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/*
* Copyright 2021 Google Inc. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef FLATBUFFERS_TABLE_H_
#define FLATBUFFERS_TABLE_H_
#include "flatbuffers/base.h"
#include "flatbuffers/verifier.h"
namespace flatbuffers {
// "tables" use an offset table (possibly shared) that allows fields to be
// omitted and added at will, but uses an extra indirection to read.
class Table {
public:
const uint8_t *GetVTable() const {
return data_ - ReadScalar<soffset_t>(data_);
}
// This gets the field offset for any of the functions below it, or 0
// if the field was not present.
voffset_t GetOptionalFieldOffset(voffset_t field) const {
// The vtable offset is always at the start.
auto vtable = GetVTable();
// The first element is the size of the vtable (fields + type id + itself).
auto vtsize = ReadScalar<voffset_t>(vtable);
// If the field we're accessing is outside the vtable, we're reading older
// data, so it's the same as if the offset was 0 (not present).
return field < vtsize ? ReadScalar<voffset_t>(vtable + field) : 0;
}
template<typename T> T GetField(voffset_t field, T defaultval) const {
auto field_offset = GetOptionalFieldOffset(field);
return field_offset ? ReadScalar<T>(data_ + field_offset) : defaultval;
}
template<typename P, typename OffsetSize = uoffset_t>
P GetPointer(voffset_t field) {
auto field_offset = GetOptionalFieldOffset(field);
auto p = data_ + field_offset;
return field_offset ? reinterpret_cast<P>(p + ReadScalar<OffsetSize>(p))
: nullptr;
}
template<typename P, typename OffsetSize = uoffset_t>
P GetPointer(voffset_t field) const {
return const_cast<Table *>(this)->GetPointer<P, OffsetSize>(field);
}
template<typename P> P GetPointer64(voffset_t field) {
return GetPointer<P, uoffset64_t>(field);
}
template<typename P> P GetPointer64(voffset_t field) const {
return GetPointer<P, uoffset64_t>(field);
}
template<typename P> P GetStruct(voffset_t field) const {
auto field_offset = GetOptionalFieldOffset(field);
auto p = const_cast<uint8_t *>(data_ + field_offset);
return field_offset ? reinterpret_cast<P>(p) : nullptr;
}
template<typename Raw, typename Face>
flatbuffers::Optional<Face> GetOptional(voffset_t field) const {
auto field_offset = GetOptionalFieldOffset(field);
auto p = data_ + field_offset;
return field_offset ? Optional<Face>(static_cast<Face>(ReadScalar<Raw>(p)))
: Optional<Face>();
}
template<typename T> bool SetField(voffset_t field, T val, T def) {
auto field_offset = GetOptionalFieldOffset(field);
if (!field_offset) return IsTheSameAs(val, def);
WriteScalar(data_ + field_offset, val);
return true;
}
template<typename T> bool SetField(voffset_t field, T val) {
auto field_offset = GetOptionalFieldOffset(field);
if (!field_offset) return false;
WriteScalar(data_ + field_offset, val);
return true;
}
bool SetPointer(voffset_t field, const uint8_t *val) {
auto field_offset = GetOptionalFieldOffset(field);
if (!field_offset) return false;
WriteScalar(data_ + field_offset,
static_cast<uoffset_t>(val - (data_ + field_offset)));
return true;
}
uint8_t *GetAddressOf(voffset_t field) {
auto field_offset = GetOptionalFieldOffset(field);
return field_offset ? data_ + field_offset : nullptr;
}
const uint8_t *GetAddressOf(voffset_t field) const {
return const_cast<Table *>(this)->GetAddressOf(field);
}
bool CheckField(voffset_t field) const {
return GetOptionalFieldOffset(field) != 0;
}
// Verify the vtable of this table.
// Call this once per table, followed by VerifyField once per field.
bool VerifyTableStart(Verifier &verifier) const {
return verifier.VerifyTableStart(data_);
}
// Verify a particular field.
template<typename T>
bool VerifyField(const Verifier &verifier, voffset_t field,
size_t align) const {
// Calling GetOptionalFieldOffset should be safe now thanks to
// VerifyTable().
auto field_offset = GetOptionalFieldOffset(field);
// Check the actual field.
return !field_offset || verifier.VerifyField<T>(data_, field_offset, align);
}
// VerifyField for required fields.
template<typename T>
bool VerifyFieldRequired(const Verifier &verifier, voffset_t field,
size_t align) const {
auto field_offset = GetOptionalFieldOffset(field);
return verifier.Check(field_offset != 0) &&
verifier.VerifyField<T>(data_, field_offset, align);
}
// Versions for offsets.
template<typename OffsetT = uoffset_t>
bool VerifyOffset(const Verifier &verifier, voffset_t field) const {
auto field_offset = GetOptionalFieldOffset(field);
return !field_offset || verifier.VerifyOffset<OffsetT>(data_, field_offset);
}
template<typename OffsetT = uoffset_t>
bool VerifyOffsetRequired(const Verifier &verifier, voffset_t field) const {
auto field_offset = GetOptionalFieldOffset(field);
return verifier.Check(field_offset != 0) &&
verifier.VerifyOffset<OffsetT>(data_, field_offset);
}
bool VerifyOffset64(const Verifier &verifier, voffset_t field) const {
return VerifyOffset<uoffset64_t>(verifier, field);
}
bool VerifyOffset64Required(const Verifier &verifier, voffset_t field) const {
return VerifyOffsetRequired<uoffset64_t>(verifier, field);
}
private:
// private constructor & copy constructor: you obtain instances of this
// class by pointing to existing data only
Table();
Table(const Table &other);
Table &operator=(const Table &);
uint8_t data_[1];
};
// This specialization allows avoiding warnings like:
// MSVC C4800: type: forcing value to bool 'true' or 'false'.
template<>
inline flatbuffers::Optional<bool> Table::GetOptional<uint8_t, bool>(
voffset_t field) const {
auto field_offset = GetOptionalFieldOffset(field);
auto p = data_ + field_offset;
return field_offset ? Optional<bool>(ReadScalar<uint8_t>(p) != 0)
: Optional<bool>();
}
} // namespace flatbuffers
#endif // FLATBUFFERS_TABLE_H_
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