write_buffer.h

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/* Copyright (C) 2021 Wildfire Games.
 *
 * 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, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * 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
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 */
 
#ifndef INCLUDED_WRITE_BUFFER
#define INCLUDED_WRITE_BUFFER
 
#include "lib/file/file.h"
 
class WriteBuffer
{
public:
    WriteBuffer();
 
    void Append(const void* data, size_t size);
    void Reserve(size_t size);
    void Overwrite(const void* data, size_t size, size_t offset);
 
    std::shared_ptr<u8> Data() const
    {
        return m_data;
    }
 
    size_t Size() const
    {
        return m_size;
    }
 
private:
    void EnsureSufficientCapacity(size_t size);
 
    size_t m_capacity;  // must come first (init order)
 
    std::shared_ptr<u8> m_data;
    size_t m_size;
};
 
 
class UnalignedWriter
{
    NONCOPYABLE(UnalignedWriter);
public:
    UnalignedWriter(const PFile& file, off_t ofs);
    ~UnalignedWriter();
 
    /**
     * add data to the align buffer, writing it out to disk if full.
     **/
    Status Append(const u8* data, size_t size) const;
 
    /**
     * zero-initialize any remaining space in the align buffer and write
     * it to the file. this is called by the destructor.
     **/
    void Flush() const;
 
private:
    Status WriteBlock() const;
 
    PFile m_file;
    std::shared_ptr<u8> m_alignedBuf;
    mutable off_t m_alignedOfs;
    mutable size_t m_bytesUsed;
};
 
typedef std::shared_ptr<UnalignedWriter> PUnalignedWriter;
 
#endif  // #ifndef INCLUDED_WRITE_BUFFER