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// Copyright 2019 Google LLC
//
// 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
//
// https://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.
// View class template for enums.
#ifndef EMBOSS_RUNTIME_CPP_EMBOSS_ENUM_VIEW_H_
#define EMBOSS_RUNTIME_CPP_EMBOSS_ENUM_VIEW_H_
#include <cctype>
#include <cstdint>
#include <string>
#include <utility>
#include "runtime/cpp/emboss_defines.h"
#include "runtime/cpp/emboss_view_parameters.h"
// Forward declarations for optional text processing helpers.
namespace emboss {
class TextOutputOptions;
namespace support {
template <class Stream, class View>
bool ReadEnumViewFromTextStream(View *view, Stream *stream);
template <class Stream, class View>
void WriteEnumViewToTextStream(View *view, Stream *stream,
const TextOutputOptions &options);
} // namespace support
} // namespace emboss
namespace emboss {
namespace support {
// EnumView is a view for Enums inside of bitfields.
template <class Enum, class Parameters, class BitViewType>
class EnumView final {
public:
using ValueType = typename ::std::remove_cv<Enum>::type;
static_assert(
Parameters::kBits <= sizeof(ValueType) * 8,
"EnumView requires sizeof(ValueType) * 8 >= Parameters::kBits.");
template <typename... Args>
explicit EnumView(Args &&...args) : buffer_{::std::forward<Args>(args)...} {}
EnumView() : buffer_() {}
EnumView(const EnumView &) = default;
EnumView(EnumView &&) = default;
EnumView &operator=(const EnumView &) = default;
EnumView &operator=(EnumView &&) = default;
~EnumView() = default;
// TODO(bolms): Here and in CouldWriteValue(), the static_casts to ValueType
// rely on implementation-defined behavior when ValueType is signed.
ValueType Read() const {
ValueType result = static_cast<ValueType>(buffer_.ReadUInt());
EMBOSS_CHECK(Parameters::ValueIsOk(result));
return result;
}
ValueType UncheckedRead() const {
return static_cast<ValueType>(buffer_.UncheckedReadUInt());
}
void Write(ValueType value) const {
const bool result = TryToWrite(value);
(void)result;
EMBOSS_CHECK(result);
}
bool TryToWrite(ValueType value) const {
if (!CouldWriteValue(value)) return false;
if (!IsComplete()) return false;
buffer_.WriteUInt(static_cast<typename BitViewType::ValueType>(value));
return true;
}
static constexpr bool CouldWriteValue(ValueType value) {
// The value can be written if:
//
// a) it can fit in BitViewType::ValueType (verified by casting to
// BitViewType::ValueType and back, and making sure that the value is
// unchanged)
//
// and either:
//
// b1) the field size is large enough to hold all values, or
// b2) the value is less than 2**(field size in bits)
return value == static_cast<ValueType>(
static_cast<typename BitViewType::ValueType>(value)) &&
((Parameters::kBits ==
sizeof(typename BitViewType::ValueType) * 8) ||
(static_cast<typename BitViewType::ValueType>(value) <
((static_cast<typename BitViewType::ValueType>(1)
<< (Parameters::kBits - 1))
<< 1))) &&
Parameters::ValueIsOk(value);
}
void UncheckedWrite(ValueType value) const {
buffer_.UncheckedWriteUInt(
static_cast<typename BitViewType::ValueType>(value));
}
template <typename OtherView>
void CopyFrom(const OtherView &other) const {
Write(other.Read());
}
template <typename OtherView>
void UncheckedCopyFrom(const OtherView &other) const {
UncheckedWrite(other.UncheckedRead());
}
template <typename OtherView>
bool TryToCopyFrom(const OtherView &other) const {
return other.Ok() && TryToWrite(other.Read());
}
// All bit patterns in the underlying buffer are valid, so Ok() is always
// true if IsComplete() is true.
bool Ok() const {
return IsComplete() && Parameters::ValueIsOk(UncheckedRead());
}
template <class OtherBitViewType>
bool Equals(const EnumView<Enum, Parameters, OtherBitViewType> &other) const {
return Read() == other.Read();
}
template <class OtherBitViewType>
bool UncheckedEquals(
const EnumView<Enum, Parameters, OtherBitViewType> &other) const {
return UncheckedRead() == other.UncheckedRead();
}
bool IsComplete() const {
return buffer_.Ok() && buffer_.SizeInBits() >= Parameters::kBits;
}
template <class Stream>
bool UpdateFromTextStream(Stream *stream) const {
return ::emboss::support::ReadEnumViewFromTextStream(this, stream);
}
template <class Stream>
void WriteToTextStream(Stream *stream,
const TextOutputOptions &options) const {
::emboss::support::WriteEnumViewToTextStream(this, stream, options);
}
static constexpr bool IsAggregate() { return false; }
static constexpr int SizeInBits() { return Parameters::kBits; }
private:
BitViewType buffer_;
};
} // namespace support
} // namespace emboss
#endif // EMBOSS_RUNTIME_CPP_EMBOSS_ENUM_VIEW_H_