CompareWriter.hpp

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/*
    MIT No Attribution
 
    Copyright 2021-2023 Mr. Hands
 
    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to
    deal in the Software without restriction, including without limitation the
    rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
    sell copies of the Software, and to permit persons to whom the Software is
    furnished to do so.
 
    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    DEALINGS IN THE SOFTWARE.
*/
 
#pragma once
 
#include "data/CompareWriterConfig.hpp"
#include "writers/Writer.hpp"
 
namespace panini
{
 
    class CompareWriter
        : public ConfiguredWriter<CompareWriterConfig>
    {
 
    public:
        inline explicit CompareWriter(const CompareWriterConfig& config = {})
            : CompareWriter(config.filePath, config)
        {
        }
 
        inline explicit CompareWriter(
            const std::filesystem::path& filePath,
            const WriterConfig& config = WriterConfig())
            : ConfiguredWriter(CompareWriterConfig{ config })
        {
            m_config.filePath = filePath;
 
            // read the previous output, if available
 
            std::ifstream stream(m_config.filePath.string(), std::ios::binary);
            m_pathExists = stream.is_open();
            if (m_pathExists)
            {
                stream.seekg(0, std::ios::end);
                m_writtenPrevious.resize(static_cast<size_t>(stream.tellg()));
                stream.seekg(0, std::ios::beg);
                stream.read(&m_writtenPrevious[0], m_writtenPrevious.size());
                stream.close();
 
                m_writtenCurrent.reserve(m_writtenPrevious.size());
            }
        }
 
        inline ~CompareWriter() override
        {
            Commit();
        }
 
        inline bool IsChanged() const override
        {
            return m_writtenPrevious != m_writtenCurrent;
        }
 
    protected:
        inline void Write(const std::string& chunk) override
        {
            m_writtenCurrent += chunk;
        }
 
        inline bool OnCommit(bool force = false) override
        {
            (void)force;
 
            std::ofstream stream(m_config.filePath.string(), std::ios::binary);
            if (!stream.is_open())
            {
                return false;
            }
 
            stream.write(m_writtenCurrent.c_str(), m_writtenCurrent.length());
            stream.close();
 
            m_writtenPrevious = m_writtenCurrent;
 
            return true;
        }
 
    protected:
        bool m_pathExists = false;
        std::string m_writtenPrevious;
        std::string m_writtenCurrent;
 
    };
 
};