SequenceSizeFieldPrefix.h

//
// Copyright 2015 - 2025 (C). Alex Robenko. All rights reserved.
//
// 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/.
 
#pragma once
 
#include "comms/Assert.h"
#include "comms/ErrorStatus.h"
 
#include <iterator>
 
namespace comms
{
 
namespace field
{
 
namespace adapter
{
 
template <typename TSizeField, typename TBase>
class SequenceSizeFieldPrefix : public TBase
{
    using BaseImpl = TBase;
    using SizeField = TSizeField;
 
    static const std::size_t MaxAllowedSize =
            static_cast<std::size_t>(SizeField::maxValue());
 
    static_assert(!SizeField::isVersionDependent(),
            "Prefix fields must not be version dependent");
 
public:
    using ValueType = typename BaseImpl::ValueType;
    using ElementType = typename BaseImpl::ElementType;
 
    SequenceSizeFieldPrefix() = default;
 
    explicit SequenceSizeFieldPrefix(const ValueType& val)
      : BaseImpl(val)
    {
    }
 
    explicit SequenceSizeFieldPrefix(ValueType&& val)
      : BaseImpl(std::move(val))
    {
    }
 
    SequenceSizeFieldPrefix(const SequenceSizeFieldPrefix&) = default;
    SequenceSizeFieldPrefix(SequenceSizeFieldPrefix&&) = default;
    SequenceSizeFieldPrefix& operator=(const SequenceSizeFieldPrefix&) = default;
    SequenceSizeFieldPrefix& operator=(SequenceSizeFieldPrefix&&) = default;
 
    std::size_t length() const
    {
        SizeField sizeField;
        sizeField.setValue(BaseImpl::getValue().size());
        return sizeField.length() + BaseImpl::length();
    }
 
    static constexpr std::size_t minLength()
    {
        return SizeField::minLength();
    }
 
    static constexpr std::size_t maxLength()
    {
        return SizeField::maxLength() + BaseImpl::maxLength();
    }
 
    bool valid() const
    {
        if ((!BaseImpl::valid()) || (!canWrite())) {
            return false;
        }
        SizeField sizeField;
        sizeField.setValue(BaseImpl::getValue().size());
        return sizeField.valid() && BaseImpl::valid();
    }
 
    template <typename TIter>
    comms::ErrorStatus read(TIter& iter, std::size_t len)
    {
        auto fromIter = iter;
        SizeField sizeField;
        auto es = sizeField.read(iter, len);
        if (es != comms::ErrorStatus::Success) {
            return es;
        }
 
        auto diff = static_cast<std::size_t>(std::distance(fromIter, iter));
        COMMS_ASSERT(diff <= len);
        len -= diff;
 
        auto count = static_cast<std::size_t>(sizeField.getValue());
        return BaseImpl::readN(count, iter, len);
    }
 
    template <typename TIter>
    void readNoStatus(TIter& iter)
    {
        SizeField sizeField;
        sizeField.readNoStatus(iter);
        auto count = static_cast<std::size_t>(sizeField.getValue());
        BaseImpl::readNoStatusN(count, iter);
    }
 
    bool canWrite() const
    {
        if (!BaseImpl::canWrite()) {
            return false;
        }
 
        if (MaxAllowedSize < BaseImpl::getValue().size()) {
            return false;
        }
 
        SizeField sizeField;
        sizeField.setValue(BaseImpl::getValue().size());
        return sizeField.canWrite();
    }
 
    template <typename TIter>
    comms::ErrorStatus write(TIter& iter, std::size_t len) const
    {
        if (!canWrite()) {
            return comms::ErrorStatus::InvalidMsgData;
        }
 
        SizeField sizeField;
        sizeField.setValue(BaseImpl::getValue().size());
        auto es = sizeField.write(iter, len);
        if (es != comms::ErrorStatus::Success) {
            return es;
        }
 
        COMMS_ASSERT(sizeField.length() <= len);
        return BaseImpl::write(iter, len - sizeField.length());
    }
 
    static constexpr bool hasWriteNoStatus()
    {
        return false;
    }
 
    template <typename TIter>
    void writeNoStatus(TIter& iter) const = delete;
};
 
}  // namespace adapter
 
}  // namespace field
 
}  // namespace comms