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// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#ifndef GOOGLE_PROTOBUF_METADATA_LITE_H__
#define GOOGLE_PROTOBUF_METADATA_LITE_H__
#include <google/protobuf/stubs/common.h>
#include <google/protobuf/arena.h>
#include <google/protobuf/generated_message_util.h>
namespace google {
namespace protobuf {
namespace internal {
// This is the representation for messages that support arena allocation. It
// uses a tagged pointer to either store the Arena pointer, if there are no
// unknown fields, or a pointer to a block of memory with both the Arena pointer
// and the UnknownFieldSet, if there are unknown fields. This optimization
// allows for "zero-overhead" storage of the Arena pointer, relative to the
// above baseline implementation.
//
// The tagged pointer uses the LSB to disambiguate cases, and uses bit 0 == 0 to
// indicate an arena pointer and bit 0 == 1 to indicate a UFS+Arena-container
// pointer.
template <class T, class Derived>
class InternalMetadataWithArenaBase {
public:
InternalMetadataWithArenaBase() : ptr_(NULL) {}
explicit InternalMetadataWithArenaBase(Arena* arena) : ptr_(arena) {}
~InternalMetadataWithArenaBase() {
if (have_unknown_fields() && arena() == NULL) {
delete PtrValue<Container>();
}
ptr_ = NULL;
}
GOOGLE_ATTRIBUTE_ALWAYS_INLINE const T& unknown_fields() const {
if (GOOGLE_PREDICT_FALSE(have_unknown_fields())) {
return PtrValue<Container>()->unknown_fields;
} else {
return Derived::default_instance();
}
}
GOOGLE_ATTRIBUTE_ALWAYS_INLINE T* mutable_unknown_fields() {
if (GOOGLE_PREDICT_TRUE(have_unknown_fields())) {
return &PtrValue<Container>()->unknown_fields;
} else {
return mutable_unknown_fields_slow();
}
}
GOOGLE_ATTRIBUTE_ALWAYS_INLINE Arena* arena() const {
if (GOOGLE_PREDICT_FALSE(have_unknown_fields())) {
return PtrValue<Container>()->arena;
} else {
return PtrValue<Arena>();
}
}
GOOGLE_ATTRIBUTE_ALWAYS_INLINE bool have_unknown_fields() const {
return PtrTag() == kTagContainer;
}
GOOGLE_ATTRIBUTE_ALWAYS_INLINE void Swap(Derived* other) {
// Semantics here are that we swap only the unknown fields, not the arena
// pointer. We cannot simply swap ptr_ with other->ptr_ because we need to
// maintain our own arena ptr. Also, our ptr_ and other's ptr_ may be in
// different states (direct arena pointer vs. container with UFS) so we
// cannot simply swap ptr_ and then restore the arena pointers. We reuse
// UFS's swap implementation instead.
if (have_unknown_fields() || other->have_unknown_fields()) {
static_cast<Derived*>(this)->DoSwap(other->mutable_unknown_fields());
}
}
GOOGLE_ATTRIBUTE_ALWAYS_INLINE void MergeFrom(const Derived& other) {
if (other.have_unknown_fields()) {
static_cast<Derived*>(this)->DoMergeFrom(other.unknown_fields());
}
}
GOOGLE_ATTRIBUTE_ALWAYS_INLINE void Clear() {
if (have_unknown_fields()) {
static_cast<Derived*>(this)->DoClear();
}
}
GOOGLE_ATTRIBUTE_ALWAYS_INLINE void* raw_arena_ptr() const {
return ptr_;
}
private:
void* ptr_;
// Tagged pointer implementation.
enum {
// ptr_ is an Arena*.
kTagArena = 0,
// ptr_ is a Container*.
kTagContainer = 1,
};
static const intptr_t kPtrTagMask = 1;
static const intptr_t kPtrValueMask = ~kPtrTagMask;
// Accessors for pointer tag and pointer value.
GOOGLE_ATTRIBUTE_ALWAYS_INLINE int PtrTag() const {
return reinterpret_cast<intptr_t>(ptr_) & kPtrTagMask;
}
template<typename U> U* PtrValue() const {
return reinterpret_cast<U*>(
reinterpret_cast<intptr_t>(ptr_) & kPtrValueMask);
}
// If ptr_'s tag is kTagContainer, it points to an instance of this struct.
struct Container {
T unknown_fields;
Arena* arena;
};
GOOGLE_ATTRIBUTE_NOINLINE T* mutable_unknown_fields_slow() {
Arena* my_arena = arena();
Container* container = Arena::Create<Container>(my_arena);
ptr_ = reinterpret_cast<void*>(
reinterpret_cast<intptr_t>(container) | kTagContainer);
container->arena = my_arena;
return &(container->unknown_fields);
}
};
// We store unknown fields as a string right now, because there is currently no
// good interface for reading unknown fields into an ArenaString. We may want
// to revisit this to allow unknown fields to be parsed onto the Arena.
class InternalMetadataWithArenaLite
: public InternalMetadataWithArenaBase<string,
InternalMetadataWithArenaLite> {
public:
InternalMetadataWithArenaLite() {}
explicit InternalMetadataWithArenaLite(Arena* arena)
: InternalMetadataWithArenaBase(arena) {}
void DoSwap(string* other) {
mutable_unknown_fields()->swap(*other);
}
void DoMergeFrom(const string& other) {
mutable_unknown_fields()->append(other);
}
void DoClear() {
mutable_unknown_fields()->clear();
}
static const string& default_instance() {
return GetEmptyStringAlreadyInited();
}
};
} // namespace internal
} // namespace protobuf
} // namespace google
#endif // GOOGLE_PROTOBUF_METADATA_LITE_H__
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