in the serialization format.
// (Note that this does not need to be bumped for Transferable-only changes,
// since they are never saved to persistent storage.)
#define JS_STRUCTURED_CLONE_VERSION 8
struct JSStructuredCloneCallbacks {
ReadStructuredCloneOp read;
WriteStructuredCloneOp write;
StructuredCloneErrorOp reportError;
ReadTransferStructuredCloneOp readTransfer;
TransferStructuredCloneOp writeTransfer;
FreeTransferStructuredCloneOp freeTransfer;
};
enum OwnTransferablePolicy {
OwnsTransferablesIfAny,
IgnoreTransferablesIfAny,
NoTransferables
};
/**
* JSStructuredCloneData represents structured clone data together with the
* information needed to read/write/transfer/free the records within it, in the
* form of a set of callbacks.
*/
class MOZ_NON_MEMMOVABLE JS_PUBLIC_API(JSStructuredCloneData) {
public:
using BufferList = mozilla::BufferList<js::SystemAllocPolicy>;
using Iterator = BufferList::IterImpl;
private:
static const size_t kStandardCapacity = 4096;
BufferList bufList_;
// The (address space, thread) scope within which this clone is valid. Note
// that this must be either set during construction, or start out as
// Unassigned and transition once to something else.
JS::StructuredCloneScope scope_;
const JSStructuredCloneCallbacks* callbacks_;
void* closure_;
OwnTransferablePolicy ownTransferables_;
friend struct JSStructuredCloneWriter;
friend class JS_PUBLIC_API(JSAutoStructuredCloneBuffer);
template <typename T, typename AllocPolicy> friend struct js::BufferIterator;
public:
// The constructor must be infallible but SystemAllocPolicy is not, so both
// the initial size and initial capacity of the BufferList must be zero.
explicit JSStructuredCloneData(JS::StructuredCloneScope aScope)
: bufList_(0, 0, kStandardCapacity, js::SystemAllocPolicy())
, scope_(aScope)
, callbacks_(nullptr)
, closure_(nullptr)
, ownTransferables_(OwnTransferablePolicy::NoTransferables)
{}
// Steal the raw data from a BufferList. In this case, we don't know the
// scope and none of the callback info is assigned yet.
JSStructuredCloneData(BufferList&& buffers, JS::StructuredCloneScope aScope)
: bufList_(mozilla::Move(buffers))
, scope_(aScope)
, callbacks_(nullptr)
, closure_(nullptr)
, ownTransferables_(OwnTransferablePolicy::NoTransferables)
{}
MOZ_IMPLICIT JSStructuredCloneData(BufferList&& buffers)
: JSStructuredCloneData(mozilla::Move(buffers), JS::StructuredCloneScope::Unassigned)
{}
JSStructuredCloneData(JSStructuredCloneData&& other) = default;
JSStructuredCloneData& operator=(JSStructuredCloneData&& other) = default;
~JSStructuredCloneData() { discardTransferables(); }
void setCallbacks(const JSStructuredCloneCallbacks* callbacks,
void* closure,
OwnTransferablePolicy policy)
{
callbacks_ = callbacks;
closure_ = closure;
ownTransferables_ = policy;
}
JS::StructuredCloneScope scope() const { return scope_; }
void initScope(JS::StructuredCloneScope aScope) {
MOZ_ASSERT(Size() == 0, "initScope() of nonempty JSStructuredCloneData");
if (scope_ != JS::StructuredCloneScope::Unassigned)
MOZ_ASSERT(scope_ == aScope, "Cannot change scope after it has been initialized");
scope_ = aScope;
}
size_t Size() const { return bufList_.Size(); }
const Iterator Start() const { return bufList_.Iter(); }
bool Advance(Iterator& iter, size_t distance) const {
return iter.AdvanceAcrossSegments(bufList_, distance);
}
bool ReadBytes(Iterator& iter, char* buffer, size_t size) const {
return bufList_.ReadBytes(iter, buffer, size);
}
// Append new data to the end of the buffer.
bool AppendBytes(const char* data, size_t size) {
MOZ_ASSERT(scope_ != JS::StructuredCloneScope::Unassigned);
return bufList_.WriteBytes(data, size);
}
// Update data stored within the existing buffer. There must be at least
// 'size' bytes between the position of 'iter' and the end of the buffer.
bool UpdateBytes(Iterator& iter, const char* data, size_t size) const {
MOZ_ASSERT(scope_ != JS::StructuredCloneScope::Unassigned);
while (size > 0) {
size_t remaining = iter.RemainingInSegment();
size_t nbytes = std::min(remaining, size);
memcpy(iter.Data(), data, nbytes);
data += nbytes;
size -= nbytes;
iter.Advance(bufList_, nbytes);
}
return true;
}
void Clear() {
discardTransferables();
bufList_.Clear();
}
// Return a new read-only JSStructuredCloneData that "borrows" the contents
// of |this|. Its lifetime should not exceed the donor's. This is only
// allowed for DifferentProcess clones, so finalization of the borrowing
// clone will do nothing.
JSStructuredCloneData Borrow(Iterator& iter, size_t size, bool* success) const
{
MOZ_ASSERT(scope_ == JS::StructuredCloneScope::DifferentProcess);
return JSStructuredCloneData(bufList_.Borrow<js::SystemAllocPolicy>(iter, size, success),
scope_);
}
// Iterate over all contained data, one BufferList segment's worth at a
// time, and invoke the given FunctionToApply with the data pointer and
// size. The function should return a bool value, and this loop will exit
// with false if the function ever returns false.
template <typename FunctionToApply>
bool ForEachDataChunk(FunctionToApply&& function) const {
Iterator iter = bufList_.Iter();
while (!iter.Done()) {
if (!function(iter.Data(), iter.RemainingInSegment()))
return false;
iter.Advance(bufList_, iter.RemainingInSegment());
}
return true;
}
// Append the entire contents of other's bufList_ to our own.
bool Append(const JSStructuredCloneData& other) {
MOZ_ASSERT(scope_ == other.scope_);
return other.ForEachDataChunk([&](const char* data, size_t size) {
return AppendBytes(data, size);
});
}
void discardTransferables();
};
/** Note: if the *data contains transferable objects, it can be read only once. */
JS_PUBLIC_API(bool)
JS_ReadStructuredClone(JSContext* cx, JSStructuredCloneData& data, uint32_t version,
JS::StructuredCloneScope scope,
JS::MutableHandleValue vp,
const JSStructuredCloneCallbacks* optionalCallbacks, void* closure);
JS_PUBLIC_API(bool)
JS_WriteStructuredClone(JSContext* cx, JS::HandleValue v, JSStructuredCloneData* data,
JS::StructuredCloneScope scope,
JS::CloneDataPolicy cloneDataPolicy,
const JSStructuredCloneCallbacks* optionalCallbacks,
void* closure, JS::HandleValue transferable);
JS_PUBLIC_API(bool)
JS_StructuredCloneHasTransferables(JSStructuredCloneData& data, bool* hasTransferable);
JS_PUBLIC_API(bool)
JS_StructuredClone(JSContext* cx, JS::HandleValue v, JS::MutableHandleValue vp,
const JSStructuredCloneCallbacks* optionalCallbacks, void* closure);
/**
* The C-style API calls to read and write structured clones are fragile --
* they rely on the caller to properly handle ownership of the clone data, and
* the handling of the input data as well as the interpretation of the contents
* of the clone buffer are dependent on the callbacks passed in. If you
* serialize and deserialize with different callbacks, the results are
* questionable.
*
* JSAutoStructuredCloneBuffer wraps things up in an RAII class for data
* management, and uses the same callbacks for both writing and reading
* (serializing and deserializing).
*/
class JS_PUBLIC_API(JSAutoStructuredCloneBuffer) {
const JS::StructuredCloneScope scope_;
JSStructuredCloneData data_;
uint32_t version_;
public:
JSAutoStructuredCloneBuffer(JS::StructuredCloneScope aScope,
const JSStructuredCloneCallbacks* callbacks, void* closure)
: scope_(aScope), data_(aScope), version_(JS_STRUCTURED_CLONE_VERSION)
{
data_.setCallbacks(callbacks, closure, OwnTransferablePolicy::NoTransferables);
}
JSAutoStructuredCloneBuffer(JSAutoStructuredCloneBuffer&& other);
JSAutoStructuredCloneBuffer& operator=(JSAutoStructuredCloneBuffer&& other);
~JSAutoStructuredCloneBuffer() { clear(); }
JSStructuredCloneData& data() { return data_; }
bool empty() const { return !data_.Size(); }
void clear();
JS::StructuredCloneScope scope() const { return scope_; }
/**
* Adopt some memory. It will be automatically freed by the destructor.
* data must have been allocated by the JS engine (e.g., extracted via
* JSAutoStructuredCloneBuffer::steal).
*/
void adopt(JSStructuredCloneData&& data, uint32_t version=JS_STRUCTURED_CLONE_VERSION,
const JSStructuredCloneCallbacks* callbacks=nullptr, void* closure=nullptr);
/**
* Release the buffer and transfer ownership to the caller.
*/
void steal(JSStructuredCloneData* data, uint32_t* versionp=nullptr,
const JSStructuredCloneCallbacks** callbacks=nullptr, void** closure=nullptr);
/**
* Abandon ownership of any transferable objects stored in the buffer,
* without freeing the buffer itself. Useful when copying the data out into
* an external container, though note that you will need to use adopt() to
* properly release that data eventually.
*/
void abandon() { data_.ownTransferables_ = OwnTransferablePolicy::IgnoreTransferablesIfAny; }
bool read(JSContext* cx, JS::MutableHandleValue vp,
const JSStructuredCloneCallbacks* optionalCallbacks=nullptr, void* closure=nullptr);
bool write(JSContext* cx, JS::HandleValue v,
const JSStructuredCloneCallbacks* optionalCallbacks=nullptr, void* closure=nullptr);
bool write(JSContext* cx, JS::HandleValue v, JS::HandleValue transferable,
JS::CloneDataPolicy cloneDataPolicy,
const JSStructuredCloneCallbacks* optionalCallbacks=nullptr, void* closure=nullptr);
private:
// Copy and assignment are not supported.
JSAutoStructuredCloneBuffer(const JSAutoStructuredCloneBuffer& other) = delete;
JSAutoStructuredCloneBuffer& operator=(const JSAutoStructuredCloneBuffer& other) = delete;
};
// The range of tag values the application may use for its own custom object types.
#define JS_SCTAG_USER_MIN ((uint32_t) 0xFFFF8000)
#define JS_SCTAG_USER_MAX ((uint32_t) 0xFFFFFFFF)
#define JS_SCERR_RECURSION 0
#define JS_SCERR_TRANSFERABLE 1
#define JS_SCERR_DUP_TRANSFERABLE 2
#define JS_SCERR_UNSUPPORTED_TYPE 3
JS_PUBLIC_API(bool)
JS_ReadUint32Pair(JSStructuredCloneReader* r, uint32_t* p1, uint32_t* p2);
JS_PUBLIC_API(bool)
JS_ReadBytes(JSStructuredCloneReader* r, void* p, size_t len);
JS_PUBLIC_API(bool)
JS_ReadTypedArray(JSStructuredCloneReader* r, JS::MutableHandleValue vp);
JS_PUBLIC_API(bool)
JS_WriteUint32Pair(JSStructuredCloneWriter* w, uint32_t tag, uint32_t data);
JS_PUBLIC_API(bool)
JS_WriteBytes(JSStructuredCloneWriter* w, const void* p, size_t len);
JS_PUBLIC_API(bool)
JS_WriteString(JSStructuredCloneWriter* w, JS::HandleString str);
JS_PUBLIC_API(bool)
JS_WriteTypedArray(JSStructuredCloneWriter* w, JS::HandleValue v);
JS_PUBLIC_API(bool)
JS_ObjectNotWritten(JSStructuredCloneWriter* w, JS::HandleObject obj);
JS_PUBLIC_API(JS::StructuredCloneScope)
JS_GetStructuredCloneScope(JSStructuredCloneWriter* w);
#endif /* js_StructuredClone_h */
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